Pasting Peak Viscosity Research Articles

Effect of Addition of Ficus exasperata and Spoudias mombin Leaves on Functional and Sensory Properties of Cassava Roots in “Lafun” Production

ABSTRACT Peeled and unpeeled cassava tubers (TMS 30572) were soaked with the leaves of Ficus exasperata (Ipin) and Spondias mombin (Iyeye) and the effects were determined on functional and sensory properties. The cassava samples were soaked in water to ferment for 72 h, pressed, dried, milled and sieved to obtain lafun flour. The lafun flour was reconstituted with hot water to produce a stiff dough and subjected to sensory evaluation using a 9-point Hedonic scale. Bulk density, water holding capacity, swelling index and dispersibility index varied from 0.53 to 0.63 g/cm 3 , 14.13 to 14.85 g/ml, 0.50 to 1.00 g/ml and 8.00 to 10.00 ml respectively. Lafun obtained from cassava steeped with F. exasperata leaves was significantly different (p lafun increased and this invariably reduced water absorption during dough preparation. Amylograph data showed that pasting time, temperature, peak viscosity, final viscosity and set-back value were between 4.00 to 5.15 min; 77.65 to 79.25°C; 331.33 to 371.17 RVU (Rapid Visco-Analyzer Unit); 225.50 to 279.00 RVU and 29.25 to 57.58 RVU respectively. Stiff dough of lafun samples obtained from unpeeled cassava steeped with F. exasperata had the highest mean scores for mouth feel, texture and overall acceptability, although all the samples were statistically similar (p > 0.05). The work revealed that F. exasperata increased the maltose equivalent and invariably reduced the level of water absorption in dough preparation. S. mombin on the other hand had no significant effect. Extract is more effective in stabilizing RPKO (hydrolytically and oxidatively) than MALE.

Physicochemical properties of new starches isolated from Dioscorea opposita Thunb. bulbils

AbstractMorphological, crystal, and physicochemical properties, such as AM content, swelling power, solubility, and pasting properties of starches isolated from three different Shanyaodou (the bulbils of Dioscorea opposita Thunb., named Huaishanyao, Xichangmaoshanyao, and Maoshanyao, respectively) were investigated. The yield of starches was in the range 12.5–20.8% (dry starch/fresh whole bulbils). The AM content of Shanyaodou starches ranged from 33.3 to 36.7%. The shape of the three bulbils starch granules varied from round to oval or elliptic. The mean particle diameter of starch granules varied from 20.17 to 26.34 µm. Shanyaodou starches exhibited a C‐type XRD pattern and the degree of crystallinity was in the range 31.0–34.9%. The pasting peak viscosity, trough viscosity, and final viscosity of Shanyaodou starches ranged from 291.1 to 414.7, 210.8 to 227.0, and 350.0 to 359.2 rapid visco units (RVU), respectively, and the pasting temperature was in the range 83.6–87.3°C. The results showed that some of the Shanyaodou starches could be used in foods production as a thickening agent. The simple method of extraction and the high yield of starch from Shanyaodou might be attractive for production of Shanyaodou starch.

Evaluation of the functional quality of cowpea-fortified traditional African sorghum foods using instrumental and descriptive sensory analysis

Despite nutritional advantages, the functional quality of cereal foods tends to decline when fortified with legumes. Traditional African cowpea-fortified sorghum foods were evaluated using instrumental and descriptive sensory analyses. Two sorghum cultivars, NS 5511 (tannin-type) and Orbit (non-tannin-type) were fortified with cowpea (70:30 ratio). Fortification reduced uji (fermented thin porridge) pasting peak viscosity and cool paste viscosity by up to 23% and 12%, respectively, probably as a result of starch content being reduced. NS 5511 injera (fermented thin flatbread) stiffness increased by up to 25%, probably due to a reduction in tannin content. Orbit injera stiffness reduced by up to 22% probably because increased protein content reduced starch retrogradation. Fortification increased the firmness of Orbit ugali (unfermented stiff porridge) by 45% and 17% as assessed by TA-XT2 Texture Analyser and the descriptive sensory panel, respectively. There was a 20% decrease in instrumental firmness of NS 5511 ugali as a result of fortification, which was not detected by the sensory panel. Fortification had generally no effect on the stickiness of ugali. Fortified ugali had a characteristic cowpea flavour. Principal component analysis (PCA) of ugali sensory attributes indicated a 30% variation due to the presence of cowpea. Most of the variation (47%) was attributed to sorghum cultivar. Sensory panel analysis concerning ugali firmness and stickiness correlated positively with the instrumental texture analysis. Fortification with cowpea affects texture and taste of traditional African sorghum foods, the extent to which largely depends on the sorghum cultivar concerned. Instrumental texture analysis relates well with human perception of sorghum food texture and can rapidly predict the effects of fortification with legumes on such foods.

Textural and sensory properties of salted noodles containing purple yam flour

The purpose of this study was to investigate the effect of the substitution of purple yam flour on the rheological properties of dough and the quality of salted noodles. The quality of salted noodles was compared in appearance, texture and sensory properties. The results indicated that the paste temperature, setback, peak and final viscosity of the pasting properties increased, but the breakdown increased as yam flour was added. A higher proportion of yam flour decreased the agitation stability, peak time and extensibility of the dough but increased the maximum resistance to extension according to farinogram and extensogram. The incorporation of yam flour at the 20% level significantly increased cooking losses and the firmness of cooked salted noodles (p<0.05). The purple yam flour supplement conferred redness to the salted noodles as a pleasant purple–red color for consumers. A sensory evaluation showed that the quality of salted noodles with a 5–15% yam flour blend is acceptable.

Functionality Enhancement of Composite Cassava Flour in the Production of Maize Tuwo (A Non-fermented Maize-Based Food Dumpling)

The study was focused on the evaluation of textural and sensory quality enhancing functionality of cassava flour in the production of maize tuwo (a non-fermented maize-based food dumpling). The cassava flour was added to maize flour at the level of 5%, 10%, 15%, 20%, 25% and 30% (w/w), respectively. The bulk density and water holding capacity of maize/cassava flour mixes ranged from 0.77–0.83 g/cm3 and 1.91–2.05 g/g, respectively, while those of 100% maize flour were 0.84 g/cm3 and 2.09 g/g, respectively. There were variations in the pasting properties of maize/cassava flour mixes including the pasting temperature (75.4–78.8°C), peak viscosity (112.1–170.0 RVU), breakdown viscosity (38.4–53.7 RVU) and final viscosity (132.1–142.2 RVU), while those of 100% maize flour were 74.6°C, 108.1 RVU, 38.1 RVU and 148.3 RVU, respectively. The colour characteristics of tuwo prepared from maize/cassava flour mixes showed an increase in the colour lightness, L*-value (68.6–71.8) and chroma, C-value (9.4–11.4) while tuwo from 100% maize flour gave 67.7 and 9.1, respectively. The cohesiveness indexes (15.4–24.2%) of tuwo from maize/cassava flour mixes increased with an increase in the quantity of cassava flour in the mix while that from 100% maize flour was 15.2%. The softness indexes (17.5–18.4°mm) of tuwo from the mixes were also higher than that from 100% maize flour (17.4°mm). The sensory quality rating of tuwo from maize/cassava flour mixes showed that tuwo from 25% cassava flour inclusion was the highest in terms of texture (hand-mouldability), taste and overall acceptability while that from 30% cassava flour inclusion was the highest in terms of colour.

Enhancement of the pasting properties of teff and maize starches through wet–heat processing with added stearic acid

This study determined the effects of stearic acid on the functional properties of teff starch, a compound granule starch in comparison to maize, a simple type granule starch. Stearic acid was incorporated into teff and maize starches and pasted (held for 5 or 120 min at 91 °C) with an RVA (Rapid Visco Analyser). Teff starch with added stearic acid (0.25 and 1.5% starch basis) did not produce a pasting peak viscosity within short holding time (5 min) compared to maize starch. The paste viscosity of both teff and maize starches with stearic acid increased by about three times with long pasting (120 min). This increase in paste viscosity occurred earlier for teff starch than maize starch. Teff starch with stearic acid was more viscous and was non-gelling. Confocal laser scanning microscopy showed that stearic acid did not diffuse in teff starch granules, but seemed to coat them. However, stearic acid diffused inside maize starch granules through channels. This microstructural difference may explain the different pasting behavior. The early high paste viscosity and non-gelling properties of the teff starch modified with stearic acid could have promising applications in foods, for example better mouthfeel with lower starch concentration.

EFFECT OF DRIED MORINGA (MORINGA OLEIFERA LAM) LEAVES ON RHEOLOGICAL, MICROSTRUCTURAL, NUTRITIONAL, TEXTURAL AND ORGANOLEPTIC CHARACTERISTICS OF COOKIES

ABSTRACT Effect of replacement of wheat flour with 5, 10 and 15% dried moringa leaves (Moringa oleifera Lam) powder (DML) on the rheological, microstructural, nutritional and quality characteristics of cookies was studied. Incorporation of increasing amount of DML from 0 to 15% increased farinograph water absorption and decreased dough stability, amylograph pasting temperature and peak viscosity. Use of DML increased dough hardness and decreased cohesiveness and spread ratio of cookies. Sensory evaluation showed that cookies incorporated with 10% DML powder were acceptable. Microstructure studies showed calcium oxalate crystals in both DML powder and cookies with DML. The starch granules appeared wrapped in cookies with 10 and 15% DML. Protein, iron, calcium, β‐carotene and dietary fiber contents increased with increasing amount of DML from 0 to 15%. The results showed the possibility of utilizing DML to improve the nutritional characteristics of cookies.PRACTICAL APPLICATIONS Moringa oleifera Lam. is a popular, fast‐growing plant widely available in India. The leaves of moringa are used as a vegetable. The leaves are rich in protein, β‐carotene, iron, calcium and fiber. Tender moringa leaves are used in dhal, soup, salad and as a substitute for spinach. The leaves also possess many medicinal properties.The baking industry in India is growing at a very fast rate and the demand for health bakery products is increasing. Biscuits and cookies generally prepared from refined wheat flour are deficient in proteins, vitamins, minerals and fiber. Use of moringa leaves in cookies not only improves nutritional value but also brings in a familiar taste. The baking industry can exploit moringa leaves as a natural and inexpensive source of nutrients to produce nutritionally superior cookies.

Evaluation of suitability of commercially available maize grains for 'tuwo' production in Nigeria

This study evaluated the physical characteristics of grains from five different maize varieties [that is, TZL Comp.3C2, TZL Comp.4C2, DMR-ESR-W, DMR-LSR-W and a market sample (Shagari variety)]. In addition, physicochemical properties of their flours, textural and sensory characteristics of tuwo (a maize-based non-fermented food dumpling) prepared from such flours were also evaluated. There were significant (p < 0.05) differences in the amylose content, kernel weight, length, width and depth of the maize varieties and their values ranged from 18.3 - 22.7%, 223.7 - 284.2 g/1000 kernels, 9.1 - 11.9, 8.1 - 9.5 and 3.6 - 4.8 mm respectively. The damaged starch value of flours ranged from 11.3-13.9% while the pasting temperature, peak viscosity, breakdown viscosity, final viscosity, setback-1 and setback-2 ranged from 73.8-76.3°C, 108.1-150.1 RVU, 18.4 - 36.9 RVU, 147.4 - 212.3 RVU, 39.2 - 93.7 RVU and 20.8 - 68.8 RVU respectively; with significant differences at p<0.05. The lightness indexes (L*-values) of maize flour and tuwo ranged from 88.6 - 90.0 and 66.3 - 68.0, respectively while the colour intensity (chroma) of maize flour and tuwo also ranged from 14.7-15.3 and 8.8 - 9.4, respectively; with significant differences at p<0.05. There were significant (p<0.05) differences in the cohesiveness indexes (13.6 - 15.4%) and softness indexes (16.5 - 17.4 mm) of the food dumpling obtained from the maize varieties. Maize tuwo prepared from DMR-LSR-W was rated highest in terms of all the sensory factors [that is, colour, texture (hand-mouldability), aroma, taste and overall acceptability. Both positive and negative correlations existed among some properties of kernel, flour and tuwo from different maize varieties. Key words: Food dumpling, maize tuwo, commercial maize, suitability.

Influence of sucrose on thermal and pasting properties of tapioca starch and xanthan gum mixtures

Abstract Sugars and hydrocolloids are used in starch-based product formulations during processing for improving the final quality of foods. Effect of sucrose (0–30%) on thermal and pasting properties of 5% w/w tapioca starch (TS) – xanthan gum (Xan) mixtures was investigated using differential scanning calorimeter (DSC), rapid visco-analyser (RVA) and rheometer. Sucrose increased gelatinization temperatures and enthalpies of TS and TS/Xan dispersions. RVA pasting temperatures, peak viscosity, final viscosity, breakdown and setback values of TS/Xan mixtures increased with increasing sucrose concentration ( p

Effect of flour production methods on the yield, physicochemical properties of maize flour and rheological characteristics of a maize-based non-fermented food dumpling.

The study was aimed at investigating the influence of flour production methods (Grit Soaking Method [GSM], Grit Non-soaking Method [GNM] and Pestle and Mortar Dehulling Method [PMDM]) on the yield, physicochemical properties of maize flour and rheological characteristics of a maize-based non-fermented food dumpling. The flour yield from the production methods ranged between 56.6 and 62.3% with GSM and GNM giving the lowest and highest values respectively. There were variations in the mean particle size (203.3-220.5 µm) and damaged starch content (12.2-14.5%) of flours obtained from the three production methods. The flours from the production methods also exhibited variations in the pasting temperature (73.2-74.6oC), peak viscosity (84.2-110.6 RVU) and final viscosity (111.4-147.4 RVU). The lightness indices (L*-values) of the flours (88.8-90.0) and maize ‘tuwo’ (66.9-67.7) were affected by the flour production methods while the chroma (C-values) of the flours (14.6-14.9) and maize ‘tuwo’ (8.9-9.1) were also affected though not significantly different (p<0.05). The cohesiveness index (15.1-15.9%) and softness index (17.2-17.8 mm) of maize ‘tuwo’ prepared from the flours also exhibited variations. Key words: Dumpling, flour, maize, 'tuwo', rheological characteristics.

Effects of cross-linking and low molecular amylose on pasting characteristics of waxy corn starch

The action of amylose within the granule of normal corn starch is investigated by changes in pasting characteristics of waxy corn starch in a Rapid Visco Analyzer (RVA), using addition of soluble amylose (DP = 18) and cross-linking with epichlorohydrin. Although waxy corn starch, containing no amylose, did not show an effect of addition of amylose on pasting characteristics, by cross-linking with epichlorohydrin, the pasting peak viscosity and breakdown were greatly enhanced and set-back (viscosity increased in the cooling process after gelatinization) was generated. The cross-linking depressed the disintegration of starch granules in the swelling process, with amylose interaction, resulting in RVA pasting characteristics similar to those seen with normal corn starch containing amylose. Set-back was essentially caused by rearrangement among modified amylopectins. Addition of sodium dodecyl sulfate (SDS) to the RVA more efficiently enhanced the effect. This indicated that amylose in normal corn starch interacts with amylopectin through locally strong linkages.

Chemical composition and physicochemical properties of green banana (Musa acuminata × balbisiana Colla cv. Awak) flour

Flour was prepared from peeled and unpeeled banana Awak ABB. Samples prepared were subjected to analysis for determination of chemical composition, mineral, dietary fibre, starch and total phenolics content, antioxidant activity and pasting properties. In general, flour prepared from unpeeled banana was found to show enhanced nutrition values with higher contents of mineral, dietary fibre and total phenolics. Hence, flour fortified with peel showed relatively higher antioxidant activity. On the other hand, better pasting properties were shown when banana flour was blended with peel. It was found that a relatively lower pasting temperature, peak viscosity, breakdown, final viscosity and setback were evident in a sample blended with peel.

Chemometric Analysis of the Gelatinization and Pasting Properties of Long‐grain Rice Starches in Relation to Fine Structure

AbstractChemometric tests were carried out to better understand the multidimensional facet of starch fine structure‐relationship concerning gelatinization and pasting properties. With Ward's hierarchical cluster analysis 20 long‐grain rice starch samples were sorted out into three clusters based on similarities in functional properties, particularly, paste peak (PV) and final viscosity (FV). The three clusters (arbitrarily named Clusters A, B, and C) exhibited a pasting profile trend of PV&lt;FV, PV˜FV, and PV&gt;FV, respectively. Cluster A samples were also lower in peak temperature, range and enthalpy of gelatinization, and swelling power. These attributes were associated with higher amylose content (AM), β‐amylolysis limit, and percentage of B1 chains (DP13‐24), but lower amylopectin weight‐average molar mass (Mw) and percentage of A chains (DP6‐12). A 5‐variable linear discriminant function correctly predicted 85% of the Ward's cluster membership of the individual cultivars. The discriminant function included the variables A, B1, and B2 (DP25‐36) chains, average chain length (ACL), and gyration radius (Rz). Fine structure variance was fully explained by a total of nine principal components, with the first three components cumulatively accounting for 74%. The leading variables included in the three rotated components pertained to amylopectin chain length distribution (A, B2, and B3+ or DP≥37 chains, and ACL) and amylopectin molar mass (Mw, Rz, and polydispersity). AM and Mw were loaded most frequently in the 4‐variable, best‐fit linear regression models for predicting gelatinization and pasting properties. A combination of at least two fine structure variables controls the functionality of rice starch.

Crumb pasting and staling properties of white and traditional Vakfıkebir breads

The crumb pasting properties of Vakfıkebir bread (VB) produced by the sourdough method traditionally and standard white bread (WB) produced by the straight dough method were investigated. For both bread types, 2 different weights of loaf were produced (500 and 1500 g). One hour after removal from the oven the loaves were wrapped in 2-layer polyethylene bags and stored at room temperature (about 20 °C) for 5 days. During storage, crumb and crust aw, pH, softness, and pasting properties of bread crumb were determined for both bread types. The aims of this study were to compare the crumb pasting properties of VB and WB and to determine the causes of changes during storage. No previous study has examined the pasting properties of any sourdough bread crumb. The pH value of bread crumb exhibited a significant positive correlation with softness (r = 0.87) and bump area (r = 0.89), and a negative correlation with pasting temperature (r = -0.62) and peak viscosity (r = -0.48). In addition, the pasting properties of VB were completely different from those of WB.

Effects of Transglutaminase on Rheology, Microstructure, and Baking Properties of Frozen Dough

ABSTRACTThe improving effects of transglutaminase (TGase) were investigated on the frozen dough system and its breadmaking quality. Rheological properties and microstructure of fresh and frozen doughs were measured using a Rapid Visco‐Analyser (RVA), dynamic rheometer, and scanning electron microscopy (SEM). The frozen doughs with three storage periods (1, 3, and 5 weeks at –18°C) were studied at three levels (0.5, 1.0, and 1.5%) of TGase. As the amount of TGase increased, hot pasting peak viscosity and final viscosity from the RVA decreased, but breakdown value increased. The TGase content showed a positive correlation with both storage modulus G′ (elastic modulus) and the loss modulus G″ (viscous modulus): G′ was higher than G″ at any given frequency. The SEM micrographs showed that TGase strengthened the gluten network of fresh, unfrozen dough. After five weeks of frozen storage at –18°C, the gluten structure in the control dough appeared less continuous, more disrupted, and separated from the starch granules, while the dough containing 0.5% TGase showed less fractured gluten network. Addition of TGase increased specific volume of bread significantly (P &lt; 0.05) with softer bread texture. Even after the five weeks of frozen storage, bread volume from dough with 1.5% TGase was similar to that of the fresh control bread (P &lt; 0.05). The improving effects of TGase on frozen dough were likely the result of the ability of TGase to polymerize proteins to stabilize the gluten structure embedded by starch granules in frozen doughs.

Influence of xanthan gum on rheological properties and freeze–thaw stability of tapioca starch

Physical properties and storage stability of tapioca starch (TS) can be modified using hydrocolloids. Xanthan gum (Xan) was investigated in this study for further application in TS-based products. The TS and TS/Xan mixtures at a total polysaccharide concentration of 5% w/w (db) were prepared. From RVA pasting profiles, pasting temperature, peak and final viscosities of TS pastes increased with increasing Xan concentration ( p < 0.05) whereas the setback values indicating the short-term retrogradation were lower ( p < 0.05). Flow curves of all TS and TS/Xan pastes from steady shear measurement exhibited shear thinning behavior. Water separation values of TS/Xan pastes were also lower than those of TS pastes alone from repeated freeze–thaw experiment, indicating Xan preventing the reassociation of starch molecules. The correlation between setback and water separation was investigated and proven to be a useful approach for predicting water separation from RVA setback value at any given freeze–thaw cycles. These results have important implications for the formulation of TS-based products with improved rheological properties and freeze–thaw stability.

Effect of Heat-Moisture Treatment on the Digestibility and Viscous Characteristics of Hard Wheat Flour and Separated Wheat Starch

The effects of heat-moisture treatment on the digestibility and viscous characteristics of hard wheat flour and separated wheat starch were examined to obtain basic data and information on texture modifier materials in food. From SEM, starch granules of heat-moisture-treated wheat flour appeared to change so as to have a flattened shape and showed adherence to other starch granules. The protein content and moisture content were not changed by heat-moisture treatment. The rate of protein degradation by pronase and the solubility of flour proteins in 0.5 M sodium chloride and water were markedly lower for the heat-moisture-treated wheat flour than for untreated native flour. The heat-moisture-treated wheat flour and separated wheat starch showed distinct peak viscosities in particular, native and heat-moisture-treated starch showed considerable differences; in their pasting temperature and peak viscosity. The apparent activation energy of native wheat flour paste at 14.7 kJ /mol was greater than that of the heat-moisture-treated wheat flour paste at 13.4 kJ/mol. In terms of starch pastes, the apparent activation energy of the heat-moisture-treated starch sample was 10.5 kJ/ mol, whereas that of the native sample was 25.9 kJ/mol.

Chemical Structure and Physical Properties of Mung Bean Starches Isolated from 5 Domestic Cultivars

Chemical structure and physical properties of starches isolated from 5 domestic mung bean cultivars (Gyungsun, Geumsung, Sunhwa, Eohul, and Jangan) were examined. The granules were jelly bean like in shape and smooth on surface, and the size was within 10 to 30 microm. Mung bean starches displayed a C(A)-type crystalline structure when judged by the X-ray diffraction patterns. Branch chain-length distribution patterns of amylopectin (AP) revealed that peak chain length of APs was at either DP (degree of polymerization) 12 or DP13. Apparent amylose contents of 5 cultivars by iodine affinity test were 31.7% to 33.8%. Mung bean APs showed a unique molecular size distribution that has not been observed from other plant-derived starches. Two distinct peaks of AP fraction were identified on the size-exclusion chromatogram, and the ratios of these 2 peaks were different depending on the mung bean cultivars. Weight-average chain length (CL(avg)) of APs was in the range of 16.9 (Eohul) and 17.5 (Geumsung). The onset temperature (T(o)) and enthalpy change (DeltaH(gel)) of starch gelatinization were 54.6 to 60.2 degrees C and 11.6 to 13.2 J/g. The DeltaH of the retrograded mung bean starches was 5.5 to 6.6 J/g, which indicated 44.5% to 52.7% of recrystallization. The pasting temperature, peak viscosity, and setback were 66.1 to 69.2 degrees C, 510 to 579 Rapid Visco Unit (RVU), and 66 to 90 RVU, respectively.

Genetic basis of 17 traits and viscosity parameters characterizing the eating and cooking quality of rice grain

A recombinant inbred line population derived from a cross between Zhenshan 97 and Delong 208 was used to analyze the genetic basis of the cooking and eating quality of rice as reflected by 17 traits (or parameters). These traits include amylose content (AC), gel consistency (GC), alkali spreading value (ASV), cooked rice elongation (CRE), and 13 parameters from the viscosity profile. All the traits, except peak paste viscosity (PKV), time needed from gelatinization to peak (BAtime), and CRE, can be divided into two classes according to their interrelationship. The first class consists of AC, GC, and most of the paste viscosity parameters that form a major determinant of eating quality. The second class includes ASV, pasting temperature (Atemp) and pasting time (Atime), which characterize cooking process. We identified 26 QTL (quantitative trait locus or loci) in 2 years; nine QTL clusters emerged. The two major clusters, which correspond to the Wx and Alk loci, control the traits in the first and second classes, respectively. Some QTL are co-located for the traits belonging to the same class and also for the traits to a different class. The Wx locus also affects on ASV while the Alk locus also makes minor contributions to GC and some paste viscosity parameters. The QTL clusters on other chromosomes are similar to the Wx locus or Alk locus, although the variations they explained are relatively minor. QTL for CRE and PKV are dispersed and independent of the Wx locus. Low paste viscosity corresponds to low AC and soft gel, which represents good eating quality for most Chinese consumers; high ASV and low Atemp, together with reduced time to gelatinization and PKV, indicate preferred cooking quality. The genetic basis of Atemp, Atime, BAtime, peak temperature, peak time, paste viscosity at 95 degrees C, and final paste viscosity is newly examined to reveal a complete and dynamic viscosity profile.

Impact of proteins on pasting and cooking properties of waxy and non-waxy rice

Changes of RVA viscosity and texture properties of waxy rice ( n=9) and non-waxy rice ( n=10) were analyzed through protein removal or disulfide bond disruption. Protease or DTT had similar effects on the pasting behavior of the waxy rice, but affected differently that of non-waxy rice. For all waxy rice flour treated with DTT or protease, the peak, breakdown and consistency viscosity values all significantly decreased, and the viscosity curves barely rose from the baseline. Pre-incubation of flours with a protease increased RVA pasting temperatures, decreased viscosities along all the points of the curves and the slopes of the linear parts of the curves for all non-waxy cultivars. DTT decreased RVA pasting temperatures and peak viscosities of all non-waxy flour, but increased breakdown viscosities in six non-waxy rice cultivars. With DTT-added cooking water, the hardness of cooked waxy and non-waxy rice, as determined by Instron, generally decreased. With DTT-added cooking water, the adhesiveness of all cooked waxy rice significantly decreased, while it increased significantly or remained the same in all cooked non-waxy rice. The above results indicated that the protein agent of a network linked by disulfide bonds increased the RVA gelatinized paste rigidity, the hardness and adhesiveness of cooked rice of all waxy cultivars, while in non-waxy cultivars, both the network and the increase of the gelatinized paste concentrations resulting from protein hydration contributed to the enhancements of the RVA paste rigidity and the cooked rice hardness.