45D-24 |
Effect of storage temperature, packaging material and process on ice frost formation, product appearance, and color in packaged frozen carrots |
D. MARTINO1, G. J. Burgess1, J. B. Harte2, and B. R. Harte1. (1) School of Packaging, Michigan State Univ., 915 Cherry Ln., Apt. H, East Lansing, MI 48823-5517, (2) Dept. of Food Science & Human Nutrition, Michigan State Univ., 114 G. Malcolm Trout FSHN Bldg., East Lansing, MI 48824-1224 Frozen packaged vegetables may be exposed to fluctuating environmental conditions during storage. This may result in an increase in amount of frost in the headspace of a packaged frozen vegetable and thus consumer avoidance. Further, since in-package ice is discarded in net weight control, serious problems with compliance to weight regulations may occur. The main objective of this work is to understand the origin of that frost and to evaluate different packaging alternatives to avoid or decrease that formation. A secondary objective is to develop a mathematical relationship to predict frost ice formation using experimental data. Baby carrots were blanched, frozen and stored at –20 °C in nylon/PE multilayer and PE bags. For the nylon/PE multilayer, vacuum and atmospheric filling processes were used. Units were drawn at monthly intervals for 6 months and evaluated for product weight loss using gravimetric procedures, product color assessment and product appearance. Half of the carrots were stored in a retail refrigeration unit one week prior to evaluation. Through four months of storage, an increase in frost is noted. With vacuum packing the amount is the highest, though the ice formed had a glassy like character and not a typical frosty appearance. For the remaining variables amount of frost formed is about the same regardless of packaging material or treatment (£2%) Carrots from bags exposed to retail refrigeration had consistently lower color values for L, a and b. The results suggest that frost formation is related to differences in water vapor pressure within the package headspace and follows a rather linear relationship with time. Vacuum appears to pull more water out of the carrots because of the large vapor pressure gradient. From the color results it seems that at retail conditions, the product experienced a more intense dehydration that led to higher oxidation of the carotenoids.
Session 45D, Food Packaging: General
|