Formation of γ-aminobutyric acid (GABA) during the natural lactic acid fermentation of cucumber

Screening and characterization of lactic acid bacteria and fermentation of gamma-aminobutyric acid-enriched bamboo shoots

In order to produce fermented bamboo shoots with functional properties, two strains of lactic acid bacteria were selected for inoculation and fermentation. One strain, Lactiplantibacillus plantarum R1, exhibited prominent potential probiotic properties (including gastrointestinal condition tolerance, adhesion ability, antimicrobial ability, and antibiotic resistance), while the other, Levilactobacillus brevis R2, demonstrated the capability of high γ-aminobutyric acid (GABA) production (913.99 ± 14.2 mg/L). The synergistic inoculation of both strains during bamboo shoot fermentation led to a remarkable increase in GABA content (382.31 ± 12.17 mg/kg), surpassing that of naturally fermented bamboo shoots by more than 4.5 times and outperforming mono-inoculated fermentation. Simultaneously, the nitrite content was maintained at a safe level (5.96 ± 1.81 mg/kg). Besides, inoculated fermented bamboo shoots exhibited an increased crude fiber content (16.58 ± 0.04 g/100 g) and reduced fat content (0.39 ± 0.02 g/100 g). Sensory evaluation results indicated a high overall acceptability for the synergistically inoculated fermented bamboo shoots. This study may provide a strategy for the safe and rapid fermentation of bamboo shoots and lay the groundwork for the development of functional vegetable products enriched with GABA.

Tasting of traditional Polish fermented cucumbers: Microbiology, morpho-textural features, and volatilome

In the present study, naturally fermented and unpasteurized cucumbers (Cucumis sativus L.) collected from 4 producers located in different regions of Poland were studied. The fermented cucumbers were characterized by significant nutritional features in terms of polyphenols content and antioxidant activity. Microbiological analyses revealed active bacterial populations of lactococci, thermophilic cocci, lactobacilli, and coagulase-negative cocci. The microbiological characterization of cucumber and brine samples through metataxonomic analysis allowed the dominant species to be detected, being Lactococcus and Streptococcus in cucumbers, and Lactiplantibacillus, Leuconostoc, Pediococcus, Secundilactobacillus, and Lentilactobacillus in brine. The isolation activity offered a clear picture of the main active lactic acid bacteria at the end of fermentation, being Pediococcus parvulus and Lactiplantibacillus plantarum group. All the studied isolates showed a good attitude in fermenting a cucumber-based broth, thus suggesting their potential application as starter or adjunct cultures for guided cucumber fermentation. Moreover, for the same isolates, strong aminopeptidase activity (due to leucine arylamidase and valine arylamidase) was observed, with potential effect on the definition of the final sensory traits of the product. Only a few isolates showed the ability to produce exopolysaccharides in synthetic medium. Of note, the presence of the hdcA gene in some Pediococcus ethanolidurans isolates also confirmed the need for a thorough characterization of starter candidates to avoid undesired adverse effects on consumer's health. No isolate showed the production of bacteriocins against Listeria innocua used as surrogate for Listeria monocytogenes. Based on the results of Headspace Solid-Phase Microextraction-Gas Chromatography/Mass Spectrometry analysis, a rich and complex volatilome, composed by more than 80 VOCs, was recognized and characterized. In more detail, the detected compounds belonged to 9 main classes, being oxygenated terpenes, alcohols, terpenes, ketones, acids, aldehydes, esters, sulfur, and sesquiterpenes.

Fermented Vegetables: Health Benefits, Defects, and Current Technological Solutions

This review summarizes current studies on fermented vegetables, analyzing the changes in nutritional components during pickling, the health benefits of fermented vegetables, and their safety concerns. Additionally, the review provides an overview of the applications of emergent non-thermal technologies for addressing these safety concerns during the production and processing of fermented vegetables. It was found that vitamin C would commonly be lost, the soluble protein would degrade into free amino acids, new nutrient compositions would be produced, and the flavor correlated with the chemical changes. These changes would be influenced by the variety/location of raw materials, the original bacterial population, starter cultures, fermentation conditions, seasoning additions, and post-fermentation processing. Consuming fermented vegetables benefits human health, including antibacterial effects, regulating intestinal bacterial populations, and promoting health (anti-cancer effects, anti-diabetes effects, and immune regulation). However, fermented vegetables have chemical and biological safety concerns, such as biogenic amines and the formation of nitrites, as well as the existence of pathogenic microorganisms. To reduce hazardous components and control the quality of fermented vegetables, unique starter cultures, high pressure, ultrasound, cold plasma, photodynamic, and other technologies can be used to solve these problems.

An overview of fermentation in the food industry - looking back from a new perspective

Fermentation is thought to be born in the Fertile Crescent, and since then, almost every culture has integrated fermented foods into their dietary habits. Originally used to preserve foods, fermentation is now applied to improve their physicochemical, sensory, nutritional, and safety attributes. Fermented dairy, alcoholic beverages like wine and beer, fermented vegetables, fruits, and meats are all highly valuable due to their increased storage stability, reduced risk of food poisoning, and enhanced flavor. Over the years, scientific research has associated the consumption of fermented products with improved health status. The fermentation process helps to break down compounds into more easily digestible forms. It also helps to reduce the amount of toxins and pathogens in food. Additionally, fermented foods contain probiotics, which are beneficial bacteria that help the body to digest food and absorb nutrients. In today's world, non-communicable diseases such as cardiovascular disease, type 2 diabetes, cancer, and allergies have increased. In this regard, scientific investigations have demonstrated that shifting to a diet that contains fermented foods can reduce the risk of non-communicable diseases. Moreover, in the last decade, there has been a growing interest in fermentation technology to valorize food waste into valuable by-products. Fermentation of various food wastes has resulted in the successful production of valuable by-products, including enzymes, pigments, and biofuels.

Production of glycerolamines based conjugated γ-aminobutyric acids using microbial COX and LOX as successor enzymes to GAD

Gamma-aminobutyric acid (γ-ABA) can be produced by various microorganisms including bacteria, fungi and yeasts using enzymatic bioconversion, microbial fermentation or chemical hydrolysis. Regenerating conjugated glycerol-amines is valid by the intervention of microbial cyclooxygenase [COX] and lipooxygenase [LOX] enzymes produced via lactobacillus bacteria (LAB) as successor enzymes to glutamate decarboxylases (GAD). Therefore, the aim of this review is to provide an overview on γ-ABA production, and microbiological achievements used in producing this signal molecule based on those fermenting enzymes. The formation of aminoglycerides based conjugated γ-ABA is considered the key substances in controlling the host defense against pathogens and is aimed in increasing the neurotransmission effects and in suppressing further cardiovascular diseases.

Influence of Isolation Temperature on Isolating Diverse Lactic Acid Bacteria from Kimchi and Cultural Characteristics of Psychrotrophs

Kimchi is a traditional Korean fermented vegetable that is stored and fermented at low temperatures. However, kimchi lactic acid bacteria (LAB) are typically isolated under mesophilic conditions, which may be inappropriate for isolating the diverse LAB. Therefore, this study investigated the suitable conditions for isolating various LAB from kimchi. Here, LAB were isolated from four kimchi samples using MRS, PES, and LBS media and varying isolation temperatures (30, 20, 10, and 5°C). Then, MRS was selected as the suitable medium for LAB isolation. A comparison of culture-dependent and culture-independent approaches indicated that 5°C was not a suitable isolation temperature. Thus, the number and diversity of LAB were determined at 30, 20, and 10°C using 12 additional kimchi samples to elucidate the effect of isolation temperature. With the exception of two samples, most samples did not substantially differ in LAB number. However, Leuconostoc gelidum, Leuconostoc gasicomitatum, Leuconostoc inhae, Dellaglioa algida, Companilactobacillus kimchiensis, Leuconostoc miyukkimchii, Leuconostoc holzapfelii, and Leuconostoc carnosum were isolated only at 10 and 20°C. The growth curves of these isolates, except Leu. holzapfelii and Leu. carnosum, showed poor growth at 30°C. This confirmed their psychrotrophic characteristics. In Weissella koreensis, which was isolated at all isolation temperatures, there was a difference in the fatty acid composition of membranes between strains that could grow well at 30°C and those that could not. These findings can contribute to the isolation of more diverse psychrotrophic strains that were not well isolated under mesophilic temperatures.

Gamma-aminobutyric acid (GABA): a comprehensive review of dietary sources, enrichment technologies, processing effects, health benefits, and its applications

Gamma-aminobutyric acid (GABA) is a naturally occurring potential bioactive compound present in plants, microorganisms, animals, and humans. Especially, as a main inhibitory neurotransmitter in the central nervous system, GABA possesses a broad spectrum of promising bioactivities. Thus, functional foods enriched with GABA have been widely sought after by consumers. However, the GABA levels in natural foods are usually low, which cannot meet people's demand for health effects. With the increasing public awareness on the food securities and naturally occurring processes, using enrichment technologies to elevate the GABA contents in foods instead of exogenous addition can enhance the acceptability of health-conscious consumers. Herein, this review provides a comprehensive insight on the dietary sources, enrichment technologies, processing effects of GABA, and its applications in food industry. Furthermore, the various health benefits of GABA-enriched foods, mainly including neuroprotection, anti-insomnia, anti-depression, anti-hypertensive, anti-diabetes, and anti-inflammatory are also summarized. The main challenges for future research on GABA are related to exploring high GABA producing strains, enhancing the stability of GABA during storage, and developing emerging enrichment technologies without affecting food quality and other active ingredients. A better understanding of GABA may introduce new windows for its application in developing functional foods.

Lentil-Based Yogurt Alternatives Fermented with Multifunctional Strains of Lactic Acid Bacteria—Techno-Functional, Microbiological, and Sensory Characteristics

A milk-alternative produced from lentil protein isolate was fermented with three multifunctional strains of lactic acid bacteria, Leuconostoc citreum TR116, Leuconostoc pseudomesenteroides MP070, and Lacticaseibacillus paracasei FST 6.1. As a control, a commercial starter culture containing Streptococcus thermophilus was used. The metabolic performance of these strains and the techno-functional properties of the resulting yogurt alternatives (YA) were studied. Microbial growth was evaluated by cell counts, acidification, and carbohydrate metabolization. The structure of the YA was investigated by textural and rheological analyses and confocal laser scanning microscopy (CLSM). Production of antifungal compounds, the influence of fermentation on the content of FODMAPs, and typical metabolites were analyzed, and a sensory analysis was performed. The results revealed an exponential microbial growth in the lentil base substrate supported by typical acidification, which indicates a suitable environment for the selected strains. The resulting YA showed a gel-like texture typical for non-stirred yogurts, and high water holding capacity. The tested strains produced much higher levels of antifungal phenolic compounds than the commercial control and are therefore promising candidates as adjunct cultures for shelf-life extension. The Leuconostoc strains produced mannitol from fructose and could thus be applied in sugar-reduced YA. Preliminary sensory analysis showed high acceptance for YA produced with Lacticaseibacillus paracasei FST 6.1, and a yogurt-like flavor not statistically different to that produced by the control. Overall, each tested strain possessed promising functionalities with great potential for application in fermented plant-based dairy-alternatives.

Fate of Bioactive Compounds during Lactic Acid Fermentation of Fruits and Vegetables

Consumption of lactic acid fermented fruits and vegetables has been correlated with a series of health benefits. Some of them have been attributed to the probiotic potential of lactic acid microbiota, while others to its metabolic potential and the production of bioactive compounds. The factors that affect the latter have been in the epicenter of intensive research over the last decade. The production of bioactive peptides, vitamins (especially of the B-complex), gamma-aminobutyric acid, as well as phenolic and organosulfur compounds during lactic acid fermentation of fruits and vegetables has attracted specific attention. On the other hand, the production of biogenic amines has also been intensively studied due to the adverse health effects caused by their consumption. The data that are currently available indicate that the production of these compounds is a strain-dependent characteristic that may also be affected by the raw materials used as well as the fermentation conditions. The aim of the present review paper is to collect all data referring to the production of the aforementioned compounds and to present and discuss them in a concise and comprehensive way.

Changes in the free amino acid profile of pickling cucumber during lactic acid fermentation

Free amino acid (FAA) profiles of fresh, acidified, naturally fermented, and starter culture fermented cucumbers were analyzed by liquid chromatography triple quadrupole mass spectrometry. Fermented cucumbers contained more total FAA than acidified cucumbers (1,302 ± 102 mg/kg and 635 ± 35 mg/kg, respectively). Total FAA content of fermented cucumber was similar regardless of brine salt levels (2-6% NaCl) and starter culture addition. Glutamine (1491.4 ± 69.3 mg/kg), γ-aminobutyric acid (GABA, 269.6 ± 21.4 mg/kg), asparagine (113.0 ± 6.4 mg/kg), and citrulline (110.3 ± 8.5 mg/kg) were the most abundant FAA in fresh pickling cucumber, whereas GABA (181.3 ± 21.5 mg/kg), isoleucine (165.2 ± 11.2 mg/kg), leucine (129.8 ± 10.9 mg/kg), and lysine (110.9 ± 5.0 mg/kg) were the most abundant in fermented cucumber. GABA and ornithine were produced during fermentation, indicating glutamate decarboxylase and arginine deiminase activities. Notably, ornithine was significantly higher in natural (63.3 ± 31.5 mg/kg) versus starter culture fermented cucumbers (3.0 ± 0.7 mg/kg). This new information on FAA composition of fresh and fermented pickling cucumbers shows the impact of fermentation conditions on cucumber amino acid profiles while providing insight for manipulating fermentations for health promotion and consumer acceptance. PRACTICAL APPLICATION: This study reports changes in the free amino acid profiles of raw, fermented and acidified cucumbers, which may be valuable for understanding the impact of these foods on human health and nutrition. This information is useful for food microbiologists studying the metabolism of lactic acid bacteria during fermentation and/or designing starter cultures and could contribute to the development of novel fermented cucumber pickle products with enhanced nutritional value.

Metaproteomics insights into fermented fish and vegetable products and associated microbes

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Increasing global population means higher demand for healthy food.

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Fish and vegetables are healthy foods, but overproduction leads to spoilage.

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Fermentation of fish/vegetables elongate their shelf lives, improved flavour and functions.

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Microbes associated with Fish/vegetable fermentation produce health conferring peptides.

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There is little review on peptides elicited during fish/vegetable fermentations.

The interest in proteomic studies of fermented food is increasing; the role of proteins derived from fermentation extends beyond preservation, they also improve the organoleptic, anti-pathogenic, anti-cancer, anti-obesogenic properties, and other health conferring properties of fermented food. Traditional fermentation processes are still in use in certain cultures, but recently, the controlled process is gaining wider acceptance due to consistency and predictability. Scientists use modern biotechnological approaches to evaluate reactions and component yields from fermentation processes. Pieces of literature on fermented fish and vegetable end-products are scanty (compared to milk and meat), even though fish and vegetables are considered health conferring diets with high nutritional contents. Evaluations of peptides from fermented fish and vegetables show they have anti-obesity, anti-oxidative, anti-inflammatory, anti-pathogenic, anti-anti-nutrient, improves digestibility, taste, nutrient content, texture, aroma properties, etc. Despite challenges impeding the wider applications of the metaproteomic analysis of fermented fish and vegetables, their potential benefits cannot be underestimated.