Sangeeta Prakash

Performance evaluation of blanched carrots dried by three different driers

The drying characteristics of carrots using a solar cabinet drier, fluidized bed drier (at temperatures 50, 60, 70 °C) and microwave oven drier (at power levels 2, 3, 4) were studied. Drying occurred mainly in the falling rate period. In the case of fluidized bed drying and microwave oven drying after the initial falling rate period, temperature or power level no longer controlled the drying rate, which was then controlled by the moisture diffusion phenomenon. Carrots dried by fluidized bed drying showed better colour, rehydration properties, greater β-carotene retention and better overall sensory acceptability than those dried by microwave oven and solar methods. The storage stability of the dried products during storage at room temperature in polyethylene of different gauges (200, 300, 400) was investigated. The 400 gauge was found to retain β-carotene content and rehydration potential of the product better than the thinner gauges.

The importance of amylose and amylopectin fine structure for textural properties of cooked rice grains.

Statistically and causally meaningful relationships are established between starch molecular structure (the molecular distribution of branched starch and the chain length distribution of debranched starch) and texture (hardness and stickiness) of cooked rice grains. The amounts of amylose chains with degree of polymerization (DP) 100-20,000, and of long amylopectin chains, positively correlated with hardness, while amylopectin chains with DP<70 and amylose molecular size both showed negative correlations with hardness (p<0.05). There was also a significant negative correlation between stickiness and the amounts of long amylopectin chains (p<0.01). For rices with similar amylose content, the amount of amylose chains with DP 1000-2000 positively correlated with hardness while size negatively correlated with hardness (p<0.05). This indicates for the first time that, regardless of amylose content, rice varieties with smaller amylose molecular sizes and with higher proportions of long amylose chains have a harder texture after cooking.

Understanding the Jasmine phenotype of rice through metabolite profiling and sensory evaluation

IntroductionAromatic rices are culturally and economically important for many countries in Asia. Investigation of the volatile compounds emitted by rice during cooking is the key to understanding the flavour of elite aromatic rice varieties.ObjectivesThe objectives of this study were to compare Jasmine-type aromatic rices from the Greater Mekong Subregion and Australia in terms of their metabolomics and sensory profiles and to draw out associations between the volatile organic compounds and human sensory perception of rice aroma.MethodsA set of aromatic rice varieties from South East Asia and Australia, along with non-aromatic controls, was grown in tropical and temperate areas of Australia. Untargeted metabolite profiling of volatile compounds, from the heated rice flour, by static headspace extraction and separation by two dimensional gas chromatography time-of-flight mass spectrometry was performed. Volatile compounds were also assayed in the standard references used in the sensory evaluation and compared to the compounds detected in the headspace of rice.ResultsWhile 2-acetyl-1-pyrroline (2-AP) was a discriminating compound, we identified several of its structural homologues, and a number of other metabolites that were consistently detected in fragrant Jasmine rice. 2-AP producing rice varieties have different sensory properties and these variations were defined by the discriminating compounds identified in each rice type.ConclusionsThe results of this study are valuable in understanding the aspects of aromatic rice that are important to consumers, and in the identification of compounds that breeding programs can use to select for pleasant aromas, enabling breeding programs to target markets with greater accuracy.

Methods of Detecting Fouling Caused by Heating of Milk

Fouling is the deposition of milk solids on heat transfer surfaces, particularly heat exchangers. It is a major industrial problem, which causes a decrease in heat transfer efficiency and shortens run times. The resultant effect is a decrease in process efficiency and economy. For studying and monitoring deposit formation, suitable fouling detectors or methods of measuring the deposit are required. This can be achieved through direct means, whereby the deposit is analyzed after a certain time, or indirectly through instrumentation for monitoring parameters such as temperature, pressure, flow rate, overall heat transfer coefficient, heat flux, and other physical properties. This article reviews the various reported fouling detection methods.

Variability in Human Bitter Taste Sensitivity to Chemically Diverse Compounds Can Be Accounted for by Differential TAS2R Activation

The human population displays high variation in taste perception. Differences in individual taste sensitivity may also impact on nutrient intake and overall appetite. A well-characterized example is the variable perception of bitter compounds such as 6-n-propylthiouracil (PROP) and phenylthiocarbamide (PTC), which can be accounted for at the molecular level by polymorphic variants in the specific type 2 taste receptor (TAS2R38). This phenotypic variation has been associated with influencing dietary preference and other behaviors, although the generalization of PROP/PTC taster status as a predictor of sensitivity to other tastes is controversial. Here, we proposed that the taste sensitivities of different bitter compounds would be correlated only when they activate the same bitter taste receptor. Thirty-four volunteers were exposed to 8 bitter compounds that were selected based on their potential to activate overlapping and distinct repertoires of TAS2Rs. Taste intensity ratings were evaluated using the general Labeled Magnitude Scale. Our data demonstrate a strong interaction between the intensity for bitter substances when they activate common TAS2Rs. Consequently, PROP/PTC sensitivity was not a reliable predictor of general bitter sensitivity. In addition, our findings provide a novel framework to predict taste sensitivity based on their specific T2R activation profile.

The molecular structural features controlling stickiness in cooked rice, a major palatability determinant.

The stickiness of cooked rice is important for eating quality and consumer acceptance. The first molecular understanding of stickiness is obtained from leaching and molecular structural characteristics during cooking. Starch is a highly branched glucose polymer. We find (i) the molecular size of leached amylopectin is 30 times smaller than that of native amylopectin while (ii) that of leached amylose is 5 times smaller than that of native amylose, (iii) the chain-length distribution (CLD: the number of monomer units in a chain on the branched polymer) of leached amylopectin is similar to native amylopectin while (iv) the CLD of leached amylose is much narrower than that of the native amylose, and (v) mainly amylopectin, not amylose, leaches out of the granule and rice kernel during cooking. Stickiness is found to increase with decreasing amylose content in the whole grain, and, in the leachate, with increasing total amount of amylopectin, the proportion of short amylopectin chains, and amylopectin molecular size. Molecular adhesion mechanisms are put forward to explain this result. This molecular structural mechanism provides a new tool for rice breeders to select cultivars with desirable palatability by quantifying the components and molecular structure of leached starch.

Gastrointestinal digestion of dairy and soy proteins in infant formulas: An in vitro study

An in vitro digestion simulating infant gastrointestinal tract studied the digestion of caseins, whey and soy proteins, commonly used in infant formulations, in the presence of proteases only (without lipolytic enzymes). 60min of gastric phase and 120min of intestinal phase coupled with gel electrophoresis, confocal microscopy, mastersizer and pH were employed to monitor the degradation of proteins, microstructure, particle size distribution and pH drop of the digesta through the in vitro digestion process. Obtained results showed around 20% of caseins and almost no components of whey were hydrolysed after 60min in the simulated stomach. In the simulated duodenal phase, 8% of α-lactalbumin was hydrolysed while caseins and β-lactoglobulin completely digested immediately and 30min respectively after addition of duodenal digestive proteases. Overall, soy proteins indicated lower level of hydrolysis than dairy proteins during in vitro infant digestion as observed by SDS-PAGE. The soy protein fractions glycinin and β-conglycinin were partially hydrolysed during the gastrointestinal phase. The observed pH drop confirms that caseins are easily digested in the duodenal phase compared to whey and soy protein. Gastric digestion resulted in a decrease of the particle size of protein aggregates, but no fat coalescence was observed during both gastric and duodenal digestions in the given conditions.

Evaluation of tilapia skin gelatin as a mammalian gelatin replacer in acid milk gels and low-fat stirred yogurt

Tilapia skin gelatin (TSG) was studied in a 3-stage process (cooling, annealing, and heating) for pure gelatin gels and in a 4-stage process (acidification, cooling, annealing, and heating) for acid milk gels and cultured yogurt. The aim was to evaluate the use of TSG as a replacement for mammalian gelatin in yogurt. In pure TSG gels, stronger gels with higher melting temperatures were formed with increasing TSG concentrations. Compared with bovine gelatin (BG), which gelled at a concentration of 2.5%, TSG gels had lower gelling (14.1°C) and melting (24°C) temperatures but comparable storage moduli during annealing. In acid milk gels, addition of TSG increased the firmness of the gels with increasing concentration. Gelling and melting points of TSG in milk gels were observed at sufficient concentrations during cooling and heating. Strands and sheets were observed in the electron micrographs of milk gels with 1% TSG and a very dense structure was observed with 2.5% TSG. Yogurt with 0.4% TSG had similar viscosity, consistency, pseudoplasticity, and thixotropy as yogurt containing 0.4% BG; no difference was perceived by sensory panelists according to a triangle test. Addition of 0.4% TSG completely prevented whey separation from the acid milk gel and yogurt. The results suggest that TSG could be a suitable replacement for mammalian gelatin in low-fat stirred yogurt.

Rheological behaviour of selected commercially available baby formulas in simulated human digestive system

A variety of formulas are available in the global market for infants (<12months old) who do not have access to mothers milk. The rheological properties of four different commercially available infant formulas - newborn, anti-reflux, soy and lactose free - in an in vitro digestive system were investigated. The enzymatic saliva when mixed with the formulas did not influence their viscosity in the mouth possibly due to the short residence time. Systematic measurement (every 15min) of viscosity during gastrointestinal digestion process revealed a decrease in viscosity as time progressed. The most interesting observation was that the viscosity of the anti-reflux formula was relatively higher compared to the other formulas throughout the simulated gastrointestinal digestion process. The results suggest that viscosity of the infant formula in the stomach may have a role to play in preventing gastroesophageal reflux.

Creation of internal structure of mashed potato construct by 3D printing and its textural properties

3D printing was used for printing mashed potatoes (MP) constructs with variable internal structures. The dimensional properties, textural and structural qualities of the printed objects were investigated as a function of infill levels (10, 40 and 70%), infill patterns (rectilinear, honeycomb and hibert curve), and number of shell perimeters (3, 5 and 7). The printed samples significantly matched the designed geometries. Hardness and gumminess were strongly related to infill levels and perimeters, but the printing paths being performed to fill the samples showed no effect on them. Firmness and Youngs modulus were only affected by infill percentage but not by perimeters and printing paths. Further, comparative assessment of 3D printed and cast samples were also conducted on the textural properties and microstructure features. Microstructure analysis indicated a uniform internal structure was obtained for cast sample. In comparison, an obvious layered structure was observed in longitudinal-sectional direction while a porous structure was obtained in cross-sectional view of 3D printed samples regardless of infill levels. 3D printed samples, even at 100% infill, were significantly (p < .05) less hard, by up to 26.75% and 28.36% in terms of hardness and gumminess, compared to cast samples. The results suggest that 3D printing considerably changes the properties of printed samples, possibly offering a new way for tailoring textural properties of printed samples through creating their internal structure.