1,721,006 research outputs found
Effect of freezing and thawing processes on high-moisture Mozzarella cheese rheological and physical properties
Full text linkHigh-moisture Mozzarella cheese is a soft, fresh cheese characterized by a short shelf-life, but a freezing process can be effective for improving its storability. In this study, the effects of two freezing/thawing methods (the presence or absence of a covering liquid during the process), three freezing conditions (ranging from −40 °C, 4.1 ± 0.6 m/s, to −25 °C, 1.3 ± 0.2 m/s) and two thawing conditions (+4 °C, 1.3 ± 0.2 m/s, +4 °C, 4.1 ± 0.6 m/s) were evaluated on Mozzarella cheese characteristics. Cheeses with a covering liquid were characterized by water absorption during thawing, lower water holding capacity, softer texture and lower rheological moduli. Frozen/thawed cheeses without the covering liquid and stored overnight with a new covering liquid, despite having a lower juiciness, were characterized by a lower degree of freezing-induced modifications and were more similar to the fresh cheese. Cheese properties were not largely affected by the freezing/thawing conditions considered here. Freezing high-moisture Mozzarella cheese has a small impact on a product's properties if it is performed without a covering liquid and is followed by an overnight rehydration step in a fresh covering liquid. Therefore, this should be the preferred method to obtain the best quality results
Analysis of Conductance Changes as a Growth Index of Lactic Acid Bacteria in Milk
No full textThe analysis of changes in conductance is a valid method to evaluate the growth and metabolic activity of lactic acid bacteria in milk. This technique allows the activity of pure strains to be monitored and the stability of the characteristics of mixed cultures to be controlled. The conductimetric method may be particularly useful for the dairy industry to control the stability of lactic acid bacteria starters. © 1993, American Dairy Science Association. All rights reserved
Application of NIR spectroscopy and image analysis for the characterisation of grated Parmigiano-Reggiano cheese
No full textGrated Parmigiano–Reggiano cheese holds a valuable market segment and its quality strictly depends on the amount of rind, size, shape of cheese particles and original cheese properties. Textural properties of the rind and inner part of the cheese significantly affect size and shape of grated particles. Rind produces a higher amount of finer and less circular particles than the inner region. Rind content established by European regulation (maximum 18%) is a major issue and could be successfully predicted by multivariate models developed on near-infrared (NIR) spectra. Image analysis (IA) was a suitable method to estimate rind percentage that was found positively correlated to number of particles, total surface covered by particles and circularity. IA and NIR spectroscopy enabled characterisation of the distribution of the particle in dimensional classes and could be used to control the maximum limit of 25% of particles finer than 0.5 mm provided by European regulation
Autocontrollo e sicurezza degli alimenti: considerazioni emergenti da esperienze nel settore caseario
No full textStructural and Physico-Chemical Changes of Mozzarella di Bufala Campana Cheese Influenced by Covering Liquid Composition
No full text: Mozzarella di Bufala Campana is an Italian protected designation of origin cheese characterized by a stretched structure, high moisture (<65%), and short shelf life (<30 days). This cheese is generally stored refrigerated in a covering liquid that is an aqueous solution containing NaCl and organic acids. Although microbial growth has been reported as the main cause of quality deterioration, physico-chemical phenomena (water/solute migration, enzymatic reactions, etc.) also play a role in determining the cheese quality and its storability. This study investigates the effect of covering liquids formulated with different percentages of NaCl (1, 2%) and types of organic acids (lactic acid, citric acid, and a 1:1 mix of both) on the evolution of some physico-chemical characteristics of the cheese (moisture, pH, electrical conductivity, color, expressible serum, texture, rheology) during a 30-day storage period. Eight cheese batches collected from different dairies were considered as replicates of the study. The % of NaCl in the covering liquid showed a strong, significant effect on the evolution of different structural, physico-chemical characteristics of the cheeses; in particular, a NaCl concentration of 2% caused the greatest extent of moisture content increase because of casein swelling during storage, accompanied by softening of the structure
Influence of the Temperature Gradient on the Growth of Thermophilic Lactobacilli Used as Natural Starters in Grana Cheese
No full textThis study investigated the evolution of the Lactobacillus species and the microbial composition of the starter during Grana cheese making. The early stages of cheese making were studied, and both the composition of the natural whey starter and its modification in response to curd cooking were considered. The growth and distribution of the thermophilic lactobacilli in the cheese at 48 h after molding was affected by the temperature gradient between the external and internal cheese zones. Growth was maximum between 0 and 6 h in the cheese exterior and between 6 and 24 h in the core. This variation occurred because the cheese interior was around 52°C 6 h after molding, which is far from the optimum for the thermophilic lactobacilli growth. Dot-blot hybridization experiments allowed the identification of up to 280 isolates. Lactobacillus helveticus predominated in the natural whey starter and in the external cheese zones. Distribution of Lactobacillus delbrueckii and the heterofermentative lactobacilli, which slowly increased from the molding until 48 h, was more variable in the internal regions than in the external regions of the cheese. This study demonstrates that the thermophilic lactobacilli behave differently during the technological process than during experiments using laboratory models
Differential scanning calorimetry application to freeze-dried milk and milk fractions
No full textThe thermal profiles of whole freeze-dried raw milk, obtained by differential scanning calorimetry (DSC) upon heating, were compared to those of their concentrate fractions (cream, skimmed milk, acid casein and whey) in order to associate the thermal peaks with the related components. Two peaks associated with fat melting, a glass transition attributed to caseins and a complex exothermic peak associated with lactose and its interactions with the other milk components were observed, in a close relation to the values of water activity of the samples. Freeze drying is the least invasive technique for drying milk, thus the results of this study may be attributed to the thermal transitions of milk components in their native state, unlike what is observed on roller- or spray-dried milk. The DSC technique is confirmed as an effective tool for the evaluation of the thermophysical properties of milk, as modified by different industrial processes
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