Changes in nutritional composition of Russet Burbank potatoes by different processing methods

Russet Burbank potatoes from the same storage lot, were processed by commercial technology and prepared for consumption as done institutionally and in the home. Products were chosen to include most of the processing or preparation steps that will influence nutrient losses, namely, boiling, baking, frying, and drying. Products were evaluated on an as-served-basis for potato solids, starch, total and reducing sugar, total and protein nitrogen, free amino acid, vitamin, and mineral contents. Comparisons of the quantity of these nutritional components in different prepared potato products were made and discussed.     

Anatomy and compositional variations within potatoes III. Gross compositional gradients

The degree of compositional variations within potato tubers has been related to the development anatomy of the tuber and to exact tissues. The principal component, starch, shows differences in granule size distributions and in composition that appear when the young tuber averages about 1/300 of mature volumetric size. These differences pertain at maturity. When starch differences have been established, growth by cell divisions diminishes and growth by cell enlargement becomes dominant. In the mature tuber the general gradients for specific gravity, percent total solids, and percent total nitrogen decrease from stem end to bud end for cortical, perimedullary and pith tissues. Relationship between specific gravity and total solids is less parallel because differences in cell size and size of minute intercellular spaces also influence tissue density. Relationship between total solids and total nitrogen gradients from cortical tissue to pith were inverse with toal nirogen being higher in those tissues of lower total solids. These variations suggest need for new approaches in basic research on tuber quality improvement.     

Influence of ethylene on black spot of potato tubers

Sound, hand harvested, whole potatoes were exposed to continuous flowing atmosphere containing air, air with 3 or 5% CO₂, and air with concentrations of 0.5, 1.0, and 10ppm C₂H₄ for periods of 1 to 11 days at 20°C. At 1-day intervals, potatoes were bruised and black spot development assessed. Development of black spot in potatoes exposed to C₂H₄ was equal to or less than in potatoes at harvest. The severity remained low during 3-day exposure to 1 ppm C₂H₄ and after transfer to 4 days in air, then increased. Severity of black spot increased in potatoes exposed to air, with intermediate response from exposure to air with CO₂. With an increase in sprouting, differences in black spot among treatments diminished. Less black spot developed in immature than in mature potatoes.     

Distribution of oxidase enzymes in potato tubers relative to blackspot susceptibility. I. Phenolases

To determine whether phenolase activity is related to susceptibility or resistance to blackspot, tissue from bud and stem ends of potato tubers was assayed for differences in monophenolase and polyphenolase activities, changes in activity due to bruising, and different forms of phenolase. No relationship between blackspot and phenolase activity was found when activities of selected tissue were determined with p-cresol, tyrosine or chlorogenic acid as substrates. A significant positive relationship was found between polyphenolase activity and blackspot susceptibility when total or soluble or particulate fractions of phenolase activity were determined with catechol. Stem tissue had a significantly higher rate of phenolase activity than did bud-end tissue, where activity was determined with p-cresol, tyrosine or catechol; no significant differences in activity between the ends were found when chlorogenic acid was used.     

Rapid development of enhanced atrazine degradation in a Dundee silt loam soil under continuous corn and in rotation with cotton

Mississippi Delta cotton (Gossypium hirsutum L.) production in rotation with corn (Zea mays L.) was evaluated in field experiments from 2000 to 2005 at Stoneville, Mississippi. Plots maintained under minimum tillage were established in 2000 on a Dundee silt loam with treatments including continuous cotton or corn and alternate cotton-corn rotations. Mineralization and dissipation of 14C [ring]-labeled atrazine were evaluated in the laboratory on soils collected prior to herbicide application in the first, second, third, and sixth years of the study. In soils collected in 2000, a maximum of 10% of the atrazine was mineralized after 30 days. After 1 year of herbicide application, atrazine-treated soils mineralized 52-57% of the radiolabeled atrazine in 30 days. By the sixth year of the study, greater than 59% of the atrazine was mineralized after 7 days in soils treated with atrazine, while soils from plots with no atrazine treatment mineralized less than 36%. The data also indicated rapid development of enhanced atrazine degradation in soils following 1 year of corn production with atrazine use. Atrazine mineralization was as rapid in soils under a rotation receiving biannual atrazine applications as in soils under continuous corn receiving annual applications of atrazine. Cumulative mineralization kinetics parameters derived from the Gompertz model (k and ti) were highly correlated with a history of atrazine application and total soil carbon content. Changes in the soil microbial community assessed by total fatty acid methyl ester (FAME) analysis indicated significant interactions of cropping system and sampling date, with FAME indicators for soil bacteria responsible for differences in community structure. Autoclaved soil lost all ability to mineralize atrazine, and atrazine-mineralizing bacteria were isolated from these plots, confirming the biological basis for atrazine mineralization. These results indicate that changes in degradative potential of a soil can occur rapidly and some changes in soil properties may be associated with cropping systems, which can contribute to enhanced atrazine degradation potential.