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We determine the effects of the technology of obtaining potato protein preparation and of different variants of enzymatic hydrolysis on the chemical and amino acid compositions of the hydrolysates obtained. Potato protein concentrates obtained through their thermal coagulation in potato juice with calcium chloride, calcium lactate or without salt addition were subjected to enzymatic hydrolysis using two commercial hydrolytic enzymes: endopeptidase (Alcalase) and exopeptidase (Flavourzyme). Chemical (contents of ash, total and coagulable protein) and amino acid compositions of the hydrolysates obtained were determined. On the ground of the findings it was stated that the type of potato protein preparation used and conditions of enzymatic modification influenced on the properties of the hydrolysates obtained. Preparations obtained during the study were characterised by similar chemical and amino acid compositions, whereas the preparation obtained through thermal coagulation with the use of calcium lactate contained insignificantly more protein and essential amino acids. The least liable to enzymatic hydrolysis was the preparation obtained by using calcium chloride, particularly when only endopeptidase was used. The application of endopeptidase enzyme enabled to obtain 60% of proteolysis efficiency and the addition of the second enzyme (exopeptidase) to the protein solution insignificantly increased the proteolysis efficiency (to ca 70%), mainly when the preparation coagulated with the use of calcium chloride was hydrolysed. Proteolysis of the protein preparations obtained with the use of two enzymes was more favourable, particularly due to the quantity of free amino acids in and amino acids composition of the hydrolysates.

This paper deals with assessment of biogas yield from mixtures of Reynoutria substrates and livestock manure. The aim was to perform laboratory experiments and suggest suitable fermenter operating conditions (dry matter content, pH, share of substrate components, thermic regime) for metanogenic digestion, then to determine its quality and assess the usability of the produced biogas.

Forty-four potato cultivars, released in the period between 1876 and the present were grown concurrently in field trials, stored simultaneously in three different environments, then evaluated for chip quality. They represented cultivars historically used and/or bred for potato chip production. Quality factors measured were tuber solids, chip color, reducing sugar levels, sucrose levels, and percent of defect-free chips. Tuber solids tended to increase in the late period cultivars, but trends were erratic. The release of Lenape marked the beginning of an increase in tuber solids that has continued to the present. There was a significant trend for lower reducing sugars and better chip color that corresponded to increasingly later cultivar release dates. Since about 1960, progress toward lower reducing sugars and better chip color has been constant, regardless of whether tubers were stored at 4.4 C, stored at 4.4 C and reconditioned, or stored at 10 C. Late period cultivars tended to have a greater percentage of defect-free chips in comparison to those released earlier, with most of the improvement coming during the last few years. This study provided evidence that potato breeders have made significant progress in developing cultivars with good chip quality. Evidence was also found that Lenape was a landmark cultivar and has been an important contributor to the observed breeding progress

A simple 1-D mathematical model for prediction of local temperatures in a layer of solid material during microwave heating and a sensitivity analysis were used to evaluate the influence of process and material parameters on vertical temperature profiles in a layer of material during heating. The distribution of applied microwave power between the upper and bottom layer surface influences the shape of the profile and the values and position of the highest and the lowest temperature in the layer. The effect of penetration depth increases with the increasing layer thickness. The effect of thermal conductivity value on temperature profile depends on the time of heating. Because of a short time of microwave heating, the effect of this parameter on temperature distribution is smaller compared to the conventional heating methods.

Two potato breeding selections were released by the United States Department of Agriculture, Agricultural Research Service on November 14, 1996, as germplasm that is highly resistant to current populations ofPhytophthora infestans (Mont.) deBary, the causal organism of potato late blight: B0718-3 and B0767-2. These two clones have been evaluated for their reaction toP. infestans in replicated plots at Presque Isle, Maine since 1990. B0718-3 is a netted white-skinned selection with good yields but low specific gravity. It is both male and female fertile and crosses readily with tetraploid Tuberosum. B0767-2 is a russet-skinned selection that is low yielding and low in specific gravity. It has not been successfully crossed; however, it may have some potential use in somatic hybridizations. Neither B0718-3 nor B0767-2 process into acceptable colored chips. Genetic material of this release has been deposited in the National Plant Germplasm System where it is available for research purposes, including development and commercialization of new cultivars.

NorValley is a multi-purpose, high-yielding, whiteskinned cultivar suitable for processing into chips, dehydrated flakes, or for table stock use. It chips directly from long-term storage at 6 C without reconditioning. NorValley has wide adaptability and is suitable for production on irrigated or non-irrigated land and has a low incidence of hollow heart. NorValley was released by the North Dakota Agricultural Experiment Station on August 22,1996.

Import demand for US frozen potatoes is estimated for Japan, Mexico, Philippines, and Thailand. Each country represents a different tier of import volume and market development (Japan--largest, most developed; Thailand--smallest, least developed). Import demand in Japan is primarily influenced by own-price and income. In the three smaller and newer markets, however, potato industry advertising and foreign investments by the US food service industry are found to be significant factors influencing import demand. Results suggest substantial growth potential exists in the export market for US frozen potatoes

Ten certified potato cultivears (Ajax, Crystal, Kennebec, Labelle, Liseta, Mondial, Norchip, Signa Gold, Spunta and Vital) were grown at Jordan University Experimental Station in 1993. At harvest, tuber subsamples of each plot were analyzed for physical properties and chemical composition. Processed chips and fries were evaluated for appearance, color, aroma, texture, taste and overall acceptability. There was significant variation in tuber weight which ranged from 108.8 (Kennebec) to 148.7 g (Labelle), specific gravity which varied from 1.022 (Mondial) to 1.191 g/ml (Spunta), total solids which ranged from 18.9 (Ajax) to 23.9% (Vial), and chemical composition. Cultivars Liseta, Signa Gold, Mondial, Kennebec and Crystal produced highly acceptable chips and fries, while Ajax, Kennebec, Norchip and Spunta produced excellent fries only. All other cultivars produced less acceptable chips and fries.

Few postemergence (POST) herbicides provide adequate control of broadleaf weeds in potato. Field experiments were conducted at Lethbridge and Vauxhall, Alberta in 1991 and 1992 to determine the suitability of rimsulfuron and HOE-075032 for selective POST control of weeds in potato. Rimsulfuron applied at 15 to 30 g ai/ha controlled flixweed, kochia, and redroot pigweed and suppressed the growth of redstem filaree. HOE-075032 at 50 to 60 g ai/ha provided comparable control. The potato cultivars, 'Shepody,' 'Norchip,' 'Russet Burbank,' 'Niska,' and 'Ranger Russet,' tolerated up to 80 g/ha rimsulfuron, but rimsulfuron at 120 g/ha caused fissures in some tubers and reduced marketable and total tuber yields. Tuber quality factors such as specific gravity and chipping ability were not affected by rimsulfuron. HOE-075032 at 15 to 30 g/ha caused fissures in tubers and reduced marketable and total tuber yield of all potato cultivars. Rimsulfuron, but not HOE-075032, provided excellent selective POST broadleaf weed control in potato.