Freezing low moisture Mozzarella cheese: changes in organic acid content

Ice crystallization and structural changes in cheese during freezing and frozen storage: implications for functional properties

Temperature-mediated preservation techniques offer a simple, scalable, effective, and fairly efficient method of long-term storage of food products. In order to ensure the uninterrupted availability of cheese across the globe, a critical understanding of its techno-functional properties as affected by freezing and frozen storage is essential. Detailed studies of temperature-mediated molecular dynamics are available for relatively simpler and homogeneous systems like pure water, proteins, and carbohydrates. However, for heterogeneous systems like cheese, inter-component interactions at sub-zero temperatures have not been extensively covered. Ice crystallization during freezing causes dehydration of caseins and the formation of concentration gradients within the cheese matrix, causing undesirable changes in texture-functional attributes, but findings vary due to experimental conditions. A suitable combination of sample size, freezing rate, aging, and tempering can extend the shelf life of high- and low-moisture Mozzarella cheese. However, limited studies on other cheeses suggest that effects and suitability differ by cheese type, in most cases adversely affecting texture and functional attributes. This review presents an overview of the understanding of the effects of refrigeration, freezing techniques, and frozen storage on structural components of cheese, most prominently Mozzarella cheese, and the corresponding impact on microstructure and functionality. Also included are the mechanism of ice formation and relevant mathematical models for estimation of the thermophysical properties of cheese to assist in designing optimized schemes for their frozen storage. The review also highlights the lack of unanimity in critical understanding concerning the effect of freezing on the long-term storage of Mozzarella cheese with respect to its functionality.

Application of Commercial Biopreservation Starter in Combination with MAP for Shelf-Life Extension of Burrata Cheese

Burrata is a fresh pasta filata cheese manufactured in Italy. Its demand on the worldwide market is constantly growing, and prolonging its shelf-life is an important challenge for the Italian dairy industry. In the present study, combining a commercial bio-protective starter and modified atmosphere packaging (MAP) was evaluated as a strategy to delay the spoilage of product quality. Three experimental samples of burrata were produced by experimental trials at the industrial level and stored for 28 days under refrigerated conditions. Two samples contained the protective starter but were packaged differently (under MAP and immersed in water), and one did not contain the starter and was packaged under MAP. A sample of burrata without a starter and immersed in water was also prepared and used as a control. The combination of MAP and bio-protective starter delayed the degradation of lactose and citric acid, used as indices of microbial activity. In fact, lower counts of Enterobacteriaceae and Pseudomonas were observed in this sample. In contrast, control burrata had the highest level of total Volatile Organic Compounds (VOC) at the end of the storage period, because of higher microbial activity. Even though all samples were judged to be unacceptable after 28 days from the sensory point of view, the sample with bio-protective starter under MAP had the best score after 21 days, obtaining a shelf-life extension of about 7 days with respect to control. In conclusion, the combination of MAP and protective starter culture could be an easy way to extend the shelf-life of burrata stored under correct refrigerated conditions.

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.

Freezing as a solution to preserve the quality of dairy products: the case of milk, curds and cheese

When thinking of the freezing process in dairy, products consumed in frozen state, such as ice creams come to mind. However, freezing is also considered a viable solutions for many other dairy products, due to increasing interest to reduce food waste and to create more robust supply chains. Freezing is a solution to production seasonality, or to extend the market reach for high-value products with otherwise short shelf life. This review focuses on the physical and chemical changes occurring during freezing of milk, curds and cheeses, critical to maintaining quality of the final product. However, freezing is energy consuming, and therefore the process needs to be optimized to maintain product's quality and reduce its environmental footprint. Furthermore, the processing steps leading to the freezing stage may require some changes compared to traditional, fresh products. Unwanted reactions occur at low water activity, and during modifications such as ice crystals growth and recrystallization. These events cause major physical destabilizations of the proteins due to cryoconcentration, including modification of the colloidal-soluble equilibrium. The presence of residual proteases and lipases also cause important modifications to the texture and flavor of the frozen dairy product.

Characterization of the Microbial Diversity and Chemical Composition of Gouda Cheese Made by Potential Probiotic Strains as an Adjunct Starter Culture

This study characterized the microbial diversity and chemical properties of Gouda cheese made by probiotics during ripening periods. Lactobacillus plantarum H4 (H4) and Lactobacillus fermentum H9 (H9), which demonstrate probiotic properties and bioactivity, were used as adjunct starter cultures. Gouda cheese made with H4 (GCP1) and H9 (GCP2) demonstrated the highest production of formic acid and propionic acid, respectively. Moreover, the bacterial diversity, including richness and evenness of nonstarter lactic acid bacteria (NSLAB), increased in probiotic cheeses. Specifically, Lactobacillus, Leuconostoc, and Streptococcaceae were present at higher concentrations in probiotic cheeses than in control Gouda cheese (GCC). The proportion of H4 in GCP1 increased and culminated at 1.76%, whereas H9 in GCP2 decreased during ripening. Peptide profiles were altered by the addition of probiotics and included various bioactive peptides. In particular, three peptide fragments are newly detected. Therefore, Gouda cheese could be used as an effective probiotic carrier for H4 and H9.

Changes in quality of nonaged pasta filata Mexican cheese during refrigerated vacuum storage

Six batches of Oaxaca cheese (a Mexican pasta filata cheese) from 3 dairy plants were sampled and vacuum-packaged at 8°C up to 24d. Counts of principal microbial groups, pH, levels of sugars, organic acids, lipolytic and proteolytic indices, and texture, color, and meltability values of cheeses were studied at d 1, 8, 16 and 24 of storage. A descriptive sensory analysis of selected taste, odor, and texture characteristics was also carried out. The main changes in the cheeses during the storage were decreases in pH, hardness, elasticity, and whiteness, and an increase in meltability. Neither lipolytic nor proteolytic activities were evident during the storage of cheeses. Storage time resulted in a gradual quality loss of unmelted cheeses. This loss of quality might be related to the decrease of hardness and the appearance off-flavors.

Effects of frozen storage and vacuum packaging on free fatty acid and volatile composition of Turkish Motal cheese

Effects of vacuum packaging and frozen storage were studied on the formation of free fatty acids (FFAs), volatile compounds and microbial counts of Motal cheese samples stored for a period of 180 days. The FFA concentration of Motal cheese samples increased throughout the storage period of 180 days. However, the FFA contents of samples stored at —18 °C showed considerably lower values than those of the samples stored at 4 °C. Palmitic (C16:0) and oleic (C18:1) acids were the most abundant FFAs in all the treatments. The volatile compounds detected by headspace solid-phase microextraction (HS-SPME) profile of Motal cheese consisted of 16 esters, 10 acids, 6 ketones, 4 alcohols, 3 aldehydes, styrene, p-cresol and m-cresol. Results showed that storage at —18 °C can limit the excessive volatile compound formation. Samples stored at 4°C with vacuum packaging showed comparatively high concentration of esters, ketones and alcohols. Samples stored without vacuum packaging at 4°C showed 2-nonanone as the most abundant volatile compound toward the end of storage period. Storage at 4°C under vacuum packaging decreased the mold—yeast counts of samples. Frozen storage could be a suitable method for storing the Motal cheese.

Biochemical patterns in ovine cheese: influence of probiotic strains

This study was undertaken to evaluate the effect of lamb rennet paste containing probiotic strains on proteolysis, lipolysis, and glycolysis of ovine cheese manufactured with starter cultures. Cheeses included control cheese made with rennet paste, cheese made with rennet paste containing Lactobacillus acidophilus culture (LA-5), and cheese made with rennet paste containing a mix of Bifidobacterium lactis (BB-12) and Bifidobacterium longum (BB-46). Cheeses were sampled at 1, 7, 15, and 30 d of ripening. Starter cultures coupled with probiotics strains contained in rennet paste affected the acidification and coagulation phases leading to the lowest pH in curd and cheese containing probiotics during ripening. As consequence, maturing cheese profiles were different among cheese treatments. Cheeses produced using rennet paste containing probiotics displayed higher percentages of alpha(S1)-I-casein fraction than traditional cheese up to 15 d of ripening. This result could be an outcome of the greater hydrolysis of alpha-casein fraction, attributed to higher activity of the residual chymosin. Further evidence for this trend is available in chromatograms of water-soluble nitrogen fractions, which indicated a more complex profile in cheeses made using lamb paste containing probiotics versus traditional cheese. Differences can be observed for the peaks eluted in the highly hydrophobic zone being higher in cheeses containing probiotics. The proteolytic activity of probiotic bacteria led to increased accumulation of free amino acids. Their concentrations in cheese made with rennet paste containing Lb. acidophilus culture and cheese made with rennet paste containing a mix of B. lactis and B. longum were approximately 2.5 and 3.0 times higher, respectively, than in traditional cheese. Principal component analysis showed a more intense lipolysis in terms of both free fatty acids and conjugated linoleic acid content in probiotic cheeses; in particular, the lipolytic pattern of cheeses containing Lb. acidophilus is distinguished from the other cheeses on the basis of highest content of health-promoting molecules. The metabolic activity of the cheese microflora was also monitored by measuring acetic, lactic, and citric acids during cheese ripening. Cheese acceptability was expressed for color, smell, taste, and texture perceived during cheese consumption. Use of probiotics in trial cheeses did not adversely affect preference or acceptability; in fact, panelists scored probiotic cheeses higher in preference over traditional cheese, albeit not significantly.

The effect of storage temperatures and packaging methods on properties of Motal cheese

The effects of storage temperature (+4 degrees C and -18 degrees C) and packaging method (nonvacuum and vacuum) on biogenic amines in Motal cheese during storage periods were investigated. In addition, dry matter, titratable acidity, total nitrogen, water-soluble nitrogen, trichloroacetic acid-soluble nitrogen, phosphotungstic acid-soluble nitrogen, free amino group (proteolysis), electrophoretic patterns of casein, and amounts of lactic acid bacteria and coliforms were determined. Storage period had a significant effect on all of the biogenic amines. When compared with vacuum packaging, normal packaging had higher amounts of putrescine, cadaverine, histamine, and tyramine. Coliforms were not found at detectable levels (<100cfu/g) in all cheese samples. Results of urea-PAGE analysis of cheese samples were in good agreement with biogenic amine results and other proteolysis parameters.

Effects of Frozen and Refrigerated Storage on Organic Acid Profiles of Goat Milk Plain Soft and Monterey Jack Cheeses

The effects of 6 mo of freezing and refrigeration on organic acid profiles of 2 types of goat milk cheese [plain soft (PS) and Monterey Jack (MJ)] were studied in comparison with those of a nonfrozen control (NFC). Three lots of commercial PS cheeses were purchased, and 3 lots of MJ cheeses were manufactured at the University dairy plant. Each lot of the 2 types of cheeses was subdivided into 4 equal portions, and one subsample of each cheese was immediately stored at 4 degrees C as the NFC for 0, 14, and 28 d. The other 3 were immediately frozen (-20 degrees C) for 0, 3, and 6 mo (0MF, 3MF, and 6MF) and subsequently thawed the next day at 4 degrees C. The samples were then stored at 4 degrees C for 0, 14, and 28 d. Organic acids were quantified using an HPLC. The PS had no pyruvic acid, and MJ contained no isotartaric acid; however, several unknown large peaks appeared between propionic and butyric acids. Differences in organic acid contents between PS and MJ cheeses were significant for all acids except citric and lactic acid. Lot effect was significant for most of the known acids, indicating that variations existed in milk composition and manufacturing parameters. Effects of storage treatments (NFC, 0MF, 3MF, and 6MF) were significant for most organic acids, except for orotic and a few unidentified acids. Aging at 4 degrees C for 4 wk had little influence on all organic acids, except butyric acid. Concentrations of butyric, lactic, propionic, tartaric, and uric acids were significantly elevated as the frozen storage period advanced. At the initial stage, there were no differences in pH and acid degree values between NFC and frozen-stored groups of both cheeses. However, acid degree values gradually increased as the refrigerated storage extended up to 4 wk, indicating that lipolysis increased as the refrigeration storage at 4 degrees C advanced. Although levels of several organic acids were changed in the goat cheeses, the prolonged frozen storage, up to 6 mo, was apparently feasible for extending storage.

Influence of Calcium and Phosphorus, Lactose, and Salt-to-Moisture Ratio on Cheddar Cheese Quality: Changes in Residual Sugars and Water-Soluble Organic Acids During Ripening

Cheddar cheese ripening involves the conversion of lactose to glucose and galactose or galactose-6-phosphate by starter and nonstarter lactic acid bacteria. Under ideal conditions (i.e., where bacteria grow under no stress of pH, water activity, and salt), these sugars are mainly converted to lactic acid. However, during ripening of cheese, survival and growth of bacteria occurs under the stressed condition of low pH, low water activity, and high salt content. This forces bacteria to use alternate biochemical pathways resulting in production of other organic acids. The objective of this study was to determine if the level and type of organic acids produced during ripening was influenced by calcium (Ca) and phosphorus (P), residual lactose, and salt-to-moisture ratio (S/M) of cheese. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), lactose at pressing (2.4 vs. 0.78%), and S/M (6.4 vs. 4.8%) were manufactured. The cheeses were analyzed for organic acids (citric, orotic, pyruvic, lactic, formic, uric, acetic, propanoic, and butyric acids) and residual sugars (lactose, galactose) during 48 wk of ripening using an HPLC-based method. Different factors influenced changes in concentration of residual sugars and organic acids during ripening and are discussed in detail. Our results indicated that the largest decrease in lactose and the largest increase in lactic acid occurred between salting and d 1 of ripening. It was interesting to observe that although the lactose content in cheese was influenced by several factors (Ca and P, residual lactose, and S/M), the concentration of lactic acid was influenced only by S/M. More lactic acid was produced in low S/M treatments compared with high S/M treatments. Although surprising for Cheddar cheese, a substantial amount (0.2 to 0.4%) of galactose was observed throughout ripening in all treatments. Minor changes in the levels of citric, uric, butyric, and propanoic acids were observed during early ripening, whereas during later ripening, a substantial increase was observed. A gradual decrease in orotic acid and a gradual increase in pyruvic acid content of the cheeses were observed during 12 mo of ripening. In contrast, acetic acid did not show a particular trend, indicating its role as an intermediate in a biochemical pathway, rather than a final product.

Comparative analysis of different plant oils by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

Different vegetable oil samples (almond, avocado, corngerm, grapeseed, linseed, olive, peanut, pumpkin seed, soybean, sunflower, walnut, wheatgerm) were analyzed using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry. A gradient elution technique was applied using acetone-acetonitrile eluent systems on an ODS column (Purospher, RP-18e, 125 x 4 mm, 5 microm). Identification of triacylglycerols (TAGs) was based on the pseudomolecular ion [M+1]+ and the diacylglycerol fragments. The positional isomers of triacylglycerol were identified from the relative intensities of the [M-RCO2]+ fragments. Linear discriminant analysis (LDA) as a common multivariate mathematical-statistical calculation was successfully used to distinguish the oils based on their TAG composition. LDA showed that 97.6% of the samples were classified correctly.

Variation in organic acids content during ripening of pickled white cheese

Nine organic acids (formic, pyruvic, lactic, acetic, orotic, citric, uric, propionic, and butyric) were analyzed during ripening of pickled White cheese for 12 mo by high-performance liquid chromatography with a reverse phase C18 (120x 5-mm) column and UV detector. The level oftotal organic acids showed an increase along the ripening period, but its composition varied during the process. Initially, lactic acid accounted for 95% of the total, after 9 and 12 mo of ripening, butyric acid constituted 20 and 27% of the total, respectively. Each organic acid presented a characteristic pattern of change during ripening. Discriminant analysis classified cheeses according to their age. Stepwise regression analysis allowed estimation of the ripening time of samples according to their organic acid levels.