Today, many different methods are applied for the correct use of foods and to prevent their deterioration. Ensuring healthy conditions for people in food consumption and consumption of healthy foods is very important for human welfare. In this study, food spoilage, the factors that cause food spoilage, its effects on a global basis, food transport systems (cold chain) and measures that prevent or delay food spoilage are discussed.

Decomposition of soil organic matter by microorganisms is a major process governing the carbon balance between soil and atmosphere which needs to be fully understood. Extracellular enzyme activity is often the limiting factor for microbial utilization of soil organic matter. Contrary to expectations, we observed that enzymatic activity rises at increasing temperatures in soils and sediments. Current climatic change will induce the increase of global mean temperatures, frequency of extreme heat events and soil temperatures during the next decades. The relevance of the increase in activity at high temperature is dependent on latitude. At latitudes around and below 40° a significant number of days per year present high temperatures. Results suggest that the hydrolytic activity of microbial extracellular enzymes is currently underestimated mainly at medium and low latitudes where soil temperatures frequently reach high values (often above 40oC). This report contributes to understand (1) the hydrolysis of soil organic matter within a latitude-dependent scenario of global warming and (2) the role of microorganisms in processing soil organic matter and their influence in carbon cycling.

Kefir is a kind of dairy drink with unique and exotic flavor that is traditionally produced from fermented milk with kefir grains included a mix of bacteria and yeasts. The phase separation during storage of kefir results in an unfavorable appearance, which is known as a defect, which can be controlled by making the cross-links between the milk proteins. In this research, the addition of the microbial transglutaminase enzyme (m-TG) to diminish the syneresis and its effect on the aromatic compounds of kefir was investigated during one-month storage at a refrigerated temperature using a solid phase microextraction method combined with a gas chromatography– mass spectrometer. The results showed that the adding of the m-TG to kefir significantly affected the syneresis of kefir and caused reduce in phase separation of kefir during storage. In total, 51 volatile compositions were isolated and identified from kefir samples using SPME-GC/MS. Most of the identified compounds include acids, alcohols, ketones, esters, and aldehydes, respectively. The results indicated that the storage time significantly affected the amount of all volatile compositions, so that some volatile compounds increased, while some volatile compounds decreased during storage. The m-TG had no effect the content of the volatile constituents except for alcohols. The findings of this study revealed that the total amounts of alcoholic and acidic compounds as well as carbon dioxide were increased during storage. On the other hand, total amounts of ketones, aldehydes and esters in kefir decreased during storage. Based on the findings of this study, it could be concluded that the use of m-TG without significant effect on the properties of aromatic compounds of kefir reduces its syneresis during storage.

Introduction: The word “ probiotic” comes from the Greek word “ pro bios” meaning “ for life” , which is the opposed of the term “ antibiotics” meaning “ against life. ” Probiotics are alive bacteria and the majority of probiotic microorganisms are belonging to the genera of Lactobacillus and Bifidobacterium. Regular consumption of probiotics in the adequate amounts have many beneficial health such as prevention of diarrhea, constipation, intestinal diseases and help to digest lactose and strengthen the immune system. On the other hand, recently the use of soy products has been progressively increased due to consumer consciousness about soy benefits. Soy probiotic yogurt is of special importance due to the presence of functional compounds such as probiotic microorganisms and natural prebiotics (raffinose, stachyose), the combination which is considered and dubbed as synbiotic. Dairy products, especially probiotic yogurt, are the most common foods that are used as probiotic products. On the other hand, yogurt production and similar products have always been accompanied with problems such as defects in texture, structure and syneresis. The functionality and structure of proteins can be modified with physical, chemical and enzymatic procedures. Enzymatic modification has been recommended as a useful technique owing to high specificity of enzymatic reactions and therefore a little risk of formation of toxic products. Transglutaminase enzyme can produce a gel with a desirable structure by forming covalent bonds between glutamine and lysine in protein systems. Therefore, the effect of application of transglutaminase enzyme in protein food systems (such as milk, yogurt, cheese, ice cream, bread, fish, meat and other food products) have been extensively studied by many researchers. So, the aim of this study was to evaluate the physicochemical and microbial properties of symbiotic soy yogurt as affected by TG-enzymatic treatment at different inulin concentrations. Material and methods: The effect of different amounts of TG-enzyme (0, 0. 015, 0. 03 and 0. 045%) and inulin (0, 1 and 2%) on physicochemical (pH, acidity, syneresis) and microbial characteristics (probiotic count) of synbiotic soy yogurt during 21 days of cold storage (1, 7, 14 and 21 days) was investigated. To prepare the synbiotic soy yoghurt samples, inulin as a prebiotic and Lactobacillus acidophilus and Bifidobacterium lactis as probiotic bacteria were used and added to the soy milk. After addition of inulin, soy milk was heated (95 ° C for 5 min) and cooled to inoculation temperature ° (45 C). After the enzyme addition, the probiotic starter culture was added and fermentation was done ° at 42 C until the pH was reached to 4. 6. Sample without TG-enzyme and inulin was considered as control yogurt. For performing analysis, data were analyzed by a completely randomized factorial design using SPSS software, version 24. The mean of treatments was compared with Duncan test at 95% confidence level. Results and discussion: The results showed that with increasing the enzyme concentration, amount of acidity and syneresis decreased while pH increased significantly (p<0. 001). This was probably due to formation of internal and interstitial bonds in protein network which causes reduction of bioavailability of organic compounds for microorganisms (reduce acidity) and increases water holding capacity (reduce syneresis). However, enzymatic treatment had no significant effect on total solids of the samples. Increasing the amount of inulin also caused a significant increase in acidity and total solids while expressively reduced pH and syneresis of yoghurt samples (p<0. 001). The reduction of syneresis as a consequence of inulin addition was probably due to water absorption and water holding capacity of this compound. The highest total solids was recorded for yogurt sample containing 2 percent inulin and the lowest was recorded for control (0 percent inulin). By passing the time of storage, pH and syneresis significantly decreased and acidity until the fourteenth day increased and thereafter decreased considerably (p<0. 001). However, there was no significant effect on the amount total solids. The results of microbial analysis showed that with increasing enzyme concentration, the survival amount of Bifidobacterium lactis decreased significantly (p<0/01). Although their number in the sample containing the highest level of enzyme was higher than standard. The formation of covalent bonds due to the addition of the TG enzyme can remove lower the molecular weight of peptides from the available microorganisms and thus reduce their growth. On the other hand, by increasing the enzyme concentration, unlike Bifidobacterium, the survival rate of Lactobacillus acidophilus increased significantly compared to the control sample, but eventually the amount was lower than the standard. By increasing the inulin concentration at level 2% the growth rate of Bifidobacterium lactis was significantly increased (p<0/01). The effect of storage period on the survival rate of Bifidobacterium showed that during storage, their number decreased significantly (p<0/05). However, the number of probiotic bacteria in all soy synbiotic yogurts at the end of 21-day maintenance were over 10 7 logcfu/g. Our results also showed significant interactions between three tested variables on the physicochemical characteristics and the probiotic counts. Conclusion: In general, the results of this study showed that the addition of enzyme and inulin during storage period did not have an adverse effect on pH and acidity and also reduced the syneresis. The sample containing 0. 045% enzyme and 2% inulin at the end of the storage period showed the least syneresis compared to the control sample. In this study, amongst two probiotic bacteria, Bifidobacterium lactis, in comparison with Lactobacillus acidophilus, was able to maintain its survival rate above the standard level. Among the different samples, the sample containing 2% inulin on the first day of storage period had the highest probiotic content. According to the results, the best synbiotic soy yogurt with acceptable probiotic count and physicochemical properties could be produced using 2% inulin and 0. 015% TG-enzyme concentration.

The present study evaluated the impact of the concentration of a microbial enzyme complex on the aerobic purification rate of domestic wastewater. A diverse and active microbial enzyme complex allows the efficient degradation of organic pollutants present in wastewater. In addition, environmental conditions, such as nutrient availability and optimum temperature, favor enzymatic activity and the performance of the purification process. For this purpose, aerobic depuration tests were carried out in a bioreactor considering three concentration levels of the microbial enzyme complex (1.0, 1.5, and 2.0 g/L), a controlled temperature of 17°C, and a dissolved oxygen concentration of 3.0 ppm. The adaptation process of the microorganisms lasted two days, with a daily decrease in the Chemical Oxygen Demand (COD) of 62.8, 71.1, and 77.9 ppm. Therefore, the removal rate increased with the concentration of the microbial enzyme complex, and the treatment time had a significant effect on the speed of purification.