61A-42 |
Freeze-thaw stability of starches |
T. WARAHO, Department of Food Science, University of Massachusetts, 118 Chenoweth Lab, Amherst, MA 01003 and P. Chinachoti. Retrogradation is enhanced when starch gels are subjected to freezing and thawing. Freezing of starch gel causes the phase separation upon ice crystal formation. Upon thawing, water can be expressed from the gel known as syneresis. The freeze-thaw stability of starch gels has been of interest because it provides critical roles in stability of frozen starch based foods. To investigate freeze-thaw stability of various starch gels. Freeze-thaw stability of wheat starch (WS), cassava starch (CS), rice flour (RF), rice starch (RS), and waxy rice starch (WRS) were examined. Starch gels were made on 8% dry starch basis using RVA. The samples were subjected to 5 freeze-thaw cycles (-15oC and 30oC). For each cycle, 2 g of gel was placed between filter paper and a 1-kg-weight (0.392 kg/in2) was applied. Syneresis was calculated by the ratio of expressed water and total gel weight. Starches varied in freeze-thaw stability. RF and WS dramatically lost expressible water in the first cycle and remained relatively constant thereafter indicating a. very high sensitivity to freeze-thaw treatments. The expressible water of RS and CS gradually increased up to 3 cycles and remained unchanged afterwords. WRS did not lose expressible water during freeze-thaw treatments representing the highest freeze-thaw stability among the five starch samples. RVA results showed a different in set-back region. The fact that only waxy rice starch was stable to freeze-thaw treatment could be related to its lack of amylose which dominated the set-back values. This work provides better understanding on freeze-thaw stability of various starches. Some of the starches can be a natural substituted of modified starches in frozen food products to improve freeze-thaw stability.
Session 61A, Carbohydrate
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