Potato, sweet, protein content

Data are not available for protein production worldwide. However, an estimate of the protein contribution provided by sweet potatoes can be made if we assume a mean dry matter content of 28% and a mean protein content of 5%. Based on these assumptions, the sweet potato provides 1.92 million metric tons of protein worldwide. The yield of protein would be 134 kg/ha using worldwide yield values or 184 kg/ha using US production values. 

Table I. Crude Protein Content (% Fresh Sweet Potato) of Ten Cultivars From Upper Mendi Grown in Different oo...

Walter et al. (38) measured the protein efficiency ratio (PER) of flour prepared from sweet potatoes which were cooked in a drying oven. Because the PER is determined on the basis of a diet containing 10% protein, the Jewel and Centennial sweet potatoes used in this study were stored until sufficient starch had metabolized to increase crude protein content to 11.25% (dry basis). When the flour was fed to Sprague-Dawley strain rats, the corrected PER values were 2.22 and 2.00 for Centennial and Jewel cultivars, respectively, compared to 2.50 for casein. Centennial had the highest PER value of the two cultivars because its NPN content was lower. The net effect of increased NPN content is to lower the amount of essential amino acids as a percentage of the total nitrogen and thus decrease the PER value. 

Why might a sweet potato plant genetically engineered for a higher protein content have a greater intolerance for nitrogen-poor soils ... 

Wash, hand-peel, chop and lyophilize each plant tissue material for 3-4 h at 25°C (e.g., soybean (Table 17.1), potato, banana, eggplant, sweet potato and artichoke (Table 17.2). Grind the dry tissue to obtain a fine powder and select the particle size using sieves of lower than 200 pm mesh. Store the dry powder in a desiccator at 25°C and use it as the enzymatic source of PPO or peroxidase in the preparation of biosensor. Determine enzymatic activity and total protein content as described in Procedure 22 (in CD accompanying this book). Prepare the carbon paste electrode with dry tissue as described in the same procedure. 

The overall objective of this chapter is to review the past, present, and future role of the sweet potato (Ipomoea batatas [L.] Lam) in human nutrition. Specifically, the chapter describes the role of the sweet potato in human diets outlines the biochemical and nutritional composition of the sweet potato with emphasis on its (3-carotene and anthocyanin contents highlights sweet potato utilization, and its potential as value-added products in human food systems and demonstrates the potential of the sweet potato in the African context. Early records have indicated that the sweet potato is a staple food source for many indigenous populations in Central and South Americas, Ryukyu Island, Africa, the Caribbean, the Maori people, Hawaiians, and Papua New Guineans. Protein contents of sweet potato leaves and roots range from 4.0% to 27.0% and 1.0% to 9.0%, respectively. The sweet potato could be considered as an excellent novel source of natural health-promoting compounds, such as p-carotene and anthocyanins, for the functional food market. 

The sweet potato Ipomoea batatas) is a very important tropical plant whose tubers are widely grown for human consumption and as a commercial source of starch. The tubers are of similar nutritional value to ordinary potatoes although of much higher dry matter and lower crude protein contents (see Table 22.1). Fresh tubers that are surplus to requirements are often cut into small pieces, sun-dried and then ground to produce a sweet potato meal, a high-energy food of low protein content. Sun-drying does not destroy the trypsin inhibitors believed to be present in the tubers, and levels in the diets of farm animals are usually restricted. 

Figure 7.11 Effect of adding crystalline sweet potato 0-amylase (87 fig protein/ml reaction mixture) on the filtration rate (ml/h) and on the reducing sugar content (measured as maltose) in the filtrate at 50°C, 15 psi, in a stirred cell system. Enzyme added ( ) no enzyme added (o).13...

MOISTURE, CARBOHYDRATE, PROTEIN, AND pT AROTENE CONTENTS OF SWEET POTATO FLOUR... 

Shortages of grains (a) forcing low-income people to resort to starchy plants, such as bananas, sweet potatoes, and cassava, for their staple foods, and (b) creating nutritional problems due to the low content of protein and other nutrients in these high-carbohydrate foods. 

Sunflower seeds—Although many Americans formerly considered this chewy product to be best suited for feeding birds, it is now sold as a snack food. The seeds keep well without refrigeration, because of their protective outer covering. Their content of copper and iron, along with protein and vitamins, makes them a much better snack item than popcorn, potato chips, and sweets. Some health food stores carry sunflower seed butter and sunflower seed meal but these items sometimes have a bitter taste, which may be due to rancidity that develops when the seed is crushed and the oil exposed to the air. 

In addition to its archetypical members, uteroferrin and bovine spleen add phosphatase, the class of purple add phosphatases includes proteins isolated from rat bone and. spleen spleens of patients with Gaucher s disease or leukemic reticuloen-dotheliosis equine uterine flushings bovine cortical bone giant ceU tumors human placenta and microorganisms . The plant enzymes include an Fe-Zn phosphatase from red kidney beans and an Fe-Fe or Mn(in) protein from sweet potato tubers . Although less well-defined and more heterogeneous than their mammalian counterparts, the color and iron content of the plant enzymes warrant their designation as purple acid phosphatases. 

The purple add phosphatases of plant origin, in contrast, comprise a more heterogeneous class of enzymes A phosphatase from sweet potato, originally thought to depend upon Mn(III) for activity has recently been shown to consist of two apparently identical 53 kDa subunits, the holoenzyme bearing two atoms of iron However, discordance in the metal content may reflect differences in the spedes of sweet potato used in the isolation procedure, the Mn(in) protein being isolated from Japanese Kin-toki and the two-iron phosphatase from local American tubers In either case, at least one of these metal atoms is likely to be coordinated to tyrosyl residue(s) to account for the intense violet color and resonance Raman spectrum of the protein No direct evidence that the iron atoms in the two-iron protein are magnetically coupled is yet available, but spectroscopic similarities between the sweet potato and animal enzymes make this a reasonable conjecture. 

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