Effect of lactic acid fermentation of watermelon juice on its sensory acceptability and volatile compounds

Analysis of Pickled Cucumber Products, Based on Microbial Diversity and Flavor Substance Detection

Changes to the microbial community during pickled cucumber fermentation were studied using the 16S rDNA technique. The changes of volatile organic compounds (VOCs) during pickled cucumber fermentation were studied by gas chromatograph-ion mobility spectrometry. At the phylum level, Cyanophyta and Proteobacteria were the dominant flora in the natural fermentation group, and Firmicutes were the dominant flora in the added-bacteria fermentation group. At the generic level, the addition of Lactobacillus led to changes in the community of the bacteria in the added-bacterial fermentation group and decreased the species abundance of other bacteria. In total, 75 volatile organic compounds were identified from naturally fermented pickled cucumber, and 60 volatile organic compounds were identified from fermented pickled cucumber with bacterial addition. The main metabolites were esters, aldehydes, acids, alcohols, ketones, alkanes, nitriles, and alkenes. These metabolites will bring their unique aroma components to the pickled cucumber. Metabolomic analysis of the O2PLS model showed that Weissella and Lactobacillus were closely and positively correlated with nine alcohols, six esters, five aldehydes, four acids, three ketones, and one pyrazine. Pseudomonas and norank_f_Mitochondria show a close positive correlation with four kinds of alcohols, two kinds of esters, one kind of aldehyde, and one kind of nitrile.

Volatilome, Microbial, and Sensory Profiles of Coffee Leaf and Coffee Leaf-Toasted Maté Kombuchas

Kombucha is a fermented beverage traditionally made from the leaves of Camelia sinensis. The market has drastically expanded recently, and the beverage has become more elaborated with new, healthy food materials and flavors. Pruning and harvesting during coffee production may generate tons of coffee leaves that are discarded although they contain substantial amounts of bioactive compounds, including those found in maté tea and coffee seeds. This study characterized the changes in volatilome, microbial, and sensory profiles of pure and blended arabica coffee leaf tea kombuchas between 3-9 days of fermentation. Acceptance was also evaluated by consumers from Rio de Janeiro (n = 103). Kombuchas (K) were prepared using black tea kombucha starter (BTKS) (10%), sucrose (10%), a symbiotic culture of Bacteria and Yeasts (SCOBY) (2.5%), and a pure coffee leaf infusion (CL) or a 50:50 blend with toasted maté infusion (CL-TM) at 2.5%. The RATA test was chosen for sensory profile characterization. One hundred volatile organic compounds were identified when all infusions and kombucha samples were considered. The potential impact compounds identified in CL K and CL-TM K were: methyl salicylate, benzaldehyde, hexanal, nonanal, pentadecanal, phenylethyl-alcohol, cedrol, 3,5-octadien-2-one, β-damascenone, α-ionone, β-ionone, acetic acid, caproic acid, octanoic acid, nonanoic acid, decanoic acid, isovaleric acid, linalool, (S)-dihydroactinidiolide, isoamyl alcohol, ethyl hexanoate, and geranyl acetone. Aroma and flavor descriptors with higher intensities in CL K included fruity, peach, sweet, and herbal, while CL-TM K included additional toasted mate notes. The highest mean acceptance score was given to CL-TM K and CL K on day 3 (6.6 and 6.4, respectively, on a nine-point scale). Arabica coffee leaf can be a co-product with similar fingerprinting to maté and black tea, which can be explored for the elaboration of potentially healthy fermented beverages in food industries.

Effects of tandem fermentation of edible mushroom and L. plantarum on sensory, polysaccharide, vitamin C, and γ-aminobutyric acid of Rosa roxburghii Tratt and coix seed beverage

A new Rosa roxburghii Tratt (RRT) and coix seed (CS) beverage rich in multi-active ingredients was developed. Edible mushrooms and L. plantarum were selected for fermentation in stages. Some physicochemical properties, γ-aminobutyric acid (GABA), polysaccharides and sensory were studied during the T. versicolor and L. plantarum fermentation. T. versicolor increased the free amino acid through enzymatic protein digestion in the early growth stage and used these amino acids to synthesize its bacteriophage protein. T. versicolor and L. plantarum increased the polysaccharide and GABA of the fermentation broth. Vitamin C was retained as much as possible, with a slight loss occurring mainly in the aerobic fermentation stage of T. versicolor. Its less loss in exchange was for a higher value of T. versicolor polysaccharide, protein enhancement, and bitterness reduction. This study provides a reference for the deep processing of Guizhou's unique agricultural products and edible mushroom fermented beverage.

Changes of Volatile Organic Compounds of Different Flesh Texture Pears during Shelf Life Based on Headspace Solid-Phase Microextraction with Gas Chromatography-Mass Spectrometry

Aroma is an important sensory factor in evaluating the quality of pear fruits. This study used headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) to analyze the volatile organic compounds (VOCs) of three crispy pears and five soft pears during shelf life, and the changes in soluble solids content (SSC) were analyzed. The results showed that the SSC of the soft pears such as Nanguoli, Jingbaili and Louis was always higher than that of the crispy pears throughout shelf life. A total of 160 VOCs were detected in the eight pear varieties. Orthogonal partial least squares discriminant analysis (OPLS-DA) and hierarchical cluster analysis (HCA) combined with predictor variable importance projection (VIP) showed that the eight pear varieties could be obviously classified into six groups according to the differences in their VOCs, and 31 differential VOCs were screened out, which could be used to differentiate between pears with different flesh textures. The results of clustering heat map analysis showed that, with the extension of shelf life, the content of each different VOC did not change much in crispy pears, whereas the difference in soft pears was larger. This study confirmed the potential of determining the optimal shelf life of different pear varieties about aroma evaluation and studying the mechanism of differences in VOCs in the future.

Dynamics changes in physicochemical properties, volatile metabolites, non-volatile metabolites, and physiological functions of barley juice during Bifidobacterium infantis fermentation

The purpose of this research was to explore the potential of Bifidobacterium infantis fermentation to modify the composition and physiological properties of barley juices. B. infantis JFM12 showed a potent capability to decrease the total sugar contents from 0.39 ± 0.01 mg/mL to 0.35 ± 0.01 mg/mL within 24 h of fermentation. The volatile metabolite profiles were enriched after B. infantis JFM12 fermentation, leading to the changes of 13 aldehydes, 11 ketones, 10 acids, 7 alcohols, and 6 esters. A total of 98 key non-volatile metabolites were identified in the barley juice between before and after B. infantis JFM12 fermentation, including 80 non-volatile metabolites that were remarkably increased and 18 non-volatile metabolites that were remarkably reduced. Furthermore, the antioxidant activities and lipase inhibitory activities of fermented barley juice were higher than those of unfermented barley juice. Overall, B. infantis JFM12 was beneficial in increasing the quality of barley juice.

Enhancement in the physicochemical properties, antioxidant activity, volatile compounds, and non-volatile compounds of watermelon juices through Lactobacillus plantarum JHT78 fermentation

In this study, the influences of Lactobacillus plantarum JHT78 fermentation on the physiological properties, antioxidant activities, and volatile/non-volatile metabolites of watermelon juices were comprehensively investigated. The results indicated that total polyphenols flavonoids and anthocyanin in the watermelon juices remarkably increased through L. plantarum JHT78 fermentation. L. plantarum JHT78 fermentation enhanced the antioxidant activities, lipase inhibition, and α-glucosidase activities of watermelon juices. A total of 62 volatile compounds were detected using HS-SPME-GC-MS, mainly including 11 acids, 8 aldehydes, 7 ketones, and 7 alcohols. The abundance of 19 volatile compounds especially for acids remarkably increased for the fermentated watermelon juice. Furthermore, non-volatile compounds detected by UHPLC-QTOF-MS revealed that L. plantarum JHT78 significantly altered the non-volatile compounds of watermelon juices, especially increased indole-3-lactic acid. The results confirmed that L. plantarum JHT78 enhanced the functionality of watermelon juices thus providing a theoretical basis for the development of LAB on plant-based beverages.

Flavour Volatiles of Fermented Vegetable and Fruit Substrates: A Review

Health, environmental and ethical concerns have resulted in a dramatic increase in demand for plant-based dairy analogues. While the volatile organic compounds (VOCs) responsible for the characteristic flavours of dairy-based products have been extensively studied, little is known about how to reproduce such flavours using only plant-based substrates. As a first step in their development, this review provides an overview of the VOCs associated with fermented (bacteria and/or fungi/yeast) vegetable and fruit substrates. Following PRISMA guidelines and using two English databases (Web of Science and Scopus), thirty-five suitable research papers were identified. The number of fermentation-derived VOCs detected ranged from 32 to 118 (across 30 papers), while 5 papers detected fewer (10 to 25). Bacteria, including lactic acid bacteria (LAB), fungi, and yeast were the micro-organisms used, with LAB being the most commonly reported. Ten studies used a single species, 21 studies used a single type (bacteria, fungi or yeast) of micro-organisms and four studies used mixed fermentation. The nature of the fermentation-derived VOCs detected (alcohols, aldehydes, esters, ketones, acids, terpenes and norisoprenoids, phenols, furans, sulphur compounds, alkenes, alkanes, and benzene derivatives) was dependent on the composition of the vegetable/fruit matrix, the micro-organisms involved, and the fermentation conditions.

Manufacture of a Potential Antifungal Ingredient Using Lactic Acid Bacteria from Dry-Cured Sausages

The growing interest in functional foods has fueled the hunt for novel lactic acid bacteria (LAB) found in natural sources such as fermented foods. Thus, the aims of this study were to isolate, identify, characterize, and quantify LAB’s antifungal activity and formulate an ingredient for meat product applications. The overlay method performed a logical initial screening by assessing isolated bacteria’s antifungal activity in vitro. Next, the antifungal activity of the fermented bacteria-free supernatants (BFS) was evaluated by agar diffusion assay against six toxigenic fungi. Subsequently, the antifungal activity of the most antifungal BFS was quantified using the microdilution method in 96-well microplates. The meat broth that showed higher antifungal activity was selected to elaborate on an ingredient to be applied to meat products. Finally, antifungal compounds such as organic acids, phenolic acids, and volatile organic compounds were identified in the chosen-fermented meat broth. The most promising biological candidates belonged to the Lactiplantibacillus plantarum and Pediococcus pentosaceus. P. pentosaceus C15 distinguished from other bacteria by the production of antifungal compounds such as nonanoic acid and phenyl ethyl alcohol, as well as the higher production of lactic and acetic acid.

Aroma profiles of sweet cherry juice fermented by different lactic acid bacteria determined through integrated analysis of electronic nose and gas chromatography-ion mobility spectrometry

Sweet cherries are popular among consumers, with a recent explosion in sweet cherry production in China. However, the fragility of these fruits poses a challenge for expanding production and transport. With the aim of expanding the product categories of sweet cherries that can bypass these challenges, in this study, we prepared sweet cherry juice fermented by three different lactic acid bacteria (LAB; Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus rhamnosus GG), and evaluated the growth, physiochemical, and aroma characteristics. All three strains exhibited excellent growth potential in the sweet cherry juice; however, Lactobacillus acidophilus and Lactobacillus plantarum demonstrated more robust acid production capacity and higher microbial viability than Lactobacillus rhamnosus GG. Lactic acid was the primary fermentation product, and malic acid was significantly metabolized by LAB, indicating a transition in microbial metabolism from using carbohydrates to organic acids. The aroma profile was identified through integrated analysis of electronic nose (E-nose) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) data. A total of 50 volatile compounds characterized the aromatic profiles of the fermented juices by HS-GC-IMS. The flavor of sweet cherry juice changed after LAB fermentation and the fruity odor decreased overall. Lactobacillus acidophilus and Lactobacillus plantarum significantly increased 2-heptanone, ethyl acetate, and acetone contents, bringing about a creamy and rummy-like favor, whereas Lactobacillus rhamnosus GG significantly increased 2-heptanone, 3-hydroxybutan-2-one, and 2-pentanone contents, generating cheesy and buttery-like odors. Principal component analysis of GC-IMS data and linear discriminant analysis of E-nose results could effectively differentiate non-fermented sweet cherry juice and the sweet cherry juice separately inoculated with different LAB strains. Furthermore, there was a high correlation between the E-nose and GC-IMS results, providing a theoretical basis to identify different sweet cherry juice formulations and appropriate starter culture selection for fermentation. This study enables more extensive utilization of sweet cherry in the food industry and helps to improve the flavor of sweet cherry products.

Effect of Six Lactic Acid Bacteria Strains on Physicochemical Characteristics, Antioxidant Activities and Sensory Properties of Fermented Orange Juices

Six lactic acid bacteria strains were used to study the effects on physicochemical characteristics, antioxidant activities and sensory properties of fermented orange juices. All strains exhibited good growth in orange juice. Of these fermentations, some bioactive compositions (e.g., vitamin C, shikimic acid) and aroma-active compounds (e.g., linalool, 3-carene, ethyl 3-hydroxyhexanoate, etc.) significantly increased in Lactiplantibacillus plantarum and Lactobacillus acidophilus samples. DPPH free radical scavenging rates in L. plantarum and Lacticaseibacillus paracasei samples increased to 80.25% and 77.83%, respectively. Forty-three volatile profiles were identified, including 28 aroma-active compounds. 7 key factors significantly influencing sensory flavors of the juices were revealed, including D-limonene, linalool, ethyl butyrate, ethanol, β-caryophyllene, organic acids and SSC/TA ratio. The orange juice fermented by L. paracasei, with more optimization aroma-active compounds such as D-limonene, β-caryophyllene, terpinolene and β-myrcene, exhibited more desirable aroma flavors such as orange-like, green, woody and lilac incense, and gained the highest sensory score. Generally, L. paracasei fermentation presented better aroma flavors and overall acceptability, meanwhile enhancing antioxidant activities.

Chemical and Sensory Characteristics of Fruit Juice and Fruit Fermented Beverages and Their Consumer Acceptance

Recent social, economic, and technological evolutions have impacted consumption habits. The new consumer is more rational, more connected and demanding with products, more concerned with the management of the family budget, with the health, origin, and sustainability of food. The food industry over the last few years has shown remarkable technological and scientific evolution, with an impact on the development and innovation of new products using non-thermal processing. Non-thermal processing technologies involve methods by which fruit juices receive microbiological inactivation and enzymatic denaturation with or without the direct application of low heat, thereby lessening the adverse effects on the nutritional, bioactive, and flavor compounds of the treated fruit juices, extending their shelf-life. The recognition of the nutritional and protective values of fruit juices and fermented fruit beverages is evident and is attributed to the presence of different bioactive compounds, protecting against chronic and metabolic diseases. Fermentation maintains the fruit's safety, nutrition, and shelf life and the development of new products. This review aims to summarize the chemical and sensory characteristics of fruit juices and fermented fruit drinks, the fermentation process, its benefits, and its effects.

Optimization of extraction process parameters of caffeic acid from microalgae by supercritical carbon dioxide green technology

Purpose

In this study, the optimization of extraction process parameters of caffeic acid content from Spirulina platensis is performed by supercritical green technology.

Methods

Especially, the optimization of supercritical carbon dioxide (SC-CO₂) extraction parameters was carried out employing Box-Behnken design (BBD) and response surface methodology (RSM). Alongside, the three levels of extraction parameters i.e. extraction pressure, extraction time and temperature have been fixed. As a response, the caffeic acid content of the extracts was determined by HPLC. The statistical analysis (ANOVA) of developed mathematical models was used in the process.

Results

The extract exhibited the highest content of caffeic acid as 72.11 µg/g of dw at the optimized extraction conditions of 360.08 bar pressure for 57.13 min extraction time at 38.31 °C temperature. Simultaneously this extract exhibited the highest content of total phenolic content (76.87 µg GAE/g dw), reducing power (2278 µg BHT/g dw), FRAP value (4.19 mM FeSO₄ equivalent/g dw) and IC₅₀ for DPPH activity (89.28 µg/mL).

Conclusion

It has been also noted that supercritical fluid extract can significantly retard the growth of microorganisms in litchi beverage. Consequently, we can also predict that isolated SC-CO₂ antioxidant containing fraction would have hopeful for foodstuff preservative.

Role of Lactic Acid Bacteria in Food Preservation and Safety

Fermentation of various food stuffs by lactic acid bacteria is one of the oldest forms of food biopreservation. Bacterial antagonism has been recognized for over a century, but in recent years, this phenomenon has received more scientific attention, particularly in the use of various strains of lactic acid bacteria (LAB). Certain strains of LAB demonstrated antimicrobial activity against foodborne pathogens, including bacteria, yeast and filamentous fungi. Furthermore, in recent years, many authors proved that lactic acid bacteria have the ability to neutralize mycotoxin produced by the last group. Antimicrobial activity of lactic acid bacteria is mainly based on the production of metabolites such as lactic acid, organic acids, hydroperoxide and bacteriocins. In addition, some research suggests other mechanisms of antimicrobial activity of LAB against pathogens as well as their toxic metabolites. These properties are very important because of the future possibility to exchange chemical and physical methods of preservation with a biological method based on the lactic acid bacteria and their metabolites. Biopreservation is defined as the extension of shelf life and the increase in food safety by use of controlled microorganisms or their metabolites. This biological method may determine the alternative for the usage of chemical preservatives. In this study, the possibilities of the use of lactic acid bacteria against foodborne pathogens is provided. Our aim is to yield knowledge about lactic acid fermentation and the activity of lactic acid bacteria against pathogenic microorganisms. In addition, we would like to introduce actual information about health aspects associated with the consumption of fermented products, including probiotics.

Genetic Analysis of Fruit Quality Traits in Sweet Watermelon (Citrullus lanatus var. lanatus): A Review

Fruit quality traits of sweet watermelon (Citrullus lanatus var. lanatus) are crucial for new product development and commercialization. Sweet watermelon fruit quality traits are affected by the compositions of phytochemical compounds, phytohormones, and fruit flesh firmness which are affected by genes, the growing environment and their interaction. These compositions determine fruit ripening, eating quality, and postharvest shelf-life. Knowledge of the genetic profile and analyses of quality traits in watermelon is vital to develop improved cultivars with enhanced nutritional compositions, consumer-preferred traits, and extended storage life. This review aims to present the opportunities and progress made on the genetic analysis of fruit quality traits in watermelon as a guide for quality breeding based on economic and end-user attributes. The first section of the review highlights the genetic mechanisms involved in the biosynthesis of phytochemical compounds (i.e., sugars, carotenoids, amino acids, organic acids, and volatile compounds), phytohormones (i.e., ethylene and abscisic acid) and fruit flesh structural components (i.e., cellulose, hemicellulose, and pectin) elicited during watermelon fruit development and ripening. The second section pinpoints the progress on the development of molecular markers and quantitative trait loci (QTL) analysis for phytochemical compounds, phytohormones and fruit quality attributes. The review presents gene-editing technology and innovations associated with fruit quality traits for selection and accelerated cultivar development. Finally, the paper discussed gene actions conditioning fruit ripening in citron watermelon (C. lanatus var. citroides [L. H. Bailey] Mansf. ex Greb.) as reference genetic resources to guide current and future breeding. Information presented in this review is useful for watermelon variety design, product profiling and development to serve the diverse value chains of the crop.

Effect of Lactic Acid Fermentation on Volatile Compounds and Sensory Characteristics of Mango (Mangifera indica) Juices

Fermentation is a sustainable bio-preservation technique that can improve the organoleptic quality of fruit juices. Mango juices were fermented by monoculture strains of Lactiplantibacillus plantarum subsp. plantarum (MLP), Lacticaseibacillus rhamnosus (MLR), Lacticaseibacillus casei (MLC), Levilactobacillus brevis (MLB), and Pediococcus pentosaceus (MPP). Volatile compounds were sorbed using headspace solid phase microextraction, separated, and identified with gas chromatography-mass spectrometry. Forty-four (44) volatile compounds were identified. The control, MPP, and MLB had higher amounts of ethyl acetate, ethyl butyrate, 2-hexenal, 2,6-nonadienal, 2,2-dimethylpropanal, β-selinene, γ-gurjunene, α-copaene, and δ-cadinene, while MLC, MLP, and MLR had higher amounts of 2,3-butanedione and a cyclic hydrocarbon derivate. Consumers (n = 80) assessed their overall liking and characterized sensory attributes (appearance, color, aroma, flavor, consistency, acidity, and sweetness) using check-all-that-apply, and penalty analysis (just-about-right). Overall liking was associated with ‘mango color’, ‘pulp’, ‘mango aroma’, ‘sweet’, ‘natural taste’, and ‘mango flavor’ that described the control, MLB, MLC and MPP. Juices MLR and MLP were described as ‘bitter’, ‘sour’, ‘aftertaste’, and ‘off-flavor’. Multivariate analysis revealed relationships between the volatile compounds, mango juices fermented by different lactic acid bacteria, and sensory characteristics. Thus, the type of lactic acid bacteria strains determined the volatile and sensory profile of mango juices.

Evaluation of Bioactive Compounds and Bioactivities in Plum (Prunus salicina Lindl.) Wine

With the increase in demand of fruit wine year by year, it is necessary to develop novel fruit wine with high functional activities. Prunus salicina Lindl. (named as Niuxin plum) is a remarkable material for brewing fruit wine owing to its suitable sugar-acid ratio, characteristic aroma and bioactive compounds. This study intends to modify the fermentation technology, identify and quantify nutritional compositions and volatile profiles, as well as bioactive substances in Niuxin plum wine, as well as evaluate the antioxidant and hypoglycemic activities in vitro of major bioactive components from Niuxin plum wine. According to single-factor and orthogonal tests, the optimal fermentation conditions of 13.1% vol Niuxin plum wine should be Saccharomyces cerevisiae Lalvin EC1118 at 0.1% and a fermentation temperature of 20°C for 7 days. A total of 17 amino acids, 9 mineral elements, 4 vitamins, and 55 aromatic components were detected in plum wine. Polysaccharides from Niuxin plum wine (named as NPWPs) served as the major bioactive components. The NPWP with a molecular weight over 1,000 kDa (NPWP-10) demonstrated extraordinary DPPH free radical scavenging capacity and α-glucosidase inhibitory activity among all NPWPs having different molecular weight. Moreover, the structural characterization of NPWP-10 was also analyzed by high performance liquid chromatography (HPLC), fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectra studies. NPWP-10 was composed of mannose, rhamnose, arabinose, galactose and galacturonic acid with molar ratios of 2.570:1.775:1.045:1.037:1. NPWP-10 contained α-configuration as the main component and β-configuration as the auxiliary component. This study highlights NPWP-10 is an importantly biological polysaccharide from Niuxin plum wine, as well as provides a scientific basis for developing the plum wine industry.