Nature of Starch Crystallinity in Parboiled Rice (original) (raw)
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International Journal of Biological Macromolecules, 2016
The research was carried out to investigate the effect of starch powder particle size, morphology, amylose content and varietal effect on physicochemical, X-ray diffraction pattern, thermal and pasting characteristics. The results indicated that starches isolated from seven traditional rice cultivars of temperate region of India have possessed higher yield (82.47 to 86.83%) with lower degree of granule damage and higher level of starch crystallinity (36.55 to 39.15%). The water and oil binding capacities were observed to correlate positively with amylose content. The bulk density and color parameters of starches were found to have linked with starch powder particle size coupled with arrangement and morphology of the starch granules. The rice cultivars having smaller starch powder particle size indicated lowest degree of crystallinity. Morphological studies revealed that the starches with tightly packed granules had greater mean granular width, while granules with openly spaced granular morphology depicted the higher values for mean granular length. The peak height index (PHI) among different starches ranged from 1.01 to 2.57 whereas the gelatinization range varied from 10.66 to 10.88. Concluding, the differences in distributional pattern of starch granule size and shape and powder particle size indicated a significant effect on the functional properties of starch.
The effects that two preparation methods (parboiling with different degrees of gelatinization and parboiling with enzymatic hydrolysis) have on the qualities of brown glutinous rice were investigated in order to optimize the pretreatment conditions of brown glutinous rice for the ready-to-eat product in retort pouch. The brown glutinous rice was parboiled at various temperatures (50, 70 and 90 0 C) and steamed at atmospheric pressure until the gelatinize level of 60, 80 and 100%. For the parboiling with enzymatic hydrolysis, the brown glutinous rice was immersed in xylanase before steamed. Results showed that parboiling not only affected the nutritional composition, color, and texture of glutinous rice but also decreased the Glycemic index (GI) to 61.3 ± 0.03 and raised the Resistance starch (RS) to 2.9 ± 0.02. There was interaction among RS, GI, and the amylopectin content of brown glutinous rice during parboiling without enzymatic hydrolysis. Amylopectin is directly proportional to GI but inversely proportional to RS. Enzymatic hydrolysis improved both the texture and the physical and chemical properties. In addition, the GI value of enzyme treated samples decreased to 62.7 ± 0.24 and the RS increased to 2.9 ± 0.05. The highest overall preference score was attained by parboiled rice which was soaked in water at 90°C and then steamed until 100%gelatinization.
Food Chemistry, 2009
Starches were isolated from three waxy rice varieties: Koganemochi (Kog), Hakuchomochi (Hak), and Kantomochi 172 (K172). Forty percent starch gels were prepared and the extent of starch gel digestibility was determined by an in vitro method. The distribution of chain lengths of amylopectin was analyzed and differential scanning calorimetry was used to analyze gelatinization and retrogradation of waxy rice starch. The K172 gel had significantly higher resistance to hydrolysis than had the other gels. The K172 starch contained lower proportions of the short chains of amylopectin and showed higher gelatinization temperature and enthalpy. The retrogradation peak was measured using waxy rice starch gels stored for 1 and 7 days at 5°C. The K172 gel was observed to retrograde more quickly and to have a greater extent of retrogradation than the other gels. The difference in amylopectin chain length distribution and recrystallinity contributed to the variation in the starch gel digestibility of waxy rice.
Carbohydrate Polymers, 2011
Digestibility of starches in four rice samples with amylose content (AC) from 1.7 to 55.4%, including a newly developed high-amylose rice, was investigated. An in vitro enzymatic starch digestion method and an AOAC method were applied to correlate rapidly digestible starch (RDS), slowly digestible starch (SDS), resistant starch (RS), and total dietary fiber (TDF) content with the AC in the samples. SDS content decreased and RS and TDF content increased with the increase in AC. The low-amylose rice (AC = 16.1%) had starch granules with weak crystalline structure and was lower in RS and TDF content even though it had a higher AC compared to waxy rice. The digestibility of the starches was not correlated with granule size or degree of crystallinity. The newly developed high-amylose rice starch exhibited a predominant B-type X-ray diffraction pattern, a great proportion of long chains in amylopectin, high gelatinization temperature, and semi-compound starch granules which are attributed to its increased resistance to enzyme digestion.
Changes in the properties of rice varieties with different amylose content on dry heat parboiling
Journal of Cereal Science, 2015
Dry heat parboiling is a unique paddy processing technique that has been scarcely exploited. Dry heat parboiling at high temperature for short time and low temperature for long time on physical and physicochemical properties of three rice varieties differing in amylose content were studied. Hardness of the kernels increased from 66.4 N, 68.8 N and 59.8 N in raw samples to 89.1 N, 86.9 N and 59.8 N in parboiled high amylose, low amylose and waxy rice samples respectively. Rapid migration and evaporation of water from severely heated kernels caused cavity formation at the centre. Irreversible damage of amylopectin structures to leachable fractions caused continuous rise of the pasting curve. Crystallinity was thereby reduced. Parboiled high amylose samples gave X-ray diffraction patterns with peaks characteristic of A, B and Vtype starch crystallinity. Crystalline starch-lipid complexes were observed in low amylose and waxy rices. The significant increase in the amount of rapidly digestible starch from 56.7%, 61.7% and 66.6% in raw samples to 92.1%, 90.8% and 94.8% respectively in severely processed rice samples and subsequent reduction in resistant starch from 24.5%, 21.2% and 18.4% to 0.4%, 1.9% and 0.1% indicated possibilities for targeted food use of the dry heat parboiled samples.
Cereal Chemistry, 2011
Cereal Chem. 88(4):414-420 Starch can be classified into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) according to its resistance to amylolytic enzymes. This study investigated the effects of cultivar and feedstock under varying parboiling conditions on the physicochemical properties and starch fractions of parboiled rice. Rice (rough or brown) was soaked, steamed under pressure, dried immediately or stored at room temperature for 24 hr prior to drying, and then treated with or without a repeated steam cycle prior to milling. The storage treatment significantly increased the retrograded amylopectin enthalpy and amylose-lipid complex melting temperature of parboiled rice. Parboiled rice samples prepared from brown rice feedstock had higher peak melting temperatures but lower enthalpy values of retrograded amylopectin than samples prepared from rough rice after the storage treatment. The pasting viscosity of parboiled rice was most affected by the repeated autoclaving treatment and cultivar. Starch fractions in parboiled rice were significantly affected by cultivar and storage and by the interactions of cultivar and parboiling conditions. The storage treatment significantly increased SDS and generally decreased RDS in parboiled rice. Parboiled rice with different SDS and RS contents can be produced by varying rice cultivar and parboiling conditions. MATERIALS AND METHODS Materials Two long-grain cultivars, Wells and XL723, that were grown in Arkansas in 2008 were provided by the University of Arkansas Rice Processing Program. Wells is the most widely grown longgrain rice in Arkansas, whereas hybrid rice cultivars such as XL723 are increasing in acreage. Rough rice samples were dried to approximately 10-12% moisture content (MC) at ambient temperature and stored in sealed plastic containers at ambient temperature for six months prior to further treatment. The apparent
Intrinsic and extrinsic factors affecting rice starch digestibility
Trends in Food Science & Technology, 2019
Background: The current incidence of obesity and type 2 diabetes is at global epidemic levels. To mitigate their impact, there is a need to develop starch-containing foods that give rise to a low and stable postprandial blood glucose response by increasing the proportion of slowly-digestible and indigestible carbohydrate content. Rice is an ideal target food for such dietary intervention because it is a staple food for over half the world's population. Scope and approach: The starch digestion of cooked white rice grains is usually complete or near complete upon consumption, but the rate of digestion is influenced by intrinsic food properties and extrinsic influences. This review provides an overview of the complex interplay between the starch granule and its interaction with non-starch components of the rice grain (intrinsic characteristics) as well as the effects of processing (extrinsic factors) on starch digestibility. Key findings and conclusions: The intrinsic properties of white rice grains play a significant role in starch digestibility which can be further enhanced after processing, especially by gelatinisation and retrogradation. Post-harvest storage conditions of rice were found to influence starch digestibility but this effect was temperature-dependent. Limited studies investigated starch-lipid and starch-protein interactions in rice, but changes to substrate accessibility have been implicated. Improving our understanding of the effects of processing on starch digestibility can provide an effective tool for food manufacturers to regulate starch digestibility of existing rice varieties.
The Physicochemical Properties of Starch Component of six Iranian Rice Cultivars
Iran Agricultural Research, 2009
Using a wide range of techniques, including differential scanning calorimetry, X-ray diffraction, Rapid Visco Analyser and Fourier Transform Infera Red Spectroscopy, some physicochemical properties of the starch fraction of six Iranian rice cultivars (Tarom, Tarome Hashemi, Neda, Ramezani, Fajr and Kamfirouzi) [1]were studied and compared. DSC data showed that starch granules of different rice cultivars had different gelatinization properties in terms of enthalpy, onset, peak and conclusion temperatures of gelatinization. All samples had similar X ray patterns (A type), different degrees of starch crystallinity. The rheological behaviour of rice powders during heating and the effects of heat processing were studied and compared in excess water from 25 to 95 °C. The samples were different in their pasting properties. This study indicates that starch properties should be mentioned as a crucial parameter determining the quality of rice cultivars.
2015
The effect of gelatinization degree during cooking on the digestibility of cooked rice was investigated through a simulated gastro-intestinal in vitro digestion technique. The changes in starch hydrolysis percentage during simulated digestion were evaluated as a cooked rice digestibility in this study. Polished medium, non-waxy rice grain was soaked into boiling water as a model cooking. The boiling time was set at 10 and 20 min to obtain two gelatinized degree samples. Slurry samples were prepared from the grain samples to examine the impact of structural change of rice grain. The kinetics of cooked rice digestibility showed that there was no significant difference in the equilibrium starch hydrolysis percentage between the grain boiled for 10 min as a partially gelatinized sample and the grain boiled for 20 min as a completely gelatinized sample. However, the large difference between raw and boiled samples was shown. It was also shown that the equilibrium percentage of slurry was ...
Rice Starch Molecular Size and its Relationship with Amylose Content
Starch - Stärke, 2007
The composition and starch molecular structure of eight rice varieties were studied. Waxy and non-waxy (long-, medium-, and short-grain) rice varieties from California and Texas were used. The amylose contents were measured using the Concanavalin A method and were found to be related to the type of rice: waxy < 1.0%, short and medium grain 8.7-15.4%, and long grain 17.1-19.9%. The weight-average molar masses (M w ) of the starches varied from 0.52 to 1.96610 8 g/mol. As would be expected, a higher M w of rice starch correlated to lower amylose content. The range of M w of amylopectin was 0.82 to 2.50 610 8 g/mol, and there was also a negative correlation of amylopectin M w with amylose content. Amylose M w ranged from 2.20 to 8.31610 5 g/ mol. After debranching the amylopectin with isoamylase, the weight-average degree of polymerization (DP w ) for the long-chain fraction correlated positively with a higher amylose content. California and Texas varieties were significantly different in their amylose content, starch M w (short-and medium-grain only), and amylopectin M w (p , 0.05).