Exploring modified rice flour and supplementation approach to enhance resistant starch content: Visco thermal and structural characterization

Supplementation of rice flour with Apple Pomace Powder (APP) and Synthetic Vinegar (SV) was investigated to reduce the glycemic potential of ready-to-eat snacks using extrusion cooking. The aim of the study was to compare the increase in resistant starch and decrease in glycemic index of modified rice flour based extrudates after supplementing the Modified rice flour with synthetic vinegar and apple pomace. The effects of independent variables-SV (3-6.5 %) and APP (2-23 %) were evaluated on resistant starch, predicted glycemic index, glycemic load, L*, a*, b*, ΔE and overall acceptability of supplemented extrudates. Design expert predicted 6 % SV and 10 % APP as desirable conditions for enhancement of resistant starch and reduction of glycemic index. Resistant Starch (RS) of supplemented extrudates increased by 88 % while as pGI and GL was decreased by 12 % and 66 % respectively as compared to un-supplemented extrudates. L* value increased from 39.11 to 46.78, a* value increased from 11.85 to 22.55, b* value increased from 10.10 to 26.22 and Δ E increased from 7.24 to 17.93 respectively in supplemented extrudates. The results suggested that apple pomace and vinegar can act in synergy to reduce the in-vitro digestibility of rice based snacks, while maintaining the sensory acceptance of the developed product. The significant (p < 0.001) decrease in the glycemic index was achieved as the supplementation level increased. The increase in RS correlates with the decrease in glycemic index and glycemic load.

Development of low glycemic index instant Phirni (pudding) mix-its visco-thermal, morphological and rheological characterization

High amylose rice (HAR) and carboxymethyl cellulose (CMC) are the preferred choices for enhancement of resistant starch content and lowering of glycemic index in dairy desserts. The effects of different levels of skimmed milk powder (SMP): HAR flour (45:55 to 75:25) and CMC (0.1 to 1%) were investigated on physical characteristics of dry-mix and on texture profile parameters, resistant starch (RS), predicted glycemic index (pGI), glycemic load (GL) and overall acceptability of phirni (a traditional milk pudding). Design expert predicted SMP (70): HAR (30) and CMC (0.8%) as optimum levels for reducing the pGI and maximizing the RS content and other quality characteristics in phirni. RS content of phirni (4.38%) prepared from optimized dry-mix (ODM) was higher while pGI (48.12) and GL (7.50) were lower as compared to phirni prepared from market dry-mix (MDM). The visco-thermal properties of ODM and MDM also showed significant variations. Storage modulus (Gʹ) and loss modulus (Gʹʹ) indicated that ODM phirni was less solid than MDM phirni. Scanning electron micrographs showed fused structures in ODM, while coarse sheet like structures were observed across the surface of MDM. Thus, ODM can be a promising substitute for the available milk desserts for diabetic patients.

Variability in waxy (Wx) allele, in-vitro starch digestibility, glycemic response and textural behaviour of popular Northern Himalayan rice varieties

Eight commonly cultivated and consumed rice varieties of Northern Himalayan regions and a popular high amylose rice variety were characterized at Wx locus and evaluated for resistant starch (RS), in-vitro starch digestibility, predicted glycemic index (pGI), glycemic load (GL) and textural parameters. Cytosine and thymine repeats (CT)n at waxy locus (Wx) showed high association with apparent amylose content (AAC). Both pGI and GL varied substantially within the selected varieties. The pGI was relatively lower in high and intermediate amylose Indica varieties compared to low amylose Japonica ones. However, Koshikari despite being a low amylose variety showed relatively lower pGI and GL, due to its higher RS, dietary fiber, protein and fat content. It was thus presumed that in addition to AAC, RS and other grain components also affect the glycemic response. Inherent resistance to enzymatic hydrolysis was also found to be higher in firm textured and less sticky rice varieties. The genotypes-Lalat, Basmati-1509 and Koshikari, in view of their low to moderate pGI and relatively higher RS content, can be explored in future breeding programmes to develop rice varieties whose consumption will help to prevent hyper/hypo glycemic responses in Northern Himalayan regions, where daily staple diet is rice.