Search

Two laboratories used three varieties of apples as materials for standardizing and correlating various physical, chemical and sensory evaluations of texture. The criteria used to evaluate the appropriateness of the objective methods were: Sensitivity to differences in texture. Relationship to sensory assessments. Agreement between laboratories. The effectiveness of the methods in detecting differences in texture due to the variety and storage conditions was remarkably similar in the two laboratories. For most of the methods, the relative standard deviation was 11% or less. Correlations among the various pairs of methods differed with variety and with the basis used to calculate the correlation coefficients. The two laboratories agreed substantially on the presence or absence of significance with respect to relationships between pairs of methods. The most appropriate objective measurement for evaluating texture appeared to be maximum force. The possibility of using specific gravity as a non-destructive method of measuring texture is suggested.

Russet Burbank potatoes were chilled at 25 F (−3.8 C), 27.5 F (−2.5 C), or 30 F (−1.1 C) for various periods of time and were then held at 45 F (7.2 C) for one or four weeks before testing. Susceptibility to injury was quite variable between the two crops and among tubers of the same lot exposed to the same treatment. The greatest amount of low temperature breakdown occurred in tubers chilled at 27.5 F (−2.5 C) for 10 hours. Flesh color, reducing sugar content, mealiness, and amount of sloughing in tubers that survived chilling were not markedly different from those in control samples although certain trends were observed indicating that the quality of chilled tubers was beginning to deteriorate. Chilling increased yellowness of flesh color in most treatments and darkness in several. Chilled tubers had a reducing sugar content slightly to moderately higher than the controls. They sloughed less than the controls and tended to be less mealy

Reproducible, objective methods which conformed closely to visual appraisal were developed for measuring color differences in either cooked or raw potatoes. Experimental samples, selected from lots stored at various temperatures for different periods of time, differed in extent of graying and yellowing. Ricing was found to be preferable to mashing as a method of cooked sample preparation. A comparison of methods of sample presentation using the Gardner Color Difference Meter showed thin-layer measurement was most successful in separating cooked samples differing in amount of yellow pigment; deep-layer measurement was most successful in separating grayed samples. A simple method for measurement of color differences in raw tubers successfully separated the samples. All three methods of sample presentation were significantly correlated with visual ranking.

Idaho-grown Russet Burbank potatoes were evaluated at monthly intervals during 12 months of storage to determine changes in mealiness, sloughing, and specific gravity. Storage treatments included untreated samples stored at 38 F, 45 F, and 52 F; two samples stored at 45 F, one of which had been treated with MH sprout inhibitor and the other with CIPC; and one untreated sample stored at 38 F and conditioned at room temperature one week before evaluation.

Reducing and total sugar assays and cooked flesh color measurements were made on Idaho-grown Russet Burbank potatoes at monthly intervals during 12 months of storage. The six storage treatments included untreated tubers stored at 38 F, 45 F, and 52 F; untreated tubers stored at 38 F followed by one week of conditioning at room temperature; tubers treated with MH-30 stored at 45 F; and tubers treated with CIPC stored at 45 F. The tubers stored at 45 F contained significantly less reducing and total sugars and were significantly lighter in color than those stored at 38 F. Tubers stored at 45 F were comparable to those stored at 52 F in sugar content and color and had a longer storage life. Treatment with MH-30 or CIPC had no effect on sugar accumulation and no important effect on color. Conditioning potatoes from storage at 38 F for one week at room temperature significantly decreased the contents of total and reducing sugars, although they remained significantly higher than those of tubers stored at 45 F. Conditioning did not reverse the yellow color which had developed during 38 F storage.

The relationships among three methods for evaluating texture (sloughing during cooking, hardness of cooked potato dice and shear press value of French fries) and some chemical constituents (Ca, Mg, K, free pectin, phytin and citrate) were investigated, using the main specific gravity classes of seven Dutch potato varieties. The interplay of these constitutents (except K) in the softening of the texture during cooking was expressed as follows: Open image in new window

Idaho-grown Russet Burbank potatoes treated with a sprout inhibitor were stored at 42 F, 45 F, and 48 F for 11 months. Monthly quality evaluations showed that tubers stored at 42 F were less mealy, contained more reducing sugars, and were yellower in color than those stored at 45 F or 48 F. The latter two treatments were not significantly different in mealiness and were generally similar in yellowness of color. Tubers stored at 48 F had less reducing sugars than those stored at 45 F. Although all treatments resulted in a gradual darkening of the potatoes during storage, differences in grayness among the three storage treatments were minor from a practical standpoint. It is suggested that a storage temperature no lower than 45 F be used to maintain the internal quality of Russet Burbank potatoes.

Thin slices of potato tissue were soaked in distilled water under various conditions of time, temperature, and volume of water. In one group of studies, the potato slices were drained and cooked in distilled water. In a second group of studies, the soak water from the potato tissue slices obtained under the various conditions was used as part of the water for cooking soaked and unsoaked potato tissue slices. The amount of tissue which did not disintegrate was weighed directly and was reported as the cooked potato weight (CPW). The CPW is inversely related to the amount of sloughing.

Russet Burbank potatoes baked with and without wrapping were held at different temperatures to determine the effect of the procedures on cooking quality. Unwrapped and foil-wrapped tubers did not differ in mealiness, color, and extent of off-flavor devlopment when judged at the time of doneness.

Thin slices of tissue from low (1.075–1.078 and high (1.092–1.094) specific gravity tubers were soaked in distilled water (100g/250ml) for 0, 1, 2, 3, 4, and 6 hours. Following the soak periods, the soak water and remaining tissues were separated and analyzed. Analyses of the soak water included pH, electrical conductivity, total solids, K, P and citric acid. The tissue analyses included total ash, alkalinity of ash, Ca, Mg, total N and phytate P. Other tissue samples were soaked the same periods of time and used to evaluate the amount of sloughing that occurred during cooking. All constituents studied diffused into the water during the soak periods. The greatest loss from the slices occurred in the first 2 to 3 hours and were similar for both specific gravity groups. After 6 hours the average amounts of material in the soak water were: total solids — 23%, P — 68%, phytate P —55%, K — 71%, total ash — 62%, total nitrogen — 56%, Ca — 35% and Mg —50%. Citric acid diffused into the soak water during the first 3 hours and the amount in the water then decreased. This apparent change may be due to metabolism of the acid. The sloughing of tissue decreased with the length of the soak period. The decrease in sloughing was highly correlated (P

Potato tissue extracts differed in their ability to cause sloughing of soaked potato tissue slices. Extracts from the bud half of the tuber caused greater sloughing than those from the stem half. Extracts from inner and outer tissue of the tuber were equally effective. Extracts from potatoes stored at 38 F generally caused more sloughing than extracts from potatoes stored at 38 F and conditioned for 1 week at 70–75 F, or from potatoes stored at 45 F or 52 F. Freshly prepared extracts were most effective in causing sloughing. When held at 0 F, their stability was maintained for extended periods. The extractives responsible for sloughing were readily soluble in water, slightly less soluble in alcohol, and insoluble in acetone. Steaming, blanching, or boiling potato tissue slices increased the sloughing properties of the extracts prepared from them. Potato tissue extracts passed through anion-cation exchange resins lost their ability to cause sloughing, showing that the components associated with sloughing are ionized compounds.

SUMMARY— Pectin jellies and potato starch pastes were prepared with aqueous extracts of potato tissue. All jellies containing potato extractives were weaker than distilled water control jellies. Jellies containing extractives from bud tissue were weaker than those containing extractives from stem tissue. Extractives from tubers stored continuously at 38°F weakened the jellies to a greater extent than those from tubers stored at 38°F and conditioned for 1 wk. Jellies containing extractives from boiled tissue were weaker than those prepared with extractives from blanched or steamed tissue. The most viscous pastes were those made with distilled water. In every case, viscosity of pastes containing extractives from raw tissue was less than half that of distilled water pastes. When extractives from blanched, steamed or boiled tissue were used, the viscosity decreased still further. The rigidity of jellies and the viscosity of pastes prepared with deionized extracts were similar to those of jellies and pastes prepared with distilled water. The data suggest that extractives leached from potato tissue increase sloughing of potato tissue during cooking by weakening the pectic materials in the intercellular cement rather than by enhancing the swelling of starch in the cells.

All anions or cations were removed from potato extract and were replaced by a single, naturally occurring anion or cation in an effort to determine the relative effect of each on the sloughing of potato tissue. The treated extracts were used in cooking soaked potato tissue slices. In the anion series, citrate caused the greatest amount of sloughing. Other cooking media and treatments in decreasing order of effectiveness were untreated extract, malate, oxalate, chloride, and distilled water. In the cation series, sodium and potassium caused significantly more sloughing than the untreated extract. Magnesium and calcium firmed the potato tissue, resulting in less sloughing than that obtained with distilled water.