Formation of protein-bound Nε-carboxymethyllysine and Nε-carboxyethyllysine in ground pork during commercial sterilization as affected by the type and concentration of sugars

Integrating time since deposition estimation of bloodstains into a DNA profiling workflow: A novel approach using fluorescence spectroscopy

Determining the time since deposition (TSD) of bloodstains is important to establish a timeline of bloodshed, while DNA profiling addresses identity (source attribution). Traditionally treated as separate processes, this study integrates TSD estimation into routine DNA profiling by analyzing typically discarded cell lysate (eluates) from spin-column-based DNA extractions. Fluorescence spectroscopy was used to analyze eluates from bloodstains deposited up to 99 weeks. Two excitation-emission matrices (EEMs) were acquired for each sample and deconvoluted using parallel factor analysis (PARAFAC) to identify individual fluorophores. For example, tryptophan demonstrated a time-dependent decrease in fluorescence. Additionally, we observed an accumulation of fluorescent oxidation products (FOX) and advanced glycation end products (AGEs) over TSD. An untargeted metabolomics high-performance liquid chromatography-mass spectrometry workflow was applied to assist with fluorophore identification. Chemometric models were used to estimate TSD from EEM fluorescence data. Boruta feature selection coupled with random forest regression outperformed all other models and achieved high accuracy, with an R2 of 0.993 and root mean square error of prediction (RMSEP) of 2.83 weeks for the full 99-week period, and an R2 of 0.987 and RMSEP of 2.06 weeks for the 1-year timeframe. Comparisons were also made between anticoagulant-free (AC-free) and anticoagulant-treated (AC-treated) bloodstains deposited up to 3 months. We noted differences in fluorescence based on AC treatment, with AC-free blood exhibiting higher FOX and lower AGE fluorescence than AC-treated blood. Our findings demonstrate the effectiveness and feasibility of integrating TSD estimation into routine forensic DNA extractions while maintaining high prediction accuracies.

Accumulation of Nε-carboxymethyllysine and Nε-carboxyethyllysine in precooked pork during cold storage and subsequent reheating

This research aimed to investigate the levels of Nε-carboxymethyllysine (CML) and Nε-carboxyethyllysine (CEL) in precooked pork (100 °C, 10 min) as affected by storage (0 °C, 0-11 d) and subsequent reheating (100 °C, 5 min). A longer storage duration led to more CML (average increased: 69-128 %) and CEL (average increased: 11-44 %) in precooked pork, while the reheating resulted in average increases of 86 % CML and 32 % CEL compared to their initial levels in precooked pork. However, the storage duration did not significantly (p > 0.05) affect CML/CEL formation in precooked pork during the subsequent reheating. The levels of CML/CEL and glyoxal/methylglyoxal had no obvious relationship, but CML formation was linked to lipid oxidation in precooked or reheated pork. The accumulation of CML and CEL in precooked meat produced during the initial precooking, storage, and reheating implies the necessity to control their generation in these products.

Formation and kinetic analysis of AGEs in Pacific white shrimp during frying

Advanced glycation end products (AGEs) are complex and heterogeneous compounds closely associated with various chronic diseases. The changes in Nε-carboxymethyllysine (CML), Nε-carboxyethyllysine (CEL), Nε-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1), and fluorescent AGEs (F-AGEs) in fried shrimp during frying (170 °C, 0-210 s) were described by kinetic models. Besides,the correlations between AGEs contents and physicochemical indicators were analyzed to reveal their intrinsic relationship. Results showed that the changes of four AGEs contents followed the zero-order kinetic, and their rate constants were ranked as kCML < kCEL ≈ kMG-H1 < kF-AGEs. Oil content and lipid oxidation were critical factors that affected the AGEs levels of the surface layer. Protein content and Maillard reaction were major factors in enhancing the CML and CEL levels of the interior layer. Furthermore, the impact of temperature on the generation of CML and CEL was greater than that of MG-H1 and F-AGEs.

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.

Effects of seasoning addition and cooking conditions on the formation of free and protein-bound heterocyclic amines and advanced glycation end products in braised lamb

The accumulation of heterocyclic amines (HAs) and advanced glycation end products (AGEs) in thermally processed meats has been arising safety concerns. The effects of cooking conditions and seasoning addition on the formation of HAs and AGEs in Chinese traditional braised lamb were investigated by UPLC-MS/MS analysis. Soy sauce significantly increased the formation of HAs and AGEs, among which light soy sauce had the greatest promoting effect (69.45-15300.62 %). Conversely, spices inhibited HAs and AGEs formation, the inhibition rate of free HAs and AGEs reached 22.06-34.72 % when using 70 % ethanol extract. Hot blanching treatment and adding soy sauce and spices at a later stage could significantly suppress HAs and AGEs production. Flavonoids, including galangin, hesperidin, narirutin, etc., were identified as key effectors in spices. These findings help to promote awareness of the formation of HAs and AGEs in braised lamb and provide valuable insights for optimizing processing techniques to minimize their production.

Proteomics analysis of the influence of proteolysis on the subsequent glycation of myofibrillar protein

Proteomics was used to study the influence of proteolysis on the glycation of myofibrillar proteins (MPs). Proteolysis by papain and proteinase K generated the highest level of amino acids (AAs) and peptides, respectively. Both the glycation degree (A value increased from 0.173 to 0.202-0.348) and speed (k value increased from 0.0099 to 0.0132-0.0145) were enhanced by proteolysis using papain and proteinase K. Proteomics analysis revealed that proteolysis largely enhanced the glycation site number in Lys, Arg and N-terminal residues (eg. Leu, Gly, Thr, Ala, Met, Ile, Phe and Val residues in myosin light chain). Proteolysis by papain preferentially acted on actin and therefore specifically increased the glycation sites from actin. Proteolysis reduced the level of aldehydes but enhanced the aromatic E-nose signals, possibly due to the combination of aldehydes with released AAs/peptides. The proteomics analysis helped to detail the relationship between proteolysis and subsequent glycation/flavour formation.

Effect of edible oil type on the formation of protein-bound Nε-(carboxymethyl)lysine in roasted pork patties

Protein-bound Nε-(carboxymethyl)lysine (CML), an advanced glycation end product within meat products, poses a potential health risk to humans. The objective of this study was to explore the impact of various edible oils on the formation of protein-bound CML in roasted pork patties. Eleven commercially edible oils including lard oil, corn oil, palm oil, olive oil, flaxseed oil, blended oil, camellia oil, walnut oil, soybean oil, peanut oil, and colza oil were added to pork tenderloin mince, respectively, at a proportion of 4 % to prepare raw pork patties. The protein-bound CML contents in the pork patties were determined by HPLC-MS/MS before and after roasting at 200 °C for 20 min. The results indicated that walnut oil, flaxseed oil, colza oil, olive oil, lard oil, corn oil, blended oil, and palm oil significantly reduced the accumulation of protein-bound CML in pork patties, of which the inhibition rate was in the 24.43 %-37.96 % range. Moreover, the addition of edible oil contributed to a marginal reduction in the loss of lysine. Meanwhile, glyoxal contents in pork patties were reduced by 16.72 %-43.21 % after roasting. Other than blend oil, all the other edible oils restrained protein oxidation in pork patties to varying degrees (between 20.16 % and 61.26 %). In addition, camellia oil, walnut oil, and flaxseed oil increased TBARS values of pork patties by 2.2-8.6 times when compared to the CON group. After analyzing the fatty acid compositions of eleven edible oils, five main fatty acids (palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid) were selected to establish Myofibrillar protein-Glucose-fatty acids systems to simulate the roasting process. The results showed that palmitic acid, oleic acid, linoleic acid, and linolenic acid obviously mitigated the formation of myofibrillar protein-bound CML, exhibiting suppression rates ranging from 10.38 % to 40.32 %. In conclusion, the addition of specific edible oil may curb protein-bound CML production in roasted pork patty by restraining protein or lipid oxidation, reducing lysine loss, and suppressing glyoxal production, which may be attributed to the fatty acid compositions of edible oils. This finding provides valuable guidance for the selection of healthy roasting oils in the thermal processing of meat products.

Processing Stage-Induced Formation of Advanced Glycation End Products in Cooked Sausages with the Addition of Spices

This study aims to evaluate the relationship between the four processing stages of cooked sausage preparation (raw, drying, baking, and steaming) and the formation of advanced glycation end products (AGEs), 1,2-dicarbonyl compounds, and lipid and protein oxidation in sausages with spices. Baking and steaming significantly promoted lipid and protein oxidation. The Nε-carboxymethyllysine (CML) content increased from 4.32-4.81 µg/g in raw samples to 10.68-16.20 µg/g in the steamed sausages. Nε-carboxyethyllysine (CEL) concentrations increased by approximately 1.7-3.7 times after steaming. The methylglyoxal concentration increased dramatically after baking and then rapidly decreased in the steaming stage. Chili promoted the formation of CML and CEL. The CEL concentration increased in samples containing garlic, but yellow mustard and garlic slightly reduced CML concentrations in the cooked sausages. The spices decreased the lipid and protein stability of the cooked sausages, increasing malondialdehyde and protein carbonyls. Lipid oxidation and 3-deoxyglucosone positively correlated with CML and CEL levels. Black pepper had no impact on CML when the sausages were baked but remarkably increased the content of both CML and CEL in the steaming stage. Thus, the impact of spices on sausages depends on both the specific spices used and the category of AGEs formed.

Changes in glycated myofibrillar proteins conformation on the formation of Nε-carboxymethyllysine under gradient thermal conditions

N^ε-carboxymethyllysine (CML), a frequently used marker of advanced glycation end products (AGEs) in food, was generated in food processing easily and caused changes in myofibrillar proteins (MPs) characterization. The relevance between glycosylated MPs structure alternation and CML formation under thermal conditions have been reported. However, the correlation mechanism was not clear yet. In this work, the influence of gradient heating (50℃, 60℃, 70℃, 80℃, and 90℃) on the different degrees of glycated MPs, which determined the correlation with CML formation in protein structural changes of MPs. In the rising stage of the CML level, glycation accelerated the fibrillation and aggregation behavior of MPs during heating and increased surface hydrophobicity and particle size. The protein cross-linking affected the protein modification caused by heating and glycation. This work highlights the substantial influences of glycosylation and thermal treatments on MPs, which transformed the MPs structural characteristics and CML level.

Formation of advanced glycation end-products in minced pork during frozen-then-chilled storage and subsequent heating

The influences of frozen-then-chilled storage of minced pork on the formation of advanced glycation end-products (AGEs) including N^ε-carboxymethyllysine and N^ε-carboxyethyllysine, and their corresponding α-dicarbonyl precursors (α-DPs; glyoxal and methylglyoxal) during storage and subsequent heating were investigated in comparison with chilled storage. During cold storage, the levels of AGEs, trichloroacetic acid-soluble peptides, and Schiff bases in minced pork continuously increased while α-DPs decreased. The 30 min heating (100 °C) resulted in 64-560% increase of AGEs in pork, corresponding with an increase of Schiff bases and decreases of α-DPs. Compared to the chilled storage, the frozen-then-chilled storage led to no significant difference (P > 0.05) on the levels of AGEs and α-DPs in raw or heat-treated pork, implying that the formation and thawing of ice crystals in pork during the frozen-then-chilled storage had minor to no effects on the formation of AGEs and their α-DPs.

Advanced Glycation End Products: A Comprehensive Review of Their Detection and Occurrence in Food

The Maillard reaction (MR) is a complicated chemical process that has been extensively studied. Harmful chemicals known as advanced glycation end products (AGEs), with complex structures and stable chemical characteristics, are created during the final stage of the MR. AGEs can be formed both during the thermal processing of food and in the human body. The number of AGEs formed in food is much higher compared to endogenous AGEs. A direct connection exists between human health and the build-up of AGEs in the body, which can result in diseases. Therefore, it is essential to understand the content of AGEs in the food we consume. The detection methods of AGEs in food are expounded upon in this review, and the advantages, disadvantages, and application fields of these detection methods are discussed in depth. Additionally, the production of AGEs in food, their content in typical foods, and the mechanisms influencing their formation are summarized. Since AGEs are closely related to the food industry and human health, it is hoped that this review will further the detection of AGEs in food so that their content can be evaluated more conveniently and accurately.

Contents and Correlations of Nε-(carboxymethyl)lysine, Nε-(carboxyethyl)lysine, Acrylamide and Nutrients in Plant-Based Meat Analogs

High temperatures applied in the production of plant-based meat analogs (PBMA) lead to the occurrence of Maillard reactions, in which harmful compounds Nε-(carboxymethyl)lysine (CML), Nε-(carboxyethyl)lysine (CEL) and acrylamide are formed. However, little research has focused on these compounds in PBMA. In this study, the contents of CML, CEL and acrylamide in 15 commercial-sold PBMA were determined by an ultra-high performance liquid chromatograph coupled with a triple quadrupole tandem mass spectrometer (UHPLC-QqQ-MS/MS). Nutrients (protein, amino acids, fatty acids and sugars) which are related to the formation of these compounds were also studied. The results showed that CML, CEL and acrylamide contents were in the range of 16.46-47.61 mg/kg, 25.21-86.23 mg/kg and 31.81-186.70 μg/kg, respectively. Proteins account for 24.03-53.18% of PBMA. Except for Met + Cys, which is the limiting amino acid of most PBMA, all other indispensable amino acids met the requirements for adults. Besides, PBMA had more n-6 fatty acids than n-3 fatty acids. A correlation analysis showed that proteins and the profiles of amino acid and fatty acid had little influence on CML but significant influence on CEL and acrylamide. The results of the present study can be used as a reference to produce PBMA with higher amounts of nutrients and lower amounts of CML, CEL and acrylamide.

Quantitation of α-Dicarbonyls, Lysine- and Arginine-Derived Advanced Glycation End Products, in Commercial Canned Meat and Seafood Products

Commercial sterilization is a thermal processing method commonly used in low-acid canned food products. Meanwhile, heat treatment can significantly promote advanced glycation end product (AGE) formation in foodstuffs. In this research, the validated analytical methods have been developed to quantitate both lysine- and arginine-derived AGEs and their precursors, α-dicarbonyls, in various types of commercial canned meat and seafood products. Methylglyoxal-hydroimidazolone 1 was the most abundant AGEs found in the canned food products, followed by Nε-(carboxyethyl)lysine, Nε-(carboxymethyl)lysine, and glyoxal-hydroimidazolone 1. Correlation analysis revealed that methylglyoxal and glyoxal were only positively associated with the corresponding arginine-derived AGEs, while their correlations with the corresponding lysine-derived AGEs were not significant. Importantly, we demonstrated for the first time that total sugar and carbohydrate contents might serve as the potential markers for the prediction of total AGEs in canned meats and seafoods. Altogether, this study provided a more complete view of AGEs' occurrence in commercial canned food products.

The effect of lactose and its isomerization product lactulose on functional and structural properties of glycated casein

Lactulose is an isomer of lactose, formed under thermal processing of milk. Alkaline conditions favor the isomerization of lactose. As reducing sugar, lactose and lactulose could participate in the Maillard reaction and cause protein glycation in milk products. In this study, the influence of lactose and lactulose on the functional and structural properties of glycated casein was investigated. The results demonstrated that compared with lactose, lactulose led to severer changes in molecular weight, more disordered spatial structure and decrease of tryptophan fluorescence intensity of casein. Besides, the glycation degree and advanced glycation end products (AGEs) results suggested that lactulose exhibited stronger glycation ability than lactose due to the higher proportion of open chain in solution. Furthermore, higher glycation degree induced by lactulose resulted in lower solubility, surface hydrophobicity, digestibility and emulsifying capacity of casein-glycoconjugates compared with lactose. The results of this study are essential for tracking the effects of harmful Maillard reaction products on the quality of milk and dairy products.

Dynamic alterations in protein, sensory, chemical, and oxidative properties occurring in meat during thermal and non-thermal processing techniques: A comprehensive review

Meat processing represents an inevitable part of meat and meat products preparation for human consumption. Both thermal and non-thermal processing techniques, both commercial and domestic, are able to induce chemical and muscle's proteins modification which can have implication on oxidative and sensory meat characteristics. Consumers' necessity for minimally processed foods has paved a successful way to unprecedented exploration into various novel non-thermal food processing techniques. Processing of meat can have serious implications on its nutritional profile and digestibility of meat proteins in the digestive system. A plethora of food processing techniques can potentially induce alterations in the protein structure, palatability, bioavailability and digestibility via various phenomena predominantly denaturation and Maillard reaction. Apart from these, sensory attributes such as color, crispness, hardness, and total acceptance get adversely affected during various thermal treatments in meat. A major incentive in the adoption of non-thermal food processing is its energy efficiency. Considering this, several non-thermal processing techniques have been developed for evading the effects of conventional thermal treatments on food materials with respect to Maillard reactions, color changes, and off-flavor development. Few significant non-thermal processing techniques, such as microwave heating, comminution, and enzyme addition can positively affect protein digestibility as well as enhance the value of the final product. Furthermore, ultrasound, irradiation, high-pressure processing, and pulsed electric fields are other pivotal non-thermal food processing technologies in meat and meat-related products. The present review examines how different thermal and non-thermal processing techniques, such as sous-vide, microwave, stewing, roasting, boiling, frying, grilling, and steam cooking, affect meat proteins, chemical composition, oxidation, and sensory profile.

Formation of advanced glycation end products in sturgeon patties affected by pan-fried and deep-fried conditions

This study compared the effects of pan-fried with low (LPF), high (HPF) amounts of oil and deep-fried (DF) on the profiles of advanced glycation end products (AGEs) in sturgeon patties. The surface color of the pan-fried patties, regardless of the amounts of oil used, visually presented more brown than deep-fried ones with higher internal temperature at the frying course of 3-9 min. Compared to LPF and HPF, DF significantly accelerated the furosine development for 6-9 min of frying, dynamically increased the accumulation of CML (Nε-carboxymethyl-lysine) and CEL (Nε-carboxyethyl-lysine) for up to 9 min of frying, and the level of CML in DF than LPF, HPF for 9 min of frying were increased by 209.6 % and 149.9 %, respectively. The oil level employed for pan-fried insignificantly influenced the formation of furosine and CML in patties. The principal component analysis further confirmed that DF patties had a greater influence on the formation of AGEs. The AGEs formation was positively associated with the temperature and amino groups, while remarkably negative correlation with moisture content. Therefore, pan-fried within 6 min of frying was recommended for the domestic cooking of sturgeon patties based on the potential formation of AGEs.

Heat-induced formation of advanced glycation end-products in ground pork as affected by the addition of acetic acid or citric acid and the storage duration prior to the heat treatments

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Organic acids affected advanced glycation end-product (AGE) levels in heated pork.

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Heat-induced AGEs in pork with citric acid (ca 0.5–1%) were reduced by 30–54%.

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Adding acetic acid at the same level led to 14–48% reduction of AGEs.

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The reduction of AGEs corresponded to decreased levels of TBARS and Schiff bases.

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Marinating time (pork & acid) did not affect the acid’s inhibiting effect for AGEs.

The heat-induced (121 °C, 10 or 30 min) formation of two potentially hazardous advanced glycation end-products (AGEs), protein-bound N^ɛ-carboxymethyllysine (CML) and N^ɛ-carboxyethyllysine (CEL), in pork as affected by citric or acetic acid (0.5, 1 g/100 pork) and the storage duration (0 °C, 0 – 8 d) prior to the heating was investigated. A longer storage time of raw pork resulted in higher levels of AGEs produced during the later heating, likely due to the accumulation of some AGE precursors during the storage. Depending on the acid level and heating time, adding acid in pork led to 30 – 54% (citric acid) or 14 – 48% (acetic acid) average reduction of heat-induced production of CML/CEL, which corresponded to the reduction of thiobarbituric acid reactive substances and Schiff bases. The marinating time of raw pork with an acid did not significantly affect (P = 0.959 – 0.998) the acid’s inhibition effect on heat-induced formation of CML/CEL.

Analysis of Glyoxal- and Methylglyoxal-Derived Advanced Glycation End Products during Grilling of Porcine Meat

The reaction of the N⁶-amino group of lysine residues and 1,2-dicarbonyl compounds during Maillard processes leads to advanced glycation end products (AGEs). In the present work, we deliver a comprehensive analysis of changes of carbohydrates, dicarbonyl structures, and 11 AGEs during the grilling of porcine meat patties. While raw meat contained mainly glyoxal-derived N⁶-carboxymethyl lysine (CML), grilling led to an increase of predominantly methylglyoxal-derived AGEs N⁶-carboxyethyl lysine (CEL), N⁶-lactoyl lysine, methylglyoxal lysine dimer (MOLD), and methylglyoxal lysine amide (MOLA). Additionally, we identified and quantitated a novel methylglyoxal-derived amidine compound N¹,N²-di-(5-amino-5-carboxypentyl)-2-lactoylamidine (methylglyoxal lysine amide, MGLA) in heated meat. Analysis of carbohydrates suggested that approximately 50% of the methylglyoxal stemmed from the fragmentation of triosephosphates during the heat treatment. Surprisingly, N⁶-lactoyl lysine was the major AGE, and based on model incubations, we propose that approximately 90% must be explained by the nonenzymatic acylation of lysine through S-lactoylglutathione, which was quantitated for the first time in meat herein.

Comparison of metabolic fate, target organs, and microbiota interactions of free and bound dietary advanced glycation end products

Increased intake of Western diets and ultra-processed foods is accompanied by increased intake of advanced glycation end products (AGEs). AGEs can be generated exogenously in the thermal processing of food and endogenously in the human body, which associated with various chronic diseases. In food, AGEs can be divided into free and bound forms, which differ in their bioavailability, digestion, absorption, gut microbial interactions and untargeted metabolites. We summarized the measurements and contents of free and bound AGE in foods. Moreover, the ingestion, digestion, absorption, excretion, gut microbiota interactions, and metabolites and metabolic pathways between free and bound AGEs based on animal and human studies were compared. Bound AGEs were predominant in most of the selected foods, while beer and soy sauce were rich in free AGEs. Only 10%-30% of AGEs were absorbed into the systemic circulation when orally administered. The excretion of ingested free and bound AGEs was approximately 90% and 60%, respectively. Dietary free CML has a detrimental effect on gut microbiota composition, while bound AGEs have both detrimental and beneficial impacts. Free and bound dietary AGEs changed amino acid metabolism, energy metabolism and carbohydrate metabolism. And besides, bound dietary AGEs altered vitamin metabolism, and glycerolipid metabolism.

Stability of carotenoids and carotenoid esters in pumpkin (Cucurbita maxima) slices during hot air drying

The levels of carotenoids and carotenoid esters in pumpkin (C. maxima) slices as affected by hot air drying (60-100 °C, 6-17 h) were assessed via an HPLC-MS/MS method. Among the 25 carotenoids and carotenoid esters identified in pumpkin flesh, xanthophyll diesters (including (all-E)-violaxanthin dipalmitate, lutein 3-O-myristate-3'-O-laurate, lutein 3-O-palmitate-3'-O-laurate, lutein 3-O-myristate-3'-O-palmitate, lutein 3-O-stearate-3'-O-myristate and lutein 3-O-stearate-3'-O-palmitate) accounted for 43% of the total carotenoids (853.6 ± 18.5 μg/g, dried weight). Dihydroxy xanthophylls, especially those containing 5,6-epoxy group, were more heat-labile than carotenes, while xanthophylls were less heat stable than their diester counterparts. The degradation rates (first-order reactions, R² = 0.983-0.992) for lutein diesters (rate constant: 0.002-0.049 h^-1) in pumpkin slices were only 10-20% of that for lutein (rate constant: 0.020-0.243 h^-1) during hot air drying, and 76-98% of lutein diesters could be retained in the final dried products.

Assessment the influence of salt and polyphosphate on protein oxidation and Nε-(carboxymethyl)lysine and Nε-(carboxyethyl)lysine formation in roasted beef patties

The impact of NaCl and tripolyphosphate (TPP)/pyrophosphate (PP) on protein oxidation and Nε-(carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) formation in roasted beef patties was investigated. The content of CML and CEL in patties treated with salts was approximately 1.1-1.7 and 1.2-3.2 times higher than that of the control samples, respectively. An increase in salt content caused higher oxidation of tryptophan and protein carbonylation with a decrease in Schiff bases (P < 0.05) and a slight decrease in lipid oxidation (P < 0.05). Significant correlations (P < 0.05) between CML, CEL, and protein oxidation measurements was found. The higher salts content, causing less cooking loss and higher moisture content, significantly correlated (P < 0.05) with CML, CEL content, and protein oxidation of the patties. The increase in CML and CEL content and protein oxidation in roasted patties with salts might be related to the pro-oxidation of salts, and also partly due to the temperature changes caused by the water-holding capacity of salts.

Comparison of two kinds of peroxyl radical pretreatment at chicken myofibrillar proteins glycation on the formation of Nε-carboxymethyllysine and Nε-carboxyethyllysine

During meat processing, two typical advanced glycation end products (AGEs), N^ε-carboxymethyllysine (CML) and N^ε-carboxyethyllysine (CEL), are generated by free radical induction. However, the impact of peroxyl radicals on myofibrillar proteins (MPs) glycosylation and CML and CEL formation is scarcely reported. In this study, two peroxyl radicals called ROO· and LOO· derived from AAPH (2,2'-azobis (2-methylpropionamidine) dihydrochloride) and linoleic acid were exposed prior to the Maillard reaction (glucosamine incubation at 37 °C for 24 h). Levels of AGEs (CML/CEL), protein oxidation (sulfhydryl/carbonyl), free amino group, surface hydrophobicity, zeta potential, particle size, intrinsic fluorescence intensity and secondary structure were determined. Together with Pearson's correlation, the assumption that free radicals promote MPs oxidation and glycation, alter the aggregation behavior and structure modification, leading to AGEs promotion has been built. In addition, the effect of dose-dependency of peroxyl radical on AGEs has also been established with different effects of peroxyl radical induction.