Abstract
The transformation of broken grains into native flours modified by extrusion is an alternative to add value to these co-products from the paddy rice processing. This study aimed to analyze the process of extrusion cooking on the physical and functional characteristics of extruded flours obtained from different rice genotypes (IRGA-417, BRS-Primavera and CNA-8502). The experimental design was completely randomized (3x2 factorial) with four original replicates and analysis of variance to assess particle size, instrumental color parameters (L*, a* and b*), water absorption index (WAI), milk absorption index (MAI), oil absorption index (OAI), water solubility index (WSI) and milk solubility index (MSI) of rice flour. The extrusion process promoted changes in all physical and functional properties of rice flour, but only WSI and color parameters were influenced by genotype and by the industrial processing. Rice flours become darker, tending to a more reddish and yellow coloration after extrusion. Native and extruded rice flours of genotypes IRGA-417, BRS-Primavera and extruded rice flour of genotype CNA-8502 showed finer particles, while native flour of genotype CNA-8502 showed coarser particles. The extruded flours of IRGA-417 genotype obtained higher expansion and luminosity, and lower values of chroma a*, chroma b* and water solubility, while the BRS-Primavera higher values of chroma a* and b*, and lower luminosity and expansion, and CAN-8502 higher water solubility and lower expansion and value of chroma a*. The extrusion process led to flours with high water and milk absorption and solubility, low oil absorption and with potential for application in instant products, regardless of genotype.
Highlights
During paddy rice processing, brown rice, full parboiled, polished and polished parboiled rice are obtained, besides hulls, bran, broken grains and grits
The use of broken grain and grits in the form of flour is an alternative for the transformation of these co-products into products of greater commercial and industrial interest, since they have low commercial value, achieving about 20% of the value paid for whole-grain rice
Broken rice grains of three genotypes were ground in a Wiley-type mill (Perten, Laboratory Mill 3100, Mainland, China) to obtain native rice flours (NRF), which were homogenized, 5 kg of each sample was placed in low density polyethylene (LDPE) container and stored at room temperature until time of analysis
Summary
Brown rice, full parboiled, polished and polished parboiled rice are obtained, besides hulls, bran, broken grains and grits. Given the global and domestic paddy rice production and the percentage of broken grains and grits (≈ 14%) (Bassinello; Castro, 2004), the estimated world generation of these co-products in 2012 was around 102.70 million tons, of these, 1,654.76 thousand tons were generated in Brazil. That the product achieves in the form of whole grains (Nabeshima; El-Dash, 2004). The use of broken grain and grits in the form of flour is an alternative for the transformation of these co-products into products of greater commercial and industrial interest, since they have low commercial value, achieving about 20% of the value paid for whole-grain rice. Rice flour has advantages such as not being allergenic, gluten-free, containing low glycemic index, low sodium contents and high proportion of digestible starches (Kadan; Bryant; Pepperman, 2003)
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