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Abstract: The relationship of steam cooking time with cellular strength of cultivars Chieftain, Kennebec, Russet Burbank and White Rose was compared within and among solids concentrations. Nitrogen fertilization had no discernible effect on cell wall strength. Cell strength of Kennebec and Russet Burbank was similar regardless of solids concentration or cooking time. However, cell strength of Chieftain and White Rose differed with solids concentration and cooking time. Knowledge of cell strength and its characteristics with cooking time appear important for understanding the differences in textural quality that exists between cultivars.

Abstract: The oil content of par-fried frozen French fries prepared by two methods, conventional and freeze-leached, was not affected by blanch temperatures when blanched for 15 minutes. Melting points of the frying oil did affect the oil content of par-fried French fries. The differences were variable and could not be explained by melting point alone. Blowing the potato strips with ambient air after the par-fry and cooling below the melting point of the frying oil had no effect on the oil content of the frozen product. Contrary to previous reports, the oil content of the French fries increased significantly as the par-frying temperature was increased from 160.0 to 185°C (320 to 365°F) with the greatest increase occurring between 171.1 and 185.0°C (340 and 365°F). The French fries par-fried 1 min at 171.1 and 185.0°C (340 and 365°F) were judged to have identical quality after finish frying 3 minutes at 185.0°C (365°F). A lower par-fry temperature or possibly a shorter par-fry time at the higher temperature would be an advantage to the processor who could use less oil and energy without adversely affecting the quality of the final consumable product.

Abstract: Mealy mashed potatoes were obtained from potato slabs steam cooked as little as 8 min. The potato slabs were undercooked by the fork test. The bud-end slabs were softer than the stem-end slabs and the compressive force to rice the potato was high. Histologically, potatoes cooked 8–18 min showed no distention of cell walls and the rupture of cells was caused by the ricing of the potato tissue. Measurement of released free starch from the ruptured cells showed the potato cell was more susceptible to rupture as the cooking time increased. Potatoes cooked 9–12 min showed no significant differences in amount of cell rupturing. The results indicated the possibility that the pectic material in the middle lamella underwent a change, which was complete at cooking time of 9–12 min, to permit forced separation of the cells without undue damage to the cells. With longer cooking time, there was breakdown of the pectic material in the primary and secondary wall increasing the susceptibility of cells to rupture.

Abstract: Russet Burbank, Norchip, Kennebec, White Rose, Red La Soda and Lenape tubers were sampled at harvest, after storage for 2 and 4 mo at 7 C, and after 3 wk at 20 C following each storage treatment. Freeze-dried tissue from the bud-end, stem-end and core was analyzed for total, and free amino acid nitrogen, and for monophenolase, polyphenolase, peroxidase, and catalase activities. Significant differences among cultivars and among different parts of the tuber were found for all nitrogen fractions and all enzyme activities. Storage treatments significantly changed the total and free amino acid nitrogen contents and polyphenolase, peroxidase, and catalase activities. When compared for total nitrogen content and catalase activity, differences among different parts of the tuber which were statistically significant were similar in all cultivars. However, when compared for free amino acid content, and monophenolase, polyphenolase and peroxidase activities, differences among different parts of the tuber which were statistically significant were dependent upon which cultivar was examined. The differences among cultivars which were statistically significant for all nitrogen fractions and all enzyme activities, except peroxidase, were not significantly changed by storage treatment. The differences among different parts of the tuber which were statistically significant for quantity of both nitrogen fractions and for all enzyme activities were not significantly changed by storage.

Abstract: Solids content and amylose/amylopectin ratios were determined in different parts of tubers of White Rose, Red La Soda, Kennebec, Russet Burbank, Norchip and Lenape at harvest, after storage at 7 C for 2 and 4 mo, and after reconditioning at 20 C for 3 wk following each storage period. In all cultivars, solids content was greatest in stem-end, lower in bud-end and lowest in core tissue. The relationships for distribution of solids among the different parts of the tubers was not changed by storage treatments in any of the cultivars. Amylose/amylopectin ratios were similar in all parts of the tuber. Both the solids content and amylose/amylopectin ratio were changed by storage, but not uniformly in all cultivars.

Abstract: Total sugar, reducing sugar, glucose, fructose, and sucrose were determined in three parts (bud-end, stem-end, and core) of tubers of White Rose, Red La Soda, Kennebec, Russet Burbank, Norchip and Lenape. Tubers were sampled at harvest, after storage for 2 and 4 mo at 7 C, and after reconditioning for 3 wk at 20 C after each storage period. The quantity of different sugar fractions varied with cultivar and changed with storage treatments. Only sucrose was uniformly distributed among the different parts of the tuber. Except for fructose and sucrose the relationships among different parts of the tuber for distribution of all other sugar fractions varied significantly with cultivar, and these relationships among parts were not significantly changed by temperature, or duration of storage.

Abstract: The solids content of adjacent potato strips cut from known locations within the tuber was found to differ significantly. These strips were identified and processed according to commercial practice. The finish fries were subjectively scored for quality. Yield and oil uptake were calculated. The solids content of individual strips from a 20 tuber sample out of a single 100 lb. bag ranged from 12% to 29%. The whole tubers ranged from 18% to 23% solids. Strips below 17% solids were shriveled, limp and soggy after processing while strips above 22% solids were rigid and crisp with a mealy interior. Oil uptake was not related to solids content. However, yield of par-fries and to a lesser extent of finish-fries increased as solids content increased.

Abstract: Tissue selected from the stem- and bud-end of reconditioned tubers having sugar-end disorder was compared by color after frying and chemical composition to tissue removed from the two ends of tubers without sugar-end disorder taken directly from cold storage at 45 F, and after reconditioning 3 weeks at 70 F. Chemical analyses of selected tissue suggested that the dark finish-fry color at the stem-end of sugar-end tubers following reconditioning at 70 F was due to the inability of the physiological systems within the tissue to convert reducing sugars to starch and/or to use these sugars in the respiratory process. Of the components analyzed, only a high reducing sugar content was associated with a dark finish-fry color. Neither sucrose nor free amino acid content was associated with the sugar-end disorder. Extending the reconditioning period at 70 F for sugar-end tubers did not lower the reducing sugar content or the darkening of the stem-end tissue on frying.

Abstract: Strips cut from cold storage (5 C), potatoes were immersed in difluorodichloromethane (R-12) from 5 to 13 sec. This rapid freezing was found to selectively damage only the frozen cells and to increase their permeability with respect to intracellular soluble materials. Subsequent immersion in water (17 to 52 C) leached the soluble materials from the frozen cells. This method of leaching in 20 min removed less than 15% of the starch released by potato strips leached at 65 C for 15 min (simulated commercial conditions). The depth of freeze determined by physical methods and by analysis of the leached surface layers showed reducing sugar removal 0.1 to 0.2 mm below the calculated average depth of freeze. In experimental lots the weight of leached materials increased with increased freezing time. Manipulating freezing depth and leaching time made it possible to achieve the required sugar removal from different lots of tubers.