Amino acid composition of freshly harvested and stored potatoes

Total amino acid contents of several important U.S. potato cultivars grown in Maine, Idaho and The Red River Valley are listed along with nitrogen content. Differences in amino acid content among cultivars were roughly proportional to differences in total nitrogen. The effect of storage on amino acids in two cultivars was minor. The limiting essential amino acids compared to egg were MET and the sulphur amino acids.     

Storage factors control germination and seedling establishment of freshly harvested true potato seed

Freshly harvested true potato(Solanum tuberosum subsp.andigena, Juz. et Buk.) seeds of the ancient Peruvian cultivar Ccompis were dried to 3.4, 4.2,5.1,6.1, and 7.3% moisture content (Dwt basis) and hermetically stored for 6 months at 15, 30, and 45C. Seeds were humidified to uniform moisture (13%) prior to monthly evaluations of germination at 27 and 17C and seedling performance under variable soil temperature. The effects of treatments on percentage of germination after 8 days at 27C were highly correlated with percentage of emergence at 10 days after sowing and foliage dry weight at 17 days. Germination at 27C increased from negligible to <90% with progressive increases in moisture, temperature, and time in storage. However, germination decreased within the first month of storing seeds at 45C with >5.1% moisture, and after 3 months seeds failed to germinate even after 8 days of lowering the temperature in the germination environment to 17C. Otherwise, germination inhibition at 27C was attributed to dormancy since most seeds readily germinated at 17C. Dormancy was sufficiently released and optimum overall performance was obtained after 2 months of storing seeds at 45C and 4.2% moisture.     

Lipid composition of potatoes during sprouting

The purpose of the study was to determine the lipid composition of potatoes during sprouting. Sprouts from Pontiac and Katahdin potatoes as well as two clones (the genetic material from crosses of a population ofSolanum andigenum from South America andSolanum tuberosum from North America) were found to be significantly higher in crude lipid than either the cortex or pith sections of the tuber. The cortex section was found to be higher in lipid than the pith section. Crude lipid was fractionated into phospholipid, neutral fat, and free fatty acids, and for each of the sections of potatoes the highest percentage of lipid was found in the phospholipid fraction. The fatty acid found in highest concentration in the phospholipid fraction was linoleic acid, but considerable quantities of linolenic and palmitic acids were also present. Synthesis of phospholipid occurs in the actively growing sprout, and compounds that interfere with lipid synthesis, particularly phospholipid synthesis, should prove to be effective sprout inhibitors.     

Glycoalkaloid composition of potatoes: Diversity and biological implications

Glycoalkaloids are important potato quality factors. Tuber-bearingSolanum species exhibit wide quantitative and qualitative diversity in glycoalkaloid contents. Some species, of interest to breeders, contain extremely high total glycoalkaloid (TGA) levels and/or unusual types of glycoalkaloids of ill-defined or unknown toxic and teratogenic properties. Characterisation of glycoalkaloid content is a dynamic and, in some cases, controversial subject. Problems associated with analytical methodology and, to a lesser extent, with environmental effects and intraspecific heterogeneity have probably been the major causes of disagreements in the literature. Recent methodological developments have facilitated more accurate and sensitive measurements of TGA levels and of individual glycoalkaloid compositions. Such measurements should be used to analyze parental material and selected hybrid progeny in breeding programs. This is particularly important when certain wildSolanum species are being exploited as undesirable levels and types of glycoalkaloid can be genetically transmitted from the wild species to hybrid progeny. Absence of glycoalkaloid assessment from a breeding program can result in wasted effort, time and money.     

Mineral composition of non-conventional leafy vegetables

Six non-conventional leafy vegetables consumed largely by the rural populace of Nigeria were analyzed for mineral composition. Mineral contents appeared to be dependent on the type of vegetables. Amaranthus spinosus and Adansonia digitata leaves contained the highest level of iron (38.4 mg/100 g and 30.6 mg/100 g dw, respectively). These values are low compared to those for common Nigerian vegetables but higher than those for other food sources. All the vegetables contained high levels of calcium compared to common vegetables, thus they could be a rich source of this mineral. Microelement content of the leaves varied appreciably. Zinc content was highest in Moringa oleifera, Adansonia digitata and Cassia tora leaves (25.5 mg/100 g, 22.4 mg/100 g and 20.9 mg/100 g dw, respectively) while the manganese content was comparatively higher in Colocasia esculenta. The concentrations of the mineral elements in the vegetables per serving portion are presented and these values indicate that the local vegetables could be valuable and important contributors in the diets of the rural and urban people of Nigeria. The mean daily intake of P, Mg, Ca, Fe, Cu and Zn were lower than their recommended dietary allowances (RDAs). However, the manganese daily intake was found not to differ significantly ( p = 0.05) from the RDA value.     

Mineral composition of some traditional Mexican teas

Teas of plant origin traditionally consumed by the Mountain Pima of Chihuahua, Mexico, were analyzed for mineral nutritional content. Fe, Cu, Zn, Ca, and Mg composition was determined for native teas made from shoots ofTagetes lucida, T. filifolia, Elytraria imbricata, andHolodiscus dumosus, and from root xylem ofCeanothus depressus andPhaseolus ritensis. Native uses of these teas are also described.     

Changes in the nutrient composition of potatoes during home preparation: I. Proximate composition

The effects of various home cooking methods on the proximate composition of four potato varieties were investigated. The results revealed significant increases in the dry matter content of tubers during oven-baking and microwave cooking. With one exception, cooking unpeeled tubers in boiling water did not significantly alter their proximate composition. Boiling peeled tubers resulted in a significant decrease in the total ash content. Except for one variety, there was a significant decrease in crude fiber in boiled peeled and oven-baked potatoes. Changes in protein values were erratic.     

The effect of cooking methods on the lipid composition of potatoes

The effect of boiling and baking in either a convential or microwave oven on the lipid content of potatoes was investigated. The crude lipid content of potatoes was lowered significantly by all methods of cooking. The loss was highest in potatoes cooked in a microwave oven, least in boiled tubers, and intermediate in tubers baked in a conventional oven. Similar trends were observed for both cortex and pith tissues. Generally, the phospholipid content followed the same trend as the crude lipid, the exception being the cortex tissue of tubers baked in the conventional oven, in which the greatest loss of phospholipid occurred. Cooking did not significantly alter the fatty acid composition of tubers. A possible relationship between the degree of cell rupturing, known to be influenced by different mechanisms of heat transfer, and the amounts of tuber lipid associated with different cooking methods was discussed.     

Lipid composition of potatoes as affected by storage and potassium fertilization

The effects of storage treatments and potassium fertilization on the phospholipid, triglyceride and free fatty acid content of Russet Burbank potatoes were determined. Thin-layer chromatography of the lipids indicated at least 18 types of lipids were present. Eight were phospholipids which were the predominant lipid class in the potatoes. Phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine and phosphatidic acid comprise the major phospholipids. A large increase in phosphatidic acid and a decrease in phosphatidylcholine were observed in potatoes stored at 5.6 C (42 F). Potatoes fertilized with 240 lbs of potassium (calculated as K₂O) had a higher content of triglycerides compared to potatoes with no fertilization. Potatoes stored at 5.6 C (42 F) exhibited a decrease in triglyceride and phospholipid content but the free fatty acids were increased. The various lipid contents of reconditioned potatoes were similar to those of freshly harvested potatoes.     

Dry matter content and mineral composition of potatoes grown in Cyprus

Summary The specific gravity and dry matter content of 193 tuber samples (cultivars: Arran Banner, Spunta, Up-to-Date, Cara) from crops grown at Kokkinochoria, the major potato growing area of Cyprus, were related to each other as follows: Dry matter (%)=−269.59+268.24×specific gravity. This regression accounted for 82.4% of the variation; the fiducial limits (P<0.05) for single determinations of specific gravity were±1.54 percentage units. The mineral contents of the tubers were similar to those reported in other countries.     

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.     

Production and chemical composition of potatoes related to placement and rate of nitrogen

Experiments with 11 N rates were conducted 3 years with Kennebec potatoes on Bodenburg silt loam in the Matanuska Valley of Alaska. Fertilizer placed in the row was compared with that mixed with the soil in the row for 2 years. Foliage and tuber samples were analyzed for chemical content. Stand reduction and decreased vigor occurred when row placed N exceeded 120–160 1b per acre. Foliage dry matter decreased 2 years as rate of N increased. Tuber dry matter was decreased one year by N rates exceed ing 100 1b per acre. U. S. No. 1 yield and dry matter with row placement of fertilizers at 40–80 1b N were highest in 2 years. When fertilizer was mixed with soil, both US No. 1 and dry matter yields increased each year with each N increment through 160 1b per acre. Increasing amounts of N tended to increase the N in foliage and tubers, the Mn in foliage but to decrease the Ca, Mg, Al, Ba, and Sr in foliage. Mixing the fertilizer with the soil as compared to placement in the row increased the Ca, Mg, Al, Ba, Fe, and Sr in foliage, and the tuber uptake of N, K, Mg, and Sr and decreased foliage N. Alaskan potato growers have doubled or tripled their rate of application of fertilizer over the past 15 years. At digging time potato plants are usually green and some growers have felt these higher fertilizer rates were supplying an excess of N which was delaying tuber maturity and decreasing tuber quality.     

Changes in the nutrient composition of potatoes during home preparation: II. Vitamins

American Journal of Potato Research - The retention of water-soluble vitamins by several potato varieties using various home preparation methods was investigated. Retention values in general...