Reduction in Biogenic Amine Content in Baechu (Napa Cabbage) Kimchi by Biogenic Amine-Degrading Lactic Acid Bacteria

This study was performed to mine biogenic amine (BA)-degrading lactic acid bacteria (LAB) from kimchi and to investigate the effects of the LAB strains on BA reduction in Baechu kimchi fermentation. Among 1448 LAB strains isolated from various kimchi varieties, five strains capable of considerably degrading histamine and/or tyramine were selected through in vitro tests and identified as Levilactobacillus brevis PK08, Lactiplantibacillus pentosus PK05, Leuconostoc mesenteroides YM20, L. plantarum KD15, and Latilactobacillus sakei YM21. The selected strains were used to ferment five groups of Baechu kimchi, respectively. The LB group inoculated with L. brevis PK08 showed the highest reduction in tyramine content, 66.65% and 81.89%, compared to the control group and the positive control group, respectively. Other BA content was also considerably reduced, by 3.76–89.26% (five BAs) and 7.87–23.27% (four BAs), compared to the two control groups, respectively. The other inoculated groups showed similar or less BA reduction than the LB group. Meanwhile, a multicopper oxidase gene was detected in L. brevis PK08 when pursuing the BA degradation mechanism. Consequently, L. brevis PK08 could be applied to kimchi fermentation as a starter or protective culture to improve the BA-related safety of kimchi where prolific tyramine-producing LAB strains are present.

Effect of Novel Bacteriocinogenic Lactobacillus fermentum BZ532 on Microbiological Shelf-Life and Physicochemical and Organoleptic Properties of Fresh Home-Made Bozai

Bacteriocinogenic Lactobacillus fermentum BZ532 with novel bacteriocin LF-BZ532 was originally isolated from Chinese cereal fermented drink, showing an antimicrobial characteristic during fermentation. This study aimed to explore the in situ antimicrobial activities of L. fermentum BZ532 and co-culturing investigation against key food pathogens, i.e., Staphylococcus aureus and Escherichia coli K-12, was conducted during fresh bozai production. The growth of spoilage bacteria was suppressed and bacterial count was reduced to a significantly low level during 48 h of co-cultures. In situ production of antimicrobial compounds expressed positive activity against S. aureus and E. coli K-12, but negative acitivity against Salmonella sp. D104. The total viable count of bozai BZ-Lf (bozai fermented with BZ532 strain) had a comparatively lower viable count than bozai BZ-C (bozai as an experimental control without BZ532) during storage of 7 days. Titratable acidity of bozai treatments (BZ-C, BZ-Lf) was increased, while pH declined accordingly during storage of 7 days. The organoleptic quality of bozai BZ-C had low sensorial scores as compared with BZ-Lf during storage. In comparison with naturally fermented bozai (BZ-C), L. fermentum BZ532 (BZ-Lf) could significantly reduce the microbial spoilage and extend the shelf-life based on microbiological examination. Conclusively, L. fermentum BZ532 can be used as a bio-protective culture for improving the safety of bozai.

Application of Natural Antimicrobial Additives and Protective Culture to Control Aerobic Spore Forming Bacteria in Low Salt Soft Cheese

There is an increasing interest in the application of natural antimicrobials instead of chemical ones to enhance the microbiological quality of dairy products. The objective of this study was to assess the effect of some natural antimicrobial additives and protective culture for reducing the usage of chemical preservatives, shelf-life extension, retarding microbial spoilage in low-salt soft cheese. The antimicrobial agents (protective culture, nisin, lysozyme, and natamycin) were studied on the activity of 28 isolates of spore-forming bacteria. Inhibitory effect of different natural antimicrobial additives as protective culture (Lactobacillus rhamnosus, 40 mg kg -1), nisin (25 mg kg -1), lysozyme (100 mg kg -1), combination of nisin and lysozyme (25 mg kg -1/100 mg kg -1), and combination of protective culture and natamycin (40 mg kg -1/25 mg kg -1) were studied on the growth of aerobic spore-forming bacteria in low-salt soft cheese during the storage period (30 days) at 4±1°C. The results revealed that the addition of different natural antibacterial additives with various concentrations had a significant effect on aerobic spore-forming bacteria, compared to other treatments and control. The growth pattern of aerobic spore-forming bacteria gradually decreased in all treatments along the storage period with variable reduction percentages in comparison with control cheese which was in continuous increment. The application of a combination of nisin and lysozyme had the most significant reduction of aerobic spore-forming bacteria, compared to control and other treatments.

Effect of selected starter cultures on production, properties and shelf life of fresh type cheese

The aim of this study was to examine the influence of different starter cultures including protective culture on the production and properties of fresh cheese. Fresh cheeses were produced from pasteurized milk by adding mesophilic starter cultures, mesophilic cultures and liquid rennet and by adding protective culture. All samples were analysed for acidity (active and titratable), microbiological quality, texture, colour and sensory properties during 21 days of cold storage. Additionally, milk fat, the total dry matter, total proteins and mineral content were determined in all cheese samples on the first day of storage. It could be observed that the used mesophilic culture in general did not affect chemical composition of cheese. As expected, during the storage period acidity in all cheeses decreased, while the number of microorganisms increased, whereby that changes were significantly slowed down in cheese produced by adding protective culture. Scores of sensory evaluation were high during the entire storage period for all cheeses, but samples containing and cheese protective cultures achieved the highest score (18.56) at the first as well as at the last day of storage (17.98). According to all analyses, it is evident that the shelf life of cheese produced by adding protective culture has been prolonged for 12 days in comparison to samples produced without protective culture, and accounted 21 days when properly cool stored. In conclusion, the addition of protective culture might be useful for extending the shelf life and maintaining sensory properties as well as colour of fresh cheese.

Effect of commercial protective cultures and bacterial fermentates on Listeria monocytogenes growth in a refrigerated high-moisture model cheese

Biopreservatives are clean-label ingredients used to control pathogenic and spoilage microorganisms in ready-to-eat foods including cheese. The efficacies of six commercial biopreservatives in controlling L. monocytogenes growth at 4°C were tested in a high-moisture model cheese (pH 6.00, 56% moisture, 1.25% salt) made of cream, micellar casein, water, salt, lactose, lactic acid, and a single protective culture (PC-1, PC-2, or PC-3, 10 6 CFU/g target) or bacterial fermentate (CM-1 or CM-2 [cultured milk] or CSV-1 [cultured sugar-vinegar blend], 0.5% or 1.0% level). Cheeses were inoculated with 3-log CFU/g L. monocytogenes (5-strain cocktail), after which 25-g samples were vacuum-sealed and stored at 4°C for 8 weeks. L. monocytogenes populations from triplicate samples were enumerated weekly on Modified Oxford agar in duplicate trials. L. monocytogenes growth (≥1-log increase) was observed in approximately 1 week in control cheese and those formulated with 10 6 CFU/g PC-1 or PC-2. Growth was delayed to 2.5 weeks in model cheeses formulated with 10 6 CFU/g PC-3 or 0.5% CM-2 and to 3 weeks with 0.5% CM-1 or CSV-1. Growth was further delayed to 6.5-7.5 weeks in model cheeses formulated with 1.0% CM-1 or CM-2, while formulation with 1.0% CSV-1 inhibited L. monocytogenes growth for 8 weeks. In a second set of experiments, the combined effect of pH and 0.5% CSV-1 on L. monocytogenes inhibition was investigated. Incorporation of 0.5% CSV-1 delayed L. monocytogenes growth to 3, 6, and >10 weeks in cheeses of pH 6.00, 5.75, and 5.50, respectively, versus growth observed in 1, 1, and 3.5 weeks in control cheeses. These data suggest that certain fermentates have greater antilisterial activity than protective cultures in directly acidified cheeses with direct biopreservative incorporation and refrigerated storage. Further research is needed to optimize conditions to prevent listerial growth utilizing protective cultures in fresh, soft cheeses.

Healthy milk snack

Cottage cheese and curd products are presented on the Russian dairy market. The latter are most popular with the addition of flavoring fillers, such as fruit and berry, nut and chocolate, and others. Despite the benefits of cottage cheese and curd products, fast food is currently in great demand. Fast food is food that is designed to satisfy hunger in a matter of minutes. It has both its advantages: fast, tasty, cheap enough; and cons: such products are high in calories, addictive, as they contain flavor enhancers, cause and exacerbate diseases of the gastrointestinal tract, etc. We offer an alternative to classic fast food – the curd product "Curd Fitness Candy". The manufacturing process of the curd product is carried out in the following sequence: acceptance and preparation of raw materials; drawing up a curd mixture and a mixture for glazing (according to the recipe); cooling; molding; glazing; second cooling; packaging and labeling. Technological equipment for the production of curd product includes molding and enrobing machines; refrigeration tunnel. The following ingredients are used as raw material sources for the curd base: cottage cheese, butter, granulated sugar and sweetener; for glaze: butter, melon or watermelon syrup, starch. In order to extend the shelf life of the product by 30%, in addition to the traditional starter culture, a protective culture is introduced in the development of the curd base. The curd product “Curd Fitness Candy” is tasty and healthy; not addictive; stored 30% longer compared to glazed curds without changing the quality characteristics; has an original shape in the form of a star, oval, rhombus, etc.; unconventional colored glaze using melon syrup, watermelon, etc.; colorful design of labeling material; small mass (per bite); rich vitamin and mineral composition; reduced amount of carbohydrates; It belongs to the group of products recommended for reduced nutrition.

Low-Fat and High-Quality Fermented Sausages

The present study, considering for the first time microbiological concerns due to the use of lemon albedo as a fat replacer, aimed at the selection of an anti-Listeria strain to be used as protective culture in low-fat southern Italian fermented sausages. In fact, these kinds of products require appropriate bio-protective strategies to avoid risks due to Listeria monocytogenes. Sixty-seven Lactiplantibacillus plantarum strains isolated from diverse sources were screened for their antimicrobial activity and their interaction with starter strains (Latilactobacillus sakei 152 and Staphylococcus xylosus MVS9). Lactiplantibacillus plantarum Lpls100, highlighting both listericidal activity and the ability to promote Staphylococcus xylosus MVS9 growth, was used as a protective strain in low-fat fermented sausages prepared with lemon albedo as a fat replacer. The effect of the albedo and the protective strain on the fermentation process and the final quality was ascertained. Results highlighted that the use of the albedo did not affect the growth of starter strains and enhanced some quality features, such as fatty acid profiles and certain sensory attributes. However, the albedo also produced a slow decrease in water activity, compromising the microbial quality. The anti-Listeria strain, enhancing coagulase negative cocci growth and exerting antimicrobial activity, avoided the inconveniences caused by the use of the albedo. Moreover, the anti-Listeria effectiveness was assessed through a challenge test using a Listeria cocktail. The study revealed that Lactiplantibacillus plantarum Lpls100, regardless of the presence of the albedo, assures a prompt inhibition of Listeria spp. Therefore, its use could be an important contribution to the quality of low-fat fermented sausages.