Investigation on biochemical basis of resistant starch with respect to physiochemical properties in cereals-millets, rice and wheat
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Date
2018-12
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present investigation was carried out to assess the physio-chemical properties of starch attributing towards resistant starch in millets (Barnyard millet; VL Madira-207, Finger millet; VL Mandua-352 and Foxtail millet; DHFT-109-3), rice (PB-2 and PD-19) and wheat (PBW-343 and UP-262). The study emphasize on the factors which influences the resistant starch in cereals. In the present study starch isolated from different cereals were viewed under SEM to analyse the shape and size of starch granules. The size of starch granules were diverse range in cereals like millets (4.6-12.23 μm) rice (6.22-177.13 μm) and wheat (2.50-198.23 μm). Small and large spherical, irregular and polygonal shape of starch granules was observed. The FTIR bands at 1047 and 1022 cm-1 gives ordered and amorphous structure of starches and absorbance ratio at 1047/1022 gives indexes of the short-range order of double helices ranged from 0.94-1.24. Total starch (57-70%), amylase (31-45%) and amylose-amylopectin ratio (0.46-0.83) was determined in different cereals under observation. The amylose content was positively correlated with resistant starch at P < 0.01 while total starch had non-significant impact on resistant starch. The other nutrient of cereals like dietary fibre (2.66-6.98%), total soluble protein (9.33-16.29%) and soluble protein fraction like albumin (1.41-2.44%), globulins (1.25-2.23%) and prolamines (2.04-2.88%) was estimated to establish the correlation with resistant starch. These other nutrient of cereals showed positive correlation with resistant starch at P < .01. In vitro digestion of native starch, gelatinized starch and retrograded starch was done at time interval of 30, 60, 90, 120 min and it was found that the rate of enzymatic digestion follows the order; Gelatinized starch > Native starch > Retrograded starch. During endosperm developmental stages at S1, S2, S3, S4 (7, 14, 21, 28 DAA) the key enzymes for starch biosynthesis like AGPase, SSS and GBSS were estimated. The activity of starch biosynthetic enzymes follows the order AGPase > GBSS > SSS in all these varieties during endosperm development. The higher activity of AGPase, GBSS and SSS found in rice comprises higher accumulation of amylose and total starch during endosperm development. The accumulation of amylose and total starch in millets was found at par to the wheat varieties which is related to the activities pattern of enzymes. All three enzymes under study showed the positive correlation with each other during endosperm development. Accumulation of amylose showed positive correlation with AGPase and GBSS, while non-significant correlation with SSS. Total starch accumulation showed positive correlation with AGPase.
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