Synergistic effects of whey protein isolate and amorphous sucrose on improving the viability and stability of powdered Lactobacillus salivarius NRRL B-30514

A protectant for Lactobacillus rhamnosus based on whey protein isolate and isomalt: Stress resistance and underlying mechanisms

Probiotics are exposed to a variety of abiotic and biotic stresses during food fermentation and production, such as acidity, heat, osmolality, and oxidation, which affect their metabolic activity and efficiency. Therefore, it is essential to develop new protective agents to maintain the activity and stability of probiotics. This study introduces a new protectant, spray-dried whey protein isolate (WPI) and isomaltose (ISO). We evaluated the effects of four WPI-ISO ratios (1:0, 2:1, 1:1, 1:2) on the physical properties, including moisture content, water activity (aw), wettability, and glass transition temperature. In addition, we evaluated the environmental tolerance of Lactobacillus rhamnosus to different WPI-ISO ratios under thermal, storage, and simulated gastrointestinal conditions. The results showed that the moisture content (< 7 %) and water activity (< 0.3) of the protectant and probiotic powders met storage stability requirements. The moisture content, water activity, wettability index (WI), and glass transition temperature decreased significantly with the addition of isomalt, thereby improving the pressure resistance of L. rhamnosus through the synergistic effect of WPI and ISO. The WPI-ISO protectant not only improved the environmental tolerance and wettability of probiotics by reducing the moisture content and water activity but also significantly improved the survival rate of L. rhamnosus under various stress conditions such as high temperature and gastrointestinal environment. L. rhamnosus maintains good activity with a viable bacterial count of over 9 lg CFU/g after 90 days of storage, demonstrating effective protection against the environment stress. This study provides a promising new strategy to improve the stability of probiotics in the food industry.

Functional Cyperus esculentus L. Cookies Enriched with the Probiotic Strain Lacticaseibacillus rhamnosus SL42

This study presents for the first time functional cookies for diabetics made with 100% organic Cyperus esculentus L. flour, either plain or enhanced with 5% polyfloral honey syrup containing the probiotic strain Lacticaseibacillus rhamnosus SL42. The flour's chemical composition and rheological and functional properties were analyzed, and 33 diabetic and semi-naive panelists assessed the cookies' sensory properties. MRS-cys agar cultures and SEM analysis evaluated SL42 survival and adhesion capacity over 21 days at 25 °C. Results showed that the flour and its extracts are rich in polyphenols and flavonoids, indicating strong antioxidant and antibacterial properties. Both cookie types met international standards when compared to commercial cookies and had similar physical properties. Sensory evaluation on day 1 revealed higher quality indicators for honey syrup-enriched cookies, but after 15 days, control cookies were preferred. The CIE LAB analysis confirmed the dietetic flour's typical dark color, with honey syrup-enriched cookies being darker. Despite textural differences, both cookies maintained detectable crispness over storage. Honey syrup-enriched cookies effectively carried L. rhamnosus SL42, remaining viable at 6.43 Log CFU per cookie after 21 days and adhering to the cookie's surface, as confirmed by SEM analysis. Further research is recommended to better understand the therapeutic value of these cookies.

Drying of probiotics to enhance the viability during preparation, storage, food application, and digestion: A review

Functional food products containing viable probiotics have become increasingly popular and demand for probiotic ingredients that maintain viability and stability during processing, storage, and gastrointestinal digestions. This has resulted in heightened research and development of powdered probiotic ingredients. The aim of this review is to overview the development of dried probiotics from upstream identification to downstream applications in food. Free probiotic bacteria are susceptible to various environmental stresses during food processing, storage, and after ingestion, necessitating additional materials and processes to preserve their activity for delivery to the colon. Various classic and emerging thermal and nonthermal drying technologies are discussed for their efficiency in preparing dehydrated probiotics, and strategies for enhancing probiotic survival after dehydration are highlighted. Both the formulation and drying technology can influence the microbiological and physical properties of powdered probiotics that are to be characterized comprehensively with various techniques. Furthermore, quality control during probiotic manufacturing and strategies of incorporating powdered probiotics into liquid and solid food products are discussed. As emerging technologies, structure-design principles to encapsulate probiotics in engineered structures and protective materials with improved survivability are highlighted. Overall, this review provides insights into formulations and drying technologies required to supplement viable and stable probiotics into functional foods, ensuring the retention of their health benefits upon consumption.

Improving the viability of powdered Lactobacillus fermentum Lf01 with complex lyoprotectants by maintaining cell membrane integrity and regulating related genes

In this study, Lactobacillus fermentum Lf01, which was screened out in the early stage of the experiment, had better fermentation performance as the research objectives, and was prepared into powder by vacuum freeze-drying technology. We used response surface methodology to optimize the composition of the mixture used to protect powdered L. fermentum. Our data demonstrated that 10% skim milk, 12% sucrose, 0.767% tyrosine, and 2.033% sorbitol ensured the highest survival rate (92.7%) of L. fermentum. We have initially explored the potential mechanism of the complex protectants through the protection effect under the electron microscope, and the analysis methods of Fourier transform infrared spectroscopy and transcriptomics. The complex protectants could effectively maintain the permeability barrier and structural integrity of cell membrane and avoid the leakage of cell contents. Transcriptomic data have also indicated that the protective effect of the complex protectants on bacteria during freeze-drying was most likely achieved through the regulation of related genes. We identified 240 differential genes in the treatment group, including 231 up-regulated genes and 9 down-regulated genes. Gene ontology (GO) and Kyoto encyclopaedia of genes and genomes (KEGG) analyses of differential expression genes (DEGs) indicated that genes involved in amino acid metabolism, carbohydrate metabolism, membrane transport, fatty acid biosynthesis and cell growth were significantly up-regulated. These new results provided novel insights into the potential mechanism of lyoprotectants at the cellular level, morphological level, and gene level of the bacteria. PRACTICAL APPLICATIONS: In our study, a strain of Lactobacillus fermentum Lf01 with good fermentation performance was selected to be prepared into powder by freeze-drying technique. Bacterial cells were unavoidably damaged during the freeze-drying process. As a result, we investigated the protective effects on L. fermentum of ten distinct freeze-dried protectants and their mixtures. We were also attempting to explain the mechanism of action of the complex protectants at the cellular level, morphological level, and gene level of the bacteria. This presents very important theoretical and practical significance for the preservation of strains and the production of commercial direct-investment starter.