Search Results (10)

Microbial fermentation is a primary method by which a variety of foods and beverages are produced. The term refers to the use of microbes such as bacteria, yeasts, and molds to transform carbohydrates into different substances. Fermentation is important for preserving, enhancing flavor, and improving the nutritional quality of various perishable foods. Historical records clearly show that fermented foods and drinks, such as wine, beer, and bread, have been consumed for more than 7000 years. The main microorganisms employed were Saccharomyces cerevisiae, which are predominantly used in alcohol fermentation, and Lactobacillus in dairy and vegetable fermentation. Typical fermented foods and drinks made from yogurt, cheese, beer, wine, cider, and pickles from vegetables are examples. Although there are risks of contamination and spoilage by pathogenic and undesirable microorganisms, advanced technologies and proper control procedures can mitigate these risks. This review addresses microbial fermentation and clarifies its past importance and contribution to food preservation, flavoring, and nutrition. It systematically separates yeasts, molds, and bacteria and explains how they are used in food products such as bread, yogurt, beer, and pickles. Larger producers employ primary production methods such as the artisanal approach, which are explored along with future trends such as solid-state fermentation, the potential of biotechnology in developing new products, and sustainability in new product development. Future research and development strategies can lead to innovations in methods that improve efficiency, product range, and sustainability. Full article

Red dragon fruit (Hylocereus polyrhizus), recognized globally for its substantial nutrient content and health benefits, has been extensively studied; studies have particularly focused on the fruit, while the composition of the stem remains less explored. This research focuses on optimizing fermentation parameters for red dragon fruit wine, specifically examining yeast-strain selection, juice-to-water dilution ratios, and yeast concentrations. Saccharomyces cerevisiae RV002 emerged as the optimal strain due to its robust performance and adaptability under adverse conditions. The study identified a 50% dilution ratio as ideal for maximizing clarity and the sensory attributes of the wine, whereas dilution ratios exceeding 90% significantly reduced ethanol content below acceptable commercial standards. An optimal yeast concentration of 1 g/L was found to balance microbial suppression and alcohol yield effectively; deviations from this concentration led to microbial contamination or impaired fermentation dynamics. Fermentation markedly altered the biochemical properties of Hylocereus polyrhizus, reducing sugar and vitamin C levels while increasing polyphenol content and antioxidant activity, thereby enhancing potential health benefits. These findings underscore the transformative effects of microbial activity on the substrate’s chemical landscape and highlight the potential of tailored fermentation strategies to enhance the utility and value of underutilized fruits in sustainable agricultural practices. Full article

The control of spoilage yeasts in wines is crucial to avoid organoleptic deviations in wine production. Traditionally, sulfur dioxide (SO₂) was used to control them; nevertheless, SO₂ influence on human health and its use is criticized. Biocontrol emerges as an alternative in wine pre-fermentation, but there is limited development in its applicability. Managing kinetics is relevant in the microbial interaction process. pH was identified as a factor affecting the interaction kinetics of Wickerhamomyces anomalus killer biocontrol on Zygosaccharomyces rouxii. Mathematical modeling allows insight into offline parameters and the influence of physicochemical factors in the environment. Incorporating submodels that explain manipulable factors (pH), the process can be optimized to achieve the best-desired outcomes. The aim of this study was to model and optimize, using a constant and a variable pH profile, the interaction of killer biocontrol W. anomalus vs. Z. rouxii to reduce the spoilage population in pre-fermentation. The evaluated biocontrol was W. anomalus against the spoilage yeast Z. rouxii in wines. The kinetic interactions of yeasts were studied at different pH levels maintained constant over time. The improved Ramón-Portugal model was adopted using the AMIGO2 toolbox for Matlab. A static optimization of a constant pH profile was performed using the Monte Carlo method, and a dynamic optimization was carried out using a method based on Fourier series and orthogonal polynomials. The model fit with an adjusted R² of 0.76. Parametric analyses were consistent with the model behavior. Variable vs. constant optimization achieved a lower initial spoilage population peak (99% less) and reached a lower final population (99% less) in a reduced time (100 vs. 140 h). These findings reveal that control with a variable profile would allow an early sequential inoculation of S. cerevisiae. The models explained parameters that are difficult to quantify, such as general inhibitor concentration and toxin concentration. Also, the models indicate higher biocontrol efficiency parameters, such as toxin emission or sensitivity to it, and lower fitness of the contaminant, at pH levels above 3.7 during biocontrol. From a technological standpoint, the study highlights the importance of handling variable profiles in the controller associated with the pH management actuators in the process without incurring additional costs. Full article

Beverages are an integral component of a person’s food package. Various types of microorganisms widely contaminate beverages. This review presents current research data aimed at identifying dominant microorganisms in beverages and molecular methods for their detection. Wine, beer, dairy drinks, and fruit juices were selected as the main objects of the study. The most contaminated beverage turned out to be fruit juice. As a result of a large number of independent studies, about 23 species of microorganisms were identified in it. At the same time, they are represented not only by bacterial and fungal organisms, but also by protozoa. Milk turned out to be the least contaminated in terms of detected bacteria. The most common pollutants of these beverages were Staphylococcus aureus, Bacillus cereus, and Vibrio parahaemolyticus. It has been established that among pathogenic genera, Salmonella sp., Campylobacter sp. and Shigella sp. are often present in beverages. One of the main tools for the quality control of beverages at all stages of their production is different types of polymerase chain reaction. The sequencing method is used to screen for microorganisms in beverages. The range of variations of this technology makes it possible to identify microorganisms in alcoholic and non-alcoholic beverages. The high specificity of methods such as PCR-RFLP, Rep-PCR, qPCR, End-point PCR, qLAMP, the molecular beacon method, and RAPD enables fast and reliable quality control in beverage production. Sequencing allows researchers to evaluate the microbiological diversity of all the studied beverages, while PCR varieties have demonstrated different fields of application. For example, PCR-RFLP, RAPD-PCR, and PCR allowed the identification of microorganisms in fruit juices, qPCR, LAMP, and the molecular beacon method in wine, LAMP and multiplex PCR in milk, and End-point PCR and Rep-PCR in beer. However, it is worth noting that many methods developed for the detection of microbial contaminants in beverages were developed 10–20 years ago; modern modifications of PCR and isothermal amplification are still poorly implemented in this area. Full article

Tokaj botrytized sweet wines are traditionally aged for several years in wood barrels or bottles. As they have significant residual sugar content, they are exposed to microbial contamination during ageing. Osmotolerant wine-spoilage yeasts are most commonly found in the Tokaj wine-growing region in the species Starmerella spp. and Zygosaccharomyces spp. For the first time, Z. lentus yeasts were isolated from post-fermented botrytized wines. Our physiological studies confirmed that these yeast strains are osmotolerant, with high sulphur tolerance and 8% v/v alcohol tolerance, and that they grow well at cellar temperature in acidic conditions. Low β-glucosidase and sulphite reductase activities were observed, whereas protease, cellulase, and α-arabinofuranosidase extracellular enzyme activities were not detected. Molecular biology analyses carried out by RFLP analysis of mtDNA revealed no remarkable differences between strains, while microsatellite-primed-PCR fingerprinting of the (GTG)₅ microsatellite and examination of chromosomal pattern revealed considerable diversity. The fermentative vigour of the tested Z. lentus strains was found to be significantly lower compared to the control Saccharomyces cerevisiae (Lalvin EC1118). It can be concluded that Z. lentus is a potential spoilage yeast in oenology which may be responsible for the initiation of secondary fermentation of wines during ageing. Full article

The yeast Brettanomyces bruxellensis is one of the most dangerous wine contaminants due to the production of phenolic off-flavors such as 4-ethylphenol. This microbial hazard is regularly tackled by addition of sulfur dioxide (SO₂). Nevertheless, B. bruxellensis is frequently found at low levels (ca 10³ cells/mL) in finished wines. Besides, consumers health concerns regarding the use of sulfur dioxide encouraged the search for alternative biocontrol measures. Recently, we found that Saccharomyces cerevisiae secretes a natural biocide (saccharomycin) that inhibits the growth of different B. bruxellensis strains during alcoholic fermentation. Here we investigated the ability of S. cerevisiae CCMI 885 to prevent B. bruxellensis ISA 2211 growth and 4-ethylphenol production in synthetic and true grape must fermentations. Results showed that B. bruxellensis growth and 4-ethylphenol production was significantly inhibited in both media, although the effect was more pronounced in synthetic grape must. The natural biocide was added to a simulated wine inoculated with 5 × 10² cells/mL of B. bruxellensis, which led to loss of culturability and viability (100% dead cells at day-12). The conjugated effect of saccharomycin with SO₂ was evaluated in simulated wines at 10, 12, 13 and 14% (v/v) ethanol. Results showed that B. bruxellensis proliferation in wines at 13 and 14% (v/v) ethanol was completely prevented by addition of 1.0 mg/mL of saccharomycin with 25 mg/L of SO₂, thus allowing to significantly reduce the SO₂ levels commonly used in wines (150–200 mg/L). Full article

Off-flavors produced by undesirable microbial spoilage are a major concern in wineries, as they affect wine quality. This situation is worse in warm areas affected by global warming because of the resulting higher pHs in wines. Natural biotechnologies can aid in effectively controlling these processes, while reducing the use of chemical preservatives such as SO₂. Bioacidification reduces the development of spoilage yeasts and bacteria, but also increases the amount of molecular SO₂, which allows for lower total levels. The use of non-Saccharomyces yeasts, such as Lachancea thermotolerans, results in effective acidification through the production of lactic acid from sugars. Furthermore, high lactic acid contents (>4 g/L) inhibit lactic acid bacteria and have some effect on Brettanomyces. Additionally, the use of yeasts with hydroxycinnamate decarboxylase (HCDC) activity can be useful to promote the fermentative formation of stable vinylphenolic pyranoanthocyanins, reducing the amount of ethylphenol precursors. This biotechnology increases the amount of stable pigments and simultaneously prevents the formation of high contents of ethylphenols, even when the wine is contaminated by Brettanomyces. Full article

Microbial contamination may represent a loss of money for wine producers as several defects can arise due to a microorganism’s growth during storage. The aim of this study was to implement a bioluminescence assay protocol to rapidly and simultaneously detect bacteria and yeasts in wines. Different wines samples were deliberately contaminated with bacteria and yeasts at different concentrations and filtered through two serial filters with decreasing mesh to separate bacteria and yeasts. These were resuscitated over 24 h on selective liquid media and analyzed by bioluminescence assay. ATP measurements discriminated the presence of yeasts and bacteria in artificially contaminated wine samples down to 50 CFU/L of yeasts and 1000 CFU/L of bacteria. The developed protocol allowed to detect, rapidly (24 h) and simultaneously, bacteria and yeasts in different types of wines. This would be of great interest for industries, for which an early detection and discrimination of microbial contaminants would help in the decision-making process. Full article

Meat products are potential vehicles for transmitting foodborne pathogens like Salmonella, S. aureus, and L. monocytogenes. We aimed to evaluate (1) the effect of the meat’s initial natural microbiota on Salmonella, S. aureus, and L. monocytogenes growth and survival in a batter to prepare a naturally fermented sausage, made with and without curing salts and wine (2) the effect of a lactic acid bacteria (LAB) starter culture and wine on the survival of the three pathogens during the manufacturing of a naturally fermented sausage made with meat with a low initial microbial load. The results revealed that the reduced contamination that is currently expected in raw meat is favorable for the multiplication of pathogens due to reduced competition. The inhibitory effect of nitrite and nitrate on Salmonella, S. aureus, and L. monocytogenes was confirmed, particularly when competition in meat was low. In any attempt to reduce or eliminate nitrite from naturally fermented sausages, the use of LAB starters should be considered to ensure an unfavorable competition environment for pathogens. In the experiment with naturally fermented sausage, chouriço, the reduction in a_w strongly inhibited the challenged pathogens, particularly when a LAB starter culture and wine were used. Full article

Food safety is one of the main concerns in the world and in wine it depends mostly on metabolites of microbial origin. The aim of this study was to investigate the occurrence of natural contaminants, ochratoxin A and biogenic amines (cadaverine, histamine, putrescine and tyramine), in Croatian commercial red wines originating from different Croatian wine-making regions. Ochratoxin A was detected in 92.8% of samples, however its concentrations in all samples were more than 10-fold lower than the limit set by the European Union (2 µg/kg), marking these wines as safe for consumption. The frequency of occurrence and measured concentrations of ochratoxin A were higher in wines produced in southern regions with highest values obtained in wines from southern Dalmatian islands. All samples were contaminated with cadaverine and putrescine, while 88.2% and 82.7% were contaminated with histamine and tyramine, respectively. Histamine concentrations ranged from below the limit of detection to 8.5 mg/L. Higher histamine concentrations were measured in wines with higher pH values which coincided with southern geographic origin. These results reinforce the need for routine detection and quantification of biogenic amines in Croatian wines to achieve better control of vinification and minimize their formation. Full article