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Fermented foods are defined as foods or beverages produced through controlled microbial growth, and the conversion of food components through enzymatic action. In recent years, fermented foods have undergone a surge in popularity, mainly due to their proposed health benefits. The aim of this review is to define and characterise common fermented foods (kefir, kombucha, sauerkraut, tempeh, natto, miso, kimchi, sourdough bread), their mechanisms of action (including impact on the microbiota), and the evidence for effects on gastrointestinal health and disease in humans. Putative mechanisms for the impact of fermented foods on health include the potential probiotic effect of their constituent microorganisms, the fermentation-derived production of bioactive peptides, biogenic amines, and conversion of phenolic compounds to biologically active compounds, as well as the reduction of anti-nutrients. Fermented foods that have been tested in at least one randomised controlled trial (RCT) for their gastrointestinal effects were kefir, sauerkraut, natto, and sourdough bread. Despite extensive in vitro studies, there are no RCTs investigating the impact of kombucha, miso, kimchi or tempeh in gastrointestinal health. The most widely investigated fermented food is kefir, with evidence from at least one RCT suggesting beneficial effects in both lactose malabsorption and Helicobacter pylori eradication. In summary, there is very limited clinical evidence for the effectiveness of most fermented foods in gastrointestinal health and disease. Given the convincing in vitro findings, clinical high-quality trials investigating the health benefits of fermented foods are warranted.

Sourdough bread production relies on metabolically active starters refreshed daily with flour and water. The stability of sourdough microbial strains is crucial for consistent bread quality. However, many bakeries lack information on the persistence of starter cultures in ongoing sourdough production. Consequently, there is growing interest in identifying microbial strains from regularly used sourdoughs that possess good functional properties and resist changes in the complex growth environment. This study aimed to evaluate the composition and stability of lactic acid bacteria (LAB) in industrial wheat (WS) and rye (RS) sourdoughs propagated over a long period. LAB isolates (n = 66) from both sourdoughs, sampled over four seasons, were identified using phenotypic methods and genotyped via ITS-PCR and ITS-PCR/TaqI restriction analysis. Eight LAB species were detected, with Lactiplantibacillus plantarum being the most dominant and stable. Nineteen distinct LAB genotypes were observed, highlighting significant diversity. The presence of identical LAB genotypes in both sourdoughs suggests microbial transfer through the environment and bakery workers. LAB in RS were found to be more stable than those in WS. These findings underscore the importance of monitoring microbial stability and diversity in industrial sourdough production to maintain consistent bread quality.

This study aimed to evaluate the influence of sourdough fermentation on the estimated glycemic index (eGI), in vitro starch digestibility, and textural and sensory properties of eight experimentally prepared sourdough breads. Wheat and whole wheat flour bread samples were produced under different fermentation conditions (25 °C and 30 °C) and fermentation methods (type-1 and type-2). In type-1 fermentation, sourdough was obtained via spontaneous fermentation. Indigenous strains (Lactobacillus brevis ELB99, Lactiplantibacillus plantarum ELB75, and Saccharomyces cerevisiae TGM55) were used for type-2 fermentation. Fermentation type and temperature significantly affected eGI, the hydrolysis index (HI), the starch fraction, and the textural properties of the samples (p < 0.05). The resistant starch (RS) content increased after fermentation, while rapidly digestible starch (RDS), HI, and eGI decreased. RS values were significantly higher in type-2 than in type-1 at the same temperature for both flour types (p < 0.05). At 25 °C, RS values were higher in both fermentation types. In the white flour samples, eGI values were in the range of 60.8–78.94 and 62.10–78.94 for type-1 and type-2, respectively. The effect of fermentation type on eGI was insignificant (p < 0.05). In the whole flour samples, fermentation type and temperature significantly affected eGI (p < 0.05). The greatest eGI decreases were in whole wheat sourdough bread at 30 °C using type-2 (29.74%). The 30 °C and type-2 samples showed lower hardness and higher specific volume. This study suggests that fermentation type and temperature could affect the eGI and the textural and sensory properties of sourdough bread, and these factors should be considered during bread production. The findings also support the consumption of wheat and whole wheat breads produced by type-2 fermentation due to higher RS and slowly digestible starch (SDS) and lower RDS and eGI values.

Sourdough is a type of dough fermented by yeast and lactic acid bacteria (LAB) used as sponge dough in bread making. Sourdough may have four classifications according to the fermentation type and the technological process used. On sourdough type I, the fermentation of yeasts and LAB present in the flour occurs spontaneously whereas in type II, fermentation occurs after the inoculation of a starter culture. Type III is simply type II sourdough dehydrated and type IV is a mixture of type I and type II sourdough, produced on laboratory scale. With LAB’s growth during fermentation, pH decreases with subsequent hydrolysis of starch and protein, favoring the growth of yeasts. The yeast in turn, releases amino acids during autolysis, contributing to the growth of LAB. Due to this synergistic growth of LAB and yeasts, the products obtained from sourdough show more concentration of flavor, more elastic dough, and a longer shelf life than bread fermented only by yeast. Although, the benefits of this technology, using sourdough, is present just in a few countries, where it is also possible to obtain the dehydrated sourdough starters, for domestic use, in local supermarkets. Due to its fermentative process complexity, this paper presents updated information about the fabrication process of sourdough, main factors affecting this process, benefits of sourdough use for bakery products, and the varieties of dehydrated sourdough commercially available throughout the world.

This research effort aimed at isolating and phenotypically characterizing lactic acid bacteria (LAB) isolates from a spontaneous rye sourdough manufactured following traditional protocols, as well as at evaluating their antimicrobial and antifungal properties as key features for future industrial applications. Thirteen LAB strains of potential industrial interest were isolated and identified to species-level via PCR. Most of the sourdough isolates showed versatile carbohydrate metabolisms. The Leuconostoc mesenteroides No. 242 and Lactobacillus brevis No. 173 demonstrated to be gas producers; thus, revealing their heterofermenter or facultative homofermenter features. Viable counts higher than 7.0 log10 (CFU/mL) were observed for Lactobacillus paracasei No. 244, Lactobacillus casei No. 210, L. brevis No. 173, Lactobacillus farraginis No. 206, Pediococcus pentosaceus No. 183, Lactobacillus uvarum No. 245 and Lactobacillus plantarum No. 135 strains, after exposure at pH 2.5 for 2 h. Moreover, L. plantarum No. 122, L. casei No. 210, Lactobacillus curvatus No. 51, L. paracasei No. 244, and L. coryniformins No. 71 showed growth inhibition properties against all the tested fifteen pathogenic strains. Finally, all LAB isolates showed antifungal activities against Aspergillus nidulans, Penicillium funiculosum, and Fusarium poae. These results unveiled the exceptionality of spontaneous sourdough as a source of LAB with effective potential to be considered in the design of novel commercial microbial single/mixed starter cultures, intended for application in a wide range of agri-food industries, where the antimicrobial and antifungal properties are often sought and necessary. In addition, metabolites therefrom may also be considered as important functional and bioactive compounds with high potential to be employed in food and feed, as well as cosmetic and pharmaceutical applications.

Sourdough bread has gained interest with the increasing demand of consumers for more natural, delicious and healthy foods. Also, consumption of whole grain flour is increasing due to the bioactive compounds it contains. This study aimed to investigate the effects of wheat variety (Tosunbey, Kenanbey, İkizce-96, Bezostaja-1), sourdough treatment [Spontaneous fermentation (SP), Lactiplantibacillus plantarum (LP), Fructilactobacillus sanfranciscensis (LS)] and sourdough level (0–10–20–30%) on the technological characteristics of whole wheat bread. The investigated factors had significant effects on pH, total titratable acidity, specific volume, color and textural parameters. The increasing levels of sourdough decreased the specific volume of whole wheat bread and increased the crumb hardness. The whole wheat sourdough breads produced with LP and LS had lower specific volumes due to the acidity, but were more favorable in terms of smell compared to SP. The hardness and chewiness of the bread samples significantly increased with the three days of storage, while the cohesiveness and springiness decreased. Wheat varieties with higher protein content and Zeleny sedimentation value had better performance for whole wheat sourdough bread production. The study showed that sourdough with selected lactic starters (LP and LS) could be used at 10–20% levels in whole wheat bread formulations to have acceptable technological and sensory characteristics.

The wheat flour-alfalfa blends containing 5 and 10 g/100 g of non-germinated and germinated alfalfa flour were examined in terms of nutritional composition (protein, lipid, starch, total dietary fibre), mineral profile, total phenolic content and antioxidant activity (ABTS, FRAP), and Mixolab rheological properties while the corresponding standard and sourdough breads were evaluated regarding physical and textural characteristics (specific volume, hardness, cohesiveness, springiness, gumminess, chewiness). The alfalfa flour inclusion resulted in increased protein (11.64–14.87%) and total dietary fibre (1.65–5.82%) contents in all blends, regardless of the alfalfa flour type but in a higher extent with 10 g/100 g inclusion level. Blends were characterised by improved mineral profile, total phenolic content (37.57–162.35 mg GAE/100 g) and antioxidant properties (ABTS: 4.37–232.79 µmol TE/100 g, FRAP: 138.05–539.16 µmol TE/100 g) particularly when non-germinated alfalfa flour in quantity of 10 g/100 g was used. Dough rheological properties were not significantly affected by the alfalfa flour type, whilst higher alfalfa flour inclusion level prolonged dough development time. Increased specific volume (2.63–3.62 cm3/g) with decreased crumb hardness (3.82–1.68 N) was recorded upon alfalfa flour incorporation and was more pronounced for sourdough bread. Overall nutrient composition of blends and technological features of the resulting breads were enhanced by alfalfa flour addition.

Many patients suspect wheat as being a major trigger of their irritable bowel syndrome (IBS) symptoms. Our aim was to evaluate whether sourdough wheat bread baked without baking improvers and using a long dough fermentation time (>12 h), would result in lower quantities of alpha-amylase/trypsin inhibitors (ATIs) and Fermentable, Oligo-, Di-, Mono-saccharides and Polyols (FODMAPs), and would be better tolerated than yeast-fermented wheat bread for subjects with IBS who have a poor subjective tolerance to wheat. The study was conducted as a randomised double-blind controlled 7-day study (n = 26). Tetrameric ATI structures were unravelled in both breads vs. baking flour, but the overall reduction in ATIs to their monomeric form was higher in the sourdough bread group. Sourdough bread was also lower in FODMAPs. However, no significant differences in gastrointestinal symptoms and markers of low-grade inflammation were found between the study breads. There were significantly more feelings of tiredness, joint symptoms, and decreased alertness when the participants ate the sourdough bread (p ≤ 0.03), but these results should be interpreted with caution. Our novel finding was that sourdough baking reduces the quantities of both ATIs and FODMAPs found in wheat. Nonetheless, the sourdough bread was not tolerated better than the yeast-fermented bread.

The study aimed to evaluate the impact of long and short fermentation on the sensory and nutritional properties of French sourdough and yeast bread. The long fermentation was performed at low temperatures, and is close to “artisanal processes”, while the short fermentation was performed at higher temperatures, and is associated with “intensive processes” used in industries. Reducing sugars and amino compounds, precursors of the Maillard reaction, were analyzed in the doughs; while aromas, acrylamide, and melanoidins were quantified in the breads. The study was completed by a sensory analysis performed by a trained panel. The results showed that the content of reducing sugars was highly influenced by the fermentation conditions. On the other hand, proteolysis was limited in both types of bread, especially in yeast bread. In yeast bread, long fermentation favored the generation of aromas from yeast metabolism in the dough, but limited the formation of aromas from the Maillard reaction in the crust. In sourdough bread, long fermentation promoted the Maillard reaction and aromas from the metabolism of lactic acid bacteria, and had a positive effect on the sensory perception of the crust and crumb. In both types of bread, long fermentation contributed to the decrease of acrylamide content, even though the overall acrylamide content was low regardless of the type of fermentation.