Evaluation of the Availability and Antioxidant Capacity of Maillard Compounds Present in Bread Crust: Studies in Caco-2 Cells

Acrylamide and HMF occurrence and bioaccessibility in instant coffee and coffee substitutes. A study on isolated and milk-combined beverages

This research evaluated the occurrence and bioaccessibility of acrylamide and HMF in commercial instant coffees (IC) and coffee substitutes (CS), considering both isolated consumption and combination with milk. There were no significant differences in acrylamide content between IC and CS samples (median: 589 vs. 671 µg/kg), but higher variability was reported for CS, probably due to their varied composition (roasted cereals, nuts, honey, dehydrated fruits, and/or chicory). Acrylamide level were always below the EU benchmark for each category. HMF contents were similar between both groups (1354-5127 mg/kg for IC and 735-7134 mg/kg for CS; median: 2890 vs. 2960 mg/kg), with no clear ingredient relationship. Since IC consumption by the Spanish population is ten times higher than that of CS, exposure to acrylamide and HMF was higher from IC (6.8 vs. 1.07 ng/kg body weight/day for acrylamide; 39.1 vs. 4.2 µg/kg body weight/day for HMF). The standardized in vitro gastrointestinal digestion protocol (INFOGEST) was used. The gastrointestinal process reduced the bioaccessibility of acrylamide up to 27.2 % in IC and to 22.4 % in CS, regardless of the presence of milk. HMF bioaccessibility from IC significantly dropped after the gastrointestinal digestion, whereas it greatly increased for CS. The presence of milk did not affect HMF bioaccessibility. These results highlight the importance of assessing food bioaccessibility in typical consumption scenarios, providing a holistic view and a realistic evaluation of the potential risks associated with acrylamide and HMF exposure in the diet.

Bioaccessibility and Genoprotective Effect of Melanoidins Obtained from Common and Soft Bread Crusts: Relationship between Melanoidins and Their Bioactivity

Bread crust constitutes an important by-product of the bakery industry, and its utilization for the isolation of melanoidins to be used as a functional ingredient can enhance its added value and contribute to health. The aim of this study was to evaluate the bioaccessibility, bioactivity, and genoprotective effect of melanoidins derived from bread crust. Bioaccessibility was assessed in gastric, intestinal digestion, and colonic fermentation fractions. The results revealed a relationship between bioaccessible melanoidins and their type (common or soft bread). No cytotoxicity effects were observed for bioaccessible fractions, as assessed by MTT and RTA methods, and they did not affect the distribution of E-cadherin in Caco-2 cells, confirming their ability to maintain membrane integrity. Furthermore, our study demonstrated that the gastrointestinal and colonic fermentation fractions successfully transported across the intestinal barrier, without affecting cell permeability, and showed antioxidant activity on the basolateral side of the cell monolayer. Remarkably, both fractions displayed a significant genoprotective effect in Caco-2 cells. Our findings provide crucial insights into the relationship between the melanoidins and their bioactivity and genoprotective effect. These results demonstrated the potential of bioaccessible melanoidins as valuable bioactive compounds for the development of functional foods, without showing toxic effects on gastrointestinal cells.

Bread melanoidins as potential new sustainable bakery ingredients: a study using fat and fat-free bakery food models

Melanoidins isolated from bakery by-products are proposed as new sustainable ingredients for bakery products. The colour, odour profile, texture, water activity, and antioxidant capacity of two bakery food models, fat and fat-free, enriched with 2% and 4% soft bread and common bread melanoidins, were analysed. The colour of the bakery food models with melanoidins was darker than that of the respective control; the fat-free models with melanoidins showed higher values of hardness than the control, while no significant effect was observed in the fat models; the water activity did not change compared to the control; the odour profile was significantly modified with different effects depending on the type of melanoidin quantity added and the food model (fat or fat-free); and the antioxidant capacity increased proportionally to the quantity of melanoidin added. In general, melanoidins from soft bread exhibited a higher effect than the melanoidins from common bread. The melanoidins isolated from both fat and fat-free bakery food models did not show cytotoxicity nor did they modify the levels of reactive oxygen species in Caco-2 cells. Therefore, the results seem to indicate the favourable potential of bread melanoidins as new sustainable ingredients for bakery products.

Processing contaminants in wheat-based foods - a systematic review, meta-analysis and bibliometric analysis

Wheat is one of the main cereals grown around the world and is the basis for several foods such as bread, cakes and pasta. The consumption of these foods raises a concern with food safety, as toxic substances such as acrylamide, 5-hydroxymethylfurfural and polycyclic aromatic hydrocarbons are formed during their processing. To assess the occurrence of processing contaminants in wheat-based foods, a systematic search was carried out in four databases: PubMed, Embase, Web of Science and Scopus. Of the 1479 results, 28 were included for a meta-analysis. Most studies (69.7%) evaluated acrylamide in bread, cookies, and pasta, while PAHs (26.2%) were determined mainly in wheat grains and pasta. HMF was the least determined contaminant (4.1%), with only four studies on cookies included in the meta-analysis. The highest concentration was for acrylamide (136.29 µg·kg-1) followed by HMF (70.59 µg·kg-1) and PAHs (0.11 µg·kg-1). Acrylamide is the main processing contaminant researched, and no studies on the subject have been found in commercial samples in some regions of the world. This result shows a gap in the dates available about process contaminants in wheat-based foods and how the levels can change depending on the process parameters and the ingredients used.

Effect of Cooking Methods on the Antioxidant Capacity of Plant Foods Submitted to In Vitro Digestion-Fermentation

The antioxidant capacity of foods is essential to complement the body's own endogenous antioxidant systems. The main antioxidant foods in the regular diet are those of plant origin. Although every kind of food has a different antioxidant capacity, thermal processing or cooking methods also play a role. In this work, the antioxidant capacity of 42 foods of vegetable origin was evaluated after in vitro digestion and fermentation. All foods were studied both raw and after different thermal processing methods, such as boiling, grilling roasting, frying, toasting and brewing. The cooking methods had an impact on the antioxidant capacity of the digested and fermented fractions, allowing the release and transformation of antioxidant compounds. In general, the fermented fraction accounted for up to 80-98% of the total antioxidant capacity. The most antioxidant foods were cocoa and legumes, which contributed to 20% of the daily antioxidant capacity intake. Finally, it was found that the antioxidant capacity of the studied foods was much higher than those reported by other authors since digestion-fermentation pretreatment allows for a higher extraction of antioxidant compounds and their transformation by the gut microbiota.

Bioactivity of food melanoidins is mediated by gut microbiota

Melanoidins are an important component of the human diet (average consumption 10 g/day), which escape gastrointestinal digestion and are fermented by the gut microbiota. In this study melanoidins from different food sources (coffee, bread, beer, balsamic vinegar, sweet wine, biscuit, chocolate, and breakfast cereals) were submitted to an in vitro digestion and fermentation process, and their bioactivity was assessed. Some melanoidins were extensively used by gut microbes, increasing production of short chain fatty acids (mainly acetate and lactate) and favoring growth of the beneficial genera Bifidobacterium (bread crust, pilsner and black beers, chocolate and sweet wine melanoidins) and Faecalibacterium (biscuit melanoidins). Quantification of individual phenolic compounds after in vitro fermentation allowed their identification as microbial metabolites or phenolics released from the melanoidins backbone (specially pyrogallol, 2-(3,4-dihydroxyphenyl)acetic and 3-(3,4-dihydroxyphenyl)propionic acids). Our results also showed that antioxidant capacity of melanoidins is affected by gut microbiota fermentation.

Enhancing the antioxidative effects of foods containing rutin and α-amino acids via the Maillard reaction: A model study focusing on rutin-lysine system

Rutin is a bioflavonoid found in many plants and derived foods, accordingly, rutin likely interacts with α-amino acids such as Lys, Ile, His or Glu to give Maillard reaction products (MRPs). The heated rutin-Lys system exhibited highest brown intensity and in vitro antioxidant activities. The 30-50 kDa rutin-Lys fraction had higher in vitro antioxidant activities than the other fractions, and at a dose of 0.4 mg/ml preserved over 90% cell viability for HepG2 cells exposed to H₂ O₂ . The dose-dependent protective effects against H₂ O₂ -induced oxidative stress of the rutin-Lys MRPs may involve the inhibition of reactive oxygen species generation, enhancement of the superoxide dismutase and catalase activities, along with the activation of the Nrf2-dependent pathway and upregulation of phase II antioxidant genes (including NQO1, HO-1, GCLG, and GCLM). PRACTICAL APPLICATIONS: Rutin is widely distributed in vegetables and grains. The Maillard reaction is a common reaction occurring during food processing, and produces Maillard reaction products (MRPs) with distinct processing and biological properties. This study shows that a 30-min thermal treatment at 120°C generates antioxidative MRPs in the rutin-Lys, rutin-His, rutin-Ile and rutin-Glu model systems, which can directly inhibit reactive oxygen species generation and enhance SOD and CAT activities while activating the Nrf2-dependent pathway and upregulating the expression of phase II detoxifying antioxidant genes. Therefore, for food systems containing phenolic antioxidants and proteins (such as rutin and Lys), one may enhance the antioxidant properties of these food systems through a 30-min thermal treatment at 120°C. Also, the resultant rutin-Lys MRPs may be isolated and used as commercial preparations of natural antioxidants.

Effects of Maillard-type caseinate glycation on the preventive action of caseinate digests in acrylamide-induced intestinal barrier dysfunction in IEC-6 cells

Dietary acrylamide has attracted widespread concern due to its toxic effects; however, its adverse impact on the intestines is less assessed. Protein glycation of the Maillard-type is widely used for property modification, but its potential effect on preventive efficacy of protein digest against the acrylamide-induced intestinal barrier dysfunction is quite unknown. Caseinate was thus glycated with lactose. Two tryptic digests from the glycated caseinate and untreated caseinate (namely GCN digest and CN digest) were then assessed for their protective effects against acrylamide-induced intestinal barrier dysfunction in the IEC-6 cell model. The results showed that acrylamide at 1.25–10 mmol L⁻¹ dose-dependently had cytotoxic effects on IEC-6 cells, leading to decreased cell viability and increased lactate dehydrogenase release. Acrylamide also brought about barrier dysfunction, including decreased trans-epithelial electrical resistance (TEER) value and increased epithelial permeability. However, the two digests at 12.5–100 μg mL⁻¹ could alleviate this dysfunction via enhancing cell viability by 70.2–83.9%, partly restoring TEER values, and decreasing epithelial permeability from 100% to 76.6–94.1%. The two digests at 25 μg mL⁻¹ strengthened the tight junctions via increasing tight junction proteins ZO-1, occludin, and claudin-1 expression by 11.5–68.6%. However, the results also suggested that the GCN digest always showed lower protective efficacy than the CN digest in the cells. It is concluded that Maillard-type caseinate glycation with lactose endows the resultant tryptic digest with impaired preventive effect against acrylamide-induced intestinal barrier dysfunction, highlighting another adverse effect of the Maillard reaction on food proteins.

Glycated caseinate digest of the Maillard-type has lower protective action than caseinate digest against acrylamide-induced barrier dysfunction in IEC-6 cells.