INFLUENCE OF PARBOILING AND FREEZING CONDITIONS ON TEXTURAL PROPERTIES OF CALIFORNIA COOKED RICE

The textural properties of thawed samples of cooked parboiled, long (Cal Belle) and short (S201) grain rice varieties were evaluated using an Instron Universal Testing Instrument (Model 1122). In general, the parboiling treatments resulted in a significant increase of hardness but a significant decrease in stickiness of both long and short grain cooked rice when freezing conditions were pooled. Freezing increased hardness and decreased stickiness of long grain cooked parboiled rice significantly regardless of parboiling conditions, however, it did not decrease the stickiness of short grain cooked parboiled rice significantly. The long grain rice was harder and less sticky than the short grain rice when cooked regardless of treatments used. Hardness was negatively correlated with stickiness indexes (r =?0.819, P < 0.001).     

BLACK TIP DISCOLORATION IN INDIAN RICE. EFFECT OF EXTENDED MILLING ON MILLING CHARACTERISTICS, CHEMICAL COMPOSITION AND COOKING QUALITY

Extended milling of rice decreased the incidence of mycoflora and reduced black tip discoloration but reduced the head rice yield and kernel weight. Protein content, ash, reducing sugars, nonreducing sugars and free fatty acids increased whereas amylose decreased significantly with the increase in the number of discolored grains. Discolored rice required significantly less time to cook, showed decreased water uptake, reduced kernel elongation and losses. Cooking time decreased; water uptake, elongation in cooked rice and gruel solid loss increased with an increase in the degree of milling. Correlation coefficients between the different variables were calculated.     

HARDNESS OF COOKED MILLED RICE BY INSTRUMENTAL AND SENSORY METHODS

Fifteen milled rice varieties covering the usual range of amylose content and cooked rice hardness were used in a collaborative study to verify the sensitivity of the present objective method for measuring cooked rice hardness. The grains were cooked either in a rice cooker using a fixed water:rice ratio of 2:1, or by boiling in excess water for the predetermined optimum cooking time for each sample followed by draining. Hardness of cooked rice was measured in an Instron Universal Testing Machine (UTM) using two methods: (1) puncture of 100 individual grains and (2) extrusion through a 30 cm² Ottawa Texture Measuring System (OTMS) cell with either a 3.2- or 4.8-mm-diam. holes plate. Hardness values were compared with sensory scores by a trained panel composed of 11 members. Sensory hardness of the rices cooked in a fixed amount of water showed very good correlation with puncture force (r = 0.94, P < 0.01) and with extrusion force through a 3.2-mm-diam. holes plate (r = 0.94). The correlation coefficient between puncture force and extrusion force was 0.97. Paired comparison test by the sensory panel on three pairs of rices verified consumers' claims with respect to preference between members of each pair and agreed with results of ranking test.     

EFFECT OF DEGREE AND PRESSURE OF MILLING ON THE STICKINESS OF MILLED PARBOILED RICE

Parboiled brown rice was milled with a McGill miller to five series of milled rice, earch series being milled with a particular milling load and comprising several samples of different degrees of milling (d.m.). The flow time, angle of repose, porosity, adhering solids and reflectance of the samples were determined as a measure of their “stickiness”. Stickiness of the rice increased sharply on milling, reaching a high peak in the range of 2–5% d.m. depending on the load used, and then delcined agian with further milling. However the peak decreases somewhat in height and alos shifted towards the right as the load used for milling was increased. Raw rice, in contrast, showed only a low and flat peak. The above behaviors seemed to be largely related to the surface fat contents of the rice samples.     

EFFECT OF ALKALI AND ALKALI-EARTH HALIDES ON TEXTURE AND COOKING YIELD OF COOKED COMMINUTED LEAN PORK

The effects of alkali-and alkali-earth halides and sulfates on the texture and cooking yield of cooked lean comminuted pork were examined. Divalent cations (Ca²⁺ and Mg²⁺) associated with Br⁻, I⁻ and SO^2-₄ imparted a firm texture to meat (peak force values of 17.1–21.1 kg as compared to 8.4 kg for the control sample devoid of any added salt). Peak force values of samples containing monovalent cations were generally low, but for most cases, were higher (P < 0.05) than that of the control. The cooking yields of samples containing divalent cations (regardless of their anion counterparts) were not different (P>0.05) from that of the control. At 200 meq/kg sample, iodides of monovalent cations as well as sodium chloride increased the cooking yield by approximately 5–20% compared to the control.     

INFLUENCE OF PARBOILING ON RICE STARCH STRUCTURE AND COOKED-RICE TEXTURE

Four varieties of rice having very high (29.4%) to low (17.6%) amylose-equivalent (AE) were parboiled by steaming at atmospheric (PB-O) and at 3 kg/cm2 (PB-3) gauge pressure. The cooked rice texture of the raw, PB-0 and PB-3 rice was determined by Viscoelastographe. Gel permeation chromatography of rice flour starch on Sepharose CL-2B, in general, indicated thermal breakdown of starch. The extent of starch breakdown and the firmness values of cooked PB-0 and PB-3 rices were reasonably well correlated suggesting that starch breakdown during parboiling may have some role to play in varying the texture of rice by parboiling. The chain profile of rice starch remained unaltered after parboiling.     

EFFECT OF THE AMOUNT AND PARTICLE SIZE OF WHEAT FIBER ON TEXTURAL AND RHEOLOGICAL PROPERTIES OF RAW,DRIED AND COOKED NOODLES

ABSTRACT

Textural and rheological properties of raw, dried and cooked noodles enriched with wheat fibers were simultaneously evaluated by a texture analyzer. Increasing wheat fiber level led to an increase in the cutting force of raw and cooked noodles and a decrease in the breaking force of dried noodle as well as extensibility of raw and cooked noodles. Generally, raw, dried and cooked fiber‐enriched noodles with small fiber size had higher breaking force and extensibility and lower cutting force than that with large fiber size. The textural properties of raw noodle are good indicators to predict the strength and elasticity of dried and cooked noodles. Both three‐term Maxwell and Peleg–Normand models were found to fit well to the stress relaxation data of cooked fiber‐enriched noodle. Significant correlations were found between empirical textural properties and fundamental mechanical stress relaxation parameters.

PRACTICAL APPLICATIONS

Texture is one of the important factors affecting the quality of noodles. The increased consumption of noodles enriched with wheat bran or purified wheat fiber is proposed for health reasons. The textural properties of fiber‐enriched noodles are affected by the type, amount and size of wheat fiber. The cutting force, tensile strength and extensibility of raw noodle are good indicators to predict the strength and elasticity of dried and cooked noodles. Results of this study suggest that raw, dried and cooked fiber‐enriched noodles with good quality can be prepared by adding 4–8% fine wheat bran or 4% fine purified wheat fiber.     

UPTAKE OF SUCROSE SOLUTION BY EXTRUDED CORN BALLS AND EFFECT ON THE TEXTURAL CHARACTERISTICS

Extruded corn balls were subjected to dip coating with sucrose solutions (0–70%) at different temperatures (20–50C) to determine several coating characteristics such as total uptake, uptake of solid and dimensionless uptake (sucrose solution uptake/water uptake). Textures of the wet sample, as well as the dried sample, were determined under compressive loading, to obtain the maximum force offered and the deformability modulus. A progressive increase in solid uptake occurs with an increase in concentration and/or temperature while the effect of the latter is low. The deformability modulus of the samples drastically increases because of the absorption of sucrose and because of drying. The desirable high dimensionless uptake can be obtained with a high concentration of sucrose at a low temperature. The uptake of solid generally shows a significant relationship (P ≤ 0.05) with other coating and textural parameters for the wet sample, but not with the dry product.     

EFFECT OF RN GENOTYPE ON YIELD AND SENSORY CHARACTERISTICS OF ENHANCED LONGISSIMUS SECTIONS

Pumping treatments with water or 4.5% sodium tripolyphosphate (STP) were evaluated on the fresh longissimus from pigs of different Rendement Napole genotypes. The longissimus muscle (32 RN/rn, 32 rn⁺/rn⁺) was divided into 3 sections and allocated to the: nonpumped, water pumped, and 4.5% STP, treatments. Following aging (14 days) chops were cut, packaged, and frozen. Boneless loin chops were cooked to internal temperatures of either 70C or 80C. Nonpumped loins resulted in the least amount of purge loss, whereas STP loins had the highest raw yield. Pumping loin sections with water and STP increased raw and cooked moisture contents. Pumping with STP increased juiciness and tenderness ratings. Increasing the endpoint temperature decreased juiciness and cooked moisture percentage. Pork from RN/rn⁺ pigs had lower shear force and higher tenderness and juiciness. These data indicate that increasing end point cooking temperature reduced pork palatability while STP pumping and the RN gene improved sensory properties.     

A NUMERICAL APPROACH TO COMPUTE TEXTURAL ATTRIBUTES OF COOKED RICE BY EXTRUSION TESTING

The cooked rice extrusion testing system consisted of a piston disc and a sample container with a pot base insert of one outlet. S _init (N/m) and S _max (N/m) are the slopes of the force–deformation curve in the packing and compression stages, respectively, and in the original method they are graphically drawn. Here, however, they were numerically computed as the differential of force to distance. The S _init and S _max from the numerical and drawing methods were compared in terms of data reproducibility and accuracy as described by coefficient of variation (CV) and correlation coefficient (CC), respectively. The numerically computed S _init and S _max showed lower CV: the new method, 0.03–0.06 and 0.03–0.06; the original method, 0.18–0.39 and 0.03–0.14, respectively. S _init by the new method showed higher CC with the adhesiveness of the samples: the new method, − 0.99; the original method, − 0.4. Therefore, the new method proved to be better in data accuracy and reproducibility.

PRACTICAL APPLICATIONS

The extrusion test is a practical instrumental method for measuring the textural properties of cooked rice. Nevertheless, its force–deformation curves are difficult to analyze quantitatively. This study attempted to improve the existing method for curve data analysis by applying a numerical method to compute the instrumental parameters. Based on the findings, this new method provided better data reproducibility and accuracy, and in terms of the instrumental parameters, can facilitate the implementation of cooked rice quality control in the field.     

INTERNATIONAL COOPERATIVE COMPARISON OF INSTRUMENT METHODS FOR COOKED RICE TEXTURE

The texture of 10 milled rices cooked by a standardized method in excess water was measured in 11 laboratories using various instrument methods that had been developed specifically for national samples. The samples selected represented a wide range of rice textures. Instrument indexes for hardness and stickiness of cooked rice generally were more sensitive than the corresponding taste panel scores in discriminating among the 10 cooked rice samples. Instrument indexes for hardness correlated positively among each other as did those for stickiness. Most hardness indexes showed significant negative correlation with stickiness indexes. Most hardness indexes were positively correlated with amylose content whereas stickiness indexes were negatively correlated with amylose content. The continued use of amylose content as an index of eating quality in a rice breeding program is justified.     

EFFECT OF THAWING METHODS ON TEXTURAL QUALITY OF SOUS-VIDE STEWED BEEF ASSESSED BY SENSORY AND INSTRUMENTAL ANALYSES

This study compared four different thawing methods using sensory test with magnitude estimation, preference test with hedonic scale and physical analyses. The four methods were tap‐water, refrigeration, microwave reheating, and boiling‐water reheating. For physical analyses, there were differences (p≤0.001) among treatments in drip loss and expressible juice. For drip loss, the microwave reheated samples were the highest and the refrigeration and tap‐water treated samples were the lowest. For expressible juice, tap‐water and refrigerated samples were higher (p≤0.01) than the microwave and boiling‐water reheated samples. Microwave and boiling‐water reheated samples had higher hardness and cheviness and lower juiciness and fiber‐looseness. The refrigerated and tap‐water thawed samples had reverse sensory properties. Naive panelists preferred the refrigerated and tap‐water treated samples to the microwave and boiling‐water reheated samples for juiciness, tenderness, and overall preference. Physical parameters from textural profile analysis were not different among the thawing methods. Expressible juice was the best indicator for sensory hardness, juiciness, fiber‐looseness and chewiness among the physical parameters. Usually a quadratic regression model fit best when expressible juice was used to predict sensory textural properties.