Real-Time Monitoring of Chemical Changes in Three Kinds of Fermented Milk Products during Fermentation Using Quantitative Difference Nuclear Magnetic Resonance Spectroscopy

Probiotic Bifidobacterium animalis ssp. lactis Probio-M8 improves the fermentation and probiotic properties of fermented milk

Probiotics are increasingly used as starter cultures to produce fermented dairy products; however, few studies have investigated the role of probiotics in milk fermentation metabolism. The current study aimed to investigate whether adding Bifidobacterium animalis ssp. lactis Probio-M8 (Probio-M8) as a starter culture strain could improve milk fermentation by comparing the physicochemical characteristics and metabolomes of fermented milks produced by a commercial starter culture with and without Probio-M8. Our results showed that adding Probio-M8 shortened the milk fermentation time and improved the fermented milk texture and stability. Metabolomics analyses revealed that adding Probio-M8 affected mostly organic acid, AA, and fatty acid metabolism in milk fermentation. Targeted quantitative analyses revealed significant increases in various metabolites related to the sensory quality, nutritive value, and health benefits of the probiotic fermented milk, including 5 organic acids (acetic acid, lactic acid, citric acid, succinic acid, and tartaric acid), 5 EAA (valine, arginine, leucine, isoleucine, and lysine), glutamic acid, and 2 essential fatty acids (α-linolenic acid and docosahexaenoic acid). Thus, applying probiotics in milk fermentation is desirable. This study has generated useful information for developing novel functional dairy products.

Advances in fermented foods revealed by multi-omics: A new direction toward precisely clarifying the roles of microorganisms

Fermented foods generally comprise a complex micro-ecosystem with beneficial microbiota, functional products, and special flavors and qualities that are welcomed globally. Single-omics analysis allows for a comprehensive characterization of the main microbial factors influencing the function, flavor, and quality of fermented foods. However, the species, relative abundance, viability, growth patterns, and metabolic processes of microorganisms vary with changes in processing and environmental conditions during fermentation. Furthermore, the mechanisms underlying the complex interaction among microorganisms are still difficult to completely understand and analyze. Recently, multi-omics analysis and the integration of multiple types of omics data allowed researchers to more comprehensively explore microbial communities and understand the precise relationship between fermented foods and their functions, flavors, and qualities. Multi-omics approaches might help clarify the mechanisms underpinning the fermentation processes, metabolites, and functional components of these communities. This review clarified the recent advances in the roles of microorganisms in fermented foods based on multi-omics data. Current research achievements may allow for the precise control of the whole industrial processing technology of fermented foods, meeting consumers' expectations of healthy products.

Application progress of intelligent flavor sensing system in the production process of fermented foods based on the flavor properties

Fermented foods are sensitive to the production conditions because of microbial and enzymatic activities, which requires intelligent flavor sensing system (IFSS) to monitor and optimize the production process based on the flavor properties. As the simulation system of human olfaction and gustation, IFSS has been widely used in the field of food with the characteristics of nondestructive, pollution-free, and real-time detection. This paper reviews the application of IFSS in the control of fermentation, ripening, and shelf life, and the potential in the identification of quality differences and flavor-producing microbes in fermented foods. The survey found that electronic nose (tongue) is suitable to monitor fermentation process and identify food authenticity in real time based on the changes of flavor profile. Gas chromatography-ion mobility spectrometry and nuclear magnetic resonance technology can be used to analyze the flavor metabolism of fermented foods at various production stages and explore the correlation between flavor substances and microorganisms.

Toward in-process technology-aided automation for enhanced microbial food safety and quality assurance in milk and beverages processing

Ensuring the safety of food products is critical to food production and processing. In food processing and production, several standard guidelines are implemented to achieve acceptable food quality and safety. This notwithstanding, due to human limitations, processed foods are often contaminated either with microorganisms, microbial byproducts, or chemical agents, resulting in the compromise of product quality with far-reaching consequences including foodborne diseases, food intoxication, and food recall. Transitioning from manual food processing to automation-aided food processing (smart food processing) which is guided by artificial intelligence will guarantee the safety and quality of food. However, this will require huge investments in terms of resources, technologies, and expertise. This study reviews the potential of artificial intelligence in food processing. In addition, it presents the technologies and methods with potential applications in implementing automated technology-aided processing. A conceptual design for an automated food processing line comprised of various operational layers and processes targeted at enhancing the microbial safety and quality assurance of liquid foods such as milk and beverages is elaborated.

Real-Time Monitoring of Yogurt Fermentation Process by Aquaphotomics Near-Infrared Spectroscopy

Automated quality control could have a substantial economic impact on the dairy industry. At present, monitoring of yogurt production is performed by sampling for microbiological and physicochemical measurements. In this study, Near-Infrared Spectroscopy (NIRS) is proposed for non-invasive automated control of yogurt production and better understanding of lactic acid bacteria (LAB) fermentation. UHT (ultra-high temperature) sterilized milk was inoculated with Bulgarian yogurt and placed into a quartz cuvette (1 mm pathlength) and test-tubes. Yogurt absorbance spectra (830-2500 nm) were acquired every 15 min, and pH, in the respective test-tubes, was measured every 30 min, during 8 h of fermentation. Spectral data showed substantial baseline and slope changes with acidification. These variations corresponded to respective features of the microbiological growth curve showing water structural changes, protein denaturation, and coagulation of milk. Moving Window Principal Component Analysis (MWPCA) was applied in the spectral range of 954-1880 nm to detect absorbance bands where most variations in the loading curves were caused by LAB fermentation. Characteristic wavelength regions related to the observed physical and multiple chemical changes were identified. The results proved that NIRS is a valuable tool for real-time monitoring and better understanding of the yogurt fermentation process.

An NMR Metabolomics Approach to Investigate Factors Affecting the Yoghurt Fermentation Process and Quality

A great number of factors can influence milk fermentation for yoghurt production such as fermentation conditions, starter cultures and milk characteristics. It is important for dairy companies to know the best combinations of these parameters for a controlled fermentation and for the desired qualities of yoghurt. This study investigates the use of a ¹H-NMR metabolomics approach to monitor the changes in milk during fermentation from time 0 to 24 h, taking samples every hour in the first 8 h and then at the end-point at 24 h. Three different starter cultures (L. delbrueckii ssp. bulgaricus, S. thermophilus and their combination) were used and two different heat treatments (99 or 105 °C) were applied to milk. The results clearly show the breakdown of proteins and lactose as well as the concomitant increase in acetate, lactate and citrate during fermentation. Formate is found at different initial concentrations depending on the heat treatment of the milk and its different time trajectory depends on the starter cultures: Lactobacillus cannot produce formate, but needs it for growth, whilst Streptococcus is able to produce formate from pyruvate, therefore promoting the symbiotic relationship between the two strains. On the other hand, Lactobacillus can hydrolyze milk proteins into amino acids, enriching the quality of the final product. In this way, better insight into the protocooperation of lactic acid bacteria strains and information on the impact of a greater heat treatment in the initial matrix were obtained. The global chemical view on the fermentations provided using NMR is key information for yoghurt producers and companies producing starter cultures.

Short communication: Effect of different kefir grains on the attributes of kefir produced with milk from Costa Rica

Kefir is an artisanal product that is gaining scientific attention due to its increase in consumption attributed to its potential health benefits. The effect on the quality attributes of kefir grains of different origin (household and commercial) and preserved with different methods (drying and freezing) was evaluated to standardize a domestic and semi-industrial process. Chemical (protein, lactose. lactic acid, ethanol, and acetic acid) as well as microbial properties (total plate count and total yeast count) were monitored during the experiment. Results show a statistical difference between the kefir grains in terms of acetic acid and ethanol percentages, which leads to the conclusion that there is a difference in the microbial populations that produce these products. Lactic acid, protein, and lactose parameters are statistically the same as well as the growth in biomass and the total population of yeast. Our results suggest that both types of kefir grains maintain a similar performance and that their metabolic capabilities are stable throughout time (taking into account that the household grains have been productive for years), meaning that domestic or semi-industrial processes could be easily standardized.

Metabolic profiling of natural and cultured Cordyceps by NMR spectroscopy

Cordyceps, a type of Chinese herbal medicine that exhibits anti-angiogenesis and tumor growth suppression effects, has recently gained increasing popularity. However, high-quality, natural Cordyceps, such as Ophiocordyceps sinensis, is very rare and difficult to obtain in large amounts. Cordyceps is cultured instead of harvested from natural sources, but the quality with respect to the ingredients has not been fully studied. In this study, we performed an NMR metabolic profiling of aqueous extracts of Cordyceps without any sample treatment to evaluate the proper species and medium and influence of two different disinfection methods. It was discovered that Cordyceps militaris fungus and silkworm chrysalis medium were suitable for cultivation of Cordyceps. Furthermore, cordycepin, a Cordyceps-specific functional compound, was produced at different growth stages during different cultivation processes, even at the mycelial stage, and was found at three times higher concentrations in cultured C. militaris compared to that in naturally occurring C. militaris.

Probiotics Biofilm-Integrated Electrospun Nanofiber Membranes: A New Starter Culture for Fermented Milk Production

Electrospun nanofiber membranes are widely investigated in the past few decades as candidates for tissue engineering, which can mimic natural extracellular matrix (ECM) and improve cell adhesion, proliferation, and expression on nanofiber membranes. However, the formation of bacterial biofilms on nanofiber membranes and application of the biofilm-integrated nanofiber membranes remain largely unknown. Here, electrospun cellulose acetate nanofiber membranes are first utilized as scaffold materials for Lactobacillus plantarum ( L. plantarum) biofilm formation. Nanofiber membranes proved to be an excellent scaffold for bacteria biofilm with high stability, where biofilms were interlocked with nanofibers forming a cohesive structure. In comparison with planktonic bacteria, L. plantarum biofilms on nanofiber membranes show excellent gastrointestinal resistance. Instead of decreasing, the number of viable cells increased after 3 h digestion in vitro. The L. plantarum biofilm-integrated nanofiber membranes were used as reusable starter cultures for fermented milk production showing excellent fermentative ability and higher survival of L. plantarum during shelf life. The viable cells in fermented milk remained at 11 log CFU/g throughout the reusable batches, which is far above the required value of 7 log CFU/g in commercial products. In addition, the produced fermented milk possesses shorter fermentation time and higher survival of probiotics during shelf life. The results suggest electrospun nanofiber membranes are ideal scaffold materials for bacteria biofilms immobilization in biotechnology and fermentation engineering, which broaden the potential use of electrospun nanofiber membranes in microbiology and strengthen the application of biofilms in fermentation engineering.