Physicochemical property changes and aroma differences of fermented yellow pea flours: role of Lactobacilli and fermentation time

Exploring the flavor changes in mung bean flour through Lactobacillus fermentation: insights from volatile compounds and non-targeted metabolomics analysis

BACKGROUND

Mung beans are highly nutritious but their leguminous flavor limits their development. Lactic acid bacteria (LAB) fermentation can decrease unwanted bean flavors in legumes and enhance their flavor. This study examined the influence of Lactobacillus fermentation on the flavor characteristics of mung bean flour (MBF) using volatile compounds and non-targeted metabolomics.

RESULTS

Lactobacillus plantarum LP90, Lactobacillus casei LC89, and Lactobacillus acidophilus LA85 eliminated 61.37%, 48.29%, and 43.73%, respectively, of the primary bean odor aldehydes from MBF. The relative odor activity value (ROAV) results showed that fermented mung bean flour (FMBF) included volatile chemicals that contributed to fruity, flowery, and milky aromas. These compounds included ethyl acetate, hexyl formate, 3-hydroxy-2-butanone, and 2,3-butanedione. The levels of amino acids with a fresh sweet flavor increased significantly by 93.89, 49.40, and 35.27% in LP90, LC89, and LA85, respectively. A total of 49 up-regulated and 13 down-regulated significantly differential metabolites were annotated, and ten metabolic pathways were screened for contributing to the flavor. The correlation between important volatile compounds and non-volatile substances relies on two primary metabolic pathways: the citric acid cycle pathway and the amino acid metabolic system.

CONCLUSION

The flavor of MBF was enhanced strongly by the process of Lactobacillus fermentation, with LP90 having the most notable impact. These results serve as a reference for identifying the flavor of FMBF. © 2024 Society of Chemical Industry.

Reduction of Beany Flavor and Improvement of Nutritional Quality in Fermented Pea Milk: Based on Novel Bifidobacterium animalis subsp. lactis 80

Peas (Pisum sativum L.) serve as a significant source of plant-based protein, garnering consumer attention due to their high nutritional value and non-GMO modified nature; however, the beany flavor limits its applicability. In this study, the effects of Bifidobacterium animalis subsp. Lactis 80 (Bla80) fermentation on the physicochemical characteristics, particle size distribution, rheological properties, and volatile flavor compounds of pea milk was investigated. After fermentation by Bla80, the pH of pea milk decreased from 6.64 ± 0.01 to 5.14 ± 0.01, and the (D4,3) distribution decreased from 142.4 ± 0.47 μm to 122.7 ± 0.55 μm. In addition, Lactic acid bacteria (LAB) fermentation significantly reduced the particle size distribution of pea milk, which was conducive to improving the taste of pea milk and also indicated that Bla80 had the probiotic potential of utilizing pea milk as a fermentation substrate. According to GC-MS analysis, 64 volatile compounds were identified in fermented pea milk and included aldehydes, alcohols, esters, ketones, acids, and furans. Specifically, aldehydes in treated samples decreased by 27.36% compared to untreated samples, while esters, ketones, and alcohols increased by 11.07%, 10.96%, and 5.19%, respectively. These results demonstrated that Bla80 fermentation can significantly decrease the unpleasant beany flavor, such as aldehydes and furans, and increase fruity or floral aromas in treated pea milk. Therefore, Bla80 fermentation provides a new method to improve physicochemical properties and consumer acceptance of fermented pea milk, eliminating undesirable aromas for the application of pea lactic acid bacteria beverage.

Legume protein fermented by lactic acid bacteria: Specific enzymatic hydrolysis, protein composition, structure, and functional properties

In recent years, with increasing emphasis on healthy, green, and sustainable consumption concepts, plant-based foods have gained popularity among consumers. As widely sourced plant-based raw materials, legume proteins are considered sustainable and renewable alternatives to animal proteins. However, legume proteins have limited functional properties, which hinder their application in food products. LAB fermentation is a relatively natural processing method that is safer than chemical/physical modification methods and can enrich the functional properties of legume proteins through biodegradation and modification. Therefore, changes in legume protein composition, structure, and functional properties and their related mechanisms during LAB fermentation are described. In addition, the specific enzymatic hydrolysis mechanisms of different LAB proteolytic systems on legume proteins are also focused in this review. The unique proteolytic systems of different LAB induce specific enzymatic hydrolysis of legume proteins, resulting in the production of hydrolysates with diverse functional properties, including solubility, emulsibility, gelability, and foamability, which are determined by the composition (peptide/amino acid) and structure (secondary/tertiary) of legume proteins after LAB fermentation. The correlation between LAB-specific enzymatic hydrolysis, protein composition and structure, and protein functional properties will assist in selecting legume protein raw materials and LAB strains for legume plant-based food products and expand the application of legume proteins in the food industry.

Effects of Fermentation with Tetragenococcus halophilus and Zygosaccharomyces rouxii on the Volatile Profiles of Soybean Protein Hydrolysates

The effects of fermentation with lactic acid bacteria (LAB) and yeast on the aroma of samples were analyzed in this work. The volatile features of different soybean hydrolysates were investigated using both GC-MS and GC-IMS. Only 47 volatile flavor compounds (VFCs) were detected when using GC-IMS, while a combination of GC-MS and GC-IMS resulted in the identification of 150 compounds. LAB-yeast fermentation could significantly increase the diversity and concentrations of VFCs (p < 0.05), including alcohols, acids, esters, and sulfurs, while reduce the contents of aldehydes and ketones. Hierarchical clustering and orthogonal partial least squares analyses confirmed the impact of fermentation on the VFCs of the hydrolysates. Seven compounds were identified as significant compounds distinguishing the aromas of different groups. The partial least squares regression analysis of the 25 key VFCs (ROAV > 1) and sensory results revealed that the treatment groups positively correlated with aromatic, caramel, sour, overall aroma, and most of the key VFCs. In summary, fermentation effectively reduced the fatty and bean-like flavors of soybean hydrolysates, enhancing the overall flavor quality, with sequential inoculation proving to be more effective than simultaneous inoculation. These findings provided a theoretical basis for improving and assessing the flavor of soybean protein hydrolysates.

Protein composition and nutritional aspects of pea protein fractions obtained by a modified isoelectric precipitation method using fermentation

Pea albumins are promising for their nutritional, biological, and techno-functional properties. However, this fraction is usually discarded in the industry due to its low protein content compared to globulin fraction and the presence of some anti-nutritional compounds. In the present study, we used an alternative method of pea protein extraction based on alkaline solubilization/isoelectric precipitation in which the reduction of pH was achieved by lactic acid fermentation using specific starters instead of mineral acids. Hence, the main objective of this study was to examine the protein profile and the content of anti-nutritional and nutritional active compounds in pea albumin-rich fractions obtained by the isoelectric extraction method without (control) or with fermentation with different lactic acid bacteria (Streptococcus thermophilus, Lactiplantibacillus plantarum, and their co-culture). Different pea cultivars (Cartouche, Ascension, and Assas) were used here for their differences in protein profile. The results revealed a higher total nitrogen content in albumin-rich fraction for fermented samples and, in particular, for co-culture. The majority of total nitrogen was determined as non-protein (~50%), suggesting the degradation of proteins by LAB to small peptides and amino acids, which were solubilized in the soluble fraction (albumin) as confirmed by size exclusion chromatography (SEC-HPLC) analysis. Moreover, the higher antioxidant activity of fermented albumin samples was attributed to the production of small peptides during extraction. Lactic acid fermentation also resulted in a significant reduction of trypsin inhibitor activity, α-galactoside, and phytic acid content of this fraction compared to control.

Yellow Field Pea Protein (Pisum sativum L.): Extraction Technologies, Functionalities, and Applications

Yellow field peas (Pisum sativum L.) hold significant value for producers, researchers, and ingredient manufacturers due to their wealthy composition of protein, starch, and micronutrients. The protein quality in peas is influenced by both intrinsic factors like amino acid composition and spatial conformations and extrinsic factors including growth and processing conditions. The existing literature substantiates that the structural modulation and optimization of functional, organoleptic, and nutritional attributes of pea proteins can be obtained through a combination of chemical, physical, and enzymatic approaches, resulting in superior protein ingredients. This review underscores recent methodologies in pea protein extraction aimed at enhancing yield and functionality for diverse food systems and also delineates existing research gaps related to mitigating off-flavor issues in pea proteins. A comprehensive examination of conventional dry and wet methods is provided, in conjunction with environmentally friendly approaches like ultrafiltration and enzyme-assisted techniques. Additionally, the innovative application of hydrodynamic cavitation technology in protein extraction is explored, focusing on its prospective role in flavor amelioration. This overview offers a nuanced understanding of the advancements in pea protein extraction methods, catering to the interests of varied stakeholders in the field.

Elucidating the effects of Lactobacillus plantarum fermentation on the aroma profiles of pasteurized litchi juice using multi-scale molecular sensory science

Three Lactobacillus Plantarum (LP), namely LP28, LP226 and LPC2W, were employed to investigate the effect on the aroma profiles of pasteurized litchi juice using E-nose, GC-IMS, GC-MS, and sensory evaluation. The E-nose results showed that pasteurization weakened the flavor profile of litchi juice, while LP fermentation effectively promoted flavor formation. The GC-MS analysis demonstrated that pasteurization significantly reduced the content of alcohols (28.51%), especially geraniol and citronellol, which give litchi juices a fruity and floral aroma. Different LP fermentation enhances the characteristic aroma and produces some new compounds that give it a strong fruity and citrus-like aroma. Moreover, 37 aroma-active compounds (OAV>1) indicated that the linalool (OAV 7504) was the highest, followed by (Z)-rose oxide (OAV 4265), 1-octen-3-ol (OAV 1055) and geraniol (OAV 764), which jointly form the main characteristic flavor. More esters were identified by GC-IMS, indicating the advantage of the combined approach for a better understanding of the impact of pasteurization and fermentation on the litchi juice. The sensory evaluation confirmed that the aroma attributes of fruity, citrus-like, floral, sweet and litchi-like were stronger for the samples fermented by LP28 than those for the other samples. The combination strategy used in this study would facilitate the awareness of litchi juice aroma and broaden our insight into the deep processing of litchi.

Effect of Bioprocessing on Techno-Functional Properties of Climate-Resilient African Crops, Sorghum and Cowpea

Sorghum and cowpea are very compatible for intercropping in hot and dry environments, and they also have complementary nutritional compositions. Thus, the crops have the potential to improve food security in regions threatened by climate change. The aim of this study was to investigate different enzymes (carbohydrate-degrading, proteases and phytases) and lactic acid bacteria (LAB) fermentation to improve the techno-functional properties of sorghum and cowpea flours. Results show that sorghum carbohydrates were very resistant to hydrolysis induced by bioprocessing treatments. Most of the protease treatments resulted in low or moderate protein solubilization (from ca. 6.5% to 10%) in sorghum, while the pH adjustment to 8 followed by alkaline protease increased solubility to 40%. With cowpea, protease treatment combined with carbohydrate-degrading enzymes increased the solubility of proteins from 37% up to 61%. With regard to the techno-functional properties, LAB and amylase treatment decreased the sorghum peak paste viscosities (from 504 to 370 and 325 cPa, respectively), while LAB and chemical acidification increased cowpea viscosity (from 282 to 366 and 468 cPa, respectively). When the bioprocessed sorghum and cowpea were tested in breadmaking, only moderate effects were observed, suggesting that the modifications by enzymes and fermentation were not strong enough to improve breadmaking.

Effects of Alkali Stress on the Growth and Menaquinone-7 Metabolism of Bacillus subtilis natto

Menaquinone-7 (MK-7) is an important vitamin K₂, synthesized from the menaquinone parent ring and seven isoprene side chains. Presently, the synthesis of MK-7 stimulated by environmental stress primarily focuses on oxygen stress, while the effect of alkali stress is rarely studied. Therefore, this study researched the effects of alkali stress on the fermentation performance and gene expression of Bacillus subtilis natto. The organism’s growth characteristics, biomass, sporogenesis, MK-7 biosynthesis, and gene expression were analyzed. After a pH 8.5 stress adaptation treatment for 0.5 h and subsequent fermentation at pH 8.5, which promoted the growth of the strain and inhibited the spore formation rate. In addition, biomass was significantly increased (P < 0.05). The conversion rate of glycerol to MK-7 was 1.68 times higher than that of the control group, and the yield of MK-7 increased to 2.10 times. Transcriptomic analysis showed that the MK-7 high-yielding strain had enhanced carbon source utilization, increased glycerol and pyruvate metabolism, enhanced the Embden-Meyerhof pathway (EMP), tricarboxylic acid (TCA) circulation flux, and terpenoid biosynthesis pathway, and promoted the accumulation of acetyl-CoA, the side-chain precursor of isoprene. At the same time, the up-regulation of transketolase increased the metabolic flux of the pentose phosphate (HMP) pathway, which was conducive to the accumulation of D-erythrose 4-phosphate, the precursor of the menadione parent ring. This study’s results contribute to a better understanding of the effects of environmental stress on MK-7 fermentation by Bacillus subtilis natto and the molecular regulatory mechanism of MK-7 biosynthesis.

Potential of Microorganisms to Decrease the "Beany" Off-Flavor: A Review

Vegetable proteins are in high demand due to current issues surrounding meat consumption and changes in eating habits, but they are still not accepted by consumers due to their strong bitterness, astringent taste, and "beany" off-flavor. This review aimed to give an overview of the "beany" off-flavor and the potential of microorganisms to decrease it. Twenty-six volatile compounds were identified from the literature as contributing to the "beany" off-flavor, and their formation pathways were identified in a legume matrix, pea. Biotechnological ways to improve the flavor by reducing these volatile compounds were then looked over. As aldehydes and ketones are the main type of compounds directly linked to the "beany" off-flavor, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) were focused on. By converting aldehyde and ketones into alcohols or carboxylic acids, these two enzymes have the potential to decrease the off-flavor. The presence of the two enzymes in a selection of microorganisms (Lactobacillus acidophilus, Limosilactobacillus fermentum, Lactiplantibacillus plantarum, Streptococcus thermophilus, Saccharomyces cerevisiae, and Gluconobacter suboxydans) was done with a catabolism and a bioinformatical study. Finally, the correlation between the presence of the enzyme and the efficacy to improve the flavor was investigated by comparison with the literature. The presence of ADH and/or ALDH in the strain metabolism seems linked to an odor improvement. Especially, a constitutive enzyme (ADH or ALDH) in the catabolism should give better results, showing that some fermentative types are more inclined to better the flavor. Obligatory fermentative strains, with a constitutive ADH, or acetic acid bacteria, with constitutive ADH and ALDH, show the best results and should be favored to reduce the amount of compounds involved in the "beany" off-flavor and diminish that off-flavor in legume proteins.

Aroma of peas, its constituents and reduction strategies - Effects from breeding to processing

Peas as an alternative protein source have attracted a great deal of interest from the food industry and consumers in recent years. However, pea proteins usually do not taste neutral and exhibit a distinct flavor, often characterized as "beany". This is usually contrasted by the food industry's desire for sensory neutral protein sources. In this review, we highlight the current state of knowledge about the aroma of peas and its changes along the pea value chain. Possible causes and origins, and approaches to reduce or eliminate the aroma constituents are presented. Fermentative methods were identified as interesting to mitigate undesirable off-flavors. Major potential has also been discussed for breeding, as there appears to be a considerable leverage at this point in the value chain: a reduction of plant-derived flavors, precursors, or substrates involved in off-flavor evolution could prevent the need for expensive removal later.