Profiles of free fatty acids, free amino acids, and volatile compounds of milk bases fermented byLactobacillus caseiGBHM-21 with different fat levels

Addressing flavor challenges in reduced-fat dairy products: A review from the perspective of flavor compounds and their improvement strategies

In recent years, the demand for reduced-fat dairy products (RFDPs) has increased rapidly as the health risks associated with high-fat diets have become increasingly apparent. Unfortunately, lowering the fat content in dairy products would reduce the flavor perception of fat. Fat-derived flavor compounds are the main contributor to appealing flavor among dairy products. However, the contribution of fat-derived flavor compounds remains underappreciated among the flavor improvement factors of RFDPs. Therefore, this review aims to summarize the flavor perception mechanism of fat and the profile of fat-derived flavor compounds in dairy products. Furthermore, the characteristics and influencing factors of flavor compound release are discussed. Based on the role of these flavor compounds, this review analyzed the current and potential flavor improvement strategies for RFDPs, including physical processing, lipolysis, microbial applications, and fat replacement. Overall, promoting the synthesis of milk fat characteristic flavor compounds in RFDPs and aligning the release properties of flavor compounds from the RFDPs with those of equivalent full-fat dairy products are two core strategies to improve the flavor of reduced-fat dairy products. In the future, better modulation of the behavior of flavor compounds by various methods is promising to replicate the flavor properties of fat in RFDPs and meet consumer sensory demands.

Design and Volatile Compound Profiling of Starter Cultures for Yogurt Preparation

Stable symbiotic starter cultures were created using selected strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus with antimicrobial activity against pathogens and necessary antibiotic sensitivity, growth kinetic parameters, and metabolic profiles. The volatile compound profiles of the obtained starter cultures were determined and their specificity was proven depending on the ratio of monocultures in each combination. The influence of the freeze-drying process on the starter cultures in relation to the production of aromatic components was investigated and it was demonstrated that this process had a significant effect on the content of the aroma-forming substances in the fermented milk. However, the influence of the pre-cooling process and crude fat content from 1.5 to 3.0% did not notably affect the levels of volatile compounds synthesized by the selected starter cultures. Comprehensive data for all volatile aromatic metabolites in the fermented milk were also obtained. These designed symbiotic starter cultures can be used to produce traditional Bulgarian yogurt with increased functional and probiotic properties.

Probiotic fermentation of polyphenols: potential sources of novel functional foods

Fermented functional food products are among the major segments of food processing industry. Fermentation imparts several characteristic effects on foods including the enhancement of organoleptic characteristics, increased shelf-life, and production of novel health beneficial compounds. However, in addition to macronutrients present in the food, secondary metabolites such as polyphenols are also emerging as suitable fermentable substrates. Despite the traditional antimicrobial view of polyphenols, accumulating research shows that polyphenols exert differential effects on bacterial communities by suppressing the growth of pathogenic microbes while concomitantly promoting the proliferation and survival of probiotic bacteria. Conversely, probiotic bacteria not only survive among polyphenols but also induce their fermentation which often leads to improved bioavailability of polyphenols, production of novel metabolic intermediates, increased polyphenolic content, and thus enhanced functional capacity of the fermented food. In addition, selective fermentation of combinations of polyphenol-rich foods or fortification with polyphenols can result in novel functional foods. The present narrative review specifically explores the potential of polyphenols as fermentable substrates in functional foods. We discuss the emerging bidirectional relationship between polyphenols and probiotic bacteria with an aim at promoting the development of novel functional foods based on the amalgamation of probiotic bacteria and polyphenols.

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Optimizing the acceleration of Cheddar cheese ripening using response surface methodology by microbial protease without altering its quality features

Cheddar cheese proteolysis were accelerated employing Penicillium candidum PCA1/TT031 protease into cheese curd. In the present study, several of the significant factors such as protease purification factor (PF), protease concentration and ripening time were optimized via the response surface methodology (RSM). The ideal accelerated Cheddar cheese environment consisted of 3.12 PF, 0.01% (v/v) protease concentration and 0.6/3 months ripening time at 10 °C. The RSM models was verified to be the most proper methodology for the maintain of chosen Cheddar cheese. Under this experimental environment, the pH, acid degree value (ADV), moisture, water activity (a_w), soluble nitrogen (SN)%, fat and overall acceptability were found to be 5.4, 6.6, 35%, 0.9348, 18.8%, 34% and 13.6, respectively of ideal Cheddar cheese. Furthermore, the predicted and experimental results were in significant agreement, which confirmed the validity and reliability of the suggested method. In spite of the difference between the ideal and commercial Cheddar cheese in the concentration of some of amino acids and free fatty acids, the sensory evaluation did not show any significant difference in aroma profile between them.

Gas chromatography-mass spectrometry based metabolomic approach to investigate the changes in goat milk yoghurt during storage

The overall goal was to utilize a gas chromatography spectrometry based metabolomics approach to investigate the metabolite changes in goat milk yoghurt during storage. A total of 129 metabolites were identified in goat milk yoghurt during 28 days refrigerated storage. Among 129, 39 metabolites were differentially regulated (p < 0.05) wherein 22 were upregulated (UR) and 17 were downregulated (DR). 17 (9 UR, 8 DR), 20 (11 UR, 9 DR) and 2 (both UR) differential metabolites were identified during storage period of 0-14, 14-28, and 0-28 days, respectively. Metabolic pathway analysis revealed that aminoacyl-tRNA biosynthesis, phenylalanine, tyrosine and tryptophan biosynthesis and phenylalanine metabolism altered during 0-14 days storage; while fatty acid biosynthesis, and propanoate metabolism altered during 14-28 days of storage. Metabolite-gene interaction analysis identified genes regulated by differentially expressed metabolites. Functional annotation of interacted genes in corroboration with that of KEGG pathway analysis provided the probable mechanisms that altered the metabolites during storage. These findings reveal comprehensive insights into the metabolite alterations during storage. This research provides practical information for developing goat milk yoghurt with enhanced bio-activities and would aid in future investigations into the nutritional research and isolation of functional compounds.

Antimicrobial Biomasses from Lactic Acid Fermentation of Black Soldier Fly Prepupae and Related By-Products

Worldwide, thousands of insect species are consumed as food or are used as feed ingredients. Hermetia illucens, ‘black soldier fly’, is one of them, and a large amount of puparia and dead adults flies are accumulated during rearing. These materials represent important wastes but no studies are still present in the literature regarding their functional properties and potential reuse. Lactic acid bacteria (LAB) are a heterogeneous group of bacteria contributing to various industrial applications, ranging from food fermentation, chemicals production to pharmaceuticals manufacturing. A LAB feature of industrial interest is their ability to produce antimicrobial metabolites. Considering the scientific and commercial interest in discovering novel antimicrobials, this work will be direct towards fermentation of insect-derived biomasses: puparia and adults insect at the end of life cycle. To the best of our knowledge, the in vitro antimicrobial activity of fermented insects is tested for the first time. This study aimed also to evaluate differences in the composition between fermented and unfermented insects, and to study whether the fermentation and the type of LAB used played a crucial role in modifying the composition of the substrate. Results firstly highlighted fermentability of this species of insects, showed that fermented black soldier flies puparium possess a high antimicrobial activity against tested pathogens. Moreover, result of chemical composition showed that fermented biomass had a higher percentage of fat and a more complex fatty acids profile.

Cooperation between Lactococcus lactis NRRL B-50571 and NRRL B-50572 for Aroma Formation in Fermented Milk

The aim of the present study was to characterize the aroma and volatile profiles of milk fermented by wild Lactococcus lactis NRRL B-50571 (FM-571) and NRRL B-50572 (FM-572) and co-fermented with both strains (co-FM). Milks fermented by these strains have been reported to have an antihypertensive effect, yet their sensory characteristics, which are of great importance for consumer acceptance of functional foods, have not been studied. In the study, volatiles were determined using solid-phase microextraction gas chromatography mass spectrometry (SPME-GC-MS) and aroma was determined by quantitative descriptive sensory analysis (QDA). Volatile compounds identified in FM-571, FM-572, and co-FM were mainly acids, alcohols, aldehydes, and ketones. FM-571 showed higher total relative volatile abundance than FM-572 or co-FM. Furthermore, the concentrations of specific amino acids (aa) were lower in FM-571 and co-FM than in FM-572. Thus, these results suggested that FM-571 or co-FM are more efficient in transforming specific aa into the corresponding volatiles than FM-572. Indeed, several alcohols and aldehydes, associated with the catabolism of these aa, were found in FM-571 and co-FM, but not in FM-572. Additionally, QDA showed that FM-571 and co-FM presented higher yeasty and cheesy aroma descriptors than FM-572. Also, total aroma intensity scores for FM-571 were higher than those for co-FM or FM-572. Thus, results suggested that the combination of these two specific wild L. lactis strains may complement amino acid catabolic routes that resulted in the enhancement or attenuation of aroma production of single strains, presenting new possibilities for the preparation of custom-made starter cultures.