Effect of milk fat concentration and gel firmness on syneresis during curd stirring in cheese-making

Physicochemical properties and survival assessment of potential probiotics in a novel dairy drink during storage

A novel fermented dairy drink utilizing microbial strains displaying potential probiotic attributes was formulated. The study constituted several experimental cohorts, including Lactiplantibacillus plantarum AB6-25, isolated from a human stool sample; Lacticaseibacillus casei K2, sourced from a koumiss sample; Lacticaseibacillus rhamnosus 3B7, derived from a traditional yogurt sample; and identical lactic acid bacteria (LAB) in combination with yeast (Saccharomyces boulardii T8-3C from chicken feces) strains. Two distinct iterations of probiotic-fermented dairy drinks were generated by introducing subcultured microorganism cultures: LAB strains at a concentration of 1% each (designated as combination A) and a blend of LAB strains at 1% each along with T8-3C at 0.5% (designated as combination B) into both whole and semi-skimmed milk matrices. The fermentation process persisted until the pH reached 4.6 under constant conditions of 37 ± 1°C. Subsequently, the samples were held at 4 ± 1°C for 15 days. The groups' physicochemical, microbiological, and sensory characteristics were determined on days 1, 8, and 15 of storage, and the protein profile was determined. Standardized regression analysis and principal component analysis evaluated the results. Fat content affected the changes in dry matter. pH decreased in all samples during storage, particularly in the yeast group. The microorganism group positively affected syneresis, whereas fat content and the interaction of fat content and the microorganism group had a negative effect. The most critical factor in the decrease in syneresis was the increase in fat content. LAB and yeasts maintained their probiotic effects during storage, with a viability level of approximately 109 and 108 cfu/mL, respectively.

The Influence of Milk Standardization on Chemical Composition, Fat and Protein Recovery, Yield and Sensory Properties of Croatian PGI Lički Škripavac Cheese

The aim of this work was to evaluate the influence of cheese milk standardization on chemical composition, fat and protein recovery, yield and sensory properties of Croatian soft Protected Geographical Indication (PGI) Lički škripavac cheese. Standardization of milk to the casein/fat ratio of 0.7 was carried out by adding skimmed milk powder (SMP) to cheese milk and by skimming part of the milk fat. Results showed that losses of fat by whey were significantly (p < 0.05) lower after Lički škripavac cheese produced from standardized milk by skimming part of the milk fat. Standardization of cheese milk by addition of SMP caused higher losses of protein (p < 0.05) and total solids (p < 0.0001) by whey. Both methods of cheese milk standardization caused a significant (p < 0.01) decrease in milk fat and fat in dry matter content in cheese. In contrast, standardization of cheese milk caused a significant (p < 0.01) increase in protein content in cheese milk. Moisture in non-fat substance (MNFS) significantly (p < 0.05) decreased. Optimization of the casein/fat ratio did not cause a significant increase in fat recovery, but protein recovery significantly increased (p < 0.01). Addition of SMP to cheese milk significantly (p < 0.01) increased actual and adjusted cheese yield. The addition of SMP led to a noticeably higher (p = 0.10) sensory score of Lički škripavac cheese.

Multiple linear regression modeling: Prediction of cheese curd dry matter during curd treatment

Cheese curd dry matter determines functional properties and process parameters during cheese manufacture. Dry matter is affected by many internal (milk composition and pre-treatment) and external (cheese process parameters) factors that are not considered in the most common models. The purpose of this study was to consider a large number of multiple linear regression models that use these internal and external factors as predictor variables, and select the most suitable of these models in order to predict the cheese curd dry matter during curd treatment. Dry matter (DM_exp,nat) was experimentally determined to create a native data set (n = 1013) for fitting the regression model. Dry matter was affected by curd treatment time (CTT), curd treatment temperature (ϑ), pH-value (pH), curd grain size (CGS), fat level (f) and degree of microfiltration (i). A large number of empirical regression models, organized into three different groups, depending on the predictors used, were developed on basis of DM_exp,nat. A Monte Carlo approach was used to select the optimal model, taking into account the value of Akaike's information criterion (AICc) and the coefficient of determination (R²) of each model. The best models were further analyzed to check for potential bias and to verify that the model assumptions were met. We considered one model of group G2 with 11 terms to most closely fit the aforementioned criteria (native data set; R² = 95.55). This model was successfully validated by an independent validation data set (n = 120; R² = 91.95).

Effect of commercial grape extracts on the cheese-making properties of milk

Grape extracts can be added to milk to produce cheese with a high concentration of polyphenols. Four commercial extracts from whole grape, grape seed, and grape skin (2 extracts) were characterized and added to milk at concentrations of 0, 0.1, 0.2, and 0.3% (wt/vol). The effect of grape extracts on the kinetics of milk clotting, milk gel texture, and syneresis were determined, and model cheeses were produced. Whole grape and grape seed extracts contained a similar concentration of polyphenolic compounds and about twice the amount found in grape skin extracts. Radical scavenging activity was directly proportional to the phenolic compounds content. When added to milk, grape extracts increased rennet-induced clotting time and decreased the clotting rate. Although differences were observed between the extracts, the concentration added to milk was the main factor influencing clotting properties. With increasing concentrations of grape extracts, milk gels showed increased brittleness and reduced firmness. In addition, syneresis of milk gels decreased with increasing concentrations of grape extracts, which resulted in cheeses with a higher moisture content. The presence of grape extracts in milk slightly increased protein recovery in cheese but had no effect on fat recovery. With whole grape or grape seed extracts added to milk at 0.1% (wt/vol), the recovery coefficient for polyphenols was about 0.63, and decreased with increasing extract concentration in milk. Better polyphenol recovery was observed for grape seed extracts (0.87), with no concentration effect. Commercial extracts from whole grape, grape seed, or grape skin can be added to milk in the 0.1 to 0.3% (wt/vol) concentration range to produce cheese with potential health benefits, without a negative effect on cheese yield.