Formation of Malondialdehyde, 4-Hydroxynonenal, and 4-Hydroxyhexenal during in Vitro Digestion of Cooked Beef, Pork, Chicken, and Salmon

Thermal processing and in vitro digestion of n-3 pork: Effects on the oxidative and digestive properties of proteins and lipids

This study assessed the oxidation of proteins and lipids, as well as the digestive properties of six different sources of n-3 pork, after treatment with four thermal processing methods (sous vide (SV), steaming (ST), boiling (BO), and frying (FR)) and in vitro digestion. Results showed antioxidant (selenium) was associated with reduced oxidation of n-3 pork during processing and digestion. SV significantly reduced the oxidation of pork proteins and lipids and the loss of polyunsaturated fatty acids (PUFAs) compared with other processing methods. After in vitro digestion, SV caused n-3 pork to exhibit higher protein and lipid digestibility, increasing the bioaccessibility of α-linolenic acid (ALA) (81.04 %), eicosapentaenoic acid (EPA) (78.16 %), and docosahexaenoic acid (DHA) (77.28 %). Therefore, selenium addition was beneficial for improving the oxidative stability of pork, and SV can minimize nutrient losses during the processing and digestion of pork and improve the bioavailability of n-3 PUFAs.

Effect of flaxseed oil cyclolinopeptides on lipid oxidation, protein oxidation, and lipid profile during in vitro digestion of high-fat beef

This study investigated the influence of flaxseed oil cyclolinopeptides (CLs) on lipid and protein oxidation during high-fat meat digestion. Fourteen CLs were identified in flaxseed oil through UHPLC-ESI-QTOF-MS/MS, with dominant CLA, CLB, CLE, and CLM. During in vitro digestion, CLs inhibited lipid oxidation products (lipid hydroperoxide, Malondialdehyde, and 4-hydroxynonenal) and protein carbonylation. Compared to other groups, the lipid (16.28 ± 0.35) and protein (17.5 ± 0.6) oxidation was significantly inhibited, and antioxidant activity was remarkably increased when the CLs content reached 200 mg/kg. Through untargeted lipidomic analysis using Q-Exactive, it was observed that CLs mitigated the formation of oxidized triglycerides (OxTG) products and enhanced the hydrolysis of lipids to generate sphingolipid and polyunsaturated fatty-acids enriched glycerophospholipids imparting nutritional value to meat. Electron spin-resonance and fluorescence quenching showed that primary radicals such as alkyl and alkoxy radicals during high-fat meat digestion with flaxseed oil CLs significantly mitigate their formation. These findings collectively indicate that consuming CLs enriched flaxseed oil could reduce lipid oxidation and enhance the nutritional value of high-fat meat during digestion.

Influence of diet and exercise on leukocyte telomere length, markers of oxidative stress and inflammation in rats

Telomere length is an important biomarker of biological aging and is affected by nutrition and physical activity. This study investigated the effects of diets with different fat contents and increased physical activity on certain pro/anti-inflammatory and oxidative stress markers and aging. The study is performed in a randomized, experimental, and controlled design with 48 rats, 8 weeks old, divided into 6 different groups (Control (C), exercise (E), unsaturated fat diet (USF), saturated fat diet (SF), unsaturated fat diet + exercise (USF + E), and saturated fat diet + exercise (SF + E)). The rats performed aerobic swimming exercise for 50 days and were fed a diet with different fat content. TAS, TOS, and MDA levels were determined by colorimetric analysis while 8-OHdG, IL-10, and TNF-α were determined by ELISA. Additionally, leukocyte telomere length is determined by the PCR method. Weight changes were also recorded. Plasma TOS, OSI, and TNF-α were lowest in the USF group and highest in the SF and SF + E groups. MDA, 8-OHdG and TG levels were highest in the SF group. The lowest IL-10 level was detected in group C. TL level was the highest in the USF group. There was also a moderate, negative, and significant correlation between telomeres and TOS, OSI, and TNF-α. The groups with the highest body weight gain were C, SF, and SF + E. Diets low in saturated fat or high in unsaturated fat, and physical activity were associated with leukocyte telomere length and alteration of oxidative and pro/anti-inflammatory markers.

Gastrointestinal fate of proteins from commercial plant-based meat analogs: Silent passage through the stomach, oxidative stress in intestine, and gut dysbiosis in Wistar rats

Plant-based meat analogs (PBMAs) are common ultra-processed foods (UPFs) included in the vegan/vegetarian diets as presumed healthy alternatives to meat and meat products. However, such health claims need to be supported by scientific evidence. To gain further insight into this topic, two commercial UPFs typically sold as meat analogs, namely, seitan (S) and tofu (T), were included in a cereal-based chow and provided to Wistar rats for 10 weeks. A group of animals had, simultaneously, an isocaloric and isoprotein experimental diet formulated with cooked beef (B). In all cases, experimental chows (∼4 kcal/g feed) had their basal protein concentration increased from 14% to 30% using proteins from S, T, or B. Upon slaughter, in vivo protein digestibility was assessed, and the entire gastrointestinal tract (digests and tissues) was analyzed for markers of oxidative stress and untargeted metabolomics. Metagenomics was also applied to assess the variation of microbiota composition as affected by dietary protein. Diets based on PBMAs showed lower protein digestibility than those containing meat and promoted an intense luminal glycoxidative stress and an inflammatory intestinal response. The fermentation of undigested oxidized proteins from T in the colon of Wistar rats likely led to formation of mutagenic metabolites such as p-cresol. The presence of these compounds in the animal models raises concerns about the potential effects of full replacement of meat by certain PBMAs in the diet. Therefore, future research might target on translational human studies to shed light on these findings.

Interrelationship of lipid aldehydes (MDA, 4-HNE, and 4-ONE) mediated protein oxidation in muscle foods

Proteins and essential fatty acids are crucial components of the human diet. However, lipids and proteins are susceptible to oxidative modification during food processing resulting in changes to their structural characteristics and functional properties. Food products rich in polyunsaturated fatty acids are highly susceptible to lipid peroxidation and generate bifunctional reactive aldehydes. Bifunctional aldehydes such as malondialdehyde (MDA), 4-hydroxy-2-nonenal (4-HNE), and 4-oxo-2-nonenal (4-ONE) readily bind to protein nucleophiles and lead to intra- or intermolecular protein cross-linking. In comparison with lipid oxidation, the degradation of proteins by prooxidants appears to be more intricate and results in a greater diversity of oxidation products. Although individual oxidation processes involving lipids and proteins received increasing attention in the past decades, the interactions between those aldehydes and protein oxidation in food have not been extensively explored. Studies indicate that the reactions of lipid and protein oxidation may take place simultaneously or independently, but oxidation products that arose from one reaction may further interact with lipids or proteins. The present review presents a perspective on reactive aldehydes and the role of aldehydes in inducing protein oxidation in muscle foods. Emphasis is focused on the interaction mechanism of the lipid, protein, and myoglobin protein oxidations. In addition, the occurrence of aldehydes derived from lipid oxidation in food systems as well as the endogenous antioxidant peptides or amino acids in meat and plant proteins are also briefly described.

Breaking down barriers: live or dehydrated dietary whole black soldier fly larvae supplementation in slow growing chickens preserve meat quality and sensory traits

This study investigated the effects of supplementing the diet of a slow-growing autochthonous chicken breed with dehydrated or live Black Soldier Fly Larvae (BSFL) on meat quality and sensory attributes. The research, conducted at the University of Turin, Italy, involved 144 male birds distributed in three experimental groups. The control group (C) was fed a basal diet in which soybean meal was completely substituted with alternative ingredients. The 2 experimental groups were administered a diet identical to the control group but supplemented with either whole dehydrated black soldier fly larvae (DL) or whole live black soldier fly larvae (LL) at a level equal to 5% expected daily feed intake of dry matter. We evaluated the following parameters: nutrient intake, slaughtering performance, physical and nutritional meat quality, fatty acid composition, proteomics, and sensory characteristics. The results demonstrated BSFL supplementation to have no detrimental effects on overall meat quality or sensory attributes. Specifically, there were no significant differences in physical meat quality parameters, nutritional composition, lipid oxidation, or protein digestibility between control and BSFL-fed groups. Fatty acid analysis revealed higher concentrations of lauric and myristic acids in BSFL-fed chicken breast (p < 0.005), suggesting potential nutritional benefits from the supplement. The proteomic analysis also showed no significant differences in the expression of abundant proteins in the breast meat between groups, indicating minimal physiological impact of BSFL supplementation. Overall, this study provides reassurance to consumers and industries about the suitability of BSFL as a sustainable feed supplement for poultry that also offers potential benefits in terms of optimizing the fatty acid profile of chicken meat.

Glucose addition and oven-heating of pork stimulate glycoxidation and protein carbonylation, while reducing lipid oxidation during simulated gastrointestinal digestion

In the present study, it was investigated if glucose addition (3 or 5%) to pork stimulates glycoxidation (pentosidine, PEN), glycation (Maillard reaction products, MRP), lipid oxidation (4-hydroxy-2-nonenal, 4-HNE; hexanal, HEX; thiobarbituric acid reactive substances, TBARS), and protein oxidation (protein carbonyl compounds, PCC) during various heating conditions and subsequent in vitro gastrointestinal digestion. An increase in protein-bound PEN level was observed during meat digestion, which was significantly stimulated by glucose addition (up to 3.3-fold) and longer oven-heating time (up to 2.5-fold) of the meat. These changes were accompanied by the distinct formation of MRP during heating and digestion of the meats. Remarkably, stimulated glyc(oxid)ation was accompanied by increased protein oxidation, whereas lipid oxidation was decreased, indicating these reactions are interrelated during gastrointestinal digestion of meat. Glucose addition generally didn't affect these oxidative reactions when pork was packed preventing air exposure and oven-heated until a core temperature of 75 °C was reached.

Insights into diosgenin against inflammatory bowel disease as functional food based on network pharmacology and molecular docking

Inflammatory bowel disease (IBD) is a growing global health problem. IBD is commonly prevalent in Europe and America and the incidence rate in Asia is on the rise due to altered dietary structure. Diosgenin is a natural steroidal saponin derived from Dioscorea plants. Diosgenin is the main active ingredient of some Chinese medicines which are mainly used to treat coronary heart disease, angina and hyperlipidemia. Recently, growing evidence has exhibited a crucial role of diosgenin and dioscin in alleviating IBD in multiple ways. However, the precise mechanism of diosgenin against IBD needs further exploration. In this study, network pharmacological and systematic bioinformatic analyses were performed to investigate the diosgenin's targets against IBD. 71 targets such as SRC, TNF and STAT3 were identified as overlapped genes between diosgenin and IBD. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis exhibited their involvement in the tyrosine kinase signaling pathway and its membrane receptors. Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor resistance and its downstream Ras-MAPK pathway and PI3K-Akt pathway might become the mechanism of diosgenin against IBD. In addition, molecular docking analysis showed that diosgenin has the massive potential of direct binding to tyrosine kinase and its receptors such as SRC, EGFR, FGFR1 and VEGFR. The results above collectively provided evidence that diosgenin is a promising nutraceutical food against IBD.

Dual effects of dietary carnosine during in vitro digestion of a Western meal model with added ascorbic acid

The beneficial role of carnosine during in vitro digestion of meat was previously demonstrated, and it was hypothesized that such benefits could also be obtained in a meal system. The current study, therefore, assessed carnosine effects on markers of lipid and protein oxidation and of advanced glycation end products (AGEs) during gastric and duodenal in vitro digestion of a burger meal model. The model included intrinsic (low) and enhanced (medium and high) carnosine levels in a mix of pork mince and bread, with or without ascorbic acid (AA) and/or fructose as anti- and prooxidants, respectively. In the presence of either AA or fructose, a carnosine prooxidative potential during digestion was observed at the medium carnosine level depending on markers and digestive phases. However, free carnosine found at the high carnosine level exerted a protective effect reducing the formation of 4-hydroxynonenal in the gastric phase and glyoxal in both the gastric and duodenal phases. Dual effects of carnosine are likely concentration related, whereby at the medium level, free radical production increases through carnosine's ferric-reducing capacity, but there is insufficient quantity to reduce the resulting oxidation, while at the higher carnosine level some decreases in oxidation are observed. In order to obtain carnosine benefits during meal digestion, these findings demonstrate that consideration must be given to the amount and nature of other anti- and prooxidants present and any potential interactions. PRACTICAL APPLICATION: Carnosine, a natural compound in meat, is a multifunctional and beneficial molecule for health. However, both pro- and antioxidative effects of carnosine were observed during digestion of a model burger meal when ascorbic acid was included at a supplemental level. Therefore, to obtain benefits of dietary carnosine during digestion of a meal, consideration needs to be given to the amount and nature of all anti- and prooxidants present and any potential interactions.

Changes in bioactive compounds present in beef burgers formulated with walnut oil gelled emulsion as a fat substitute during in vitro gastrointestinal digestion

BACKGROUND

The partial or total substitution of animal fat by a gelled emulsion elaborated with cocoa bean shell and walnut oil in beef burgers was assessed in terms of the stability of the bioactive compounds (polyphenolic and methylxanthines compounds, and fatty acid profile), bioaccessibility, colon-available indices (CAIs), and lipid oxidation after in vitro gastrointestinal digestion (GID).

RESULTS

No free polyphenolic compounds were detected in the soluble fraction after the GID of reformulated beef burgers. Reductions were obtained in the bound fraction with respect to the undigested sample from 47.57 to 53.12% for protocatechuic acid, from 60.26 to 78.01% for catechin, and from 38.37 to 60.95% for epicatechin. The methylxanthine content decreased significantly after GID. The theobromine content fell by between 48.41 and 68.61% and the caffeine content was reduced by between 96.47 and 97.95%. The fatty acid profile of undigested samples was very similar to that of digested samples. In the control burger the predominant fatty acids were oleic acid (453.27 mg g-1 ) and palmitic acid (242.20 mg g-1 ), whereas in reformulated burgers a high content of linoleic acid (304.58 and 413.35 mg g-1 ) and α-linolenic acid (52.44 and 82.35 mg g-1 ) was found. As expected, both undigested and digested reformulated samples presented a higher degree of oxidation than the control sample.

CONCLUSIONS

The reformulated beef burgers with cocoa bean shells flour and walnut oil were a good source of bioactive compounds, which were stable after in vitro gastrointestinal digestion. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effectiveness of a covered oil-free cooking process on the abatement of air pollutants from cooking meats

Cooking events can generate household air pollutants that deteriorate indoor air quality (IAQ), which poses a threat to human health and well-being. In this study, the emission characteristics and emission factors (EFs) of air pollutants of different meats (beef, lamb, chicken, pork, and fish) cooked by a novel oil-free process and common with-oil processes were investigated. Oil-free cooking tends to emit lower total volatile organic compound (TVOC) levels and fewer submicron smoke particles and can reduce the intake of fat and calories. However, TVOC emissions during oil-free cooking were significantly different, and the lamb EFs were nearly 8 times higher than those during with-oil cooking. The particle-bound polycyclic aromatic hydrocarbon (ƩPPAH) and benzo(a)pyrene-equivalent (ƩBaPeq) EFs during with-oil cooking ranged from 76.1 to 140.5 ng/g and 7.7-12.4 ng/g, respectively, while those during oil-free cooking ranged from 41.0 to 176.6 ng/g and 5.4-47.6 ng/g, respectively. The ƩPPAH EFs of chicken, pork, and fish were lower during oil-free cooking than during cooking with oil. Furthermore, the ƩBaPeq EFs of beef, chicken, pork, and fish were lower during oil-free cooking than during cooking with oil. Therefore, it is recommended to use the oil-free method to cook chicken, pork, and fish to reduce ƩPPAH and ƩBaPeq emissions, but not recommended to cook lamb due to the increase of ƩBaPeq emissions. The with-oil uncovered cooking EFs of aldehydes ranged from 3.77 to 22.09 μg/g, and those of oil-free cooking ranged from 4.88 to 19.96 μg/g. The aldehyde EFs were lower during oil-free covered cooking than with-oil uncovered cooking for beef, chicken, and fish. This study provides a better realizing of new cooking approaches for the reduction of cooking-induced emission, but further research on the effects of food composition (moisture and fat) and characteristics is needed.

Effect of fiber-bound polyphenols from highland barley on lipid oxidation products of cooked pork during in vitro gastrointestinal digestion

BACKGROUND

The gastrointestinal (GI) tract is a major site of lipid oxidation, and the lipid oxidation products are related to an increased risk of various chronic diseases. In this study, the inhibition capacity of bound-polyphenol rich insoluble dietary fiber (BP-IDF) from highland barley (HB) to lipid oxidation was evaluated during simulated GI digestion.

RESULTS

We found that the level of lipid hydroperoxides (LOOH) and aldehydes were significantly inhibited when highland barley bound-polyphenol rich insoluble dietary fiber (HBBP-IDF) co-digestion with cooked pork. The lipid oxidation products were more effectively scavenged during simulated gastric digestion, with inhibition of 77.4% for LOOH, 52.3% for malondialdehyde, 46.5% for 4-hydroxy-2-hexenal and 48.7% for 4-hydroxy-2-nonenel, respectively. The fiber-bound polyphenols are the principal scavengers of lipid oxidation products.

CONCLUSION

These findings suggest that HBBP-IDF could be used as a functional ingredient able to scavenge lipid oxidation products across the GI tract. © 2023 Society of Chemical Industry.

Defining the nuanced nature of redox biology in post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a mental health disorder that arises after experiencing or witnessing a traumatic event. Despite affecting around 7% of the population, there are currently no definitive biological signatures or biomarkers used in the diagnosis of PTSD. Thus, the search for clinically relevant and reproducible biomarkers has been a major focus of the field. With significant advances of large-scale multi-omic studies that include genomic, proteomic, and metabolomic data, promising findings have been made, but the field still has fallen short. Amongst the possible biomarkers examined, one area is often overlooked, understudied, or inappropriately investigated: the field of redox biology. Redox molecules are free radical and/or reactive species that are generated as a consequence of the necessity of electron movement for life. These reactive molecules, too, are essential for life, but in excess are denoted as "oxidative stress" and often associated with many diseases. The few studies that have examined redox biology parameters have often utilized outdated and nonspecific methods, as well as have reported confounding results, which has made it difficult to conclude the role for redox in PTSD. Herein, we provide a foundation of how redox biology may underlie diseases like PTSD, critically examine redox studies of PTSD, and provide future directions the field can implement to enhance standardization, reproducibility, and accuracy of redox assessments for the use of diagnosis, prognosis, and therapy of this debilitating mental health disorder.

4-Oxo-2-nonenal (4-ONE)-Induced Degradation of Bovine Skeletal Muscle Proteins

Lipids are an important component of meat, as they provide desirable sensory characteristics and nutritional benefits. However, lipids are susceptible to degradation through oxidation and produce toxic oxidative byproducts. 4-Oxo-2-nonenal (4-ONE) is an oxidative byproduct that is highly reactive and cytotoxic. In this study, we investigated the influence of 4-ONE-induced protein degradation on fresh and gastric digested bovine skeletal muscle proteins. The results indicated that 4-ONE naturally forms in fresh muscle proteins. We report here for the first time that 4-ONE causes severe degradation of bovine skeletal muscle proteins. An SDS-PAGE gel analysis showed evidence that the skeletal muscle proteins attenuated over the incubation time, as the density of the protein bands faded significantly after 120 h. Additionally, protein and band density analyses showed a significant decrease in protein abundance and band densities throughout the incubation time. This study revealed that the lipid oxidation byproduct, 4-oxo-2-nonenal (4-ONE) is responsible for causing skeletal muscle protein degradation. Future studies should assess the bioprotective role of antioxidants and other food ingredients for their potential to prevent the formation and/or detoxification of 4-ONE in meat.

Modulation of 1,2-Dicarbonyl Compounds in Postprandial Responses Mediated by Food Bioactive Components and Mediterranean Diet

Glycoxidative stress with the consequent generation of advanced glycation end products has been implied in the etiology of numerous non-communicable chronic diseases. During the postprandial state, the levels of 1,2-dicarbonyl compounds can increase, depending on numerous factors, including characteristics of the subjects mainly related to glucose metabolism disorders and nutritional status, as well as properties related to the chemical composition of meals, including macronutrient composition and the presence of dietary bioactive molecules and macromolecules. In this review, we examine the chemical, biochemical, and physiological pathways that contribute to postprandial generation of 1,2-dicarbonyl compounds. The modulation of postprandial 1,2-dicarbonyl compounds is discussed in terms of biochemical pathways regulating the levels of these compounds, as well as the effect of phenolic compounds, dietary fiber, and dietary patterns, such as Mediterranean and Western diets.

Assessment of a Diterpene-Rich Rosemary (Rosmarinus officinalis L.) Extract as a Natural Antioxidant for Salmon Pâté Formulated with Linseed

The use of natural plant extracts with standardised antioxidant properties is a growing strategy to stabilise food products. The use of a rosemary lipophilic extract (RLE), obtained from the by-product of high-yield selected plants and rich in polyphenols (334 mg/g, with diterpenes such as carnosic acid and carnosol as main compounds), is here proposed. Four RLE doses (0, 0.21, 0.42 and 0.63 g/kg) were tested in a salmon pâté formulated with sunflower oil and linseed, which was pasteurised (70 °C for 30 min) and subjected to storage at 4 °C and 600 lux for 42 days. Rosemary diterpenes resisted pasteurisation without degrading and showed antioxidant activities during the shelf-life of pasteurised pâté. RLE addition led to increased peroxide value (from 3.9 to 5.4 meq O_2/kg), but inhibited formation of secondary oxidised lipids such as malondialdehyde (from 1.55 to 0.89 mg/g) and cholesterol oxidation products (from 286 to 102 µg/100 g) and avoided discolouration (slight brownness) in the refrigerated pâté. However, this did not entail relevant changes in fatty acid content or in the abundance of volatile organic compounds from oxidised lipids. Increasing the RLE dose only improved its antioxidant efficacy for some oxidation indexes. Thus, the oxidative deterioration of these types of fish emulsion can be naturally controlled with rosemary extracts rich in diterpenes.

Different Effects of Vitamin C-Based Supplements on the Advance of Linseed Oil Component Oxidation and Lipolysis during In Vitro Gastrointestinal Digestion

Although widely consumed, dietary supplements based on Vitamin C contain high doses of this compound, whose impact on lipid oxidation during digestion needs to be addressed. Therefore, the effect of seven commercial supplements and of pure l-ascorbic acid and ascorbyl palmitate on linseed oil during in vitro gastrointestinal digestion was tackled. The advance of lipid oxidation was studied through the generation of oxidation compounds, the degradation of polyunsaturated fatty acyl chains and of gamma-tocopherol, by employing Proton Nuclear Magnetic Resonance. Supplements containing exclusively l-ascorbic acid enhanced the advance of linseed oil oxidation during digestion. This was evidenced by increased formation of linolenic-derived conjugated hydroxy-dienes and alkanals and by the generation of conjugated keto-dienes and reactive alpha,beta-unsaturated aldehydes, such as 4,5-epoxy-2-alkenals; moreover, gamma-tocopherol was completely degraded. Conversely, supplements composed of mixtures of ascorbic acid/salt with citric acid and carotenes, and of ascorbyl palmitate, protected linseed oil against oxidation and reduced gamma-tocopherol degradation. The study through Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry of the volatile compounds of the digests corroborated these findings. Furthermore, a decreased lipid bioaccessibility was noticed in the presence of the highest dose of l-ascorbic acid. Both the chemical form of Vitamin C and the presence of other ingredients in dietary supplements have shown to be of great relevance regarding oxidation and hydrolysis reactions occurring during lipid digestion.

Effect of inoculation with Penicillium chrysogenum on chemical components and fungal communities in fermentation of Pu-erh tea

Developing an effective method to improve the quality of Pu-erh tea is of great scientific and commercial interest. In this work, Penicillium chrysogenum P1 isolated from Pu-erh tea was inoculated in sterilized or unsterilized sun-dreid green tea leaves to develop pure-culture fermentation (PF) and enhanced fermentation (EF) of Pu-erh tea. Spectrophotometry and high performance liquid chromatography determined that contents of free amino acids (FAA), total tea polyphenols and eight polyphenolic compounds in PF were significantly lower than these in non-inoculation control test (CK) (P < 0.05), whereas the contents of soluble sugars and theabrownins (TB) in PF were significantly higher (P < 0.05) than in CK. A total of 416 volatile compounds were detected by headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry. Comparison to CK, 124 compounds in PF were degraded or decreased significantly [Variable importance in projection [(VIP) > 1.0, P < 0.05, fold change (FC) < 0.5], whereas 110 compounds in PF were formed or increased significantly (VIP > 1.0, P < 0.05, FC > 2). Compared with normal fermentation (NF), the levels of gallic acid, (+)-catechin, (-)-epicatechin and 64 volatile compounds in EF were significantly lower (VIP > 1.0, P < 0.05, FC < 0.5), whereas the levels of FAA and 39 volatile compounds were significantly higher (VIP > 1.0, P < 0.05, FC > 2). Amplicon sequencing of fungal internal transcribed spacer 1 (ITS1) revealed that P. chrysogenum P1 didn't become the dominant fungus in EF; while the fungal communities in EF were different from those in NF, in that the relative abundances of Blastobotrys bambusae and P. chrysogenum in EF were higher, and the relative abundances of Aspergillus niger and Kluyveromyces marxianus in EF were lower. Overall, inoculation of P. chrysogenum in unsterilized sun-dreid green tea leaves changed the the fungal communities in fermentation of Pu-erh tea, and chemical compounds in fermented tea leaves, i.e., the levels of TB and the compounds responsible for the stale flavor, e.g., 2-amino-4-methoxybenzothiazole were increased, resulting in improvement of the sensory quality, including mellower taste and stronger stale flavor.

Physicochemical attributes, oxidative stability, and microbial profile of boneless sirloin and bone-in T-bone steaks from Hanwoo steer with reference to dry-aging

We investigated the comparative physicochemical attributes, oxidative stability, and microbial characteristics of 28 days dry-aged meat in between boneless sirloin (gluteus medius) and bone-in T-bone steaks (infraspinatus) muscles from Korean Native Hanwoo Steer (KNHS). Results reveal that regardless of the muscles, dry-aging increased protein content and water-holding capacity (WHC) (p < 0.05). Meat from infraspinatus-aged muscle led to darker meat with higher pH values than un-aged meat (p < 0.05). However, fat content, CIE a*, and CIE b* remained unchanged in both muscles at aging. At aged meat, thiobarbituric acid reactive substances (TBARS) values from bone-in infraspinatus muscle was 2.5-fold higher than boneless gluteus medius muscle (p < 0.05). Dry-aging led to an increase in the contents of total unsaturated fatty acids (UFAs), monounsaturated fatty acids (MUFAs), and UFA/saturated fatty acids (SFA) in both muscles (p < 0.05). Furthermore, gluteus medius aged muscle concentrated with olic acid (C18:1) compared to infraspinatus aged muscle. Irrespective of the muscles, dry-aging enhanced the total free amino acids (FAAs) as well as tasty, and bitter amino acid contents whereas decreased the tasty/bitter amino acids (p < 0.05). Aromatic amino acid, tryptophan that converted to serotonin was 2-fold higher in boneless gluteus medius muscle than bone-in infraspinatus muscle at pre and post aging processes (p < 0.05). Aged Infraspinatus muscle increased total bacteria (p < 0.05) while no salmonellaspp. was detected in both muscles. Taken together, our study confirms that 28 days dry-aging profiling the quality characteristics of boneless sirloin (gluteus medius) and bone-in T-bone steaks (infraspinatus) distinctly while gluteus medius aged steak performs better owing to oxidative stability and functional compounds than infraspinatus aged steak.

The Influence of Butter and Oils on Oxidative Reactions during In Vitro Gastrointestinal Digestion of Meat and Fish

Oxidative reactions during cooking and gastrointestinal digestion of meat and fish lead to the formation of various lipid- and protein oxidation products, some of which are toxic. In the present study, it was investigated how the addition of 3% butter or oils affect lipid- and protein oxidation during cooking and in vitro digestion of meat (chicken thigh, chicken breast, beef) and fish (mackerel, cod). These muscle foods were selected based on their differences in heme-Fe and PUFA contents, and n-6/n-3 PUFA ratio, and therefore varying potential to form oxidation products during digestion. Without additional fat, mackerel digests displayed the highest n-3 PUFA oxidation (4-hydroxy-2-hexenal, propanal, thiobarbituric reactive acid substances), and chicken digests the highest n-6 PUFA oxidation (4-hydroxy-2-nonenal, hexanal), whereas both lipid- and protein oxidation (protein carbonyl compounds) were low in cod and beef digests. Lipid oxidative reactions were generally not altered by the addition of butter to any muscle matrix, whereas the addition of fish oil and safflower oil in different ratios (3:0, 2:1, 1:2, 0:3) as n-3 PUFA and n-6 PUFA source respectively, stimulated oxidative reactions, especially during digestion of beef. Since beef was considered the muscle matrix with the highest potential to stimulate oxidation in the added fat substrate, in a second experiment, beef was cooked and digested with 3% butter or seven commercial vegetable oils (sunflower-, maize-, peanut-, rapeseed-, olive-, rice bran- or coconut oil), all labeled ‘suitable for heating’. No relevant oxidative reactions were however observed during digestion of beef with any of these commercial vegetable oils.

Lipid oxidation and aldehyde formation during in vitro gastrointestinal digestion of roasted scallop (Patinopecten yessoensis) - the role of added antioxidant of bamboo leaves

This study investigated lipid oxidation and aldehyde formation in roasted scallop during in vitro gastrointestinal digestion, and the effects of co-digestion of antioxidant of bamboo leaves (AOB) on this process. The results showed that the contents of lipid hydroperoxides (LOOH), conjugated dienes (CD), and Schiff bases (SB) were increased during gastrointestinal digestion. Besides, malondialdehyde (MDA) levels and total aldehyde formation decreased initially at the gastric stage but increased at the intestinal stage. The results of HPLC-ESI-MS/MS analysis showed that the contents of hexanal (HEX), trans, trans-2,4-octadienal (ODE), trans, trans-2,4-decadienal (DDE), 4-hydroxyhexenal (HHE) and 4-hydroxynonenal (HNE) in the digestive juices were all initially decreased and then increased during gastrointestinal digestion. Meanwhile, the content of acrolein, propanal, and trans-2-pentenal at the end of intestinal digestion was lower than that in the initial stage of gastric digestion. Additionally, the digestion of roasted scallop caused significant oxidation of polyunsaturated fatty acids (PUFAs) and release of free fatty acids (FFA) in the intestinal phase, which were positively related to aldehyde production. However, co-digestion of AOB significantly reduced lipid oxidation and formation of lipid oxidation products (LOOH, CD, SB, and aldehyde) during gastrointestinal digestion, indicating that the addition of AOB was effective in reducing gastrointestinal lipid oxidation.

Protein carbonylation in food and nutrition: a concise update

Protein oxidation is a topic of indisputable scientific interest given the impact of oxidized proteins on food quality and safety. Carbonylation is regarded as one of the most notable post-translational modifications in proteins and yet, this reaction and its consequences are poorly understood. From a mechanistic perspective, primary protein carbonyls (i.e. α-aminoadipic and γ-glutamic semialdehydes) have been linked to radical-mediated oxidative stress, but recent studies emphasize the role alternative carbonylation pathways linked to the Maillard reaction. Secondary protein carbonyls are introduced in proteins via covalent linkage of lipid carbonyls (i.e. protein-bound malondialdehyde). The high reactivity of protein carbonyls in foods and other biological systems indicates the intricate chemistry of these species and urges further research to provide insight into these molecular mechanisms and pathways. In particular, protein carbonyls are involved in the formation of aberrant and dysfunctional protein aggregates, undergo further oxidation to yield carboxylic acids of biological relevance and establish interactions with other biomolecules such as oxidizing lipids and phytochemicals. From a methodological perspective, the routine dinitrophenylhydrazine (DNPH) method is criticized not only for the lack of accuracy and consistency but also authors typically perform a poor interpretation of DNPH results, which leads to misleading conclusions. From a practical perspective, the biological relevance of protein carbonyls in the field of food science and nutrition is still a topic of debate. Though the implication of carbonylation on impaired protein functionality and poor protein digestibility is generally recognized, the underlying mechanism of such connections requires further clarification. From a medical perspective, protein carbonyls are highlighted as markers of protein oxidation, oxidative stress and disease. Yet, the specific role of specific protein carbonyls in the onset of particular biological impairments needs further investigations. Recent studies indicates that regardless of the origin (in vivo or dietary) protein carbonyls may act as signalling molecules which activate not only the endogenous antioxidant defences but also implicate the immune system. The present paper concisely reviews the most recent advances in this topic to identify, when applicable, potential fields of interest for future studies.

Thermal processing implications on the digestibility of meat, fish and seafood proteins

Thermal processing is an inevitable part of the processing and preparation of meat and meat products for human consumption. However, thermal processing techniques, both commercial and domestic, induce modifications in muscle proteins which can have implications for their digestibility. The nutritive value of muscle proteins is closely related to their digestibility in the gastrointestinal tract and is determined by the end products that it presents in the assimilable form (amino acids and small peptides) for the absorption. The present review examines how different thermal processing techniques, such as sous-vide, microwave, stewing, roasting, boiling, frying, grilling, and steam cooking, affect the digestibility of muscle proteins in the gastrointestinal tract. By altering the functional and structural properties of muscle proteins, thermal processing has the potential to influence the digestibility negatively or positively, depending on the processing conditions. Thermal processes such as sous-vide can induce favourable changes, such as partial unfolding or exposure of cleavage sites, in muscle proteins and improve their digestibility whereas processes such as stewing and roasting can induce unfavourable changes, such as protein aggregation, severe oxidation, cross linking or increased disulfide (S-S) content and decrease the susceptibility of proteins during gastrointestinal digestion. The review examines how the underlying mechanisms of different processing conditions can be translated into higher or lower protein digestibility in detail. This review expands the current understanding of muscle protein digestion and generates knowledge that will be indispensable for optimizing the digestibility of thermally processed muscle foods for maximum nutritional benefits and optimal meal planning.

Protective effects of dietary carnosine during in-vitro digestion of pork differing in fat content and cooking conditions

Muscle carnosine represents an important health advantage of meat. Ground pork samples with intrinsic or added carnosine; fat content; and cooked under low or high intensity as a 2 × 2 × 2 factorial were digested in-vitro. Changes in free carnosine and in markers of lipid (hexanal, 4-hydroxynonenal (4-HNE), malondialdehyde (MDA) and protein (protein-carbonyls, thiols) oxidation, and of advanced glycation end-products (AGEs) N^ε -(carboxymethyl)lysine (CML) were determined in the saliva, gastric, and duodenal digests. During digestion, the different markers overall indicated increased oxidation and decreased free carnosine. Increasing pork carnosine level significantly reduced protein carbonyls, loss of thiols, and 4-HNE during in-vitro gastric digestion, irrespective of fat and cooking level of the meat. Increased carnosine also significantly reduced hexanal, MDA and CML up to the duodenum phase in moderately cooked lean pork. Besides substantiating the formation of AGEs during digestion, these results show a potentially important role of dietary carnosine occurring in the gastrointestinal tract. PRACTICAL APPLICATIONS: The ailments epidemiologically associated with red meat consumption could be counteracted by ingesting carnosine into meat. The health advantages of dietary carnosine, however, have never been demonstrated during digestion, a unique and complex oxidative environment compounded by the composition and cooking of the meat. The results obtained substantiated that AGEs formation occurred in-vitro in the GIT. They also showed that increased carnosine had an immediate health beneficial role during pork digestion in reducing the formation of different harmful molecules, including AGEs, modulated by the composition and cooking of the meat. However, in exerting this protective role in the GIT, the remaining free level of carnosine, gradually decreased during digestion. Carnosine, as an important meat compositional factor may, depending on the fat content and cooking conditions, change the image of meat from representing a health risk to a health benefit. Carnosine level may also explain discrepancies observed in the literature.

Pork Liver Pâté Enriched with Persimmon Coproducts: Effect of In Vitro Gastrointestinal Digestion on Its Fatty Acid and Polyphenol Profile Stability

Agrofood coproducts are used to enrich meat products to reduce harmful compounds and contribute to fiber and polyphenol enrichment. Pork liver pâtés with added persimmon coproducts (3 and 6%; PR-3 and PR-6, respectively) were developed. Therefore, the aim was to study the effect of their in vitro gastrointestinal digestion on: the free and bound polyphenol profile (HPLC) and their colon-available index; the lipid oxidation (TBARs); and the stability of the fatty acid profile (GC). Furthermore, the effect of lipolysis was investigated using two pancreatins with different lipase activity. Forty-two polyphenols were detected in persimmon flour, which were revealed as a good source of bound polyphenols in pâtés, especially gallic acid (164.3 µg/g d.w. in PR-3 and 631.8 µg/g d.w. in PR-6). After gastrointestinal digestion, the colon-available index in enriched pâté ranged from 88.73 to 195.78%. The different lipase activity in the intestinal phase caused significant differences in bound polyphenols' stability, contributing to increased lipid oxidation. The fatty acids profile in pâté samples was stable, and surprisingly their PUFA content was raised. In conclusion, rich fatty foods, such as pâté, are excellent vehicles to preserve bound polyphenols, which can reach the colon intact and be metabolized by the intestinal microbiome.

Novel sample treatment method for the determination of free (E)-4-hydroxy-2-nonenal in meat products by liquid chromatography/tandem mass spectrometry using 4-hydroxy-2-nonenal-d3 as internal standard

RATIONALE

(E)-4-Hydroxy-2-nonenal (HNE) is a reactive secondary product of lipid oxidation with biological significance. The analysis of HNE is a challenge due to its volatility and high activity. Developing sample preparation and analytical tools for the determination of free HNE is crucial for better understanding the actual level of free HNE in meat products.

METHODS

Liquid nitrogen freezing, subzero-temperature extraction and derivatization were employed for meat sample treatment. Liquid chromatography/tandem mass spectrometry with electrospray ionization in negative ion mode was used for the determination of free HNE after isotope-coded derivatization.

RESULTS

High repeatability and good recoveries with a limit of quantification as low as 0.25 pmol/g were found. Nineteen out of 24 samples, including chilled/processed meat products and meat-based instant foods, were found to contain free HNE with a range of 0.014-1.160 nmol/g.

CONCLUSIONS

The proposed method showed satisfactory reliability, sensitivity and accuracy. We believe that such a sample preparation strategy will provide a powerful tool for better understanding the actual level of free HNE in meat products.

Formation and disappearance of aldehydes during simulated gastrointestinal digestion of fried clams

The formation and disappearance of aldehydes during simulated gastrointestinal digestion (SD) of fried clams was investigated in order to shed light on the underlying mechanism. Results from the thiobarbituric acid reactive substance (TBARS) and fluorometric assays using a specific aldehyde probe indicated that the SD (with lipase) of fried clams initially reduced (at the gastric stage), but subsequently increased (mainly at the intestinal stage) the contents of total aldehydes. Meanwhile, eight specific aldehydes including propanal, acrolein, trans-2-pentenal, hexanal, trans,trans-2,4-octadienal, trans,trans-2,4-decadienal, 4-hydroxy-hexenal and 4-hydroxy-nonenal in the digested meal were determined by using a high-performance liquid chromatography-tandem electrospray ionization mass spectrometry (HPLC-ESI-MS/MS) method. Results indicated that the changes in the trend of the contents of the eight aforementioned aldehydes were similar to those of total aldehydes during SD (with lipase) of fried clams. However, a similar SD process without lipase time-dependently reduced the contents of total and individual aldehydes. Moreover, lipid classes and free fatty acids (FFAs) in the digested meal were determined to reveal the degree of hydrolysis of lipids during the SD process. Results indicated that the SD (with lipase) of fried clams significantly hydrolyzed triacylglycerols (TAG) and polar lipids (PL) and produced FFAs, but the SD process without lipase resulted in negligible lipid hydrolysis. Thus, our results demonstrated a positive correlation between lipid hydrolysis and aldehyde generation during the SD of fried clams. Alternatively, unsaturated FFAs instead of TAG and PL could have served as the main precursors for aldehyde generation due to their high oxidative susceptibility.

Food matrixes play a key role in the distribution of contaminants of lipid origin: A case study of malondialdehyde formation in vegetable oils during deep-frying

Vegetable oils are increasingly replacing animal fats in diets, but malondialdehyde (MDA), a peroxidation product of these oils, has been regarded as toxic; this necessitated investigation of MDA formation during consumption. This study investigated MDA formation in four vegetable oils during frying French fries (FF) and fried chicken breast meat (FCBM) at 180 °C for 7 h. Results showed that MDA contents were lower in oils used for frying foods than in control oils, mainly because MDA was incorporated into the foods. MDA content was lower in FF, but higher in FCBM, due to the different food components. Model oil and food system analyses yielded similar results. MDA bound the hydrophobic helical structure in starch-based FF, but was exhibited greater reactivity with nucleophilic groups in protein-based FCBM, resulting in stronger interaction with FCBM than with FF. Our results indicated the existence of distinct mechanisms underlying MDA migration in different food matrixes.

4-hydroxy-2-alkenals in foods: a review on risk assessment, analytical methods, formation, occurrence, mitigation and future challenges

Undoubtedly, significant advances were performed concerning 4-hydroxy-2-alkenals research on foods, and their formation by double oxidation of polyunsaturated fatty acids. But further studies are still needed, especially on their occurrence in foods enriched with n-3 and n-6 fatty acids, as well as in foods for infants and processed foods. Major factors concerning the formation of 4-hydroxy-2-alkenals were discussed, namely the influence of fatty acids composition, time/temperature, processing conditions, salt, among others. Regarding mitigation, the most effective strategies are adding phenolic extracts to foods matrices, as well as other antioxidants, such as vitamin E. Exposure assessment studies revealed 4-hydroxy-2-alkenals values that could not be considered a risk for human health. However, these toxic compounds remain unaltered after digestion and can easily reach the systemic circulation. Therefore, it is crucial to develop in vivo research, with the inclusion of the colon phase, as well as, cell membranes of the intestinal epithelium. In conclusion, according to our review it is possible to eliminate or effectively decrease 4-hydroxy-2-alkenals in foods using simple and economic practices.

Influence of linseed and antioxidant-rich diets in pig nutrition on lipid oxidation during cooking and in vitro digestion of pork

Enrichment of pig diets with polyunsaturated fatty acids (PUFA) is considered an emerging strategy to increase their intake in the human diet. However, PUFA are particularly vulnerable to oxidative reactions leading to the generation of toxic compounds. The aim of this study was to evaluate the effect of supplementation of pig diets with extruded linseed (L), either or not in combination with synthetic antioxidants (E, tocopheryl-acetate and selenium) or natural extracts (P, grape-skin and oregano), and basal diet (C, without linseed) on the oxidative stability in raw, grilled and in vitro digested pork. The diet supplementation with antioxidant-rich ingredients resulted in the accumulation of specific metabolites in meat. Actually, 11 different phenolic- and 6 tocopherol-derived metabolites were identified by UHPLC/HR-MS. These metabolites were potentially correlated with the reduction in the oxidative phenomena occurring during meat cooking and digestion. Specifically, 16% and 35% reduction in the amounts of lipid hydroperoxides and TBA-RS were assessed after cooking of meat from P diet, respect to the L diet. Diet supplementations with α-tocopheryl acetate and selenium reduced the oxidative reactions only during meat cooking. A significant reduction was attended at the end of in vitro digestion, showing about 24% and 34% hydroperoxides and TBA-RS concentration reductions, respectively, in P diet samples respect to the L ones. Thus, our study suggests that the appearance of phenolic metabolites in meat could be associated to a reduction in the oxidative phenomena during meat cooking and digestion.

Protective effects of Clostridium butyricum against oxidative stress induced by food processing and lipid-derived aldehydes in Caco-2 cells

The human body is almost always facing the oxidative stress caused by foodborne aldehydes such as glyoxal (GO) and methylglyoxal (MGO), 4-hydroxyhexenal (HHE), and 4-hydroxynonenal (HNE). When these aldehydes build up, they can cause a range of harm. However, a probiotic, Clostridium butyricum, can increase nuclear factor erythroid-2 related factor 2 (Nrf2) and may have the potential to relieve oxidative stress. If C. butyricum is indeed resistant to aldehydes, the advantages (accessibility, convenience, and safety) will be of great significance compared with drugs. Unfortunately, whether C. butyricum can play a role in alleviating toxic effects of foodborne aldehydes in the intestine (the first line of defense against food-derived toxin) was unclear. To investigate these, we measured the viability, ROS, autophagy, and inflammatory cytokine expression of Caco-2 which were co-cultured with C. butyricum and stimulated by the four aldehydes via Nrf2 pathway (Staphylococcus aureus and Enterococcus faecium as controls). Then, we explored the link among C. butyricum, NLRP6, and Nrf2 signaling pathways when facing the stimuli. In the present study, we demonstrated that Clostridium butyricum relieved the oxidative stress induced by the aldehydes in Caco-2. Most interestingly, we found a "complementary" relationship between NLRP6 and Nrf2 in C. butyricum treatment under aldehyde stress. Our research not only makes a contribution to the popularization of C. butyricum as a probiotic-rich food instead of medicines but also sheds new light on the application of subsequent microecological formulation of C. butyricum. KEY POINTS: • The adverse effects are caused in a dose-dependent manner by foodborne aldehydes. • Clostridium butyricum can significantly ameliorate oxidative stress. • There is a "complementary" relationship between the NLRP6 and Nrf2 signaling pathways. • Using Clostridium butyricum foods to alleviate oxidative stress shows great prospects.

Commercial luncheon meat products and their in vitro gastrointestinal digests contain more protein carbonyl compounds but less lipid oxidation products compared to fresh pork

Because of the large diversity in processed meat products and the potential involvement of oxidation processes in the association between red and processed meat consumption and chronic diseases, the concentration of oxidation products after gastrointestinal digestion of commercial luncheon meat products was investigated. A broad spectrum of meat products (n = 24), displaying large variation in macro- and micronutrient composition and processing procedures, was digested in vitro by simulating digestion fluids of the human gastrointestinal tract. Lipid and protein oxidation was assessed in the meat products before digestion and in the corresponding digests by measurement of free malondialdehyde, 4-hydroxy-2-nonenal, hexanal and protein carbonyl compounds. Compared to an unprocessed cooked pork mince, that was included as a reference in the digestion experiment, levels of lipid oxidation products were low in the digests of most meat products. Only the digests of Parma ham had slightly higher or comparable levels as the reference pork. In contrast, protein carbonyl compounds were comparable or up to 6 times higher in the processed meat products compared to the reference pork. Particularly raw-cooked and precooked-cooked meat products and corresponding digests had higher protein carbonyl levels, but also lower protein contents and higher fat to protein ratios. In conclusion, most luncheon meat products and corresponding digests contained lower amounts of free lipid oxidation products, but more protein carbonyl compounds compared to the reference pork.

Can Meat and Meat-Products Induce Oxidative Stress?

High meat and meat-products consumption has been related to degenerative diseases. In addition to their saturated fatty acids and cholesterol contents, oxidation products generated during their production, storage, digestion, and metabolization have been largely implicated. This review begins by summarizing the concept of meat and meat-products by the main international regulatory agencies while highlighting the nutritional importance of their consumption. The review also dials in the controversy of white/red meat classification and insists in the need of more accurate classification based on adequate scores. Since one of the negative arguments that meat receives comes from the association of its consumption with the increase in oxidative stress, main oxidation compounds (malondialdehyde, thermaloxidized compounds, 4-hydroxy-nonenal, oxysterols, or protein carbonyls) generated during its production, storage, and metabolization, are included as a central aspect of the work. The review includes future remarks addressed to study the effects meat consumption in the frame of diet-gene interactions, stressing the importance of knowing the genetic variables that make individuals more susceptible to a possible oxidative stress imbalance or antioxidant protection. The importance of consumed meat/meat-products in the frame of a personalized nutrition reach in plant-food is finally highlighted considering the importance of iron and plant biophenols on the microbiota abundance and plurality, which in turn affect several aspects of our physiology and metabolism.

Metabolic Signatures of 10 Processed and Non-processed Meat Products after In Vitro Digestion

The intake of processed meat has been associated with several adverse health outcomes such as type II diabetes and cancer; however, the mechanisms are not fully understood. A better knowledge of the metabolite profiles of different processed and non-processed meat products from this heterogeneous food group could help in elucidating the mechanisms associated with these health effects. Thirty-three different commercial samples of ten processed and non-processed meat products were digested in triplicate with a standardized static in vitro digestion method in order to mimic profiles of small molecules formed in the gut upon digestion. A metabolomics approach based on high-resolution mass spectrometry was used to identify metabolite profiles specific to the various meat products. Processed meat products showed metabolite profiles clearly distinct from those of non-processed meat. Several discriminant features related to either specific ingredients or processing methods were identified. Those were, in particular, syringol compounds deposited in meat during smoking, biogenic amines formed during meat fermentation and piperine and related compounds characteristic of pepper used as an ingredient. These metabolites, characteristic of specific processed meat products, might be used as potential biomarkers of intake for these foods. They may also help in understanding the mechanisms linking processed meat intake and adverse health outcomes such as cancer.

Potential Adverse Public Health Effects Afforded by the Ingestion of Dietary Lipid Oxidation Product Toxins: Significance of Fried Food Sources

Exposure of polyunsaturated fatty acid (PUFA)-rich culinary oils (COs) to high temperature frying practices generates high concentrations of cytotoxic and genotoxic lipid oxidation products (LOPs) via oxygen-fueled, recycling peroxidative bursts. These toxins, including aldehydes and epoxy-fatty acids, readily penetrate into fried foods and hence are available for human consumption; therefore, they may pose substantial health hazards. Although previous reports have claimed health benefits offered by the use of PUFA-laden COs for frying purposes, these may be erroneous in view of their failure to consider the negating adverse public health threats presented by food-transferable LOPs therein. When absorbed from the gastrointestinal (GI) system into the systemic circulation, such LOPs may significantly contribute to enhanced risks of chronic non-communicable diseases (NCDs), e.g. cancer, along with cardiovascular and neurological diseases. Herein, we provide a comprehensive rationale relating to the public health threats posed by the dietary ingestion of LOPs in fried foods. We begin with an introduction to sequential lipid peroxidation processes, describing the noxious effects of LOP toxins generated therefrom. We continue to discuss GI system interactions, the metabolism and biotransformation of primary lipid hydroperoxide LOPs and their secondary products, and the toxicological properties of these agents, prior to providing a narrative on chemically-reactive, secondary aldehydic LOPs available for human ingestion. In view of a range of previous studies focused on their deleterious health effects in animal and cellular model systems, some emphasis is placed on the physiological fate of the more prevalent and toxic α,β-unsaturated aldehydes. We conclude with a description of targeted nutritional and interventional strategies, whilst highlighting the urgent and unmet clinical need for nutritional and epidemiological trials probing relationships between the incidence of NCDs, and the frequency and estimated quantities of dietary LOP intake.

Effect of rosemary extract on lipid oxidation of cooked pork during simulated gastric digestion

BACKGROUND

Oxidation of food lipids occurs in the gastrointestinal tract, resulting in potential adverse health effects. Rosemary extract (RE), as one of the most popular naturally sourced antioxidants, is widely used in the food industry. However, the effect of RE on lipid oxidation during gastrointestinal digestion has not been well investigated. Therefore, this study aimed to evaluate the effect of RE on lipid oxidation of cooked pork during simulated gastric digestion.

RESULTS

Results showed that RE at 12.5, 25, 50, and 100 mg kg^-1 pork effectively decreased the formation of malondialdehyde during simulated gastric digestion of cooked pork. RE also effectively mitigated the decline of fatty acids during the simulated gastric digestion of pork. The total phenolic content in RE was calculated to be 170.67 mg gallic acid equivalent (GAE) g^-1 . RE dissolved in distilled water (pH 6.5) or potassium hydrogen phthalate-hydrochloric acid buffer solution (0.2 mol L^-1 , pH 3.0) both exhibited strong 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activities as well as ferric reducing capacity. The inhibitory effects of RE on lipid oxidation of cooked pork during simulated gastric digestion may be attributed to the phenolic compounds with antioxidant properties.

CONCLUSION

The results lend support to the possible application of rosemary or RE as a rich source of natural antioxidants to inhibit the oxidation of food lipids during gastrointestinal digestion. © 2019 Society of Chemical Industry.

The key role of ovalbumin in lipid bioaccessibility and oxidation product profile during the in vitro digestion of slightly oxidized soybean oil

The behaviour of slightly oxidized virgin and refined soybean oils during in vitro digestion was studied by 1H nuclear magnetic resonance (1H NMR) and solid phase microextraction-gas chromatography/mass spectrometry. The main objectives were to analyze lipolysis extent and oxidation during digestion, and to assess the impact of two different proportions of ovalbumin on both processes. At the same time γ-tocopherol fate was monitored, when possible, by 1H NMR. The results reveal that the initial oxidation degree of the oils negatively influences the lipolysis extent, reducing the bioaccessibility of the major oil components, which include some essential fatty acids. Although the low ovalbumin proportion tested does not significantly affect lipolysis, this is greatly enhanced when ovalbumin is added at a high level, improving lipid bioaccessibility. It has also been shown that oxidation does not seem to have occurred to a great enough extent during digestion for it to be detected from polyunsaturated acyl group degradation. Moreover, the changes observed in the oxidation product profile of the starting oils after digestion can be considered to be due mainly to the transformation of the initially present hydroperoxides, whose concentration diminishes in the digested samples to give hydroxy-dienes, epoxides and aldehydes. In presence of a high ovalbumin proportion, hydroperoxide reduction to hydroxy-dienes is favoured and lower levels of aldehydes and epoxides are observed. This latter could be due to a diminution in their generation and/or to their reaction with ovalbumin. A high proportion of this protein in the system also increases γ-tocopherol bioaccessibility.

Influence of minor components on lipid bioaccessibility and oxidation during in vitro digestion of soybean oil

BACKGROUND

Minor components of edible oils could influence their evolution during in vitro digestion. This might affect the bioaccessibility of lipid nutrients and the safety of the ingested food. Bearing this in mind, the evolution of virgin and refined soybean oils, which are very similar in acyl group composition, has been studied throughout in vitro digestion using ¹ H nuclear magnetic resonance (NMR) and solid-phase microextraction-gas chromatography /mass spectrometry, focusing on lipolysis and oxidation reactions. The fate of γ-tocopherol, the main antioxidant present in soybean oil, has also been analyzed with ¹ H NMR.

RESULTS

There were no noticeable differences in lipolysis between the two oils that were studied. The extent of oxidation during digestion, which was very low in both cases, was slightly higher in the virgin type, which showed lower tocopherols and squalene concentrations than the refined one, together with a considerable abundance of free fatty acids. This can be deduced both from the appearance after digestion of conjugated hydroperoxy- and hydroxy-dienes only in the virgin oil, and from its higher levels of volatile aldehydes and 2-pentyl-furan. Under in vitro digestion conditions, the formation of epoxides seemed to be favored over other oxidation products. Finally, although some soybean oil essential nutrients like polyunsaturated fatty acids exhibited no significant degradation after digestion, γ-tocopherol concentration diminished during this process, especially in the virgin oil.

CONCLUSION

Although the minor component composition of the soybean oils did not affect lipolysis during in vitro digestion, it influenced the extent of their oxidation and γ-tocopherol bioaccessibility. © 2019 Society of Chemical Industry.

Metabolites analysis for cold-resistant yeast (Wickerhamomyces anomalus) strains own antioxidant activity on cold stored fish mince

The effect of eight cold-resistant yeast strains (J3, J7, J8, J9, J12, J15, J18, and J25) of Wickerhamomyces anomalus on the lipid oxidation of cold stored fish mince (4 °C) were investigated. And the metabolites of these yeast were determined with gas chromatography-mass spectrometry. These strains could effectively inhibit the increase of hydroperoxides value (p < 0.05), and the inhibiting rate was positively correlated with the content of isolongifolene, xylitol, turanose, thymol-glucoside, and uridine. Especially, the J3, J7, J8, J9, J12, and J18 could eliminate a large part of thiobarbituric acid reactive substances (TBARS) (p < 0.05), the eliminating rate was proportionate to the aldehyde dehydrogenase activity. Several bacteriostatic metabolites were detected: thymol-glucoside, 2-phenylethanol, cedro, and 2,4-bis (1,1-dimethylethyl) phenol. In addition, W. anomalus produced many metabolites with fruit and floral notes. In conclusion, cold-resistant W. anomalus strains own antioxidant activity were potential new bio-preservatives in the cold storage of muscle products.