Microbial and Sensory Analysis of Soy and Cow Milk-Based Yogurt as a Probiotic Matrix for Lactobacillus rhamnosus GR-1

Multiphasic and mixture lactic acid bacteria screening approach for the removal of antinutrients and off-flavors present in a pea, oat and potato blend

The antinutrients and off-flavors present in plant-based foods are some of the major organoleptic and consumer acceptance drawbacks considered when developing plant-based fermented dairy alternatives (PBFDA). Here, we investigated a combination of genotypical and phenotypical consecutive screening methods to find out the optimal single- and combination of lactic acid bacteria (LAB) strains based on volatile off-flavors, phenolic acids, saponins, and trypsin inhibitor degradation through the fermentation of a pea, oat, and potato (POP) blend. Lactiplantibacillus plantarum strains were the most optimal for the partial/complete degradation of p-coumaric (>98 %) and ferulic acid (10-20 %) compounds in the POP blend. Leuconostoc pseudomesenteroides strains, and their PII-type proteinases were demonstrated to be effective degrading trypsin inhibitors. Also, specific Leuconostoc mesenteroides and L. plantarum strains achieved higher degradation rates of plant saponins such as avenacoside A (10-40 % degradation) and soyasaponin B (55-75 % degradation) present, correlated with their β-glucosidase activity (30-50 U/mL). Strict heterofermentative LABs such as Leuconostoc spp. strains were significantly better at removing hexanal, pentanal, benzaldehyde, and nonanal up to 85 % after 6 h. Finally, 384 combinations of 2 and 3 LAB selected strains (L. plantarum - L. mesenteroides - L. pseudomesenteroides) were tested at different strain-ratios, which demonstrated synergistic effects at degrading ferulic acid to more than 80 %, increasing acidification rates, and producing higher concentrations of diacetyl and acetoin (up to 3.28 and 28.13 µg/g sample) when L. pseudomesenteroides 1993 was included in the mix. This study demonstrated the potential of using unconventional plant-adapted LAB strains as starter cultures for the elimination of multiple unwanted compounds for the development of higher quality PBFDA without the use of conventional dairy-based LAB isolates. Finally, the screening approach could be used for microbial screening purposes throughout the development of starter cultures for plant-based yogurts, cheese, and other non-dairy fermented products.

The Quality and Flavor Changes of Different Soymilk and Milk Mixtures Fermented Products during Storage

This study explored the effects of two mixed fermentation methods: one was fermenting a soymilk and milk mixture by a lactic acid bacteria fermenting agent at 0.1 g/kg and 42 °C until the acidity was 70 °T, which was set as the MFSM method, and the other was fermenting milk alone by lactic acid bacteria at 42 °C for 12 h, placing it in a 4 °C refrigerator after acidification for 24 h and then mixing it with soymilk at a 1.5:1 ratio and storing the mixture at 4 °C, which was set as the SMFSM method. The quality and flavor of the soymilk and milk mixture products were investigated on the 0th, 15th and 30th days during storage. The changes in acidity, pH, number of viable bacteria, viscosity, water-holding capacity, texture, rheological properties, sensory quality and volatile flavors were determined. The results showed that compared with the fermented soymilk and milk mixtures under the MFSM method, the samples of fermented soymilk and milk mixtures under the SMFSM method showed a significant slowdown of acidification during storage, so that the sensory quality of the products was almost unaffected by acidity on the 30th day of storage. Furthermore, the number of viable bacteria was greater than 7 log cfu/mL. The water holding capacity did not change significantly until the 30th day. There was also no whey precipitation, indicating good stability. The samples in SMFSM mode had higher aromatic contents and beans during storage than the fermented soymilk and milk mixtures in MFSM mode. The rich variety of volatile flavors and the presence of acetoin, 2-heptanone, and (E,E)-3,5-octadien-2-one throughout the storage period allowed the samples to maintain a good sensory flavor during storage.

The roles of brewers' spent grain derivatives in coconut-based yogurt-alternatives: Microstructural characteristic and the evaluation of physico-chemical properties during the storage

Water soluble coconut extract (WSCE) was reported as a suitable matrix for probiotic delivery as yogurt alternatives. The study aimed to evaluate the roles of brewers' spent grain (BSG) derivatives in enhancing the properties of WSCE-based yogurt alternatives. BSG flour (BSGF) and 3 different protein extracts (BSGPs) including protein control (BSGP-C), protamex treatment (BSGP-P), and protamex combined with flavourzyme treatment (BSGP-PF) were incorporated in WSCE-based yogurt alternatives. Confocal laser scanning microscopy showed that BSGPs prepared with protease treatment generated less dense fat distribution and more homogenous globules compared to that in WSCE control yogurt. It also resulted in a softer, denser and more homogenous matrix. The modification in microstructural properties was aligned with differences in several functional groups including ⍺-glycosidic bond and hydroxyl groups from polysaccharides, aliphatic ethers and acid functional groups as well as aromatic hydrocarbons of lignin, amide I, acetyl groups and amide III. BSGF and BSGPs increased the mechanical properties, viscosity and modified flow behaviour properties demonstrating its ability in maintaining textural and gel formation. After 14 days of storage, maintenance in flow behaviour, syneresis and mechanical properties was identified. Furthermore, BSG derivatives enhanced lactic acid production up to 3 folds. In conclusion, BSG derivatives maintained the microstructure and gel formation, improved the properties of WSCE-based yogurt alternatives and preserved its behaviour during 14 days of storage.

Development of Probiotic Almond Beverage Using Lacticaseibacillus rhamnosus GR-1 Fortified with Short-Chain and Long-Chain Inulin Fibre

Plant-based beverages are growing in popularity due to the rise of vegetarianism and other health trends. A probiotic almond beverage that combines the properties of almonds, inulin, and Lacticaseibacillusrhamnosus GR-1 may meet the demand for a non-dairy health-promoting food. The purpose of this study was to investigate the viability of L. rhamnosus GR-1 and pH in five fermented almond beverage samples, supplemented with either 2% or 5% (w/v) short-chain or long-chain inulin over 9 h of fermentation and 30 days of refrigerated storage. All almond beverage samples achieved a mean viable count of at least 107 CFU/mL during 9h of fermentation and 30 days of refrigerated storage. The probiotic almond beverage supplemented with 2% (w/v) short-chain inulin had a significantly higher mean microbial count (p = 0.048) and lower pH (p < 0.001) throughout fermentation, while the control and the long-chain inulin treatments had the lowest viable counts and acidity, respectively. This study shows that the addition of short-chain and long-chain inulin had no adverse effects on the viability of L. rhamnosus GR-1. Therefore, the probiotic almond beverage has the potential to be a valid alternative to dairy-based probiotic products.