Dry matter content of apical and basal portions of Russet Burbank potatoes
Studies were made over a 4-year period of some factors affecting the dry matter content of the apical and basal portions of growing Russet Burbank potatoes. The greatest difference between portions was obtained from tubers of the normally irrigated plots of 1969. The amounts in the two portions in 1970 were nearly equal throughout the growing season. The major differences between the 2 years was a slightly cooler June and warmer maximum temperatures in July of the 1970 growing season. Moisture stress, particularly, early in the stage of tuber development (1972 season) caused a switch in amount of dry matter in the apical and; basal portions. Stress later in the development stage (1969 season) did not cause a switch. Fertility level was not as influential as moisture stress in affecting the ratio of dry matter in the two ends, whether under stress or normal moisture conditions.
Mechanical separation of potatoes into specific gravity groups shows promise for the potato chip industry
In recent years much research has been done to determine the factors responsible for good cooking quality in potatoes and toward the development of methods, other than cooking, which are a reliable index of cooking quality. Goldwaite (5) and Stevenson (14) have concluded that no two potato tubers are exactly alike in composition whether from the same variety or the same hill. Brewell (3) Clark (4) and Smith (11) have shown that even though wide differences in composition between individual tubers do occur that they can be graded into a more uniform cooking product by means of a specific gravity separation. Brewell (3) and others have stated that present grade standards for potatoes give no indication as to how a potato will cook and Brewell (3) Smith (11) and Clark (4) have suggested brine solutions of varying densities for making selections for mealiness. Because of the great variation in composition and cooking quality of individual tubers, and because it is possible to separate potatoes into cooking quality grades by means of specific gravity, a project to develop a machine capable of separating potatoes into specific gravity groups on a commercial scale was undertaken; and a machine capable of separating 12,000 pounds of potatoes per hour into two specific gravity groups, with an accuracy of from 3 to 4 per cent was developed (7). Recently the importance of specific gravity to the potato chip industry was pointed out by the work of Whiteman (15) and Smith (12-13). They showed that for any given variety the high specific gravity tubers yield a higher per cent of chips, absorb less fat in frying, and the chips are a lighter more attractive color than those produced from the lower specific gravity tubers. To test the effectiveness of the specific gravity grader in separating potatoes for the chip industry a study was undertaken in cooperation with the Greeley Spud Chip Company.
Change in the physical condition of starch of the potato during precooking heating
SummaryIn the processing of dehydrated mashed potatoes it has been found that a heating treatment before cooking improves the quality of the product. The temperatures of preheating are at or just above the temperature of gelatinization of potato starch granules, 60° C. Data presented here show-that gelatinized starch retrogrades, that is, becomes less soluble, if held at these temperatures. The rates of retrogradation at three temperatures. 60°, 65°, and 75° C, were about the same. After 60 minutes of preheating there was little further decrease in dissolved starch. Increasing cooking time of samples that were not preheated increased the amount of starch dissolved. These data suggest that the improved quality of dehydrated mashed potato products is due, in part at least, to a retrogradation of the starch. This retrogradation may account for the greater firmness and lack of sloughing of potatoes that are heated before cooking.