Impact of Air-Drying Temperature on Antioxidant Properties and ACE-Inhibiting Activity of Fungal Fermented Lentil Flour

Screening of the effect of new food prototypes based on fermented lentil and quinoa flours on the colonic microbiota of older adults through a static in vitro colonic fermentation model

In view of the increasing demand for plant-based protein alternatives, along with the increased protein requirements of older adults, the formulation of new food concepts based on protein-rich ingredients from legumes or pseudo-cereals seems a promising approach. Previous studies have found that solid-state fermentation can improve the nutritional value and digestibility of plant-based commodities; however, scarce evidence exists regarding the effect on prebiotic potential. This study aimed to compare the effect of fermented and unfermented quinoa and lentil flours on the colonic microbiota, as well as that of new food prototypes (gels and breads) made with the flours. After simulating static colonic fermentation of the substrates by using a pool faecal inoculum obtained from four older adults, the microbiota composition (16S rRNA gene sequencing) and short-chain fatty acids (SCFA, gas chromatography GC-FID) were determined. The results showed statistically significant changes in the microbiota at the genus taxonomic level in the range of -5.8% to +17.6% relative abundance. Common findings in all experiments were increased Bacteroides, Acidaminococcus and Parabacteroides and decreased Asteroleplasma, Oscillospiraceae UCG-002 group and Alistipes, as well as increased SCFA production. Overall, the food matrix (flour, gel or bread) was the variable that most affected the changes in the microbiota composition and diversity, while the impact of fermentation of the lentils or quinoa was not statistically significant for most cases. Concretely, the gel-like prototypes produced the most beneficial changes in microbiota composition, while the bread-like formulations were more favourable for increased SCFA and decreased bSCFA production. In conclusion, new food prototypes based on lentil and quinoa flour could have beneficial prebiotic potential. However, few additional advantages were observed from previous solid-state fermentation for obtaining the fermented lentils and quinoa flour.

Mechanical Properties and In Vitro Digestibility of Fermented Lentil and Quinoa Flour Food Prototypes for Older Adults

Background/Objectives: The increase in the older adult population worldwide and the need to switch to vegetal-origin protein consumption for environmental sustainability point to legumes and pseudocereals as alternative ingredients in new food formulations. This study aimed to assess the impact of food structure and fungal fermentation on the digestibility of new food prototypes made with quinoa and/or lentil flours addressed to older adults. Methods: Four gels and six breads were elaborated and subjected to mechanical analysis and simulated gastrointestinal in vitro digestion. Then, proteolysis, lipolysis, and amylolysis were analysed. Results: Gels made with fermented quinoa or lentil flours exhibited less hardness and required less force, suggesting better adequacy for mastication. In terms of digestibility, using fermented flours led to increased proteolysis and reduced starch hydrolysis. Conclusions: Our results support future studies in the field aimed at supplying older adults with adapted foods to satisfy their nutritional needs to prevent sarcopenia and other health issues.

In vitro digestibility and angiotensin converting enzyme (ACE) inhibitory activity of solid-state fermented fava beans (Vicia faba L.)

Reducing the content of quickly absorbed carbohydrates and saturated fats in snack formulations while increasing the consumption of high-quality proteins are effective strategies to prevent obesity in childhood. Thus, the nutritional value, digestibility, and functionality of fava beans (Vicia faba L.) fermented with Pleurotus ostreatus were examined as potential ingredients for food design. Solid-state fermentation enhanced the protein content by 16% with a rise in essential (25%) and non-essential (15%) amino acids while decreasing total carbohydrate content and tannin levels. Moreover, fermentation modified the amino acid profile released during digestion, increasing amino acids such as valine, isoleucine, and threonine, which are vital for health and development in childhood. Furthermore, the bioaccessible fraction of the fermented bean showed a 60% of ACE inhibition and improved magnesium bioaccessibility. Consequently, fava beans fermented with Pleurotus ostreatus emerged as a new ingredient in the development of new protein-rich snacks tailored for children and adolescents.

Impact of Fava Bean (Vicia faba) Processing on Quality Characteristics and Digestibility of a Protein-Rich Snack

The impact of fava bean processing methods (soaking, autoclaving, fermentation) on a legume-based bars' quality, protein characteristics, and digestibility was shown. The antioxidant and the angiotensin-converting enzyme-inhibitory capacity before and after in vitro digestion were investigated to reveal the potential advantages of fava bean usage for snacks. All bars have demonstrated high protein content, varying from 22.1 to 25.1 g/100 g DB. Based on the fermented fava beans of Pleurotus ostreatus, the samples were characterized by a higher concentration of essential amino acids by 8.6% and a reduction of tannins by 18.5% compared with bars based on soaked fava beans. Sensory evaluation improved the color, texture, and overall acceptability of the bars with fermented legumes. Various types of bean processing did not significantly affect the protein digestibility of the bars. The fermentation method positively affected the angiotensin-converting enzyme-inhibitory properties of bars and increased by 16.5% (before digestion) and 15% (after digestion) compared with other samples. After digestion, samples were characterized by a high level of Fe bioaccessibility (100, 83, and 79% for the bars based on soaked, autoclaved, and fermented fava beans, respectively) and increased total phenolic content. These findings highlight the potential health benefits of fava bean usage for snack products.

Protein digestibility and ACE inhibitory activity of fermented flours in older adults and standard gastrointestinal simulation

Consumption of essential amino acids responsible for muscle protein synthesis is important in preventing sarcopenia among older individuals. This population may experience gastrointestinal disorders that inhibit protein digestibility, making it crucial to address. Therefore, solid-state fermentation (SSF) using Pleurotus ostreatus and air drying has been suggested as a means of improving the protein digestibility of lentils and quinoa. SSF combined with air drying at 70 °C resulted in a slight increase in protein hydrolysis compared to unfermented samples. SSF was found to boost the proportion of small peptides to 35 %. Following digestion, SSF and drying yielded bioactive peptides of 1400 and 450 Da, with a range of 11 % to 28 %, respectively, and peptides < 190 Da making up 60 % of the total. SSF promoted valine, leucine, and isoleucine generation; however, hot air drying reduced free amino acids due to the amino acid-reducing sugar bonding but was never lower than the initial content of its unfermented counterpart. Furthermore, SSF and drying at 70 °C improved the release of hydrophobic amino acids (>70 mg/g dry basis) and negatively charged amino acids (>20 mg/g dry basis) in lentils during digestion. The SSF samples exhibited lower angiotensin converting enzyme (ACE) inhibitory activity, ≤35 %, compared to unfermented flours after digestion. However, the ACE inhibitory activity increased in SSF-dried samples, in part because of melanoidins generated during drying. Finally, lower values of protein digestibility and thus smaller peptides, amino acid profile, and ACE inhibitory activity of fermented flours were found in the older adult digestion model.

Flours from fermented lentil and quinoa grains as ingredients with new techno-functional properties

The need to provide novel, nutritious plant-based products requires seeking high-value, sustainable protein sources, like quinoa and lentils, having an increased digestibility and lacking antinutrients. Fungal fermentation has evidenced enhanced nutritional value of flours obtained from these grains. However, research into techno-functional properties, essential to the new product development, is lacking. This study investigated the techno-functional properties of flours made from lentil and quinoa after fermenting them with Pleurotus ostreatus and subjecting them to two drying techniques (lyophilisation and hot air drying). In both cases, the fermentation led to noteworthy improvements in swelling and water holding capacity, especially in those lyophilised than those dried. In contrast, the emulsifying, foaming, thickening, and gelling capacities decreased significantly. The loss of abilities was more severe for dried grains than for lyophilized ones. The thermomechanical analysis of the fermented flours showed lower thickening and gelling potential compared to untreated flours. Microscopy images revealed that the state and structure of starch granules were affected by both fermentation and drying processes. Starch granules in lentils were partly pre-gelatinised and trapped in the cotyledon cell, resulting in limited thickening and gelling abilities. In contrast, in quinoa, starch underwent pre-gelatinisation and retrogradation during the fermentation process, promoting the production of resistant starch and increasing fibre content. This study presents the potential of treated flours as ingredients possessing unique attributes compared to protein and fibre-rich conventional products.

Volatile profile of quinoa and lentil flour under fungal fermentation and drying

Solid-state fermentation reportedly improves the nutritional and sensory properties of legumes and pseudocereals. This study examined changes in the volatile profile using HS-SPME-GC-MS of two varieties of lentil and quinoa flour fermented with Pleurotus ostreatus and dried using hot-air drying and lyophilisation. Fermentation significantly increased the volatile profile. Pardina lentil flour showed a 570% increase in its volatile profile, and 10 compounds were created. In white quinoa, the total area rose from 96 to 4500, and 30 compounds were created. Compounds such as 1-octen-3-ol, benzaldehyde, 3-octanone and hexanal were generated during fermentation, providing a sweet, grassy, cocoa flavour. Hot-air drying led to decrease of over 40% in total peak area. Dried fermented flour retained higher levels of compounds that provide a sweet, cocoa aroma. Air-drying temperature had no significant influence on the volatile profile. This a allows the inclusion of these flours in a wide variety of food products.

In Vitro Digestion Assessment (Standard vs. Older Adult Model) on Antioxidant Properties and Mineral Bioaccessibility of Fermented Dried Lentils and Quinoa

The growing number of older adults necessitates tailored food options that accommodate the specific diseases and nutritional deficiencies linked with ageing. This study aims to investigate the influence of age-related digestive conditions in vitro on the phenolic profile, antioxidant activity, and bioaccessibility of minerals (Ca, Fe, and Mg) in two types of unfermented, fermented, and fermented dried quinoa and lentils. Solid-state fermentation, combined with drying at 70 °C, significantly boosted the total phenolic content in Castellana and Pardina lentils from 5.05 and 6.6 to 10.5 and 7.5 mg gallic acid/g dry weight, respectively, in the bioaccessible fraction following the standard digestion model, compared to the unfermented samples. The phenolic profile post-digestion revealed elevated levels of vanillic and caffeic acids in Castellana lentils, and vanillic acid in Pardina lentils, while caffeic acids in Castellana lentils were not detected in the bioaccessible fraction. The highest antioxidant potency composite index was observed in digested fermented dried Castellana lentils, with white quinoa samples exhibiting potency above 80%. Mineral bioaccessibility was greater in fermented and fermented dried samples compared to unfermented ones. Finally, the digestive changes that occur with ageing did not significantly affect mineral bioaccessibility, but compromised the phenolic profile and antioxidant activity.