Tahira Mohsin Ali

Morphological, Physicochemical, and Pasting Properties of Modified White Sorghum (Sorghum bicolor) Starch

Starch isolated from white sorghum (nWSS) was subjected to chemical modifications to prepare acid thinned (aWSS), oxidized (oWSS), and dual modified acetylated-oxidized (aoWSS) white sorghum starch. Chemical modifications resulted in roughness on the surface of sorghum starch granules. Solubility and paste clarity improved significantly due to the three modifications. Pasting temperature, peak viscosity, and time to reach peak viscosity of modified starches was significantly less than nWSS. Reassociative tendency was curtailed in modified starches as is evident by the decline in setback viscosity. At 8% starch concentration, oWSS and aoWSS completely failed to form a proper gel network.

Functional and Morphological Characterization of Low-Substituted Acetylated White Sorghum (Sorghum bicolor) Starch

Starch isolated from white sorghum (Sorghum bicolor) was acetylated by addition of acetic anhydride at concentrations of 3%, 6%, and 9% w/w of starch under alkaline conditions to produce starch acetates of three different degrees of substitutions. Morphological characterization through scanning electron microscopy revealed roughness on the surface of acetylated starch granules. The modified biopolymer exhibited improved swelling power, solubility, water binding capacity, and paste clarity compared to its native counterparts. Decrease in percent syneresis and gel hardness and extent of reduction in percent transmittance indicate reduced retrogradation tendency of white sorghum starch acetates.

Effect of succinylation on functional and morphological properties of starches from broken kernels of Pakistani Basmati and Irri rice cultivars.

Starch extracted from broken kernels of Basmati and Irri rice varieties of Pakistani rice were subjected to modification by addition of succinic anhydride at levels of 2%, 4% and 5% based on dried weight of starch. The succinyl content of Irri rice starch increased with the concentration of succinic anhydride. Scanning electron micrographs revealed presence of dents and fusion of rice starch granules. Swelling power and water retention capacity (WRC) significantly improved after succinylation while on refrigerated storage percent decline in paste clarity of modified rice starches was stable as compared to native Basmati (BC) and Irri (IC) rice starches. Succinylation also reduced solubility, pasting temperature (PT) and gel hardness of starch gels. Improvement was observed in cold storage stability of rice starch succinates as evident from textural profile analysis.

Effect of pentosans addition on pasting properties of flours of eight hard white spring wheat cultivars.

The effects of water extractable pentosans (WEP) and water unextractable pentosans (WUP) on pasting properties in flours of eight different hard white spring wheat (HWSW) cultivars was studied. WEP and WUP isolated from a hard wheat flour were added to each of the cultivars at 1% and 2% level. The results indicated that WEP exhibited a pronounced effect on pasting properties as compared to WUP and variety. Univariate analysis of variance (ANOVA) was used to evaluate sources of variation. The variety significantly (P < 0.001) influenced all the pasting parameters. WUP caused significant (P < 0.001) variation in paste viscosities (except breakdown). WEP influenced more pronouncedly the hot paste, cold paste, breakdown and setback viscosities with F values—221.802, 214.286, 98.073 and 120.159, respectively. Variety-by-WEP interaction exhibited significant (P < 0.01) influence on pasting time, peak, hot paste and cold paste viscosities. Whereas, variety-by-WUP interaction only significantly (P < 0.001) influenced the pasting- time and -temperature. Duncan’s test was used to analyze the significant difference (P < 0.05) within the variety. The results revealed that WUP did not induce significant (P < 0.05) influence on all the pasting parameters, whereas, WEP influenced significantly (P < 0.05) the paste viscosities of some of the varieties. It was also found that the addition of WEP remarkably reduced the setback, hot paste, cold paste viscosities and increased the breakdown viscosity in all cultivar flours. The effect of WEP was greater at higher level of supplementation on paste viscosities.

Thermal Characterization of Native and Modified White Sorghum (Sorghum Bicolor) Starch

Gelatinization and retrogradation characteristics of native and modified white sorghum (Sorghum bicolor) starches were studied using differential scanning calorimetry. The biopolymer was modified through acetylation, oxidation, and acid thinning reactions to prepare single- and dual-modified white sorghum starches. The results revealed that peak gelatinization temperature (Tp) of AWSS (acetylated white sorghum starch) and AOWSS (acetylated-oxidized white sorghum starch) was less than that of NWSS (native white sorghum starch), while oxidation and acid thinning significantly increased the peak gelatinization temperature. Gelatinization enthalpy (ΔH) of ATWSS (acid-thinned white sorghum starch) was the least among both native and modified starches, which indicates weakening of starch granules after acid modification. Rate of retrogradation was lower in AWSS, OWSS, and AOWSS than NWSS, whereas acid thinning increased the rate of retrogradation. After 12 days of refrigerated storage at 4°C, percent retrogradation was in the order ATWSS > NWSS > AWSS∼AOWSS > OWSS. However, percent increment in retrogradation enthalpy was the least in AWSS.

Influence of different molar concentrations of acid on morphological, physicochemical and pasting properties of Pakistani Basmati and Irri rice starches

Starches extracted from two dominant varieties of rice, Basmati and Irri were subjected to acid hydrolysis by preparing starch slurry of 35% (w/v) in HCl solutions of concentrations 0.1M, 0.3M and 0.8M. The scanning electron micrographs showed that granular morphology of starches significantly changed after acid hydrolysis. Acid thinning improved the solubility of starches whereas decline was observed in swelling power and water retention capacity. Paste clarity of both acid treated Basmati and Irri rice starches reduced gradually upon cold storage. Also reduction in values of pasting, peak viscosity, hot paste viscosity, cold paste viscosity and set back were observed in acid thinned Basmati and Irri rice starches. The DE values increased with the increase in HCl concentration for both Basmati and Irri starch. The hardness of 0.8M HCl treated Basmati starch gel was found significantly lower than all treated and untreated starches. The gelatinization enthalpy for Basmati starch significantly reduced after acid hydrolysis with 0.1M, 0.3M and 0.8M HCl solutions at p <0.05.

Utilization of chemically modified pearl millet starches in preparation of custards with improved cold storage stability

Custards were prepared using five ingredients: milk powder, modified pearl millet starch, sugar, vanilla essence and water. The effect of adding hydroxypropylated starch (HPS), succinylated starch (SUS), oxidised starch (OXS) and acetylated starch (ACS) on cold storage stability, pasting, textural and sensory properties was studied and compared to custards containing native pearl millet starch (NS). Interestingly, all chemically modified starches reduced syneresis and no water weeping was observed in custard sample incorporating hydroxypropylated starch (HPC) even after 7days of cold storage. Viscoamylographic analysis revealed that custard containing succinylated starch (SUC) had the highest peak viscosity (108.8 BU), whereas HPC showed the least set back viscosity (19.0 BU). Sensory results suggested that assessors preferred HPC over other custards. Custards are preferred for their chewy semi-solid texture. Incorporation of hydroxypropylated starch (HPS) increased hardness, gumminess and chewiness which subsequently led to higher sensory scores during subjective analysis. Also, no retrogradation peak was observed for HPS and acetylated starch (ACS) when rescanned after 14 days. Thus, it could be concluded that HPS could be used in custards to confer low temperature stability by reducing syneresis.

Effect of Annealing on Morphological and Functional Properties of Pakistani White Sorghum (Sorghum bicolor) Starch

The present study reports the effect of annealing on the morphological and functional properties of starch isolated from white sorghum grains. Scanning electron micrographs of native white sorghum starch (NWSS) revealed the presence of spherical and polygonal shaped granules with random distribution of surface pores. The diameter of surface pores ranged between 213-275 nm in NWSS. The size of small and large granules in NWSS ranged between 5-7 µm and 11-21 µm, respectively. There was no significant difference in the size and shape of NWSS and annealed white sorghum starch (AWSS) granules. However, the diameter of surface pores doubled after annealing. The AWSS showed reduced swelling power, solubility and water binding capacity. Pasting temperature increased from 73.4°C in NWSS to 75.8°C in AWSS. The pasting profile of annealed starches showed reduction in peak viscosity, breakdown viscosity, cold paste viscosity and set back viscosity. Paste clarity improved on annealing while, the extent of reduction in percent transmittance after 72 hours of storage was higher for NWSS suggesting use of annealed starch in high clarity products.

Characterization and utilization of hydroxypropylated rice starches for improving textural and storage properties of rice puddings

This work investigated the effect of hydroxypropylation on the physicochemical characteristics of Basmati and Irri rice starches with milk and water. The effect of hydroxypropylated starches on the storage, texture stability and sensory characteristics of rice pudding was studied. Pudding was prepared by replacing 3%, 5% and 10% of Irri rice flour with native and hydroxypropylated starches isolated from two predominant rice varieties of Pakistan; Irri and Basmati. Syneresis was not observed in pudding made with hydroxypropylated starches and native basmati starch. On the contrary, pudding prepared with Irri rice flour and Irri starches showed poor keeping quality. Sensory analysis showed that modification of rice starches did not significantly alter the color, flavor, taste and overall acceptability of pudding. The results suggested that rice pudding, a very popular dessert of South Asia could be prepared with improved storage characteristics using hydroxypropylated starches without altering the taste and acceptability of the product.

Effect of Nongerminated and Germinated Legumes on Antioxidant, Functional, and Sensory Characteristics of Rice Puddings

The present study aimed to broaden the concept of nutraceutical products by increasing the nutritional and functional properties of rice pudding, locally known as kheer, with improved physicochemical and sensory traits. Three germinated legumes—namely, lentils (Lens culinaris), green gram (Vigna radiata), and black gram (V. mungo)—were added at 5, 15, and 25% levels (based on total milk weight) in rice puddings, and rice pudding without legumes was considered the control. Results showed that germinated legumes compared with their nongerminated counterparts were rich in dietary antioxidants and phenolic content of the puddings. Rice pudding incorporating 5% nongerminated and germinated lentil, 5% nongerminated green gram, 5–25% germinated green gram, and 5% nongerminated and germinated black gram showed peak viscosity similar to that of the control, suggesting that the legumes could be incorporated into pudding without bringing any significant changes in peak viscosity of rice pudding. Moreover, it was als...