Influence of milk-clotting enzyme concentration on the alphas1-casein hydrolysis during soft cheeses ripening

Effects of the Autochthonous Probiotic Bacteria Lactobacillus plantarum B and Lactococcus lactis Subsp. lactis S1 on the Proteolysis of Croatian Cheese Ripened in a Lambskin Sack (Sir iz Mišine)

This study aims to determine the effects of the autochthonous probiotic bacteria Lactobacillus plantarum B (currently Lactiplantibacillus plantarum) and Lactococcus lactis subsp. lactis S1 on proteolysis during the ripening of Sir iz mišine—a Croatian cheese which ripens in a lambskin sack. Sir iz mišine was produced in four different variants: (1) from raw milk without starter cultures, and from pasteurized milk with added (2) Lactococcus lactis ssp. lactis S1, (3) Lactobacillus plantarum B, or (4) a starter culture consisting of a mixture of Lactococcus lactis ssp. lactis S1 and Lactobacillus plantarum B (1:1). The addition of Lactobacillus plantarum B alone or in combination with Lactococcus lactis subsp. lactis S1 noticeably increased the alpha and beta indices because of the synergistic activity between the enzymes responsible for primary proteolysis and added autochthonous bacteria. Cheese produced from raw milk had the lowest (12.16%) content of WSN%TN. The highest WSN%TN content was found in cheese produced with combined probiotic bacteria (30.40%) and Lactococcus lactis ssp. lactis S1 (29.74%). Cheese with added combined probiotic bacteria had a noticeably higher content of TCA-SN%TN, indicating a synergistic performance among autochthonous probiotic bacteria. In conclusion, autochthonous probiotic bacteria, in addition to having a functional value, can improve the ripening properties of cheese.

Spatiotemporal Characterization of Texture of Crescenza Cheese, a Soft Fresh Italian Cheese

Crescenza cheese is a soft fresh cheese without rind, typically manufactured using a high amount of rennet. It is characterized by a fast proteolysis that causes changes in texture and leads to the so-called defect of “colatura” that is the tendency of the matrix to freely flow in the outer part of the cheese and generate spatial inhomogeneities into the cheese. In this paper, the textural properties of Crescenza were evaluated for cheeses manufactured using two types of rennet and starter cultures. Cheese texture was monitored during a 3-week shelf life considering a possible spatial variability of the matrix. At the beginning of the shelf life, a certain spatial inhomogeneity was observed from the center to the edge of the cheese block for all the trials. The firmness decreases from the center to the outer part of the block. During storage, hardness showed a decrease during 1st wk of storage; moreover, from days 7 to 21, cheese increased its hardness in the center and decreased it in the outer part of the block, resulting in a higher spatial inhomogeneity of the cheese. The textural measurements can be a useful tool to define the quality of Crescenza cheese during shelf life.

Characterisation of proteolysis profile of Argentinean sheep cheeses made by two different production methods

BACKGROUND

In this work the proteolysis profiles of Argentinean sheep cheeses made by two different production methods were studied in order to develop products with typical and defined features. Cheeses with a starter of Streptococcus thermophilus, curd cut to corn grain size, washed and heated to 43 degrees C (S cheeses) and cheeses with a mixed starter of Streptococcus thermophilus, Lactobacillus helveticus and Lactobacillus bulgaricus, curd cut to rice grain size, unwashed and heated to 47 degrees C (L cheeses) were manufactured. The cheeses were ripened at 12 degrees C and 80% relative humidity for 180 days and samples were taken throughout this period.

RESULTS

Gross composition and primary proteolysis were similar for both types of cheeses. Streptococci counts diminished from 10(9) to 10(7) colony-forming units g(-1) during ripening in both S and L cheeses. Lactobacilli counts in L cheeses decreased during ripening and disappeared at 180 days. L cheeses had significantly lower pH values and showed higher peptidolysis than S cheeses. Triangle sensory evaluation indicated important differences between the two types of cheeses.

CONCLUSION

S cheeses had a low proteolysis level and a soft flavour, making them appropriate for consumption after a short ripening time. L cheeses had a higher proteolysis level and more intense sensory characteristics, making them appropriate for consumption after a longer ripening time.

Proteolysis in Mozzarella Cheeses Manufactured by Different Industrial Processes

The objective of the present study was to investigate the influence of stretching temperature, fat content, and time of brining on proteolysis during ripening of Mozzarella cheeses. Seventeen cheese-making experiments (batches) were carried out on an industrial scale on successive days, following the standard procedure with some modifications. Fat content of cheese milk, temperature at the stretching step, and time of brining varied from one batch to another as required by the experimental design, outlined by a surface response model. Proteolysis was assessed during ripening of samples, which was prolonged for at least 3 mo, by means of electrophoresis, nitrogen fractions, and soluble peptide mapping. The amount of soluble nitrogen at pH 4.6 was not significantly different in cheeses obtained by diverse procedures, but it increased during ripening of all samples. This result was coincident with the breakdown of alpha(s1)- and beta-caseins evidenced by electrophoresis, which reached similar extents at late stages of ripening, regardless of the cheese-making process. Multivariate analysis on soluble peptide profiles obtained by liquid chromatography also detected sample grouping according to ripening time, but did not evidence any separation caused by the cheese-making technology. We concluded that the changes in the cheese-making process assayed in this work were insufficient to produce significant differences in proteolysis of the cheeses. Ripening time had more influence on proteolysis of Mozzarella cheeses than any other assayed variable.

Rheology, Microstructure, and Functionality of Low-Fat Iranian White Cheese Made with Different Concentrations of Rennet

A batch of full-fat (23% target fat) and 3 batches of low-fat (6% target fat) Iranian white cheese with different rennet concentrations (1-, 2-, and 3-fold the normal usage) were produced to study the effect of fat content reduction and promoted proteolysis on the textural and functional properties of the product. Cheese samples were analyzed with respect to their rheological parameters (uniaxial compression and small amplitude oscillatory shear), meltability, microstructure, and sensory characteristics. Reduction of fat content from 23 to 6% had adverse effects on the texture, functionality, cheese-making yield, and sensory characteristics of Iranian white cheese. Fat reduction increased the instrumental hardness parameters (storage modulus, stress at fracture, and Young's modulus of elasticity), decreased the cheese meltability and yield, and made the microstructure more compact. Doubling the rennet concentration reduced values of instrumental hardness parameters, increased the meltability, and improved the sensory impression of texture. Although increasing the rennet concentration to 2-fold the normal usage resembled somewhat the low-fat cheese to its full-fat counterpart, it appeared to cause more reduction in yield. Increasing the rennet concentration 3-fold the normal usage produced a product slightly more elastic than the low-fat cheese with normal concentration of rennet. Increasing the rennet concentration to 2-fold the normal usage was useful for improving the textural, functional, and sensory properties of low-fat Iranian white cheese.

Influence of residual milk-clotting enzyme on alpha(s1) casein hydrolysis during ripening of Reggianito Argentino cheese

Milk-clotting enzyme is considered largely denatured after the cooking step in hard cheeses. Nevertheless, typical hydrolysis products derived from rennet action on alpha(s1)-casein have been detected during the ripening of hard cheeses. The aim of the present work was to investigate the influence of residual milk-clotting enzyme on alpha(s1)-casein hydrolysis in Reggianito cheeses. For that purpose, we studied the influence of cooking temperature (45, 52, and 60 degrees C) on milk-clotting enzyme residual activity and alpha(s1)-casein hydrolysis during ripening. Milk-clotting enzyme residual activity in cheeses was assessed using a chromatographic method, and the hydrolysis of alpha(s1)-casein was determined by electrophoresis and high performance liquid chromatography. Milk-clotting enzyme activity was very low or undetectable in 60 degrees C- and 52 degrees C-cooked cheeses at the beginning of the ripening, but it increased afterwards, particularly in 52 degrees C-cooked cheeses. Cheese curds that were cooked at 45 degrees C had higher initial milk clotting activity, but also in this case, there was a later increase. Hydrolysis of alpha(s1)-casein was detected early in cheeses made at 45 degrees C, and later in those made at higher temperatures. The peptide alpha(s1)-I was not detected in 60 degrees C-cooked cheeses. The results suggest that residual milk-clotting enzyme can contribute to proteolysis during ripening of hard cheeses, because it probably renatures partially after the cooking step. Consequently, the production of peptides derived from alpha(s1)-casein in hard cheeses may be at least, partially due to this proteolytic agent.

Proteolysis on Reggianito Argentino Cheeses Manufactured with Natural Whey Cultures and Selected Strains of Lactobacillus helveticus

Reggianito Argentino cheese is traditionally manufactured with whey starter cultures that provide typical and intense flavor but can cause poor quality standardization. In this study, the influence of natural and selected starters on Reggianito Argentino cheese proteolysis was investigated. Cheeses were manufactured with three strains of Lactobacillus helveticus (SF133, SF138 and SF209) cultured individually in sterile whey and used as single or mixed starters. Control cheeses were made with natural whey starter culture. Cheeses were analyzed to determine gross composition, as well as total thermophilic lactic flora. Proteolysis was assessed by N fractions, electrophoresis and liquid chromatography. Gross composition of the cheeses did not significantly differ, while viable starter cell counts were lower for cheeses made with strain SF209 alone or combined with other strains. Soluble N at pH 4.6 was the same for cheeses made with natural or selected starters, but soluble N in 12% trichloroacetic acid and 2.5% phosphotungstic acid was significantly higher in cheeses made with starters containing strain SF209. Nitrogen fractions results indicated that natural whey starter cultures could be replaced by several starters composed of the selected strains without significant changes to proteolysis patterns. Starter cultures prepared only with SF209 or with the three selected L. helveticus strains produced cheese products with significantly more proteolysis than control cheeses. Chromatographic profiles analyzed by principal components showed that three main peaks on chromatograms, presumptively identified as Tyr, Phe, and Trp, explained most of variability. Principal component scores indicated that cheese samples were grouped by ripening time, which was confirmed by linear discriminant analysis. On the contrary, samples did not cluster by Lactobacillus strain or type of starter.