Does Fermentation Really Increase the Phenolic Content in Cereals? A Study on Millet

Co-decoding dynamics in volatiles and sensory profiles of Zhaiji millet vinegar during aging by integrating multiple flavor characterization techniques and chemometrics

Zhaiji millet vinegar (ZJMV) is a signature acidic condiment. To investigate the effect of aging on the flavor of ZJMV, here gas chromatography-mass spectrometry (GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS), electronic nose, electronic tongue, and quantitative descriptive analysis were used to characterize the flavor profiles of ZJMV for five aging years (2 to 10 years). GS-MS and GC-IMS identified 84 and 44 volatile organic compounds (VOCs), with the most abundant alcohols and esters (p < 0.05). Notably, the number of VOCs in the ZJMV gradually decreased with increasing aging time, while the overall concentration peaked in the third year. Sensory evaluation indicated that aging enhanced roasty and umami and moderated other attributes such as spice-like. Additionally, 15 potential flavor markers (p < 0.05, variable importance projection ≥1.2) and 23 odor-active compounds (odor activity values ≥1) were screened. Our results provide new insights for improving the ZJMV flavor quality.

Sensory Properties and Acceptability of Fermented Pearl Millet, a Climate-Resistant and Nutritious Grain, Among Consumers in the United States-A Pilot Study

Millets are climate-resistant, potential alternatives to wheat that could provide environmental, food security, and health benefits (e.g., lower glycemic index). However, millets are high in phytic acid, which reduces the bioavailability of essential minerals. Millets are often fermented in Africa and parts of Asia to improve bioavailability and, thus, nutritional value, but both unfermented and fermented millets may have flavors unfamiliar to Western cultures. We conducted two pilot studies on sensory perception and liking of whole grain, United States pearl millet (Pennisetum glaucum), in a group of U.S. consumers. In a preliminary study, we compared pearl millet treated under five different conditions (0, 48, and 96 h of fermentation fully submerged in either distilled water or in a 5% NaCl solution at 28 °C). We found that 96 h of spontaneous fermentation in water, an inexpensive and accessible technique consistent with consumer demand for minimally processed foods, reduced phytic acid by ~72%. However, consumers (n = 12) rated flatbreads made with fermented pearl millet as more bitter and sour than flatbreads made with unfermented pearl millet. In a second study, participants (n = 30) rated liking and purchase intent for whole wheat bread with 0 to 50% (w/w) substitution of pearl millet flour. Replacing up to 20% of wheat with fermented or unfermented pearl millet had no measurable effect on liking or purchase intent. More extensive substitution compromised liking, particularly with fermented pearl millet. More work is needed, but so far, there appear to be no sensory barriers to at least partial substitution of whole-grain pearl millet for wheat in whole wheat bread for United States consumers.

Effects of different processing methods on phenolic compounds in flaxseed meal

This study examined effects of different processing methods on phenolic compounds in flaxseed meal. The optimal SE treatment was 1.0 MPa for 3 min, and the contents of total flavonoids and phenolic acid were 2.26 times and 1.63 times of the control group, respectively. Notably, erucic acid increased 85.76 %. Optimal extrusion conditions (15 % moisture content, 140 °C, 29 hz) led to the presence of rutin and a 2.81 times increase in protocatechuic acid content over the control. Fermenting with 3 % Bacillus subtilis for 4 days yielded gallic acid in bound form and vanillic acid in free form, with protocatechuic acid increasing 40.65 % compared to the control. Among all the treatments, extrusion produced the highest levels of phenolic compounds in flaxseed meal. Each treatment significantly increased the open ring isomer ester phenol (SDG) compared to the control. Overall, various processing methods impacted the phenolic content and composition in flaxseed meal differently.

Biofortification, metabolomic profiling and quantitative analysis of vitamin B12 enrichment in guava juice via lactic acid fermentation using Levilactobacillus brevis strain KU15152

BACKGROUND

Chemical fortification and dose supplementation of vitamin B12 are widely implemented to combat deficiency symptoms. However, in situ, fortification of vitamin B12 in food matrixes can be a promising alternative to chemical fortification. The present study aimed to produce vitamin B12-rich, probiotic guava juice fermented with Levilactobacillus brevis strain KU15152. Pasteurized fresh guava juice was inoculated with 7.2 log CFU mL-1 L. brevis strain KU15152 and incubated for 72 h at 37 °C anaerobically. The antioxidants, total phenolic compounds, vitamin B12 production, sugars, organic acids, pH and viable count were analyzed at 24, 48 and 72 h of incubation. The fermented juice was stored at 4 °C, and the changes in its functional properties were analyzed at 7-day intervals up to 28 days of storage.

RESULTS

During fermentation, the bacteria cell count was increased from 7.01 ± 0.06 to 9.76 ± 0.42 log CFU mL-1 after 72 h of fermentation and was decreased to 6.94 ± 0.34 CFU mL-1 during storage at 4 °C after 28 days. The pH, total soluble solids, crude fiber, citric acid and total sugars decreased, while titratable acidity, total protein, antioxidants, phenolic compounds and lactic acid contents increased during fermentation. The fermented guava juice exhibited higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS)) radical scavenging activities (85.97% and 75.97%, respectively) at 48 h of fermentation. The concentration of active vitamin B12 in the sample reached 109.5 μg L-1 at 72 h of fermentation. However, this concentration gradually decreased to 70.2 μg L-1 during the storage period. During storage for 28 days at 4 °C, both the fermented and control guava juices exhibited a decline in antioxidant and phenolic compound concentrations. Furthermore, the addition of 20% honey and guava flavor enhanced the organoleptic properties and acceptability of fermented guava juice.

CONCLUSION

The value-added fermented guava juice could be a novel functional food product to combat vitamin B12 deficiency. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Physiochemical, Bio, Thermal, and Non-Thermal Processing of Major and Minor Millets: A Comprehensive Review on Antinutritional and Antioxidant Properties

Millets are recognized as future foods due to their abundant nutrition and resilience, increasing their value on the global stage. Millets possess a broad spectrum of nutrients, antinutrients, and antioxidants, making it imperative to understand the effects of various processing methods on these components. Antinutritional factors interfere with the digestibility of macro-nutrients and the bioavailability and bio accessibility of minerals. This necessitates methods to reduce or eliminate antinutrients while improving nutritive and antioxidant value in food. This review aims to elucidate the rationale behind processing choices by evaluating the scientific literature and examining the mechanisms of processing methods, categorized as physiochemical, bio, thermal, novel non-thermal, and their combination techniques. Physiochemical and bioprocessing methods alter antinutrients and antioxidant profiles through mass transfer, enzyme activation, product synthesis, microbial activity, and selective removal of grain layers. Thermal methods break functional bonds, modify the chemical or physical structures, enhance kinetics, or degrade heat-labile components. Non-thermal techniques preserve heat-sensitive antioxidants while reducing antinutrients through structural modifications, oxidation by ROS, and break down the covalent and non-covalent bonds, resulting in degradation of compounds. To maximize the trade-off between retention of beneficial components and reducing detrimental ones, exploring the synergy of combination techniques is crucial. Beyond mitigating antinutrients, these processing methods also stimulate the release of bioactive compounds, including phenolics, flavonoids, and peptides, which exhibit potent health-promoting properties. This review underscores the transformative potential of processing technologies in enhancing millets as functional ingredients in modern diets, promoting health and advancing sustainable food practices.

Maximizing the Nutritional Benefits and Prolonging the Shelf Life of Millets through Effective Processing Techniques: A Review

Maximizing the nutritional benefits and extending the shelf life of millets is essential due to their ancient significance, rich nutrient content, and potential health benefits, but challenges such as rapid rancidity in millet-based products underscore the need for effective processing techniques to enhance their preservation and global accessibility. In this comprehensive review, the impact of diverse processes and treatments such as mechanical processing, fermentation, germination, soaking, thermal treatments like microwave processing, infrared heating, radio frequency, nonthermal treatments like ultrasound processing, cold plasma, gamma irradiation, pulsed light processing, and high-pressure processing, on the nutritional value and the stability during storage of various millets has been examined. The review encompasses an exploration of their underlying principles, advantages, and disadvantages. The technologies highlighted in this review have demonstrated their effectiveness in maximizing and extending the shelf life of millet-based products. While traditional processes bring about alterations in nutritional and functional properties, prompting the search for alternatives, novel thermal and nonthermal techniques were identified for microbial decontamination and enzyme inactivation. Advancements in millet processing face challenges including nutrient loss, quality changes, resource intensiveness, consumer perception, environmental impact, standardization issues, regulatory compliance, and limited research on combined methods.

Enhancing the nutritional value and antioxidant properties of foxtail millet by solid-state fermentation with edible fungi

Foxtail millet is typically dehulled before consumption or processing. However, foxtail millet bran also contains abundant phenolic compounds and other nutrients. Edible fungi have rich extracellular enzyme systems; are environmentally friendly and safe for consumption; and have been shown to effectively degrade lignin and cellulose. This study aimed to screen edible fungi that can effectively ferment undehusked foxtail millet, improving its nutritional value and antioxidant properties through solid-state fermentation (SSF). The results demonstrated that fermentation utilizing Pleurotus geesteranus exhibited significant improvements in both the phenolic compound content and antioxidant properties of foxtail millet, with the optimal fermentation period determined to be 30 days. The physical and functional properties of fermented undehusked foxtail millet (FFM) flour were effectively improved, increasing crude protein, vitamin C, and crude polysaccharide contents by 11.46%, 27.78%, and 54.17%, respectively. In vitro scavenging activities of FFM were 73.19%, 93.86%, and 63.75% for 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS·+), and superoxide anion radicals (O2 -), respectively. The total antioxidant capability (T-AOC) and superoxide dismutase (SOD) activity of FFM were 1.01 mM Trolox equivalents (TE)/g and 89.05 U/g, respectively. Additionally, T-AOC, SOD, and glutathione peroxidase (GSH-Px) activities increased, whereas malondialdehyde (MDA) levels decreased in the heart, liver, and kidneys of mice treated with FFM flour, indicating enhanced antioxidant capacity. Therefore, fermentation with edible fungi is suitable for improving the nutritional composition and antioxidant properties of foxtail millet.

Assessment of Sourdough Fermentation Impact on the Antioxidant and Anti-Inflammatory Potential of Pearl Millet from Burkina Faso

Millet, a gluten-free cereal, has received attention for its environmental friendliness and higher protein content than other grains. It represents a staple food in many African countries, where fermentation is traditionally used for preserving food products and preparing different cereal-based products. This study aimed to assess the impact of sourdough fermentation on bioactive compounds and antioxidant and anti-inflammatory properties of pearl millet from Burkina Faso. Phenolic compounds were investigated spectrophotometrically and by HPLC-DAD. The antioxidant activity of unfermented (MF) and fermented (FeMF) millet was evaluated in vitro by spectrophotometric and fluorometric assays and ex vivo on oxidized human erythrocytes for hemolysis inhibition. Finally, the potential anti-inflammatory effect of FeMF and MF was evaluated on human adenocarcinoma cell line (HT-29) exposed to TNF-α inflammatory stimulus. Results revealed significantly higher levels of polyphenols, flavonoids, and in vitro antioxidant activity following millet fermentation. Notable differences in phenolic composition between FeMF and MF are observed, with fermentation facilitating the release of bioactive compounds such as gallic acid, quercetin, and rutin. A dose-dependent protection against oxidative hemolysis was observed in both FeMF- and MF-pretreated erythrocytes. Similarly, pretreatment with FeMF significantly reduced the levels of inflammatory markers in TNF-α-treated cells, with effects comparable to those of MF. Fermentation with sourdough represents a simple and low-cost method to improve the bioactive compounds content and in vitro antioxidant activity of millet flour with promising nutraceutical potential.

Metabolomics and in-vitro bioactivities studies of fermented Musa paradisiaca pulp: A potential alpha-amylase inhibitor

The in-vitro synthesis of bio-compounds via fermentation is a promising route for bioactive molecules intended for disease control and management. Therefore, this study evaluated the effect of fermentation on the antioxidants, antihyperglycemic and anti-inflammatory properties and the resultant chemometric phytochemical profiles of unripe plantain fruits. The results revealed that Escherichia coli and Propionibacterium spp. are suspected as the key fermenters. The E coli showed negative results to the pathogenicity test; Propionibacterium appeared to be opportunistic. A significant increase in the total polyphenols and protein and decreased flavonoids was recorded in the phytochemical profile of the methanolic extract of the fermented unripe plantain pulp; however, the ascorbic acid content was not significantly altered. The 1H NMR fingerprint showed that there is a closely related chemical shift among the shorter fermentation time (days 2-6) and the unfermented, while the more extended fermentation periods (days 7-12) with enhanced bioactivities were closely related based on the chemometrics analyses. Furthermore, the UPLC-QTOF-MS analysis annotated the presence of bioactive compounds in the day-9 fermented sample: polyhydroxy glucose conjugates (3-Methoxy-4-hydroxyphenyl 6-O-(3,4,5-trihydroxybenzoyl)-beta-D-glucopyranoside), short chain peptide (leucyl-glycyl-glycine), amino acid derivatives (4-Aminophenylalanine, and N-Acetylhistidine), linear and cyclic fatty acid derivatives (palmitoyl putrescine, ricinoleic acid, phytosphingosine, gabalid, rubrenoic acid, 2-aminocyclopentanecarboxylic and cystodienioc acid). The synergistic effect of these newly formed compounds and the increase in the phenolic content of the day-9 fermented unripe plantain may account for its more potent antioxidant, anti-inflammatory and antihyperglycemic activity. Therefore, the products obtained from the day 9 fermentation of unripe plantain pulp may serve as potential nutraceutical agents against gastro-enteric sugar digestion and absorption and sugar-induced oxidative stress, inflammation and metabolic disease.

Proso Millet (Panicum miliaceum L.) as Alternative Source of Starch and Phenolic Compounds: A Study on Twenty-Five Worldwide Accessions

Proso millet has been proposed as an effective anti-diabetic food thanks to the combined action of polyphenols and starch. This study aimed to characterize the chemical composition of twenty-five accessions, in order to enhance this cereal as an alternative to available starch for food applications or to propose new food ingredients with health benefits. Proso millet contained a high percentage of starch, reaching values of 58.51%. The amylose content showed high variability, with values ranging from 1.36 to 42.70%, and significantly higher values were recorded for the white accessions than for the colored ones. High-resistant starch content (13.41-26.07%) was also found. The HPLC-MS analysis showed the same phenolic pattern in all the samples. Cinnamic acids are the most abundant compounds and significant differences in their total content were found (0.69 to 1.35 mg/g DW), while flavonoids were only detected in trace amounts. Statistical results showed significantly higher antiradical activity in the colored accessions than in the white ones.

Millet Fermented by Different Combinations of Yeasts and Lactobacilli: Effects on Phenolic Composition, Starch, Mineral Content and Prebiotic Activity

Millet is the sixth-highest yielding grain in the world and a staple crop for millions of people. Fermentation was applied in this study to improve the nutritional properties of pearl millet. Three microorganism combinations were tested: Saccharomyces boulardii (FPM1), Saccharomyces cerevisiae plus Campanilactobacillus paralimentarius (FPM2) and Hanseniaspora uvarum plus Fructilactobacillus sanfranciscensis (FPM3). All the fermentation processes led to an increase in minerals. An increase was observed for calcium: 254 ppm in FPM1, 282 ppm in FPM2 and 156 ppm in the unfermented sample. Iron increased in FPM2 and FPM3 (approx. 100 ppm) with respect the unfermented sample (71 ppm). FPM2 and FPM3 resulted in richer total phenols (up to 2.74 mg/g) compared to the unfermented sample (2.24 mg/g). Depending on the microorganisms, it was possible to obtain different oligopeptides with a mass cut off ≤10 kDalton that was not detected in the unfermented sample. FPM2 showed the highest resistant starch content (9.83 g/100 g) and a prebiotic activity on Bifidobacterium breve B632, showing a significant growth at 48 h and 72 h compared to glucose (p < 0.05). Millet fermented with Saccharomyces cerevisiae plus Campanilactobacillus paralimentarius can be proposed as a new food with improved nutritional properties to increase the quality of the diet of people who already use millet as a staple food.

Phenolic Profile, Antioxidant Activity and Amino Acid Composition of Moringa Leaves Fermented with Edible Fungal Strains

Solid-state fermentation (SSF) is widely recognised as a technique to increase the bioactive potential and nutritional value of plant materials. However, the effect of this biotreatment differs for individual substrates. This study aimed to evaluate the impact of SSF with filamentous fungi (Rhizopus, Aspergillus, and Neurospora) on a moringa leaf phenolic profile, antioxidant activity, and amino acid composition. A total of 43 phenolic compounds were determined in the dried leaves analysed by HPLC-ESI-TOF-MS. The leaves contained 11.79 mg/g of free phenolics: flavonols (80.6%, mainly quercetin and kaempferol glycosides), hydroxycinnamic acid derivatives (12.3%), vitexin and vicenin (6.9%), and a small amount of lignan (isolariciresinol isomers). The result of the 1-day fermentation was a slight enhancement in the concentration of individual free phenolics (flavones) and the antioxidant activity of the leaves. However, extending the incubation period caused a significant decrease in those parameters and cannot be recommended for obtaining a food fortificant from moringa leaves. In contrast, the 3-day fermentation with N. intermedia led to a 26% average accumulation of individual amino acids. Therefore, the SSF with Neurospora can be a promising method for improving the nutritional composition of moringa leaves and needs further investigation.

Nutritional Evaluation of Sea Buckthorn “Hippophae rhamnoides” Berries and the Pharmaceutical Potential of the Fermented Juice

Sea buckthorn is a temperate bush plant native to Asian and European countries, explored across the world in traditional medicine to treat various diseases due to the presence of an exceptionally high content of phenolics, flavonoids and antioxidants. In addition to the evaluation of nutrients and active compounds, the focus of the present work was to assess the optimal levels for L. plantarum RM1 growth by applying response surface methodology (RSM), and to determine the impact of juice fermentation on antioxidant, anti-hypertension and anticancer activity, as well as on organoleptic properties. Sea buckthorn berries were shown to contain good fiber content (6.55%, 25 DV%), high quality of protein (3.12%, 6.24 DV%) containing: histidine, valine, threonine, leucine and lysine (with AAS 24.32, 23.66, 23.09, 23.05 and 21.71%, respectively), and 4.45% sugar that provides only 79 calories. Potassium was shown to be the abundant mineral content (793.43%, 22.66 DV), followed by copper and phosphorus (21.81 and 11.07 DV%, respectively). Sea buckthorn juice exhibited a rich phenolic, flavonoid and carotenoid content (283.58, 118.42 and 6.5 mg/g, respectively), in addition to a high content of vitamin C (322.33 mg/g). The HPLC profile indicated that benzoic acid is the dominant phenolic compound in sea buckthorn berries (3825.90 mg/kg). Antioxidant potentials (DPPH and ABTS) of sea buckthorn showed higher inhibition than ascorbic acid. Antimicrobial potentials were most pronounced against Escherichia coli BA12296 (17.46 mm). The probiotic growth was 8.5 log cfu/mL, with juice concentration, inoculum size and temperature as the main contributors to probiotic growth with a 95% confidence level. Fermentation of sea buckthorn juice with L. plantarum RM1 enhanced the functional phenolic and flavonoid content, as well as antioxidant and antimicrobial activities. The fermentation with L. plantarum RM1 enhanced the anti-hypertension and anticancer properties of the sea buckthorn juice and gained consumers’ sensorial overall acceptance.

Performance of Thermoplastic Extrusion, Germination, Fermentation, and Hydrolysis Techniques on Phenolic Compounds in Cereals and Pseudocereals

Bioactive compounds, such as phenolic compounds, are phytochemicals found in significant amounts in cereals and pseudocereals and are usually evaluated by spectrophotometric (UV-VIS), HPLC, and LC-MS techniques. However, their bioavailability in grains is quite limited. This restriction on bioavailability and bioaccessibility occurs because they are in conjugated polymeric forms. Additionally, they can be linked through chemical esterification and etherification to macro components. Techniques such as thermoplastic extrusion, germination, fermentation, and hydrolysis have been widely studied to release phenolic compounds in favor of their bioavailability and bioaccessibility, minimizing the loss of these thermosensitive components during processing. The increased availability of phenolic compounds increases the antioxidant capacity and favor their documented health promoting.

Microbial Bioconversion of Phenolic Compounds in Agro-industrial Wastes: A Review of Mechanisms and Effective Factors

Agro-industrial wastes have gained great attention as a possible source of bioactive compounds, which may be utilized in various industries including pharmaceutics, cosmetics, and food. The food processing industry creates a vast amount of waste which contains valuable compounds such as phenolics. Polyphenols can be found in soluble (extractable or free), conjugated, and insoluble-bound forms in various plant-based foods including fruits, vegetables, grains, nuts, and legumes. A substantial portion of phenolic compounds in agro-industrial wastes is present in the insoluble-bound form attached to the cell wall structural components and conjugated form which is covalently bound to sugar moieties. These bound phenolic compounds can be released from wastes by hydrolysis of the cell wall and glycosides by microbial enzymes. In addition, they can be converted into unique metabolites by methylation, carboxylation, sulfate conjugation, hydroxylation, and oxidation ability of microorganisms during fermentation. Enhancement of concentration and antioxidant activity of phenolic compounds and production of new metabolites from food wastes by microbial fermentation might be a promising way for better utilization of natural resources. This review provides an overview of mechanisms and factors affecting release and bioconversion of phenolic compounds in agro-industrial wastes by microbial fermentation.

Ameliorative and Antioxidative Potential of Lactobacillus plantarum-Fermented Oat (Avena sativa) and Fermented Oat Supplemented with Sidr Honey against Streptozotocin-Induced Type 2 Diabetes in Rats

The ameliorative and antioxidative stress effects of probiotic-enriched fermented oat (FOE) or fermented oat with honey (HFOE) extracts on streptozotocin-induced diabetes in rats were examined. The total phenolic content (TPC) and antioxidant activity (AOA) were increased in FOE and HFOE after 72 h of fermentation, and γ-aminobutyric acid (GABA) reached 7.35 mg 100 g-1 in FOE and 8.49 mg 100 g-1 in HFOE. The β-glucan levels were slightly decreased to 2.45 g 100 g-1 DW in FOE and 2.63 g 100 g-1 DW in HFOE. The antidiabetic and hypolipidemic properties of FOE and HFOE were studied in a designed animal model with seven treated groups for 6 weeks. Groups were treated as follows: group 1 (negative group, NR) and group 2 (diabetic rats, DR) were administered 7 mL distilled water orally per day; group 3 (DR + MET) rats were orally administered 50 mg standard drug Metformin kg-1 daily; group 4 (DR + FOE1) diabetic rats were orally administered 3.5 mL FOE daily; group 5 (DR + FOE2) rats were orally administered 7 mL FOE daily; group 6 (DR + HFOE1) rats were orally administered 3.5 mL HFOE daily; and group 7 (DR + HFOE2) rats were orally administered 7 mL HFOE daily. The HFOE at the high dose had a synergistic effect, lowering random blood glucose (RBG) and fasting blood glucose (FBG). The hypolipidemic potential of HFOE at the high dose was indicated by significant reductions in triglycerides (TG), total cholesterol (CHO), high- and low-density lipoproteins (HDL and LDL), and very-low-density lipoproteins (VLDL). In addition, 7 mL of HFOE improved liver and kidney function more effectively than other fermented extracts or Metformin. As well as the antioxidant enzyme activity, reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and malonaldehyde (MDA) were significantly enhanced after the administration of HFOE at 7 mL by 68.6%, 71.5%, 55.69%, and 15.98%, respectively, compared to the DR group. In conclusion, administration of L. plantarum-fermented oats supplemented with honey demonstrated antidiabetic effects and a potential approach for controlling glucose levels and lipid profiles, and protecting against oxidative stress.

Effect of Different Processing Methods on the Millet Polyphenols and Their Anti-diabetic Potential

Interest in polyphenols has grown due to their beneficial effect on diabetes attenuation. Millets are ancient crops that are rich in polyphenols and used for both food and feed. They are grown worldwide and are adapted to production under dry, hot conditions. The polyphenols found in millets have anti-diabetic properties. However, millet is usually consumed after being processed by heating, germination, fermentation, and other processing methods, which may alter polyphenol content and thus affect their anti-diabetic potential. This mini-review profiles the effects of different processing methods on millet polyphenols and how changes in millet polyphenols affect the hypoglycemic effect of millet. Future studies are needed to compare the anti-diabetes potential of millet polyphenols before and after processing and to explore ways to minimize polyphenol losses and thus maintain their hypoglycemic effect in final products.

HPTLC and FTIR Fingerprinting of Olive Leaves Extracts and ATR-FTIR Characterisation of Major Flavonoids and Polyphenolics

The aim of this study was to analyse the effect of spontaneous microbial maceration on the release and extraction of the flavonoids and phenolics from olive leaves. Bioprofiling based on thin-layer chromatography effect-directed detection followed by ATR-FTIR spectroscopy proved to be a reliable and convenient method for simultaneous comparison of the extracts. Results show that fermentation significantly enhances the extraction of phenolic compounds and flavonoids. The polyphenolic content was increased from 6.7 µg GAE (gallic acid equivalents) to 25.5 µg GAE, antioxidants from 10.3 µg GAE to 25.3 µg GAE, and flavonoid content from 42 µg RE (rutin equivalents) to 238 µg RE per 20 µL of extract. Increased antioxidant activity of fermented ethyl acetate extracts was attributed to the higher concentration of extracted flavonoids and phenolic terpenoids, while increased antioxidant activity in fermented ethanol extract was due to increased extraction of flavonoids as extraction of phenolic compounds was not improved. Lactic acid that is released during fermentation and glycine present in the olive leaves form a natural deep eutectic solvent (NADES) with significantly increased solubility for flavonoids.

Millet: A review of its nutritional and functional changes during processing

Millets are a major source of human food, and their production has been steadily increasing in the last decades to meet the dietary requirements of the increasing world population. Millets are an excellent source of all essential nutrients like protein, carbohydrates, fat, minerals, vitamins, and bioactive compounds. However, the nutrients, bioactive compounds, and functions of cereal grains can be influenced by the food preparation techniques such as decortication/dehulling, soaking, germination/malting, milling, fermentation, etc. This study discusses the nutritional and functional changes in millet during different traditional/modern processing techniques, based on more than 100 articles between 2013 and 2020 from Web of Science, Google Scholar, FAO, and USDA databases. Our results concluded that processing techniques could be useful to combat undernourishment and other health issues. Moreover, this review provides detailed information about millet processing, which is advantageous for industry, consumers, and researchers in this area.

Biliaderis C. Fermented Cereal-based Products: Nutritional Aspects, Possible Impact on Gut Microbiota and Health Implications

Fermentation, as a process to increase the security of food supply, represents an integral part of food culture development worldwide. Nowadays, in the evolving functional food era where new sophisticated technological tools are leading to significant transformations in the field of nutritional sciences and science-driven approaches for new product design, fermentation technology is brought to the forefront again since it provides a solid foundation for the development of safe food products with unique nutritional and functional attributes. Therefore, the objective of the present review is to summarize the most recent advances in the field of fermentation processes related to cereal-based products. More specifically, this paper addresses issues that are relevant to nutritional and health aspects, including their interrelation with intestinal (gut) microbiome diversity and function, although clinical trials and/or in vitro studies testing for cereal-based fermented products are still scarce.