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Patel, Jigneshkumar S.

Nutritional and Food Sciences

2008

MS

Previous studies have shown that storage temperature influences the formation of calcium lactate crystals on Cheddar cheese surfaces. However, the mechanisms by which crystallization is modulated by storage temperature are not completely understood. The objectives of this study were to evaluate the effect of storage temperature 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 2 surfaces to give six 10-mm thick slabs, 4 of which were randomly assigned to 4 different storage temperatures: 1, 5, 10°C, and weekly cycling between 1 and 10°C. Samples were stored for 30 wk. Following the onset of visible surface crystals, digital photographs of 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 discrete crystals were chosen and evaluated biweekly for radius, area and circularity. The entire experiment was conducted in duplicate. The effects of storage time and temperature on crystal number and total crystal area were evaluated by ANOVA according to a repeated measures design. Crystal number and total crystal area increased significantly during storage in a temperature dependent manner as follows: 5°C<1°/1O°C<1O°C<1°C. However, storage temperature did not appear to have a major effect on the growth rates and shapes of the individual crystals.
The objective of the second study was to compare crystal nucleation and growth rates on the external surface (exposed to smoking) and a subsurface cut 10 mm below the external surface after smoking (not exposed to smoking) during storage under 4 different temperature conditions. Three vacuum packaged random weight (ca. 300g) retail samples of natilrally 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 rnm from the 2 surfaces to give six 10-mm thick slabs. 4 of which were randomly assigned to 4 different storage temperatures: 1, 5, 10°C, and weekly cycling between 1 and 10°C.
Samples were stored for 30 wk. Following the onset of visible surface crystals, digital photographs of the external surfaces and subsurfaces were taken bi-weekly and evaluated by iinage 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 cheese surface, storage temperature and storage time on crystal number and total crystal area were evaluated by ANOVA according to a repeated measures design. The number of crystals and total surface area occupied by crystals were significantly higher at the external surface compared to the subsurface. Onset of visible crystals at the subsurface was delayed by ca. 20 wk compared to the external surface. However, the growth rates and shapes of the individual crystals selected did not appear to differ greatly. The data suggest that the surface of naturally smoked cheese is altered in a manner that favors nucleation site formation, increased crystal number and early onset.