Test for measuring the stretchability of melted cheese

Insights into the impact of complex phosphates on acid-induced milk fan gel properties: Texture, rheological, microstructure, and molecular forces

Milk fan cheese, a type of stretched -cheese, presents challenges in its stretch-forming. This study investigated the impacts of complex phosphates (sodium tripolyphosphate and sodium dihydrogen phosphate, STPP-DSP) on the gelling properties of acid-induced milk fan gel and the mechanisms contributing to its stretch-forming. The treatment of milk fan gel with STPP-DSP resulted in improved functional and textural properties compared with the control group. In particular, drawing length increased significantly from 69.67 nm to 80.33 nm, and adhesiveness increased from 1737.89 g/mm to 1969.79 g/mm. The addition of STPP-DSP also led to increased viscosity, elastic modulus (G'), and viscous modulus (G"). Microstructural analysis revealed the formation of a fibrous structure within the gel after STPP-DSP treatment, facilitating uniform embedding of fat globules and emulsification. Structural analysis showed that the addition of STPP-DSP increased β-fold and decreased random coiling of the gel, facilitating the unfolding of protein structures. Additionally, UV absorption spectroscopy and excitation-emission matrix spectroscopy results indicated the formation of a chelate between STPP-DSP and milk fan gel, increasing protein-protein molecular interactions. Evidence from differential scanning calorimetry and x-ray diffraction demonstrated the formation of sodium caseinate chelate. Fourier transform infrared spectroscopy and zeta potential analysis revealed that the sodium caseinate chelate formed through hydrophobicity, hydrogen bonding, and electrostatic forces. These findings provided theoretical insights into how phosphates can improve the stretch-forming of milk fan gel, facilitating the application of phosphate additives in stretched -cheese processing.

Sensory, textural, physico-chemical and enzymatic characterization of melted cheese with added potato and carrot peels

Food waste is one of the biggest societal problems in the globe due to its detrimental consequences on the environment. According to estimates from the Food and Agriculture Organization, this comes to about 1.3 billion tonnes per year. The current study aims to produce sustainable food products with high nutritional value by incorporating food waste. For the extraction of economically relevant products such as dietary fibers, biopolymers, natural antioxidants, and food additives, potato and carrot peel represent an inexpensive, valuable, and conveniently available resource. Cheese is a functional dairy product that people eat for its high nutritional content, which aids in the treatment of conditions including diabetes, obesity, hypertension, and digestive problems in addition to giving them energy. Thus a control sample and 10 samples of melted cheese with various amounts of potato and carrot peelings were prepared. To explore the nutritional value of potato and carrot peels in melted cheese, an analysis was conducted on the fluctuation of physicochemical (acidity, pH, dry matter, water activity, and salt content) and enzymatic (L-lactic acid, lactose, D-glucose, and D-galactose) parameters. Consumer acceptability of the products was assessed by textural and sensory analysis. During the whole storage period, the samples of melted cheese with potato and carrot peels recorded higher values than the control sample, the results obtained for them being better. Samples with added potato or carrot wastes were more stable over time, as compared to control samples.

Application of a Tensile Test Method to Identify the Ductile-Brittle Transition of Caramel

During cutting of foods, tensile stresses in front of the blade are responsible for the separation of the material. Therefore, tensile tests can be helpful to gain knowledge on deformation properties related to pre-fracture cutting behavior as well as on phenomena in the fracture zone, which are velocity-dependent in viscoelastic materials. The aim of this work was to apply a tensile test method for model caramels to investigate their behavior and to identify conditions where the ductile-brittle transition occurs. After executing pre-trials, tensile velocity, caramel moisture, and temperature were the parameters that were varied for this purpose. In general, increasing velocity, decreasing temperature, and decreasing moisture resulted in a stiffer response and caused a shift from a ductile to a more brittle behavior, attributable to reduced viscous contributions to the material and longer relaxation times. Fracture strain was notably lower than the maximum plastic elongation in the ductile case, but we observed equalization close to the ductile-brittle transition point for our material. This study serves as basis for an in-depth research on the complex deformation and fracture phenomena during cutting of viscoelastic food systems, including numerical modeling.

Effect of Packaging and Portioning on the Dynamics of Water–Fat Serum Release from Fresh Pasta Filata Soft Cheese

The aim of the present study was to analyze the impact of cheese fragmentation and packaging on the dynamics of water–fat serum released from pasta filata cheese made from cow’s milk and its mixture with sheep’s milk. The addition of sheep’s milk reduced the amount of leachate from the vacuum-packed cheeses and did not cause as much loss of gloss as in the case of cow’s milk cheeses. This was also reflected in the microscopic images of the cheese samples. Consumers showed less acceptance of cow’s milk pasta filata cheeses than cheeses made with a mixture of cow’s and sheep’s milk (they had the same fat content, acidity, hardness, and oiling-off, but better stretching). The data describing water–fat serum release from pasta filata cheese within 24 h of unpacking was modeled with the use of the feed-forward artificial neural networks, whose architecture is based on Multi-Layer Perceptron with a single hidden layer. The model inputs comprised four independent variables, including one quantitative (i.e., time) and the other qualitative ones, which had the following states: type of raw material (cow’s milk, cow-sheep’s milk), way of sample portioning (whole, quarters, slices), packing method (vacuum packed and packed in brine).

The stretchability of Mozzarella cheese evaluated by a temperature-controlled 3-prong hook test

Stretchability is one of the most important functional properties of Mozzarella cheese, but no objective and widely accepted technique exists for evaluation; most of the cheese stretchability tests are influenced by the ambient conditions. This paper demonstrates a technique, which is novel and relatively simple, to evaluate the stretchability of Mozzarella cheese objectively. In an oil bath, melted cheese is stretched by a hook probe, controlled by an Instron tensile tester (Instron Corp., Norwood, MA); cheese strands are lifted from the melted cheese reservoir to a stretch length of 300 mm, when the load and extension data are recorded by the Instron tensile tester. This test overcomes other tests' drawbacks, such as subjective stretching speeds and variations in ambient temperature and humidity. Through the test comparison on standard Mozzarella, the modified stretching test in an oil bath has greater repeatability than the original test without oil bath. From the load and extension curve, the yield load is measured to evaluate the stretchability. In the meantime, the inversion point extension of necking is also measured based on polymer study, producing more repeatable results than the yield load. The modified 3-prong hook test was applied to Mozzarella cheese samples with different processing conditions, including the screw conditions (screw time, speed, and temperature), draining pH, calcium content, and fat content, and significant differences were found between these samples and the control sample.

Evaluation of Mozzarella Cheese Stretchability by the Ring-and-Ball Method

The functional quality of Mozzarella cheese is defined by its ability to melt and stretch. Currently used methods to evaluate the stretchability of Mozzarella cheese are empirical and lack control of moisture loss and temperature. The typical fork test, the imitative tensile stretch test, and the 3-pronged-hook probe tensile test all expose the test samples to ambient conditions during stretching and thus give poorly reproducible results. An objective method developed in our laboratory to evaluate stretchability of cheese is based on the principle of the Ring-and-Ball method used to measure the softening point of polymers. This technique, which controls temperature and moisture loss, was used to quantify the stretchability of Mozzarella cheese. Average stretch length varied between 4 to 9 cm between the youngest and the oldest cheese samples. The method was found to be sensitive enough to discriminate between cheeses of different ages. The results showed that the technique is reproducible and gives reliable stretch length and stretch length vs. time data, which was further used to estimate extensional viscosity of the test sample. Age-related differences were reflected in extensional viscosity that decreased from 17.4 to 13.6 kPa.s with increase in age.

Proteolytic specificity of Lactobacillus delbrueckli subsp. bulgaricus influences functional properties of mozzarella cheese

Low-moisture part-skim Mozzarella cheeses were manufactured from 2% fat milk and aged for 21 d. Treatments included cheeses made with one of three different strains of Lactobacillus delbrueckii ssp. bulgaricus in combination with a single strain of Streptococcus thermophilus. A fourth, control treatment consisted of cheeses made with only S. thermophilus. Although total proteolytic ability of these strains, as indicated by the o-phthaldialdehyde analysis, was similar in each of the three strains of L. bulgaricus, these strains exhibited different proteolytic specificities toward the peptide, alpha(s1)-CN (f 1-23). On the basis of their alpha(s1)-CN (f 1-23) cleavage patterns and a previously described classification, these strains were assigned to the groups I, III, and V. The objective of this study was to investigate the influence of lactobacilli proteolytic systems, based on specificity toward alpha(s1)-CN (f 1-23), on functionality of part-skim Mozzarella cheese. Moisture, fat, protein, salt-in-moisture, and moisture in nonfat substances content of cheeses made with groups I, III, and V strain were similar. Control cheese had a lower moisture content than did other treatments. Significant differences were observed in functional properties between cheeses manufactured using groups III and V strains. Cheeses made with groups I and III strains were similar in their meltability, hardness, cohesiveness, melt strength, and stretch quality. Meltability and cohesiveness increased with age, while melt strength and stretch quality decreased with age for all cheeses. Additionally, HPLC showed that total peak areas of water-soluble peptides derived from cleavage of alpha(s1)-CN (f 1-23) by different strains of lactobacilli could be highly correlated to meltability and stretch characteristics of cheeses made with those strains.