UVM Theses and Dissertations
Format:
Print
Author:
Valentine, Elissa
Dept./Program:
Nutritional and Food Sciences
Year:
2008
Degree:
MS
Abstract:
Previous studies have shown that loose packaging favors the formation of calcium lactate crystals on the surface of Cheddar cheese. However, the mechanism by which crystallization is accelerated by loose packaging is not well understood. The objectives of this study were to evaluate the effect of packaging tightness on: 1) the number of discrete visible crystals formed per unit of cheese surface area; 2) growth rate and shape of discrete crystals (as measured by radius, area, and circularity); 3) percentage of total cheese surface area occupied by crystals. Three vacuum packaged random weight (ca. 300 g) retail samples of naturally smoked Cheddar cheese, produced from the same vat of cheese, were obtained from a retail source. The samples were cut parallel to the longitudinal axis at a depth of 10 mm from the surface to give six 10-mm thick slabs, 3 of which were randomly assigned to 3 different levels of packaging tightness: 10 mbar (very tight), 70 mbar (slightly loose), and 960 mbar (very loose). Samples were stored at 1°C for 30 wk.
Following the onset of visible surface crystals, digital photographs of the external smoked surfaces were taken bi-weekly and evaluated by image analysis for number of discrete crystal regions and total surface area occupied by crystals. Also, specific individual crystals were chosen and evaluated bi-weekly for radius, area and circularity. The entire experiment was conducted in duplicate. The effects of storage time and packaging tightness on crystal number and total crystal area were evaluated by ANOVA according to a repeated measures design. Loose packaging caused large, significant increases in the number of discrete crystals formed per unit of surface area and the total surface area occupied by crystals. However, packaging tightness did not appear to have a major effect on the growth rate or shape of individual crystals that were chosen for analysis. The data indicate that loose packaging primarily increased the number of nucleation sites on the cheese surface that subsequently developed into discrete visible crystals.
Following the onset of visible surface crystals, digital photographs of the external smoked surfaces were taken bi-weekly and evaluated by image analysis for number of discrete crystal regions and total surface area occupied by crystals. Also, specific individual crystals were chosen and evaluated bi-weekly for radius, area and circularity. The entire experiment was conducted in duplicate. The effects of storage time and packaging tightness on crystal number and total crystal area were evaluated by ANOVA according to a repeated measures design. Loose packaging caused large, significant increases in the number of discrete crystals formed per unit of surface area and the total surface area occupied by crystals. However, packaging tightness did not appear to have a major effect on the growth rate or shape of individual crystals that were chosen for analysis. The data indicate that loose packaging primarily increased the number of nucleation sites on the cheese surface that subsequently developed into discrete visible crystals.