Starch content of potato

Starch content of potato dry matter is calculated as follows ... 

In recent years, a new research method was developed to determine total starch content of potato dry matter by comparing the gelatinization enthalpy of potato dry matter and standard starch using differential scanning calorimetry (DSC) (Liu et al., 2005). 

A chimeric gene encoding antisense RNA for ADPGlc PPase, reducing the expression of the enzyme (Muller-Rober et al, 1992) to between 2 and 5% of the wild type, reduced starch content of potato tubers by the same percentage the number of tubers increased, but their weight decreased. 

FIGURE 16.1 Preparative SEC of short-chain (scb) branched glucans of small" (<3S /u.m) starch granules of potato species Ostara separated on Sephacryl S-1000 (88 X 2.6 cm) eluent 0.005 M NaOH the normalized chromatogram (area = 1.0) was constructed from an off-line determined carbohydrate content of succeeding 5-ml fractions flow rate 0.67 ml/mln V d = 185 ml, V, = 460 ml fraction I high dp fraction fraction 2 low dp fraction. 

This by-product comprises the residue after starch removal. The composition of the dehydrated product can be quite variable (Edwards and Livingstone, 1990) depending on the content of potato solubles. The product has characteristics similar to those of raw potato and is not suitable for feeding to poultry. 

Table 6.5 Amylose contents of potato starch with different granular sizes and at different radial locations41...

Phosphorus content of potato starch (Geddes et al, 1965) varies during development of the tubers it increases from being undetectable in the amylose of tubers of 1-cm diameter, to 0.005% in tubers 8 to 9 cm in diameter, and, in amylopectin, from 0.029% in the 1-cm diameter to 0.049% in the largest (8- to 9-cm tubers). 

This equation well describes the relation between water content of potato starch and Tg as given in Figure 16.3a the relation is less perfect for several other binary mixtures. Many low-moisture foods are mixtures of polymers, water, and several other small-molecule components. Prediction of Tg from composition then is generally uncertain in practice a (narrow) transition range rather than a sharp transition point is often observed. 

In potatoes Solarium tuberosum) the main component is starch. The starch content of the dry matter is about 700 g/kg this carbohydrate is present in the form of granules that vary in size depending upon the variety. The sugar content in the dry matter of mature, freshly lifted potatoes rarely exceeds 50 g/kg, although values in excess of this figure in stored potatoes have been obtained. The amoimt present is affected by the temperature of storage, and values as high as 300 g/kg have been reported for potatoes stored at 21 °C. 

Starch Starch is the most important and abundant food polysaccharide. Starch is predominantly derived from plant seed, such as wheat, maize, rice, oats, and rye, and from plant roots, such as potatoes. Legumes and vegetables also contribute to the starch content of the diet. Bread and pasta are popular forms of starch, while tropical starchy foods, such as plantains, cassava, sweet potatoes, and yams are increasingly contributing to carbohydrate intake. Starch accounts for 20-50% of total... 

For dry starch, the concentrated starch milk is dewatered (40% water) by rotary vacuum filters or channel centrifuges and finally dried to a water content of 20% by flash dryers. The yield of starch depends on the initial starch content of the potatoes (17-21% fresh weight). 

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