On the basis of Microbiology of the food chain-Estimation of measurement uncertainty for quantitative determinations (ISO 19036) and Guidelines for the estimation of measurement uncertainty of food microbiological quantitative detection (RB/T 228-2023), the top-down method was used to design an experimental scheme for uncertainty evaluation in three different quantitative assays by using raw and fermented milk as samples. The uncertainty evaluation for total colony number included technical uncertainty (utech), matrix uncertainty (umatrix) and Poisson distribution uncertainty (upoisson); when the result was 9.4 × 104 CFU/mL, the extended uncertainty was 0.31 (lg (CFU/mL)). The uncertainty evaluation for maximum probable number (MPN) included utech, umatrix, and uncertainty based on the most probable number (uMPN); when the result was 24 MPN/g, the extended uncertainty was 0.94 (lg (MPN/g)). The uncertainty evaluation for total colony number that needs to confirm target microorganisms included utech, umatrix, upoisson, and confirmatory uncertainty (uconf); when the result was 22 CFU/g, the extended uncertainty was 0.29 (lg (CFU/g)).

This study was conducted to reveal the effect of milk-clotting enzyme (MCE) produced by Bacillus licheniformis on the texture of Cheddar cheese during ripening. Cheddar cheese and Cheddar cheese analogue were prepared with the MCE and designated as CDF and CD3, respectively, and commercial chymosin was used as a control (CCF).The changes in the texture, rheology and microstructure of cheese during ripening were analyzed. The results were as follows: The hardness of the three cheeses increased with maturation time, while the elasticity and chewiness presented a downward trend. The hardness, springiness and chewiness of CDF were the lowest. The scanning electron microscope (SEM) results showed that the compactness of the protein structure decreased with increasing maturity, and the structure of CDF was looser than that of CCF. The rheological results showed that the storage modulus and loss modulus decreased with increasing ripening time up to six months and increasing sweep temperature. The tan δ value decreased during the ripening process, indicating that the fluidity of cheese decreased with increasing ripening time. The fluidity and fusibility of CDF were better than those of the other groups. The above results indicated that the mechanical properties of cheese made with Bacillus licheniformis MCE were better than those made with commercial rennet, while the latter had harder texture and denser protein network structure.

Hydrolyzed protein formula not only solves the problem of allergy or intolerance to cow’s milk proteins in infants and young children, but also meets the nutritional needs. Degree of hydrolysis is an important parameter to evaluate hydrolyzed protein formula. However, there are currently no methods available to determine the degree of hydrolysis of hydrolyzed protein formula. This article presents a brief introduction to the basic concepts of hydrolyzed protein formula and its degree of hydrolysis, and summarizes the existing methods for detecting the degree of hydrolysis of proteins. We expect this review to provide a reference for the establishment of detection methods for the degree of proteolysis of hydrolyzed protein formula.

In this study, a low-fat Cheddar cheese was developed using polymerized whey protein (PWP) as a fat replacer and Lactobacillus helveticus as an auxiliary culture, and the effects of PWP on the physicochemical properties of cheese were studied. Results showed that addition of PWP and Lactobacillus helveticus increased the contents of moisture, protein, free amino acids and volatile compounds and lactic acid bacterial population, and markedly improved sensory characteristics and acceptance of cheese. Addition of PWP reduced the fat ripening period, and increased pH 4.6-soluble nitrogen (SN) fraction by 9.45% and 12 g/100 mL trichloracetic acid (TCA)-SN fraction by 11.74% after ripening. Cheese yield was not affected by adding PWP or the auxiliary culture. All the data indicated that polymerized whey protein can be used as a promising fat replacer for developing low-fat Cheddar cheese with good texture and sensory properties.

Brown yogurt is a new type of yogurt with a burned flavor formed by the nonenzymatic Maillard reaction and silky smooth mouthfeel that contains high-quality nutrients and has become a new hotspot in the yogurt market. As Gansu province is one of the major livestock production areas and dairy processing bases in China, this region is bound to development the brown yogurt industry and seize market share. This article reviews the current status of the development of Gansu’s brown yogurt industry and existing problems. This review covers a summary of the history of the development of this industry and the problems encountered during the development process, the barriers to and driving forces for the research and development of brown yoghurt, the current status and challenges of brown yogurt processing, and the current trends and future prospects of brown yogurt.

Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains were isolated from commercial yogurts using selective media, and physiological and biochemical tests, sugar fermentation experiments and 16S rDNA homology analysis were used to identify the isolated strains. Genotyping of the strains was performed by pulsed field gel electrophoresis (PFGE). It was found that both Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus were detected in all yogurt samples. Streptococcus thermophilus had the same genotyping only in two yogurts, while other Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains were different in different yoghurts. The results showed that PFGE was an effective method for genotyping of different strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus.

In recent years,exopolysaccharides produced by food-grade bacteria has aroused great interest.worldwide.In addition to the biological effects on their producers themselves,bacterial exopolysaccharides are widely applied in the agricultural,food,pharmaceutic as well as chemical industries for their prominently biological activities and processing properties.In this paper,the roles of some bacterial exopolysaccharides in biofilm formation and their chemical structures and prospects for application are reviewed.Further investigation on bacterial exopolysaccharides is also suggested.

This study researched the effect of homogenization and post-sterilization of shelf-stable yoghurt the morphology of modified starch granules as one of its ingredients. It was demonstrated that with increasing either homogenization temperature or pressure, more starch granules were broken down. The optimal homogenization temperature was between 60 and 63 ℃ and the optimal pressure was in the range of 15–20 MPa. The starch granules further swelled under line pressure during ultra high temperature (UHT) processing, and they gradually enlarged or even cracked with an increase in either line pressure (up to 7 bar) or reflux cycles. Increased temperature up to 80 ℃ during UHT processing resulted in breakdown of more starch granules.

This study investigated the gelatinization properties of three types of modified starch and their application in long shelf-life yogurt. The three types of modified starch were physically modified starch (PMS), acetylated distarch phosphate (ADSP), hydroxypropyl distarch phosphate (HDSP). The results showed that the granular structure of the three kinds of starch remained intact after gelatinization. They all had strong shear resistance, and ADSP and HDSP showed stronger shear resistance and higher gelatinization temperature than PMS. Adding 2% (m/m) modified starch in long shelf-life yogurt increased its apparent viscosity, water holding capacity, viscoelasticity, yield stress, and storage stability. ADSP was better to improve the quality of long shelf-life yogurt than HDSP and PMS.

The influence of whey protein concentrate (WPC80) added to fermented skim milk drink on its stability was studied. The stability of fermented skim milk drink with different concentrations of whey protein concentrate was evaluated by particle size distribution, centrifugal analysis and Turbiscan analysis. The results showed that fermented milk drink containing 30% WPC80 had the smallest particle size and smallest centrifugal sediment. The turbiscan analysis showed distinctly that the fortified drink produced less sediment than the fermented milk drink with no added WPC80.

This study used a quadratic rotation-orthogonal composite experimental design with four independent variables at five levels each to establish optimal process conditions for industrial production of Mozzarella cheese. The process conditions investigated in this study included fermentation time, clotting time, whey pH and the amount of added NaCl. A regression model to optimize these process conditions was proposed and validated for its statistical significance. The optimal process conditions that provided the maximum yield of Mozzarella cheese (24.78%) were determined as follows: fermentation time 27.5 min, clotting time 37.5 min, whey pH 6.3, and addition of 2.07% NaCl. The resulting cheese had a nice flavor, a close, smooth and flexible texture and a homogeneous color and its fiber-drawing capacity, meltability and foaming properties were good. All these parameters were comparable to those of laboratory-made cheese and met the quality requirements for use in pizza. The optimized process parameters are suitable for large-batch production of Mozzarella cheese in industrial practice.

This study investigated the effect of addition of protein isolates from three different plants (pea, mung and soybean) on cheese properties to find the most suitable plant protein for application in cheese. Milk coagulation properties (coagulation time, curd strength and whey OD value) and textural properties (elasticity, cohesiveness and chewiness) were comparatively tested on the three cheese samples. Moreover, sensory evaluation was carried out fuzzy judgment as well. Results showed that pea protein isolate provided better quality of cheese than the other two protein isolates.