Applicability of Confocal Raman Microscopy to Observe Microstructural Modifications of Cream Cheeses as Influenced by Freezing

Confocal Raman microscopy is a promising technique to derive information about microstructure, with minimal sample disruption. Raman emission bands are highly specific to molecular structure and with Raman spectroscopy it is thus possible to observe different classes of molecules in situ, in complex food matrices, without employing fluorescent dyes. In this work confocal Raman microscopy was employed to observe microstructural changes occurring after freezing and thawing in high-moisture cheeses, and the observations were compared to those obtained with confocal laser scanning microscopy. Two commercially available cream cheese products were imaged with both microscopy techniques. The lower resolution (1 µm/pixel) of confocal Raman microscopy prevented the observation of particles smaller than 1 µm that may be part of the structure (e.g., sugars). With confocal Raman microscopy it was possible to identify and map the large water domains formed during freezing and thawing in high-moisture cream cheese. The results were supported also by low resolution NMR analysis. NMR and Raman microscopy are complementary techniques that can be employed to distinguish between the two different commercial formulations, and different destabilization levels

A Randomized Trial of Intravenous Amino Acids for Kidney Protection

Background Acute kidney injury (AKI) is a serious and common complication of cardiac surgery, for which reduced kidney perfusion is a key contributing factor. Intravenous amino acids increase kidney perfusion and recruit renal functional reserve. However, the efficacy of amino acids in reducing the occurrence of AKI after cardiac surgery is uncertain. Methods In a multinational, double-blind trial, we randomly assigned adult patients who were scheduled to undergo cardiac surgery with cardiopulmonary bypass to receive an intravenous infusion of either a balanced mixture of amino acids, at a dose of 2 g per kilogram of ideal body weight per day, or placebo (Ringer's solution) for up to 3 days. The primary outcome was the occurrence of AKI, defined according to the Kidney Disease: Improving Global Outcomes creatinine criteria. Secondary outcomes included the severity of AKI, the use and duration of kidney-replacement therapy, and all-cause 30-day mortality. Results We recruited 3511 patients at 22 centers in three countries and assigned 1759 patients to the amino acid group and 1752 to the placebo group. AKI occurred in 474 patients (26.9%) in the amino acid group and in 555 (31.7%) in the placebo group (relative risk, 0.85; 95% confidence interval [CI], 0.77 to 0.94; P=0.002). Stage 3 AKI occurred in 29 patients (1.6%) and 52 patients (3.0%), respectively (relative risk, 0.56; 95% CI, 0.35 to 0.87). Kidney-replacement therapy was used in 24 patients (1.4%) in the amino acid group and in 33 patients (1.9%) in the placebo group. There were no substantial differences between the two groups in other secondary outcomes or in adverse events. Conclusions Among adult patients undergoing cardiac surgery, infusion of amino acids reduced the occurrence of AKI

Effect of freezing and thawing processes on high-moisture Mozzarella cheese rheological and physical properties

High-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

Application of NIR spectroscopy and image analysis for the characterisation of grated Parmigiano-Reggiano cheese

Grated 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

Analysis of Conductance Changes as a Growth Index of Lactic Acid Bacteria in Milk

The 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