Abstract:
The objectives of this research were to determine the appropriate conditions in preparing pretato raw material and in processing of good quality frozen prefried potato patties acceptable to the consumers. Blanching was investigated and it was found that the suitable conditions were: shredding the potato with the perforation of 3.6 and 6.2 mm and blanching them with water (95 ํC) for 2 and 3 min respectively. In the next stage, processing variables were studied and it was revealed that shredded potatoes with a size of 6.2 mm, forming by using pregelatinized starch as binder and frying at 190 ํC for 3 min. were appropriate parameters in preparation of the product. Subsequently, the effects of varying the deep-fat frying time at 190 ํC for prefrozen potato patties and frozen potato patties were performed and the suitable conditions being ; frying time for prefrozen potato-1 min or frying time for frozen potato-2 min. Salt was then use to improve the flavor of the product and the proper level was 0.5% (based on the potato weight). Appropriate air blast freezing time; the freezing air temperature being -32 ํC and the central temperature of the sample being -18 ํC, was 42 min and appropriate liquid nitrogen freezing conditions; the temperatures being varied at 4 levels, were at a temperature of -60 ํC and with a time of 4 min 23 sec. Subsequently, variables affecting the qualities of the product including means of freezing ; i.e. liquid nitrogen and air blast freezing and methods of preparation of the product for consumption ; i.e. deep-fat frying at 190 ํC and baking in the oven at 250 ํC were compared and it was apparent that frying affected the product's qualities. In order to improve the color of the product, it was found that sodium acid pyrophosphate (SAPP) at 0.075% (weight/volume) helped maintain good color. Finally, the developed product was prepre in order to investigate the effects of varying levels of SAPP in blanching water, means of freezing and freezing storage time on the physical, chemical, sensory and microbiological properties; i.e. the product being packed in Nylon laminated with LLDPE bags and kept frozen at -18 ํC. It was obvious that liquid nitrogen freezing resulted in less% weight loss,% thawing loss and % heating loss but in higher sensory characteristic scores including appearance and texture when compared to air blast freezing. Blanching potato raw material with SAPP (0.075% weight/volume) yielded the product with higher lightness and yellowness and the tendency of decreasing lighness and increasing TBA values were inferior when compared to blanching with ordinary water. The product kept for 5 months still had the overall preference score between like moderately and like very much and the total plate count (TPC) and yeast and mold counts were still less than 300 colonies/g.