Elaine T. Champagne

Effect of Enzyme Concentration and Storage Temperature on the Formation of Slowly Digestible Starch from Cooked Debranched Rice Starch

Non-waxy and waxy starch suspensions were debranched with pullulanase followed by heating and cooling to form products with a mixture of rapidly digestible (RDS), slowly digestible (SDS) and resistant starches (RS). Products with a range of digestibility were formed by controlling the enzyme concentration (2 and 10 g of pullulanase per 100 g of starch), time of hydrolysis (2 to 24 h) and cooling temperature (1, 15, and 30 °C). Higher enzyme concentration and less time for debranching resulted in maximum formation of SDS while longer times increased RS. RDS decreased with increasing SDS and RS. Holding at 1 °C produced a product with highest proportion of SDS. Holding at 15 °C produced a starch that is relatively more resistant to digestion. Holding at 30 °C produced the smallest amount of SDS but the same amount of RS as with samples cooled at 1 °C. The most SDS was produced by debranching waxy starch with 10 g of pullulanase per 100 g of starch for 4 h and subsequent storage at 1 °C.Therefore, waxy starches would be more suitable to make SDS.

Agricultural byproducts as adsorbents for metal ions in laboratory prepared solutions and in manufacturing wastewater

Abstract Byproducts of soybean and cottonseed hulls, rice straw and sugarcane bagasse were evaluated as metal ion adsorbents in aqueous solutions. Adsorption capacities were determined by adsorption isotherms using the Langmuir model. Their adsorption capacities for Zn(II) were: soybean hulls > cottonseed hulls > rice straw > sugarcane bagasse. Capacities varied from 0.52 to 0.06 meg/g dry weight of byproduct. Rice straw and sugarcane bagasse were not evaluated further in this study because of their low adsorptive capacities (≤ 0.12 meq/g). At a subsaturating concentration of metal ion (100 mg/L), soybean and cottonseed hulls adsorbed high levels (95.6–99.7%) of Cr(III), Co(II), Cu(II), Ni(II) or Zn(II). The ability of soybean and cottonseed hulls to sequester metal ions was further evaluated with three different samples of manufacturing wastewater. These wastewaters had environmentally unacceptable concentations of Zn(II) , Cu(II) and Ni(II). Soybean and cottonseed hulls adsorbed similar amounts of these...

Prediction of cooked rice texture quality using near-infrared reflectance analysis of whole-grain milled samples

ABSTRACT Rice quality is based on chemical and physical properties affecting its appearance, flavor, and texture characteristics. Sensory quality can be assessed by a combination of descriptive sensory and physicochemical property evaluations. The purpose of the present study was to assess the potential of near-infrared reflectance spectroscopy (NIRS) and NIRS in combination with other physicochemical measurements for the determination of sensory texture attributes in whole-grain milled rice samples. Six rice samples representing combinations of variety and growing locations received treatments of two degrees of milling and five drying conditions to achieve final moisture levels of 12 or 15% (n = 120). Quality measurements of the cooked rice included sensory and instrumental texture analyses. Quality measurements of the uncooked rice included amylose and protein (chemical reference), whiteness, transparency, and degree of milling (appearance units of milled rice), and NIRS analyses. Partial least squares ...

Effects of Postharvest Processing on Texture Profile Analysis of Cooked Rice

ABSTRACT The effects of drying conditions, final moisture content, and degree of milling on the texture of cooked rice varieties, as measured by texture profile analysis, were investigated. Instrumentally measured textural properties were not significantly (α = 0.05) affected by drying conditions, with the exception of cohesiveness. Cohesiveness was lower in rice dried at lower temperatures (18°C or ambient) than in that dried at the higher commercial temperatures. Final moisture content and degree of milling significantly (α = 0.05) affected textural property values for adhesiveness, cohesiveness, hardness, and springiness; their effects were interdependent. The effects of deep milling were more pronounced in the rice dried to 15% moisture than that dried to 12%. In general, textural property values for hardness were higher and those for cohesiveness, adhesiveness, and springiness were lower in regular-milled rice dried to 15% moisture than in that dried to 12%. In contrast, hardness values were lower an...

Rice Aroma and Flavor: A Literature Review

ABSTRACT Descriptive sensory analysis has identified over a dozen different aromas and flavors in rice. Instrumental analyses have found over 200 volatile compounds present in rice. However, after over 30 years of research, little is known about the relationships between the numerous volatile compounds and aroma/flavor. A number of oxidation products have been tagged as likely causing stale flavor. However, the amounts of oxidation products, singly or collectively, that need to be present for rice to have stale or rancid flavor have not been established. Only one compound, 2-acetyl-1-pyrroline (2-AP; popcorn aroma) has been confirmed to contribute a characteristic aroma. Furthermore, 2-AP is the only volatile compound in which the relationship between its concentration in rice and sensory intensity has been established. This article discusses the challenges of measuring aroma and flavor instrumentally and by human sensory panels and reviews research examining the effects of genetic, preharvest, and postha...

Functional and Digestive Characteristics of Extruded Rice Flour

ABSTRACT Waxy (short grain), long grain, and parboiled (long grain) rice flours were extruded using three different temperatures and five different water feed rates. The water absorption and water solubility index of the extrudates was 0.67–5.86 and 86.45–10.03%, respectively. The fat absorption index was similar to that of unextruded flours with an average value of 0.96 g/g ± 0.12. Bulk density decreased with an increase in moisture, except waxy rice, which had a quadratic relationship. The viscosity profiles for long grain and parboiled rice were similar. Both initially increased in viscosity (>130 RVU), then decreased to ≈40 RVU. The final viscosity was ≈60 RVU. Waxy rice viscosity remained low ( 0.05) except for long gr...

Effects of Degree of Milling, Drying Condition, and Final Moisture Content on Sensory Texture of Cooked Rice

ABSTRACT Different cultures have different preferences for cooked rice flavor and texture characteristics. These differences provide opportunities for U.S. rice varieties to fit into global markets to meet consumer demands worldwide. It is important to assess the properties of U.S. rice varieties and determine the factors that influence their eating quality. Cooked rice texture attributes can be affected by postharvest handling practices, such as degree of milling, drying condition, and final moisture. This article reports the effects of postharvest handling parameters on the texture of cooked medium- and short-grain rice varieties grown in Arkansas (AR) and California (CA), as measured by descriptive sensory analysis. The rice samples were Bengal (AR), Koshihikari (AR), Koshihikari (CA), M-401 (AR), M-401 (CA), and M-202 (CA). The six rice varieties were regular- or deepmilled and dried under one of five drying conditions to achieve final moisture levels of 12 or 15% (n = 120). A trained sensory panel de...

Effect of Cooling, and Freezing on the Digestibility of Debranched Rice Starch and Physical Properties of the Resulting Material

Ten percent non-waxy and waxy starch suspensions were debranched with pullulanase followed by heating and cooling (1 °C) to crystallize and/or gel. Products with a range of textures can be made depending on the type (waxy and non-waxy) of starch used. The water holding capacity was 35% and 84% for waxy and non-waxy cooled debranched starch, respectively, at 4 h of cooling and did not change. The hardness of the debranched waxy and non-waxy starch continued to increase beyond 24 h up to 45 g and 245 g of force, respectively. The particle size of precipitates of non-waxy and waxy debranched starch was 45 micrometer and 4 micrometer after 4 h of cooling and did not change. Cooling of debranched non-waxy starch at 1 °C for 12 h without agitation decreased digestibility by 59%; with stirring digestibility decreased by 42% after 24 h of cooling. Freezing of debranched cooled waxy and non-waxy starch does not effect the decreases in digestibility. Particle size of debranched, cooled/freeze-thawed, dried, and milled starch affects digestibility.

Sensory and Instrumental Relationships of Texture of Cooked Rice from Selected Cultivars and Postharvest Handling Practices

ABSTRACT Measurement of cooked rice texture attributes by sensory and instrumental methods is important because of the increased popularity of rice and rice products by globally diverse cultures. Many factors influence cooked rice texture, including cultivar, physicochemical properties, postharvest handling practices (milling degree, drying conditions, and final moisture), and cooking method. Information on the relationships between sensory, physical, and chemical characteristics will lead to better methods to quickly evaluate and predict end-use qualities, which will help to match rices with specific characteristics to populations that demand those attributes. This article reports the relationships between two modes of measuring texture attributes of rices: sensory and instrumental texture analyzers. Six medium- and short-grain rice samples differing by cultivar or growing location were dried to achieve final moisture levels of 12 or 15% and then regular- or deep-milled (n = 120). Correlations between in...

Use of enzymes in the processing of protein products from rice bran and rice flour

Large quantities of rice bran and broken rice are generated as co-products during the milling of rice. Rice bran and, to a lesser extent, broken rice are under-utilized. The protein they contain is particularly nutritious and hypoallergenic for use in foods. However, to enhance the use of rice proteins, it is desirable to develop effective methods to separate or concentrate the protein component from these rice co-products. In this investigation, rice bran and rice flour from broken rice were treated with starch and carbohydrate-hydrolysing enzymes including α-amylase, hemicellulase, and cellulase. The enzymatic processing of rice bran resulted in soluble and insoluble rice products, with protein content ranging from 10% to 27%. In the case of rice flour, the starch component was effectively solubilized, and the insoluble fraction was found to contain up to 79% protein. Processing conditions were discussed, and the protein-enriched products were analysed for chemical, physical, and functional properties.