Freezing and Thawing Conditions Affect the Gel Stability of Different Varieties of Rice Flour

The freeze‐thaw stabilities of three different rice flour gels (amylose rice flour with 28% amylose, Jasmine rice flour with 18% amylose and waxy rice flour with 5% amylose) were studied by first freezing at –18 °C for 22 h and subsequent thawing in a water bath at 30 °C, 60 °C and 90 °C, or by boiling in a microwave oven. The freeze‐thaw stability was determined for five cycles. Starch gels thawed at higher temperature exhibited a lower syneresis value (percent of water separation) than those thawed at lower temperature. Amylose rice flour gels gave the highest syneresis values (especially at the first cycle). The Jasmine rice flour gels gave a higher syneresis value than the waxy rice flour gel. Except for freezing by storage at –18 °C and thawing at 30 °C, there was no separation of water at any cycle when waxy rice flour gel was thawed at any temperature, irrespectively of the freezing methods used. Cryogenic Quick Freezing (CQF) followed by storage at –18 °C and then thawing (by boiling or by incubation at any other temperatures) gave lower syneresis values than all comparable samples frozen by storage at –18 °C. The order of syneresis values for the three types of rice flour was waxy rice flour < Jasmine rice flour < amylose rice flour. The syneresis values and the appearance of starch gels, which had gone through the freeze‐ thaw process, suggested that the order of freeze‐thaw stability of gels for the three types of rice flour was waxy > Jasmine > amylose rice flour.     

Effects of water requirement and substitution level on wheat–rice noodles with hydrocolloids

Substitution of wheat flour with rice flour in noodles can increase rice flour utilization, reduce cost, and lower the allergenicity of wheat gluten. High‐AM rice flour (32.5%) was used to dilute high‐protein wheat flour (14.8%) on account of its excellent gel‐forming properties. Target noodles should obtain qualities comparable to noodles made from all‐purpose wheat flour (10.4% protein). RSM technique was applied for optimization of substitution level, water requirement and hydrocolloid level. The coefficient of determination (R²) showed that only substitution level and water requirement could predict textural characteristics and lightness (L*) of cooked noodles. Increased amounts of rice flour resulted in a decrease in all cooked noodle textural qualities but an increase in L*. Water absorption of rice flour was significantly higher than that of wheat flour; therefore, increased water content of substituted wheat noodles was necessary. However, water requirement should correspond well with rice substitution level. CMC was observed to be more appropriate for use in wheat–rice noodles. Wheat–rice noodles were not significantly different from wheat noodles at 30–47% substitution, water requirement 43.5–59%, and 1.2–1.5% CMC. The addition of 1.5% Na₂CO₃ resulted in a significant improvement in cooked wheat–rice noodle texture (p ≤ 0.05).     

Effect of storage on resistant starch content and in vitro starch digestibility of some pressure‐cooked cereals and legumes commonly used in India

Resistant starch (RS) is that fraction of starch, which escapes enzymic hydrolysis in the small intestine and passes in the colon. Effect of storage time (12 and 24 h) and temperature (4 °C and 25 °C) was studied on RS content of the pressure‐cooked cereal and legume grains/seeds and their flours. RS content was observed to increase in the stored cereals and legumes, with more enhanced increase in the flour samples stored at refrigeration temperature for longer duration (41.4% in wheat flour and 85.4% in pea flour). Significant positive correlations were observed between RS content (4 °C, 24 h) and amylose (y = 0.388 × –5.948, r = 0.840, P ≤ 0.05, n = 7) as well as between % increase in insoluble dietary fibre content (4 °⁰C, 24 h) and amylose (y = 2.257 × –27.724, r = 0.971, P ≤ 0.05, n = 7). Reduced in vitro starch digestibility of the cooked/stored samples (4 °C, 24 h) was observed when compared to freshly cooked samples.     

The effect of rice flour on pasting and particle size distribution of green gram (Phaseolus radiata, L. Wilczek) dried batter

The effect on the pasting characteristics of green gram flour of the addition of rice flour was studied. The gelatinization temperature decreased from 75 °C for the control to 72 °C for samples containing different levels of rice flours. Average particle size of dried batter mix increased with the addition of varying percentages of rice (10, 15, 20 and 25%) from a control value of 236 μm to a maximum 310 μm. The addition of rice flour to green gram increased the water absorption in line with the amount of rice flour added. When rice flour was added, the protein content of the mixed sample of green gram batter and rice flour was reduced accordingly and the fat absorption in the samples also decreased. The foaming capacity of native ground flour, measured after 0.5 min, was double (130 mL) that of dried green gram batter (60 mL) which had been prepared by soaking, wet grinding and drying.     

Physicochemical,antioxidant properties and in vitro digestibility of wheat–purple rice flour mixtures

The physicochemical characteristics, antioxidant properties and in vitro digestibility of high‐antioxidant content flours made from different combinations of Thai purple rice flour and refined wheat flour from 25%, 50% to 75% (w/w) were investigated and these were compared with whole flour from purple rice and refined wheat flour. The increase in substitution levels of purple rice flour affected all the functional properties of flours, at the same time the levels of dietary fibre, protein digestibility and antioxidant compositions were also changed. The purple rice flour exerted a particularly strong effect on starch digestibility as the purple rice increased to 50% in the mixture. Moreover, purple rice flour showed lower amounts of rapidly digested starch (RDS), whereas slowly digested starch (SDS) of whole flour from purple rice and 75% substitution purple rice flour was found to be the highest for all samples. The in vitro starch digestibility of all samples also showed a positive correlation between dietary fibre and antioxidant compounds. Overall, the addition of purple rice flour improved the final nutritional properties, notably a lower predicted glycaemic index, and a higher antioxidant potential, which are two important nutritional properties for human health.     

Structural properties of high-protein,low glycaemic index (GI) rice flour

Low glycaemic index (GI) rice flour was prepared by the enzymatic hydrolysis method. The protein content of treated (high-protein, low GI) rice flour was about 3.5 times higher than untreated rice flour, suggesting its use in infant formula or other protein-fortified food products. The GI of untreated and treated rice flour was found to be 88.0 ± 0.2 and 46.1 ± 0.2, respectively. High-protein, low-GI rice flour was studied for thermal and structural properties, which showed significant (p < 0.05) differences from untreated rice flour. The results of thermal properties showed a decrease in transition temperatures and enthalpy of gelatinization. The ratio of peaks at 1045 cm^?1 and 1015 cm^?1 of treated rice flour was significantly (p<0.05) lower than that of untreated rice flour. This could be ascribed to the loss of crystallinity due to enzymatic degradation. These results further support the decrease in transition temperatures and enthalpy of gelatinization. The results of the rheological studies of high-protein, low-GI rice flour revealed that both untreated and treated rice flour samples exhibited non-Newtonian shear-thinning flow behaviour (n < 1), which is characterized by a decrease in viscosity with an increase in shear rate.     

Effect of Levilactobacillus brevis TISTR 860 and Lactiplantibacillus plantarum TISTR 951 on gamma-aminobutyric acid content in fermented rice flour and rice noodles (Kanomjeen)

This research aimed to reduce the fermentation time of fermented rice flour for fermented rice noodles (Kanomjeen) to 24 h by adding the initial starter cultures, which are Levilactobacillus brevis TISTR 860 (LB) and Lactiplantibacillus plantarum TISTR 951 (LP) alone in rice slurry to achieve the quality and high gamma-aminobutyric acid (GABA) content. The initial pH value of rice slurry was adjusted to 4.5 and enriched with 2% of monosodium glutamate (MSG) before fermentation. LP was able to produce lactic acid and reduced pH better than LB but produced GABA in less content. Expanding fermentation time induced decreasing in viscosity and whiteness of flour. Fermented rice noodles provided better tensile strength and elasticity. In conclusion, LB could produce GABA in the amount of 21.80 mg/100 g dry basis in 24 h with good quality.     

Starch Structure and Digestibility of Rice High in Resistant Starch

Starch digestibility and starch structure of a high‐resistant starch (RS) rice (RS111) was compared to that of a wild rice type (R7954). RS111 exhibited high RS content and incomplete starch hydrolysis in both cooked rice and retrograded rice flour. High RS rice RS111 had a higher λ_max of absorbance and blue value of iodine‐binding starch complex and contained a higher percentage of intermediate chains of amylopectin than R/954. X‐ray diffraction pattern of RS isolated from cooked high RS rice displayed a mixture of B‐ and V‐type that was more resistant to starch hydrolysis by alpha‐amylase. Resistant starch in RS111 is composed mainly of linear amylose and some low‐molecular‐weight amylopectin.     

GELATINIZATION BEHAVIOR OF GRAINS AND FLOUR IN RELATION TO PHYSICO-CHEMICAL PROPERTIES OF MILLED RICE (ORYZA SATIVA L.)

ABSTRACT

Physico‐chemical properties of milled rice grains of 13 japonica varieties were evaluated. The rice varieties differed in appearance. One sample had long grains (6.61 mm), two had short grains (5.27–5.32 mm) and the rest had grains of medium length (5.52–6.55 mm). The shape (length/width) of grains varied from bold (1.58–1.9) to medium (2.06–2.37). The protein content was high in all samples (7.82 to 9.72% on dry mass). Almost all, with exception of one cultivar (Osogovka), which had intermediate amylose content (23.3%), were low amylose varieties (12–19.4% amylose). Their minimum cooking time varied from 17.5 to 22.5 min. Significant correlations (P < 0.05) were established between some physico‐chemical characteristics of evaluated rice cultivars. Elongation during minimum cooking time was correlated with protein content (r = 0.6899), shape (?0.7137), thickness (0.7234) and width (0.9134) of grains. The rice flour paste viscosity correlated significantly with shape (0.6148) and length (0.7353) of grains. On the basis of the established results, it was concluded that appearance of milled rice could be used as indicator for predicting gelatinization behavior: elongation ratio (length after minimum cooking time/length of the grains) of the rice grains and viscosity of rice flour during cooking.

PRACTICAL APPLICATIONS

Results from this research constitute a useful tool to predict the gelatinization behavior of milled grains and flour of japonica rice varieties, on the basis of grain appearance. The appearance is critical in acceptability of rice varieties by the consumers. The possibility to predict rice grain behavior during cooking on the basis of its appearance could be an additional attribute or market value for consumer choice. The results could be used in selection of rice variety for rice grits or flour production and use in special applications.

     

Impact of the fungal protease produced by Fusarium culmorum on the protein quality and breadmaking properties of winter wheat

Samples artificially infected by Fusarium culmorum were analyzed to assess the effects of Fusarium infection on the protein quality of winter wheat (Triticum aestivum L.). The Fusarium infection did not noticeably influence either the crude protein content or the water absorption ability of the wheat flour. The protease activity found in the wheat flour was inversely correlated to the sedimentation value. In contrast, it was positively correlated to both the free amino acid content and the degree of infection as expressed in Fusarium protein equivalents (FPE) quantified by an enzyme-linked immunosorbent assay. A distinct reduction in the content of both total glutenin and high molecular weight glutenin subunits was detected in the seriously infected samples (FPE>20 µg g^–1). The infection with Fusarium impaired the dough quality and led to a deformed loaf shape. The fungal protease was active over both a wide range of temperatures (from 10 to 100 °C) and a wide range of pH values (from 4.5 to 8.5). The maximum protease activity was displayed at 50 °C in the pH range 6.0–8.0. This property indicates that the protease produced by F. culmorum may impair storage proteins throughout all the processing procedures associated with wheat flour, thereby causing weak dough properties and, consequently, unsatisfactory bread quality.     

DETERMINATION OF THE PROTEIN CONTENT IN RICE BY THE DIGITAL CHROMATIC METHOD

ABSTRACT

The feasibility of using digital chroma measurements to determine the protein content in rice was investigated using red, green and blue (RGB) chroma values to reflect color change. The protein content of rice samples ranged from 5 g/100 g to 13 g/100 g. There was a significant negative linear correlation (r < −0.98) between the protein content in rice and the chroma values of relevant protein solutions treated with biuret reagent. Of all the tricolor values, the G value was the optimal parameter to reflect the chroma difference of the protein solutions. It had a higher correlation coefficient (r < −0.99) and was more sensitive to subtle differences in protein content than R or B values. With a similar structure and the same reaction conditions, rice samples with known protein content were found to be more accurate calibrating substances. The results determined by the digital chromatic method are not significantly different from that of the Kjeldahl method. With the advantages of high precision, easy operation and high efficiency, the method is suitable for applications in quality evaluation and supervising practice in the field of rice circulation.

PRACTICAL APPLICATIONS

A new method to determine the protein content of rice was studied by combining digital image analysis technology and a traditional chemical approach. The study forms a part of the technology foundation to develop quality evaluation systems for rice.

     

Influence of Acid Treatment on Physicochemical Properties of Aged Rice Flour

This study investigated the influence of citric acid and ascorbic acid solutions (0.0–0.9% w/w) on the physicochemical properties of 12 month aged rice flour (aged) using 0.7 month rice flour (fresh) as the reference. The results showed that rice storage did not affect the chemical composition. However, 12 month aged rice flour showed an increase in formation of disulfide bonds and amylose-lipid complexes which could restrict starch granules from swelling during gelatinization. Moreover, 12 month aged rice flour showed an increase in gelatinization temperature and enthalpy. Acid treatment did not break the formed disulfide bond but reduced the protein content in the acid-treated 12 month aged rice flour producing a significant increase in granular swelling and thus increased peak viscosity (p ≤ 0.05) but caused a reduction in retrogradation. The excess concentration (0.9% w/w acid solution) induced granule rupture. Aging of rice also affected the textural properties of freeze-thaw gels, increasing the hardness value but this was reduced by the addition of acids.     

Effect of Freezing Rate and Starch Granular Morphology on Ice Formation and Non-Freezable Water Content of Flour and Starch Gels

Ice formation and non-freezable water (W_NFW) of rice flour and tapioca starch gels were studied at two different freezing rates (–10 and –100°C/min) using differential scanning calorimetry. Ice crystal growth was observed in the slow freezing but not in the fast one. Ice melting enthalpies, however, were similar since more ice formed in holding and reheating steps. Melting enthalpy of fully gelatinized systems with water contents ~ 0.50–0.66 was associated to starch composition and granule morphology. Highly swollen tapioca starch gave the lowest enthalpy and the highest W_NFW (0.40 g/g dry starch versus 0.32 and 0.38 g/g dry starch of normal and waxy rice flours, respectively). The further studies revealed that the W_NFW values were associated to swelling power, solubility, and granule morphology.     

Empirical Modeling of Starch Ester Synthesis from Octenylsuccinic Anhydride

In the present work, response surface methodology (RSM) was used to determine the mathematical relationship between octenylsuccinic anhydride (OSA) treated maize starch and the octenylsuccinylation reaction conditions. A second‐order polynomial model was chosen to approximate the relationship between the response variable (y, as the degree of substitution “DS” used to define the extent of the octenylsuccinylation) and the three regressors, x₁ as the temperature, x₂ as the time and x₃ as the pH. Analysis of variance (ANOVA) showed a high R² coefficient of 0.9905, thus ensuring a satisfactory adjustment of the selected model with the experimental data. Only temperature‐pH interaction was found to have a non‐significant effect. The positive sign for the regression coefficient of the temperature variable indicated that the y_DS increased with the increased levels of this factor from 25 to 45°C. The negative sign for the coefficient of time and also pH indicated that y_DS decreased as either the time or pH increased in the region of the tested range. The negative coefficients of the interaction between x₂ and x₃ indicated that a simultaneous increase in reaction time with decrease in pH of the esterification reaction led to an increase in y_DS. Maize starch octenylsuccinate synthesis on basis of its DS value was optimized for the three independent variables tested in this study. The predicted value for the DS was 0.02 where temperature, time and pH of the reaction were 28.0°C, 8.1 h, and pH 7.11, respectively. Results of some of the selected physicochemical properties of starch, tested in the present work were also discussed.     

Effect of rice variety,rice flour concentration and enzyme levels on composite bread quality

A study was conducted to determine the suitability of substituting portions of wheat flours with rice flours for breadmaking. The levels of substitution were 50, 100, 150 and 200 g kg^?1. Two kinds of enzymes, barley malt and fungal amylase, were added to composite flours, and their effects on the volume and quality of the rice-based bread were determined. The results showed that the enzymes, levels of replacement and the varieties of rice had significant effects on weight, specific volume and overall acceptability of the bread samples. However, the enzymes did not have significant effects on the volume, protein and fat contents or on the character and color of the crust in the sensory analysis. Comparisons were made of the nutritional and sensory qualities of the bread made entirely from wheat flour, and the sample which performed best, the bread with 50 g kg^?1 of flour from low amylose variety (183.3 g kg^?1) with barley malt, showed non-significant differences. The overall acceptability of the products showed that it is acceptable to substitute wheat flour with flours generated from rice up to the 150 g kg^?1 replacement level only.     

PHYSICOCHEMICAL PROPERTIES OF GLUTEN-FREE PANCAKES FROM RICE AND SWEET POTATO FLOURS

Gluten‐free pancakes were prepared using rice flour and rice flour replaced with various amounts, at 10, 20 and 40%, of sweet potato flour. Textural properties of the cooked pancakes, such as hardness and chewiness generally increased with time after cooking, whereas they decreased with increased sweet potato flour replacement. On the other hand, cohesiveness decreased with time, but increased with increased sweet potato flour in the pancake. Nutritional properties of the rice–sweet potato pancakes, such as protein content, dietary fiber, total carbohydrate and calories were generally comparable with those of their wheat counterpart. The only significant difference was in the beta‐carotene content, which increased from 5.2 to 236.1 μg/g when sweet potato flour was incorporated, from 0 to 40%, into the rice pancake formulation.     

Effect of soaking and phytase treatment on phytic acid,calcium, iron and zinc in rice fractions

With the aim to maximise phytic acid removal and minimise losses of dry matter and minerals (Ca, Fe, Zn) in rice, three products (whole kernels and flour milled from white and brown rice; and bran, all from the same batch of variety Kenjian 90-31) were soaked in demineralized water at 10 °C (SDW), NaAc buffer of pH 3.5 at 10 °C (SAB), and 500 U L⁻¹ phytase of pH 5.5 at 50 °C (SPS). In whole kernels and flour of white rice, phytic acid removal was 100% by all treatments; losses of dry matter, Ca, Fe, and Zn were 2–5%, 12–63%, 9–10%, and apparent gain of 63–72%, respectively. In whole brown rice, SAB removed 75% phytic acid, and SPS 100% from flour; dry matter, Ca, Fe, and Zn losses were 1–16%, 26–56%, 39–45%, and 23–24%. In rice bran, SPS removed 92% phytic acid, and SAB 50%; dry matter, Ca, Zn, and Fe losses were 20%, 48%, 63%, and apparent gain of 5%, respectively.     

Impact of brown foxtail millet (Setaria italica) flour on thermo-mechanical properties of flours from different rice varieties

The physical, functional and thermo-mechanical properties of rice flours prepared from long, round and medium rice grain and of foxtail millet (Setaria italica) flour were investigated. The impact of foxtail millet flour addition on the thermo-mechanical properties to the rice flours was also explored. Rice flour from long grain had higher amylose content (26.37%), while the rice flour from round grain had better hydration properties compared to the other rice flours. The dough from long grain rice flour exhibited higher starch gelatinisation temperature and cooking stability and lower starch retrogradation compared to the other investigated rice flours. Foxtail millet flour addition to the rice flours exerted a lower impact on the thermo-mechanical properties of the dough based on rice flour from long grain compared to the other investigated rice flours. These differences might be due to the differences in terms of starch properties and proximate composition of the flour samples.     

Enhancement of the nutritional status of beef patties by adding flaxseed flour

Flaxseed flour was used as a functional ingredient in the production of beef patties. Beef patties were produced with five different formulations; the addition of 3%, 6%, 9%, 12% and 15% flaxseed flour. Control samples were formulated with 10% and 20% fat addition. Raw and cooked beef patties were analyzed for moisture, protein, fat, ash, pH, color parameters and fatty acid profiles. Beef patties were evaluated for cooking loss and sensory properties. Fat and ash content of raw patties increased, while moisture and protein content decreased with increased flaxseed flour. The same trend (except fat content) was also observed after cooking. The addition of flaxseed flour did not affect pH values of raw and cooked beef patties. The addition of flaxseed flour improved the cooking loss but, increased the energy value (as kcal/100 g). L and a values of raw beef patties containing flaxseed flour were close to controls with 10% fat. α-linolenic acid content of raw and cooked beef patties increased as the level of flaxseed flour increased. The PUFA/SFA ratio increased from 0.04 in the control with 10% fat to 0.62 in the raw beef patties with 15% flaxseed flour. The n-6/n-3 ratio decreased from 5.76 in the control with 10% fat to 0.36 in the raw beef patties with 15% flaxseed flour. The nutritional status of beef patties was enhanced with minimal composition and sensory changes with 3% or 6% flaxseed flour addition.