Effect of high pressure treatment applied on starter culture or on semi-ripened cheese in the quality and ripening of cheese in brine

Evaluating the Quality of Cheese Slices Packaged with Na-Alginate Edible Films Supplemented with Functional Lactic Acid Bacteria Cultures after High-Pressure Processing

The aim of the current study was to assess the efficacy of Na-alginate edible films as vehicles for delivering lactic acid bacteria (LAB) with functional properties to sliced cheeses, with or without high-pressure processing (HPP). A three-strain LAB cocktail (Lactococcus lactis Τ4, Leuconostoc mesenteroides Τ25 and Lacticaseibacillus paracasei Τ26) was incorporated into Na-alginate solution in a final population of 9 log CFU/mL. The cheese slices (without or with HPP treatment at 500 MPa for 2 min) were packaged in contact with the LAB edible films (LEFs), and subsequently vacuum packed and stored at 4 °C. Cheese slices without the addition of films, with or without HPP treatment, were used as controls. In all cases, microbiological, pH and sensory analyses were performed, while the presence and the relative abundance of each strain during storage was evaluated using Random Amplified Polymorphic DNA-PCR (RAPD-PCR). In addition, organic acid determination and peptide analysis were performed using high-performance liquid chromatography. The results showed that in cheeses without HPP treatment, the microbiota consisted mostly of mesophilic LAB and lactococci (>7.0 log CFU/g), while HPP caused a reduction in the indigenous microbiota population of approximately 1−1.5 log CFU/g. In the LEF samples, the populations of mesophilic LAB and lactococci were maintained at levels of >6.35 log CFU/g during storage, regardless of the HPP treatment. Sensory evaluation revealed that the LEF samples without HPP had a slightly more acidic taste compared to the control, whereas the HPP-LEF samples exhibited the best organoleptic characteristics. RAPD-PCR confirmed that the recovered strains were attributed to the three strains that had been entrapped in the films, while the strain distribution during storage was random. Overall, the results of the study are promising since the functional LAB strains were successfully delivered to the products by the edible films until the end of storage.

Proteolytic Development and Volatile Compounds Profile of Domiati Cheese under Modified Atmosphere Packaging

This study explored the impacts of modified atmosphere packaging (MAP) treatment on the proteolytic development and volatile compounds of Domiati cheese during storage. Domiati cheese samples were kept for 75 days at refrigerator temperature, under aerobic packaging (C1) or vacuum (C2). In parallel, other Domiati cheese samples were kept under MAP, at different levels of CO2 and N2, as follows: 10% CO2/90% N2 (D1), 15% CO2/85% N2 (D2), 25% CO2/75% N2 (D3), 100% CO2 (D4), and 100% N2 (D5). The normal control (C1) treatment showed the highest reduction in pH from 6.64 at zero time to 6.23 and 6.01 after 40 and 75 days of storage, respectively. On the other hand, the under-vacuum samples (C2) showed the lowest reduction in pH, from 6.64 at zero time to 6.49 and 6.28 after 40 and 75 days of storage, respectively. Proteolysis during cheese storage was lower in MAP of cheeses than in the C1 treatment. Total free amino acids (FAAs) were higher in C1 treatment than other cheeses during the whole storage period. The lowest level of total FAA was detected in D4 treatment after 75 days of storage. Volatile acids, aldehydes, ketones, and esters compounds were detected in all treatments during storage, but particularly higher in aerobic packaging than the other treatments after 75 days. The level of each acid compound increased with storage period, and the increases were particularly clear in pentanoic acid, hexanoic acid, heptanoic acid, benzoic acid, and n-decanoic acid. The normal control (C1) showed high contents of the different volatile ketone compounds. However, the samples packaged under 100% N2 (D5) showed the significantly highest levels of all the volatile ketones after 75 days of storage, particularly 2-pentanone, acetoin, methyl isobutyl ketone, 2-heptanone, 2-nonanone, and 2-undecanone. Some important compounds contributing to the good flavor of the cheese are acetic acid, butanoic acid, pentanal, benzaldehyde, acetoin, and 2,3-butanedione. The CO2 and N2 treatments exerted significant changes in all groups during the storage of cheese. All cheese samples showed gradual increases in CO2 co-occurring with parallel decreases in N2 during refrigerated storage periods, except for D4 treatment (100% CO2), which showed a decrease. A significant decrease in O2 level occurred in C1 treatment during cold storage.

A Review of the Preservation of Hard and Semi-Hard Cheeses: Quality and Safety

Cheese is a dairy product with potential health benefits. Cheese consumption has increased due to the significant diversity of varieties, versatility of product presentation, and changes in consumers’ lifestyles. Spoilage of hard and semi-hard cheeses can be promoted by their maturation period and/or by their long shelf-life. Therefore, preservation studies play a fundamental role in maintaining and/or increasing their shelf-life, and are of significant importance for the dairy sector. The aim of this review is to discuss the most effective methods to ensure the safety and sensory quality of ripened cheeses. We review traditional methods, such as freezing, and modern and innovative technologies, such as high hydrostatic pressures, chemical and natural vegetable origin preservatives, vacuum and modified atmosphere packaging, edible coatings and films, and other technologies applied at the end of storage and marketing stages, including light pulses and irradiation. For each technology, the main advantages and limitations for industrial application in the dairy sector are discussed. Each type of cheese requires a specific preservation treatment and optimal application conditions to ensure cheese quality and safety during storage. The environmental impact of the preservation technologies and their contribution to the sustainability of the food chain are discussed.

Kinetics of proteolysis in stored Mongolian cheese at ice-temperatures and split-split-plot analysis of storage factors affecting cheese quality

Mongolian cheese is non-fermented cheese, which easily deteriorates during storage because of hydrolysis. The freezing points of sucrose and sucrose-free cheese were measured -5.16 °C and -4.29 °C, respectively. Ice-storage temperatures of -2 °C and -4 °C were used and 0 °C was used as reference temperature. In this study, the changes of proteolytic indexes (PI) and total viable counts (TVC) of cheese at different ice-temperatures during storage were studied. The PIs of all treatments increased over storage time, which conformed to the Arrhenius first-order kinetic model. The shelf lives of sucrose and sucrose-free cheese were predicted. In addition, -4 °C effectively suppressed the increases in TVC and PIs. The split-split-plot design was applied in comparing the effects of cheese type, the storage time and storage temperature on PI. Storage time was the most important factor followed by cheese type and storage temperature.

Change of proteolysis and sensory profile during ripening of Cheddar-style cheese as influenced by a microbial rennet from rice wine

To test the potential of a novel microbial rennet isolated from traditional fermented rice wine for cheese making, Cheddar-style cheese made with this enzyme was studied for changes in composition, proteolysis, and sensory profile during 90 days of ripening in comparison with a control cheese made with a commercial rennet. The initial proteolysis assay of the microbial rennet on milk proteins indicated a notable increase in the hydrolysis of casein components (α-, β-, and κ-caseins) but no effect on whey proteins upon increasing the concentration of the enzyme. Correspondingly, compared to cheese made with commercial rennet, the use of the microbial rennet in Cheddar-style cheese resulted in significantly higher primary and secondary proteolysis in the later stages of ripening (60-90 days ripening) and thus a softer texture and the formation of more volatile compounds and free amino acids (FAAs) despite its lower moisture content (41.7%, w/w). Though the cheese made with the microbial rennet was found to contain bitter-taste FAAs (1,000 mg/100 g), the combined effect of other-taste FAAs, including sweet (231 mg/100 g), umami (225 mg/100 g), and tasteless (361 mg/100 g) FAAs, in the cheese attenuated the bitter taste of the cheese. This analysis was in accordance with the sensory evaluation, which showed no significantly different sensory scoring between the cheeses made with the microbial and commercial rennets. The present study demonstrated a novel approach to evaluate the bitter taste of ripened cheese. The results of this study suggest the potential of the microbial rennet from rice wine to serve as a new source of milk-clotting agents in cheese making.

Effects of Proteolytic and Lipolytic Enzyme Supplementations on Lipolysis and Proteolysis Characteristics of White Cheeses

Effects of proteolytic (Neutrase, Bacillus subtilis-originate, 0.20 (P1) and 0.40 g 100 L-¹ (P2)) and lipolytic (Piccantase A, Mucor miehei-originated, 0.05 (L1) and 0.10 g 100 L-¹ (L2)) enzyme supplementations to cheese milk on lipolysis and proteolysis characteristics of 90-day ripened cheese samples were investigated in this study. While enzyme supplementation did not have significant effects on titratable acidity, fat and protease-peptone nitrogen ratios of cheese samples, dry matter, salt, protein, water soluble nitrogen, 12% trichloroacetic acid soluble nitrogen ratio (TCA-SN), 5% phosphotungstic acid soluble nitrogen (PTA-SN), casein nitrogen ratios, penetrometer value, total free fatty acids (TFFA) and total free amino acids (TFAA) were significantly influenced by enzyme supplementations. Individual free amino acids (15 of them) were also determined. Free amino acid contents of enzyme-supplemented cheeses were higher than the control cheese and the values increased in all cheese samples with the progress of ripening (p < 0.05). The highest amino acids in all periods of ripening were identified as glutamic acid, lysine, proline and aspartic acid. The major (Ca, P, Na, K, Mg) and minor (Zn, Fe, Cu, Mn) mineral levels of cheeses decreased with the progress of ripening and the effects of enzyme supplementations on these attributes (except for magnesium and manganese) were found to be significant (p < 0.01). As to conclude, enzyme supplementations increased proteolysis and lipolysis and accelerated ripening and thus reduced ripening durations. Especially the enzyme ratios in P1 and L1 cheeses were found to be suitable for reducing the ripening period in White cheese without any adverse effects.

Effect of high pressure on structural modifications and enzymatic activity of a purified X-prolyl dipeptidyl aminopeptidase from Streptococcus thermophilus

PepX aminopeptidase from Streptococcus thermophilus ACA DC 0022, used in Greek Feta cheese manufacturing, was purified. PepX comprises two subunits of equal molecular mass estimated, using SDS-PAGE and native-PAGE electrophoresis, to be 86 kDa. The effects of high pressure processing (100-450 MPa, combined with 20-40 °C) on purified PepX activity and structure were studied. Activation of the enzyme was observed after processing at 100-200 MPa and 20-30 °C. More intense processing conditions led to enzyme inactivation. PepX HP-induced conformational changes were also investigated through application of Circular Dichroism spectroscopy (CD). Pressures up to 200 MPa resulted in a structurally molten globule-like state where PepX maintained its secondary structure but the tertiary structure was substantially affected and enzyme activity increased. Both secondary and tertiary structures were affected severely by higher pressures (450 MPa), which reduced enzyme activity.