Some aspects of cooked potato texture and appearance. II. Potato cell size stability during cooking and freezing

Slices of potato tuber tissue were cooked in water on microscope slides on a Koffler hot stage. At various temperatures during heating and cooling photographs of sets of potato cells were made. After cooling the tissue was frozen. Further photographs were made after thawing and reheating to 75C. The sizes of the individual cells were measured on the photographs. No swelling of the cells was observed under any of the conditions imposed. The hypothesis that starch gelatinization causes distention of potato cell walls during cooking was not supported by the results. Several suggestions were made for other roles of the starch in potato texture.     

Some aspects of total losses during storage and reconditioning of potato tubers

Summary Total losses during storage and reconditioning of several Polish varieties and strains in comparison with the American varietyKennebec are discussed. Several varieties or strains show such high losses that they are not acceptable for processing after storage. Susceptibility to loss is an attribute which must be taken into account when assessing varieties.     

Some effects of low-oxygen atmospheres on potato tubers

American Journal of Potato Research - White Rose potatoes were held in 21, 5, 1, and 1/2% O2 at 68, 59, and 41 F to test their response to atmospheres low in O2 during a simulated transit period of...     

Quality of potato tubers as affected by freezing: I. texture,ascorbic acid and enzymatic discoloration

The effect of freezing on the turgor, ascorbic acid content and enzymatic discoloration of Katahdin and Atlantic potatoes was studied. Tubers were exposed to a temperature of ?20°C for 24 hrs. then thawed for 1 hr. at 20°C before analysis. Frozen tubers were then compared with unfrozen controls. Both varieties lost turgor following freezing and exuded a sticky liquid with increased thawing time. At the end of 3 hrs. thawing, a sponge-like texture was observed in both varieties. In both varieties freezing resulted in a significant reduction (p<.01) in ascorbic acid and phenolic content (p<.01). Enzymatic discoloration was also significantly reduced (p<.01) in both varieties.     

The textural analysis of cooked potato. 3. Simple methods for determining texture

Summary Separate methods were developed for measuring softness, i.e. ease of cutting, and dryness, i.e. the tendency to cell separation. Pieces of potato tissue 30 mm long and 10 mm square were cooked in boiling water for 5, 10 or 15 min. To measure softness, the force required to cut the tissue with a thin stainless steel wire, inserted into a razor cut 1 mm deep, was recorded. To measure dryness, the tuber segments were crushed between two plates to half their original thickness and the crushed tissue separated on a 1 mm sieve. The <1 mm fraction consisted largely of single cells and was measured by its packed volume. Both softness and dryness increased with cooking time in a range of six cultivars. There was some correlation between them, and a closer correlation between dryness and specific gravity. The results agreed with previous organoleptic texture determinations.     

Sap extraction device for sampling potato leaves and tubers

An adaptation of a metal shop crimping machine with knurled rollers and driven with a foot-switch activated, geared-down electric motor was used to express sap from potato foliage or tuber pieces placed in triangular polythylene envelopes. Approximately 150–180 leaf samples/hour were processed by one operator. This sap extraction system eliminated the need for washing the rollers between samples and prevented contamination between samples. It worked equally well with oat or sorghum foliage.     

Storage of potato tubers under water. Preliminary investigations

Summary Potato tubers stored under water at 1°C do not accumulate sugars. The addition of aseptic agents (hydrogen peroxide, thymol) allows them to be stored without any microbial spoilage. During storage for up to 8 weeks the tubers were acceptable as a food product. Because of the possibility of the practical application of this method of storage, it is planned to investigate it in full detail.     

Evaluation of procedures for detection of pectolyticErwinia spp. on potato tubers

The effectiveness of a tuber incubation method for detection ofErwinia carotovora var.atroseptica andE. carotovora var.carotovora in potato tubers was compared with a lenticel sampling procedure. In the first method, tubers were injured by puncturing lenticels with sterile toothpicks, then wrapped in moist paper towels and polyvinylidene film, and placed in closed chambers flushed with N₂. In later experiments, wrapping tubers in two layers of polyvinylidene film and incubation in air was found to be as effective as the single layer of polyvinylidene and incubation in chambers flushed with N₂. Isolations were made on a selective crystal violet pectate (CVP) medium from homogenized samples of tissue removed from soft rot lesions developing around injured lenticels. In the second method, 10 lenticels/tuber were aseptically removed with a scalpel and homogenized in distilled water; the suspension was plated on CVP. The first method was less tedious and slightly more effective than the lenticel sampling method. In a preliminary survey, these methods were used to detectErwinia infestations in small samples of certified seed potato tubers from Maine, Minnesota, Montana, New York, North Dakota, and Wisconsin. PectolyticErwinia spp. were detected in at least one sample from each state except Montana. The percentage of tubers withErwinia infestations varied from 0–100% among samples. Characterization ofErwinia isolates showed that bothE. carotovora var.carotovora andE. carotovora var.atroseptica were present. PectolyticErwinia spp. on symptomless potato seed tubers may serve as inoculum sources for blackleg and soft rot diseases.     

Mineral element content of potato plants and tubers vs. yields

Linear equations for estimating the amounts of N, P, K, Ca, Mg and S removed from the soil as a function of yield are given for Russet Burbank potatoes. The equations were obtained from chemical analyses of potatoes grown using various ratios and rates of fertilizer, planting dates and harvest dates during 1966 to 1969 in the Columbia Basin of the state of Washington. The percentage mineral element composition of the tubers remained relatively uniform for the different ratios and rates of fertilizer but varied some due to the length of season. The correlation coefficients of chemical composition of the vines with chemical composition of tubers were low as were those relating amount in vines to yield. The correlation coefficients relating amounts of elements in the tubers to yield were 0.9 or greater.     

A rapid micro-starch quantitation method for potato callus and its application with potato tubers

The procedure described was developed as a micro-starch method for potato callus tissue (0.1-0.2% starch on a fresh weight basis) and then evaluated with macro-starch samples of potato tubers harvested during three physiological stages of development. This method consisted of the following steps: (a) a mild alkaline-sonic extraction of starch from lyophilized 80% aqueous ethanol-washed samples, (b) starch hydrolysis of the neutralized, filtered extracts by 1 N HC1, and (c) the determination of liberated glucose by the specific glucose oxidase system. Results with this procedure were as sensitive and accurate (SD ± 0.86%) as with other starch-specific methods with more extensive starch isolation and purification steps.