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Effects of Prolonged Storage at Freezing Temperatures on Starch and Baking Quality of Frozen Doughs

¹Graduate research assistant, Department of Cereal Science, North Dakota State University, Fargo, ND 58105. Present Address: Byrnes and Kiefer Co., Callery, PA 16066. ²Research chemist, USDA-ARS Hard Red Spring/Durum Wheat Quality Laboratory, Fargo, ND 58105. Mention of vendor or proprietary product does not constitute a guarantee or warranty of the vendor or product by the USDA, and does not imply its approval to the exclusion of other vendors or products that may also be suitable. ³Corresponding author. E-mail: lgrant@badlands.nodak.edu Fax: 701-239-1377.

The effects of prolonged frozen storage on the starch, rheological, and baking properties of doughs were investigated. Four hard red spring (HRS) wheat cultivars exhibiting consistently different gluten characteristics were used. Gelatinization properties of starches isolated from fresh and thawed frozen doughs over 16 weeks of frozen storage were examined using differential scanning calorimetry (DSC). Significance of results varied with cultivar, but all cultivars showed a significant increase in ΔH with increased frozen storage time, indicating water migration and ice crystallization. The amount of freezable water in frozen doughs increased for all cultivars with frozen storage, but the rate of increase varied. Glupro showed a consistent increase in freezable water during frozen storage (41.6%), which may be associated with its high protein content and strong gluten characteristics. Rheological strength of the frozen doughs which was determined by decreases in extensigraph resistance and storage modulus (G′), declined throughout frozen dough storage. Proofing time increased from 45 min for fresh doughs to an average of 342 min for frozen doughs stored 16 weeks. Concomitantly, loaf volumes decreased from an average of 912 cm³ for fresh doughs to an average of 738 cm³ for the frozen doughs. Longer proof times and greater loaf volume loss were obtained for the cultivars exhibiting greater gluten strength characteristics.