Cryo-Scanning Electron Microscopy Investigation of the Texture of Cooked Potatoes
The texture of steam-cooked potatoes was investigated by examining the fracture planes of four different cultivars, using cryo-scanning electron microscopy (cryo-SEM), which yielded a good preservation of the hydrated structures in potato tissue . For all cultivars , fracturing after steam -cooking took place between cells preferentially alongside the cell walls. However, textural difference appeared from the degree of intercellular contact, the cell shape and the appearance of cell surfaces. Cells in the fracture planes of firm potatoes had large intercellular contacts. In this case, most of the cells were flat and cell surfaces showed folds and cracks . For mealy potatoes , it appeared that cells in the fracture planes had little intercellular contacts . The cells were round and turgid and had smooth surfaces . In conclusion, the structure of cell wall and middle lamella , and the starch content , appear to be important parameters to distingui sh firm and mealy cultivars. Key \Vords: Cell, cryo-scanning electron microscopy , potato, cultivar , steam-cooking, texture, fracture plane, pectin, starch, cell wall. Initial paper received March 19, 1992 Manuscript received September 8, 1992 Direct inquiries to J.T. van Marte Telephone number: 31 8370 75060 Fax number: 31 837
Sensory evaluation of the texture of steam-cooked table potatoes
SummaryThe texture of steam-cooked potatoes from ten cultivars was sensory evaluated after two, four and nine months storage for three consecutive years. The sensory data were analyzed using Principal Component Analysis (PCA) and regression analysis. PCA revealed that the first two principal components explained 95% or more of the variance between the data. The first principal component was dominated by the descriptorsmealy (M)/crumbly (A/M) on the positive side and the descriptorswaxy (A/M) on the negative side. The descriptorfirm (M) had a high positive loading on the second principle component. Regression analysis showed that cultivar effects dominated storage effects. Based on these data, a proposal is made to divide the ten cultivars in four groups which differ for the descriptorsmealy (M)/crumbly (A/M), waxy (A/M) andfirm (M).During storage, potato texture became morewaxy (A/M) andsticky (A/M) with respect to both appearance and mouthfeel. Other changes in texture as a result of storage were strongly cultivar dependent.
Effect of Soybean Cyst Nematode (Heterodera glycines) on Yield of Resistant and Susceptible Soybean Cultivars Grown in Ohio.
Soybean (Glycine max) producers in Ohio rarely use soybean cyst nematode (Heterodera glycines, SCN)-resistant cultivars because of concerns over limited yield potential and lack of resistance to Phytophthora sojae. A two-year study was initiated to determine grain yield and nematode population increase on soybean cyst nematode-resistant cultivars in maturity groups II and III in production fields. Sites differed in soil texture, nematode densities, and P. sojae infestation at a number of locations in Ohio. Soil was assayed for nematode densities before planting and at harvest. Yields of resistant cultivars averaged 0% to 18% higher than those of susceptible cultivars in fine-textured soils with average preplant populations ranging from 463 to 14,330 SCN eggs/100 cm(3) soil. In coarse-textured soils, yields of susceptible cultivars were 21% to 56% less than the resistant cultivars with average preplant densities ranging from 1,661 to 15,558 SCN eggs/100 cm(3) soil. The reproductive index ranged from 0.1 to 5.5 for resistant cultivars and 0.4 to 112 for susceptible cultivars. In 1993, yield of P. sojae-susceptible, nematode-resistant 'Asgrow A 3431' was as high as yield of the P. sojae-resistant, nematode-susceptible cultivar 'Resnik' in a Phytophthora-infested field. The nematode-resistant cultivars Madison Experimental 131527 and Asgrow A3431 had higher yields than AgVenture AV1341 and susceptible cultivars Resnik and Kenwood when compared over five nematode-infested sites. Nematode-resistant cultivars were found to be excellent alternatives to currently grown susceptible cultivars for managing SCN where group III cultivars are used. However, better cultivar alternatives may be needed for sites with combined Phytophthora root rot and cyst nematode problems.