Sweet potato varieties

Odongo, B., Mwanga, R.O.M., and Niringiye, N. 2004. Promoting improved sweet potato varieties and processing technologies in Lira, Pallisa and Soroti Districts. Final Technical Report, October 2004-12-09. NAARI, Kampala, Uganda. 

Lupine seed, though used primarily in animal feeds (see Feeds AND FEED ADDITIVES), does have potential for use in human appHcations as a replacement for soy flour, and is reported to contain both trypsin inhibitors and hemagglutenins (17). The former are heat labile at 90°C for 8 minutes the latter seem much more stable to normal cooking temperatures. Various tropical root crops, including yam, cassava, and taro, are also known to contain both trypsin and chymotrypsin inhibitors, and certain varieties of sweet potatoes may also be impHcated (18). 

One of the more recent innovative approaches was to look for new micro-organisms and novel carbohydrate substrates. The early fermentations used sugar beet or cane molasses, various syrups, sweet potato starch or glucose itself and the micro-organism was always an Aspergillus spp. In the early 1930 s it was found that yeasts would produce dtric add from acetate. Since then a variety of yeasts, prindpally Candida spp., has been shown to convert glucose, w-alkanes or ethanol to dtric add with great effidency. 

Starch is obtained from a variety of plant sources. Corn, cassava, sweet potato, wheat, and potato are the major sources of food starch while sorghum, barley, rice, sago, arrowroot, etc. serve as minor sources of starch in different localized regions of the world (Gaillard, 1987 Ratnayake and Jackson, 2003). Raw starch granules do not disperse in cold water. This limits the use of raw native starches for food as well as industrial applications, and therefore starch is often cooked during product-manufacturing... 

The solubility of P-carotene in supercritical fluids has been studied extensively [81 to 85], The extraction of P-carotene from a wide varieties of natural sources has also been described like alfalfa-leaf protein concentrates [86], carrots [34,87], sweet potatoes [88], and algae [89],... 

The methodology depends on the known carotenoid distribution in plant tissues, which can be classified into three main groups (1) those in which the vitamin A value is due almost exclusively to /3-carotene (e.g., green leafy vegetables, peas, broccoli, sweet potatoes, tomatoes, watermelon, mango) (2) those in which primarily a- and /3-carotene account for the vitamin A value (e.g., carrots, some varieties of squash) and (3) those in which /3-cryptoxanthin and /3-carotene are the major contributors (e.g., cashew, apple, peach, persimmon, loquat) (60). 

Purple, iron-containing acid phosphatases have been purified from animal sources and from some plant sources.350 However, the purple acid phosphatase from the sweet potato contains manganese, the purple colour arising from an intense absorption band at about 515 nm. There is some doubt over the stoichiometry, in that the dimeric enzyme may contain one351 or two352 Mn2+, apparently depending on the variety of sweet potato. The iron acid phosphatases contain two Fe atoms. 

Sorptive capacity is one of the most important properties, and it has been investigated by many authors for several varieties of starch.331-333,335,419 Sair and Fetzer,420 and also Rakowski,331-333 compared the water-retention capacities of wheat, arrowroot, and potato starch, and the results were similar. Among the following starch varieties, the sorptive capacity decreases in the order given potato > arrowroot > wheat. The order potato > corn > wheat was reported by El-Khawas et al.42] Nara el a/.407 reported the order potato > tapioca > waxy rice > sweet potato > rice Smolina422 reported the orders potato > maize > rice > wheat at low humidity and potato > rice > maize > wheat at high humidity. These orders do not agree with the order reported in Table XVII on the effect of desiccation on the water retention of starch. Based on these data, the... 

Studies on the adsorption of Congo Red on starch803-812 have shown that potato starch does not adsorb that dye. In contrast to Acridine Orange, this dye enables determination of the amylose content in varieties of starch. The following percentages of amylose have been reported812 wheat, 23 corn, 15 rice, 16 tapioca, 16.5 sweet potato, 2.8 and potato, 1.8. These results are suspect because of the relatively low amylose concentrations reported, particularly for sweet potato and potato. 

The isolation of the first manganese-containing acid phosphatase was reported in 1971 from the juice of the sweet potato (Kokei No. 14) (67). The enzyme was unique in that it was distinctly purple, the color resulting from a broad absorption band with a maximum at 555 nm. The enzyme was determined to be 110 kDa, composed of two 55-kDa subunits. The purple enzyme was capable of hydrolyzing a variety of biologically relevant phosphates as well as inorganic pyrophosphate [Eq. (2)]. Emission spectroscopy revealed the presence of Mn (68). 

Pedaling past hillsides blanketed with sweet potato plants and some of the 60 varieties of mango trees that grow here, Ozzie described a cooperative culture where folks catch fish and tend crops to earn cash, but also barter their skills and harvest for goods and services they need. 

A variety of methods are used for identification and authentication, ranging from microscopes to the most complex and sophisticated scientific instruments available. In the examples provided in this chapter, we consider the microscopic identification of species-specific starch grains from South America to identify early traces of plant domestication. An SEM is used to identify plant remains from the Pacific and the very early spread of sweet potatoes from South America westward. A petrographic microscope is used to characterize the micromorphology and identify the contents of house floors in a prehistoric site in British Columbia. Finally GC/MS instrumentation is used to identify the chocolate contents of distinctive ceramic jars found in Chaco Canyon, New Mexico. 

Figure 1 Numbers of feeding holes, eggs laid and droppings of adult Cylas puncticollis on root plugs of two varieties of sweet potato - after 24 hours (n = 16), (sem = standard error of the mean)...

The chemical profile of New Kawogo root latex, which is also presented in Figure 3, contained peaks for 1, 2 and 4 but also contained 3, tentatively identified as octadecyl caffeate. This compound appears to be present at much lower concentrations in the variety Tanzania. Compounds 1 and 3 have not previously been found in sweet potato and so are reported here for the first time. When the synthetic compound 2 (100% E-form) was left in solution for 3 days at room temperature a second compound appeared, eluting approximately 30 seconds earlier and with a similar mass spectrum and a UV spectrum consistent with the Z-form of coumaric acid. Thus it is presently proposed that the peak eluting in fi ont of 4 in Figure 3 is the Z-form of 4 since this peak has an identical MS to 4 and a UV spectrum consistent with the Z-form of octadecyl /7-coumarate. 

There was a significantly higher concentration of caffeic and coumaric acid esters in New Kawogo latex as compared to those found in the variety Tanzania (Figure 3). The incorporated compounds increased the mortality of 2" instar larvae significantly (Figure 4). This effect was dose-dependent. This clearly shows that the compounds are active and affect the development of Cylas weevils in sweet potato, and could account for the differences in resistance among varieties. 

The identification of all these esters on the root surface is also significant in the effort to identify resistance mechanisms in Afncan sweet potato to C puncticollis particularly since they affect early development of larvae and may also affect egg laying behaviour. Thus breeding for varieties with higher quantities of hexadecylcafifeic and hexadecyl-/ -coumaric acids offers a viable option in the effort to develop varieties with resistance against the weevil C. puncticollis. However, the findings in this study are in contrast to earlier reports on other resistant African sweet potato cultivars, whaie it was postulated that resistance in sweet potato could have been due to the so-called pseudo-resistance described in the introduction. 

Studies performed on the etherification of potato amylose and amylopectin with (diethylamino)ethyl chloride showed that amylose in the starch granule was more reactive than amylopectin.2429 However, the relative reactivity of both starch components could be changed by physical pretreatment of the granules, for instance, by milling, heat-moisture treatment, freeze-thawing, and chemisorption. The physicochemical properties of amino starches depend on the starch variety reacted 2430 Among potato, sweet potato, rice, wheat, and tapioca starch studied, the last reacted most readily. 

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