Concentration and preservation of lactic acid bacteria (LAB) starter cultures for food production guarantee the long-term delivery of stable cultures in terms of viability and functional activity. One method that has commonly been used to prepare dried starter cultures for food applications is freeze-drying. During freeze-drying, the bacterial cells are exposed to stresses such as freezing, drying, and long-term exposure to low-water activity. Additionally, another added stress is introduced during the rehydration process. The purpose of this study was to evaluate the survival rates and fermentation performance of three (3) freeze-dried lactic acid bacterial cultures previously isolated from Ghanaian traditional fermented milk. LAB cultures, i.e., Lactobacillus delbrueckii, Lactococcus lactis and Leuconostoc mesenteroides were frozen in the chamber of a Telstar (Lyoquest) laboratory freeze dryer for 10 hrs at -55 °C (as single and combined cultures) using skimmed milk and cassava flour as cryoprotectants held in plastic or glass cryovial. For viability during storage, freeze-dried LAB cultures were stored in a refrigerator (4 °C) and at room temperature (25 °C) for 4-weeks. The survival of freeze-dried cultures was determined by growth kinetics at 600nm (OD₆₀₀). The performance of freeze-dried LAB cultures after 4-weeks storage was determined by their growth and acidification of milk during yogurt fermentation and consumer sensory evaluation of fermented milk using a 9-point hedonic scale. The survival rates for LAB ranged between 60.11% and 70.91% following freeze-drying. For single cultures, the highest survival was recorded for Lactobacillus delbrueckii (L12), whereas for combined cultures, the highest survival was observed for Lactococcus lactis (L3) combined with Lactobacillus delbrueckii (L12). During the fermentation process all the freeze-dried LAB cultures were able to acidify yogurt to a pH below 4, while yogurt produce from the spontaneous fermentation was characterized by low acidification. Yogurt fermented with freeze-dried lactic acid bacteria cultures, either single or combined strains, showed improved acceptability as compared to the spontaneously fermented yogurt. The consumer acceptability results showed that yogurts produced with combined starter culture of Lactoccus lactis and Lactobacillus delbrueckii or single culture of Lactococcus lactis were the most preferred products with Lactococcus lactis and Lactobacillus delbrueckii possessing high survival rates and high consumer acceptability in yogurt production. These findings are crucial and can be adopted for large-scale production and commercialization of yogurt production, however, in-depth investigation on the effects of freeze-drying and long-term storage on survival and performance of selected LAB cultures are needed.

Many dairy industries use their own starter cultures rather than Direct vat set culture because of their novelty and specific sensory characteristic it provides to their products. Starter culture rotation is not always possible, if the process involves the use of novel strains. The presence of bacteriophages in the environment leads to the quality instability of the product leads to the unexpected fermentation failure. In this context, a study of the prevalence of bacteriophages in the different sectors of dairy environment is carried out. The Screening of the phages has been undertaken with cheese and yoghurt cultures in the production and processing area. Three tests have been carried out to isolate the phages. Viz., turbidity test, double layer plaque assay, Spot test. Two natural temperate phages have been isolated from the cheese and yoghurt culture. Whereas the samples from the dairy processing environment is negative for phages. The temperate phages belong to the Siphoviridae family. Certain processing area where there is no involvement of starter culture e.g., paneer whey also showed the presence of phages in the whey, which indicates the air borne transmission of phages. Thus, the goal of this article is to make the quality assurance program associated with the production process of the fermented dairy products for the presence of phages in the dairy environment, with special emphasis on the preventive aspects related to this problem in the dairy fermentative industry.

Traditional grain vinegar is fermented using multiple acetic acid bacteria (AAB) at various temperatures. A single AAB showed high acid–producing ability at 30 °C with a 5% alcohol concentration and an initial pH adjusted to 4.0. Multiple AAB were similar to single AAB, but the optimal initial pH was 3.0. Acid production ability according to the type of AAB was higher in multiple AAB than that for single AAB. That is, using multiple AAB helped to increase the titratable acidity of traditional grain vinegar. In addition, increasing the titratable acidity and content of volatile flavor compounds was advantageous when two, rather than four, AAB types were mixed and used. Titratable acidity was high at medium temperatures (30 °C), but volatile flavor compounds increased at low temperatures (20 °C) under multiple AAB. A 16S rDNA–based microbiome taxonomic profiling analysis identified differences in beta diversity due to multiple AAB and fermentation temperatures. In particular, beta diversity analysis revealed a specific pattern when a mixture of Acetobacter ascedens GV–8 and Acetobacter pasteurianus GV–22 were fermented at low temperature (20 °C). Therefore, we propose the application of multiple AAB with acidic and flavor–producing properties in traditional grain vinegar.

The objective of the present study was to develop and optimize an efficient growth media for Lactobacillus delbrueckii ssp. bulgaricus, an essential dairy starter culture, uses plant-based nitrogen sources. The composition of the de Man, Rogosa, and Sharpe (MRS) culture medium was modified, and the nitrogen content was replaced by alternative nitrogen sources X-Seed N7 and N5 in various blends of 3% and 1.5%. Results showed that bacterial growth was higher with the N7 and N5 nitrogen source blends at 3% and 1.5%. Similarly, the optical densities of the L. bulgaricus strains were higher in the N7 and N5 blends (1.5/3%) compared to the MRS medium. Although there was no significance in bacterial counts for both the MRS and the N7 and N5 media, a significant difference between the control medium and the optimized growth media was noted. Our results thus suggest that the alternative nitrogen sources X-Seed N7 and N5 can substantially support the growth of lactic acid bacteria as shown with L. bulgaricus. Moreover, the presence of complex nitrogen sources rich in free nucleotides, amino acids, and peptides enhanced L. bulgaricus growth. Our results support the development of cost-effective and plant-based growth media for LAB cultures and potential benefits to the food and dairy industries. Additional research is warranted to improve buffering capacity for higher cell counts.

Arthrospira platensis, commercially known as Spirulina, is a fresh-water cyanobacterium that is gaining even more attention in the last years due to its high biological and nutritional value. For this reason, it has been employed in several food applications, to obtain or enhance functional and technological properties of cheese, yogurt, bread, cookies or pasta. The aim of this work was to evaluate the potential boosting effect of two different concentrations (0.25% and 0.50%) of Arthrospira platensis on the fermentation capability of several starter LAB strains, 1 probiotic and 4 commercial mix culture. These strains were used to ferment three different substrates and their fermentation behaviors were evaluated by impedance analyses together with rheological and color measurements. It was demonstrated that the booster effect took place, but it was variable and dependent not only on the strain or mix culture used, but also on the substrate and Arthrospira platensis concentration. Also, rheological and color modifications were found to be dependent of these factors.

The development trends of the modern world of power electronics dictate the requirements for the use of AC voltage converters as soft starters for induction motors. A direct connection of the motors to the mains voltage negatively affects both the motor itself and the mains system as a whole due to high starting currents values, which entail, as a rule, more frequent accidents and shorter the drive system service life. The paper presents a study of the control system of a multi-zone AC voltage regulator. The use of capacitive voltage dividers will also compensate for the consumed reactive power. The article analyzes the features of modern soft starters, describes the circuit design, presents a mathematical calculation by the method of algebraization of differential equations, a performed simulation modeling in Matlab/Simulink, and also an assembled experimental stand for further research. Particular attention is paid to the definition of the multizonality concept of the proposed converter and the analysis of the control method. The developed algorithm of the double-loop automatic control system will minimize the influence of induction motors on the mains voltage, and thus improve electromagnetic compatibility.

Whey is the main by-product of the dairy industry and contains sugars (lactose) and proteins (especially serum proteins and, at lesser extent, residual caseins), which can be valorized by the fermentative action of yeasts. In the present study, we characterized the spoilage yeast fraction inhabiting natural whey starter (NWS), the undefined starter culture of thermophilic lactic acid bacteria used in Parmigiano Reggiano (PR) cheesemaking, and evaluated thermotolerance, mating type, and the aptitude to produce ethanol and bioactive peptides from whey lactose and proteins, respectively, in a selected pool of strains. We found that PR NWS yeast population consists of other species (Saccharomyces cerevisiae, Wickerhamiella pararugosa, and Torulaspora delbrueckii) in addition to the well-documented Kluyveromyces marxianus, with multiple biotypes scored within each species. Haploid and diploid K. marxianus strains were identified through MAT genotyping, while thermotolerance assay allowed the selection of strains suitable to grow up to 48 °C. In whey fermentation assay, one thermotolerant strain was suitable to release ethanol with yield of 86.5%, while another candidate was able to produce the highest amounts of both ethanol and bioactive peptides with potentially anti-hypertensive function. The present work demonstrated that PR NWS is a reservoir of ethanol and bioactive peptides producer yeasts, which can be exploited to valorize whey, in agreement with the principles of circularity and sustainability.

Animal products, in particular dairy and fermented products, are natural, major sources of lactic acid bacteria (LAB). Due to their antimicrobial properties, LAB are used in humans and in animals, with beneficial effects, as probiotics or in the treatment of a variety of diseases. In livestock production, LAB contribute to animal performance, health, and productivity. In the food industry, LAB are applied as bioprotective and biopreservation agents, contributing to improve food safety and quality. However, some studies have described resistance to relevant antibiotics in LAB, with the concomitant risks associated to the transfer of antibiotic resistance genes to foodborne pathogens, their potential dissemination throughout the food chain, and the environment. Here, we summarize the application of LAB in livestock and animal products, as well as the health impact of LAB in animal food products. In general, the beneficial effects of LAB on the human food chain seem to outweigh the potential risks associated with their consumption as part of animal and human diets. However, further studies and continuous monitorization efforts are needed to ensure their safe application in animal products and in the control of pathogenic microorganisms, preventing the possible risks associated with antibiotic resistance and, thus, protecting public health.

This mini-review deals with some non-starter lactic acid bacteria (NSLAB) species with a controversial nature known to be both human and animal pathogens but also health-promoting and probiotic. The focus is put on Lactococcus garvieae, two Streptococcus species (Str. uberis and Str. parauberis), four Weissella species (W. hellenica, W. confusa, W. paramesenteroides and W. cibaria) and Mammalicoccus sciuri which worldwide are often found within the microbiotas of different kinds of cheese, mainly traditional artisanal ones made from raw milk and/or relying on environmental bacteria for their ripening. Based on literature data, their virulence and health-promoting effects are examined, and some of the mechanisms of these actions are investigated. Additionally, their possible roles in cheese ripening are also discussed. The analysis so far showed that, in general, the pathogenic and the beneficial strains, despite belonging to the same species, show pretty different genetic constitutions. Yet, when the safety of a given strain is assessed, genomic analysis on its own is not enough, and a polyphasic approach is needed including additional physiological and functional tests.