Potential reactions of thermal process contaminants during digestion

Catalytic elevation effect of methylglyoxal on invertase and characterization of MGO modification products

Reactive carbonyl species can modify digestive enzymes upon intake due to their electrophilic nature. This study evaluated the effects of methylglyoxal (MGO), glyoxal, acrolein, and formaldehyde on invertase, an enzyme presents in digestive tract. Unexpectedly, MGO enhanced, rather than inhibited, invertase activity. Moreover, MGO counteracted the inhibitory effects of the other three carbonyls on invertase activity. Kinetic analyses revealed that 150 mmolLexp.-1 MGO resulted in a 2-fold increase in the Km and a 3.3-fold increase in Vmax, indicating that MGO increased the turnover rate of sucrose while reducing the substrate binding affinity of invertase. Additionally, MGO induced dynamic quenching of fluorescence, reduced free amino groups, increased hydrophobicity, the content of Amadori products, fluorescent and nonfluorescent AGEs, and amyloid fibrils of invertase. The specific modifications responsible for the elevated activity of MGO on invertase require further investigation.

Acrylamide, hydroxymethylfurfural and furfural in ready-to-eat foods consumed by child population: Presence, risk assessment and future perspectives

Food intake contributes to adequate growth and neurodevelopment of children. Ready-to-eat foods, frequently consumed by this population, are sources of acrylamide (AA), hydroxymethylfurfural (HMF) and furfural (FF). In this sense, a review of the AA, HMF, and FF presence in ready-to-eat foods was evaluated through a systematic search to infer the risk of exposure in the child population. About 75.8%, 24.2%, and 21% of the studies found AA, HMF, and FF in ready-to-eat foods, respectively. AA is predominant in processed and ultra-processed foods, while HMF and FF are commonly found in fruit-based foods. Only 17.7% of the studies assessed the children's risk of exposure, based on the contaminant concentration in ready-to-eat food and not after gastrointestinal digestion, a more realistic measure. Therefore, with the obtained information and found gaps, it is expected that new strategies will be proposed to assess the vulnerability of the child population to these processing contaminants.

Glyoxal and methylglyoxal formation in chocolate and their bioaccessibility

The objective of this study was to assess the effects of simulated digestion on the formation of α-dicarbonyl compounds (α-DCs) in chocolates. For that purpose, the concentrations of glyoxal and methylglyoxal in chocolates were determined through High-Performance Liquid Chromatography (HPLC) analysis before and after in vitro digestion. The initial concentrations ranged from 0.0 and 228.2 µg/100 g, and 0.0 and 555.1 for glyoxal and methylglyoxal, respectively. Following digestion, there was a significant increase in both glyoxal and methylglyoxal levels, reaching up to 1804 % and 859 %, respectively. The findings indicate that digestive system conditions facilitate the formation of advanced glycation end product (AGE) precursors. Also, glyoxal and methylglyoxal levels were found to be low in chocolate samples containing dark chocolate. In contrast, they were found to be high in samples containing hazelnuts, almonds, pistache, and milk. Further studies should focus on α-DCs formation under digestive system conditions, including the colon, to determine the effects of gut microbiota.

Influence and mechanism of food matrices onto the TBBQ-eliminated performance during in-vitro digestion

Food matrices greatly impact TBBQ content during digestion, while lacking sufficient research and understanding. This study investigated the influence and mechanism of fried foods on the TBBQ-eliminated performance during in-vitro digestion. The results indicated that TBBQ content varied significantly among food matrices after in-vitro digestion, with the highest in peanuts (38.3%). The correlation analysis revealed that proteins remarkably facilitated TBBQ-eliminations while fats decreased the TBBQ-eliminated rate. The TBBQ-eliminated performance of proteins, protein digestive mixtures, and amino acids uncovered that sulfhydryl groups were crucial reactive groups to eliminate TBBQ, and TBBQ-eliminated rates under intestinal pH (8.0) were faster than gastric pH (1.5). Additionally, fats significantly reduced the protein-triggered TBBQ-eliminations, originating that the oil-water interface increased the interaction difficulty between lipophilic TBBQ and proteins. Thus, this work provided an in-depth understanding of food matrices (especially proteins and fats) in TBBQ eliminations to enlighten the promising TBBQ-risk-reduced strategies with high-protein and low-fat foods.

Qualitative and quantitative assessment of key aroma compounds, advanced glycation end products and heterocyclic amines in different varieties of commercially roasted meat products

Studies on the interactions and links between aroma and hazardous compounds were inadequately investigated. A complete analysis was conducted on the key aroma compounds, typical hazardous compounds and their precursors in 25 samples of roasted meats. Forty-nine aroma compounds were identified as essential odorants with odor-activity values exceeds 1. Nε-carboxymethyl lysine (CML, 11.78-49.32 μg/g) and Nε-carboxyethyl lysine (CEL, 8.48-171.00 μg/g) were identified as representative advanced glycation end products (AGEs) of meats with high concentrations. Harman and Norharman were typical heterocyclic aromatic amines. Meanwhile, correlation analysis indicated that aldehyde and alcohols showed a negative correlation with AGEs (p < 0.01), while pyrazines might affect the formation of Harman and Norharman. The furaldehyde, 1-hexanol, 2, 4-Decadienal, AGEs, and creatine were regarded as potential biomarkers that distinguished different roasted meat products. Therefore, the study could provide new insights for synergistic regulation of aroma and hazardous compounds in roasted meat products.

Processing parameters in breadmaking and bioaccessibility of acrylamide and 5-hydroxymethylfurfural

This study aimed to evaluate the fate in digestive steps, bioaccessibility and diffusion of acrylamide (AA) and 5-Hydroxymethylfurfural (5-HMF) in bread samples produced under different processing parameters. AA and 5-HMF were determined in every sample ready-to-eat, after every digestion step and in the digested after crossing the dialysis membrane. The contaminants were extracted by QuEChERS method and determined by HPLC-PDA. Doubling fermentation time (from 60 to 120 min) increased the level of AA by 1.2-fold, and it decreased the level of 5-HMF by 1.4-fold. A combination of 60 min fermentation and 20 min baking led to the lowest levels of AA (1.71 mg/kg) and 5-HMF (0.50 mg/kg). There was no increase in AA level in the gastric stage however, the 5-HMF level increased. Both contaminant levels had increased in the intestinal stage. This fact showed that the determination of the contaminants in the ready-to-eat product did not reflect their actual bioaccessibility because the digestive enzymes and pH variation may affect the release and detection of AA and 5-HMF accumulated in the baking stage. The initial levels of 5-HMF were correlated to the baking time, and initial levels of AA were correlated to the fermentation time. From the bioaccessible levels of AA and 5-HMF, approximately 90 % (5 mg/kg) and 100 % (6.5 mg/kg) crossed the dialysis membrane respectively. Initial and bioaccessible levels of AA were above the security recommendations for bread (50 µg/kg), which is a concern considering the daily consumption of this food. This study showed that focusing on a combination of processing parameters could be a promising strategy to decrease the bioaccessibility of both contaminants in bread.

Vegetable extracts: Effective inhibitors of heterocyclic aromatic amines and advanced glycation end products in roasted Mackerel

The formation of hazardous substances, heterocyclic aromatic amines (HAAs) and advanced glycation end products (AGEs), in roasted mackerel with different cooking temperatures (180, 210, 240 °C) and vegetable extracts (celery, carrot and yam extracts) in a preheated oven was investigated. The results indicated that the introduction of vegetable extracts had inhibitory effects on HAAs and AGEs during thermal processing, especially celery extracts. Benefiting from the addition of vegetable extracts, the roasted mackerel keep high quality against lipid/protein oxidation, avoids nutrition loss of polyunsaturated fatty acids, and flavor is promoted. We also examined the variation of key precursors, including creatine, creatinine, reducing sugars, amino acids and attempted to explain the molecular pathway of inhibition of the formation of the hazardous substances by vegetable extracts. The results provide theoretical support to develop technologies for inhibiting hazardous substances formation during fish processing, which is important for food manufacturers and consumers for producing healthier meat products.

Mechanisms of action of coffee bioactive compounds - a key to unveil the coffee paradox

The knowledge of the relationship between the chemical structure of food components with their mechanisms of action is crucial for the understanding of diet health benefits. This review relates the chemical variability present in coffee beverages with the mechanisms involved in key physiological events, supporting coffee as a polyvalent functional food. Coffee intake has been related with several health-promoting properties such as neuroprotective (caffeine, chlorogenic acids and melanoidins), anti-inflammatory (caffeine, chlorogenic acids, melanoidins, diterpenes), microbiota modulation (polysaccharides, melanoidins, chlorogenic acids), immunostimulatory (polysaccharides), antidiabetic (trigonelline, chlorogenic acids), antihypertensive (chlorogenic acids) and hypocholesterolemic (polysaccharides, chlorogenic acids, lipids). Nevertheless, caffeine and diterpenes are coffee components with ambivalent effects on health. Additionally, a large range of potentially harmful compounds, including acrylamide, hydroxymethylfurfural, furan, and advanced glycation end products, are formed during the roasting of coffee and are present in the beverages. However, coffee beverages are part of the daily human dietary healthy habits, configuring a coffee paradox.

Studies on the Reaction of Dietary Methylglyoxal and Creatine during Simulated Gastrointestinal Digestion and in Human Volunteers

The reactive 1,2-dicarbonyl compound methylglyoxal (MGO) is consumed with food and its concentrations decrease during digestion. In the present paper, the reaction of MGO with creatine, arginine, and lysine during simulated digestion, and its reaction with creatine during the digestion in human volunteers, was studied. Therefore, simulated digestion experiments with a gastric and an intestinal phase were performed. Additionally, an intervention study with 12 subjects consuming MGO-containing Manuka honey and creatine simultaneously or separately was conducted. Derivatization with o-phenylenediamine and HPLC–UV was used to measure MGO, while creatine and glycated amino compounds were analyzed via HPLC–MS/MS. We show that MGO quickly reacts with creatine and arginine, but not lysine, during simulated digestion. Creatine reacts with 56% of MGO to form the hydroimidazolone MG-HCr, and arginine reacted with 4% of MGO to form the hydroimidazolone MG-H1. In the intervention study, urinary MG-HCr excretion is higher in subjects who consumed MGO and creatine simultaneously compared to subjects who ingested the substances separately. This demonstrates that the 1,2-dicarbonyl compound MGO reacts with amino compounds during human digestion, and glycated adducts are formed. These contribute to dietary glycation products consumed, and should be considered in studies investigating their physiological consequences.

Heterocyclic aromatic amines induce Neuro-2a cells cytotoxicity through oxidative stress-mediated mitochondria-dependent apoptotic signals

Heterocyclic aromatic amines (HAAs) are a class of hazardous compounds produced in food thermal processing. These compounds raise concerns because they have mutagenic and carcinogenic properties. However, the neurotoxicity of these compounds has received limited attention. Here, the toxic effects of three HAAs, i.e. 9H-pyrido[3,4-b]indole (Norharman), 1-methyl-9H-pyrido[3,4-b]indole (Harman), and 2-amino-3-methylimidazole[4,5-f]quinoline (IQ) were investigated in Neuro-2a cells model. The results showed that the survival rate of cells decreased in a dose-dependent manner and apoptosis occurred after exposure to the three HAAs for 24 h and 48 h. Their neurotoxicity was ranked as Harman > Norharman > IQ. Further, treatment of Harman, Norharman, or IQ at 50 and 100 μM for 48 h led to intracellular REDOX imbalance, which was manifested as increased ROS and malondialdehyde (MDA) levels, decreased GSH/GSSG ratio, and reduced SOD and CAT activities. Moreover, Norharman and Harman up-regulated the expression level of nuclear factor erythroid 2-related factor 2 (Nrf2), as well as the mRNA levels of Heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoredutase1 (NQO1), while IQ had no significant effect on the levels of Nrf2, HO-1, and NQO1. Additionally, Harman, Norharman, or IQ exposure significantly reduced mitochondrial membrane potential and intracellular ATP levels and up-regulated the levels of apoptosis-related genes and proteins. Collectively, our finding suggested that HAAs were neurotoxic, with mechanisms related to induction of oxidative stress and mitochondrial dysfunction.

Investigation of formation of well-known AGEs precursors in cookies using an in vitro simulated gastrointestinal digestive system

The present study investigated the influence of in vitro stimulated digestion system on the content of glyoxal and methylglyoxal in commercial cookies. Glyoxal and methylglyoxal levels in different cookie samples were analyzed before and after in vitro digestion with High Performance Liquid Chromatography. Initial glyoxal and methylglyoxal values ranged between 42.9 and 126.6 µg/100 g, and between 22.9 and 507.3 µg/100 g, respectively. After in vitro digestion, formation of glyoxal and methylglyoxal values were increased up to 645% and 698%, respectively. The results revealed that in vitro stimulated digestion conditions strongly increased the amount of glyoxal and methylglyoxal in cookies. The amount of fructose was found to be more effective on the formation of both GO and MGO than those of glucose and sucrose. Further studies are needed to extensively investigate glyoxal and methylglyoxal formation under in vitro conditions in such foods.

Glycine and serine markedly eliminate methylglyoxal in the presence of formaldehyde via the formation of imidazole salts

l-glycine and l-serine are the building blocks of proteins and exhibit various biological activities. This work found that l-glycine and l-serine show low scavenging capacity for methylglyoxal at moderate conditions (pH 7.0, 37 °C). However, they efficiently eliminate methylglyoxal and formaldehyde when the two aldehydes co-exist, via generation of imidazole salt, a compound formed by one molecule of methylglyoxal and formaldehyde, and two molecules of amino acids. The imidazole salts were identified in biscuits and fried potato crisps. Moreover, the formation of imidazole salts greatly decreased the cytotoxicity of their precursors, methylglyoxal and formaldehydes. This finding suggests that glycine and serine can be used to scavenge these two harmful aldehydes both after intake and during food processing.

Analysis of the evolution of potential and free furfural compounds in the production chain of infant formula and risk assessment

Furfural compounds are produced during infant formula production when heat treatment is involved. In this study, a robust method was established for determining potential and free furfural compounds (furfural, 5-methyl-2-furfural, 2-acetylfuran and 5-hydroxymethyl-2-furfural) using a modified QuEChERS technique coupled with GC-MS/MS. Further, 36 samples of two batches, covering the whole infant formula production chain were analyzed by the method to investigate how furfurals evolved during process. Then risk assessment was conducted using the Toxtree and T.E.S.T. software and evaluated by hazard quotient. Results showed the contents of bound and free 5-hydroxymethyl-2-furfural demonstrated largest increase during spray-drying (6-11 times) and homogenization stages (12-33 times), respectively. As the sum up of bound and free 5-hydroxymethyl-2-furfural, potential 5-hydroxymethyl-2-furfural was found can cause safety risks in the production chain due to the high hazard quotient value (3.11), indicating it should be controlled in homogenization and spray-drying stages.

Contribution of starch to the flavor of rice-based instant foods

Increased consumption of instant foods has led to research attention, especially rice-based instant foods. Starch, one of the most important components of rice, significantly affects food quality. However, the mechanisms by which starch contributes to rice-based instant foods flavor are poorly understood in many cases. The review aims to describe the common mechanisms by which starch contributes to food flavor, including participating in flavor formation, and affecting flavor release throughout starch multiscale structure: particle morphology, crystal structure, molecular structure. Five specific examples of rice-based instant foods were further analyzed to summarize the specific contribution of starch to flavor, including instant rice, fermented rice cake, rice noodles, fried rice, and rice dumplings. During foods processing, reducing sugars produced by heating or enzymatic hydrolysis of starch participate in Maillard reaction, caramelization and thermal degradation, which directly or indirectly affect the formation of flavor compounds. In addition, adsorption by granules, encapsulation by retrograded V-type crystal, and controlled release by starch gel all contribute to rice-based instant food flavor qualities. These mechanisms jointly contribute to flavor compounds formation and release. Proper theoretical application and improved processing methods are needed to promote the high-quality, mechanization, and automation of rice-based instant foods production.