Sila Bhattacharya

Tamarind Seed: Properties, Processing and Utilization

Tamarind seed is an underutilized byproduct of the tamarind pulp industry. Only a small portion of the seed, in the form of tamarind kernel powder (TKP), is used as a sizing material in the textile, paper, and jute industries. Though many applications of this seed are possible, there have been hardly any other uses for it including using it as an additive in food formulations. The excellent gelling cum adhesive characteristics of the decorticated seed powder can lead to several applications in food and pharmaceutical industries which are evident by the number of research papers as well as patent applications. This article thus focuses on the possibilities of using the seed in several food and non-food industries with particular reference to physical and engineering properties, hydration behavior, rheological properties, functional and nutritional characteristics, and the processing of the tamarind seed for wider applications.

Kinetics on colour changes in rice due to parboiling

Changes in colour values of rice during parboiling were examined. Hunter L, a and b values, chroma and total colour difference of paddy (var. IR20) were determined during soaking at 70C for 3 h followed by steaming at different pressures (101-304 kPa) for up to 60 min. Response surfaces were developed for colour against time and pressure. Colour changes generally followed zero-order kinetics, and activation energies for chroma and total colour difference were 22.1 and 11.1 kJ mol-1, respectively. Low steaming pressures and short times minimised colour changes in rice during parboiling, although it is concluded that higher pressures can be used if steaming time is restricted to a few minutes, after which colour of parboiled rice increases sharply.

Rheology of cooked debranned maize flour suspensions

Rheological behaviour of cooked debranned corn flour suspensions was compared with debranned-degermed suspensions. Usefulness of rheological models for calculating yield stress and correlating shear rate and shear stress data was also investigated. Corn (12-14% moisture on a dry wt. basis) was debranned by conditioning with 4% water for 5 min followed by milling for 1.5 min. The milled sample was dried at 40C for 24 h. Corn flour was analysed for moisture, crude fat, ash and crude protein. 2, 4, 6, 8 and 10% suspensions of corn flour were prepared. Each suspension was heated to 60C, then to 95C for 20 min, then cooled rapidly to 60C and subjected to rheological measurements (shear rate, shear stress and yield stress). Cooked debranned corn flour suspensions were pseudoplastic in behaviour and exhibited yield stress like debranned-degermed samples. An increase in concn. of corn flour in the cooked suspensions increased the yield stress and consistency index, but decreased the flow behaviour index. The experimentally determined yield stresses were lower than those calculated from different rheological models. Herschel-Bulkley and Mizrahi-Berk models provided the best fit at all flour concn.

Kinetics of hydration of raw and roasted corn semolina.

Abstract Hydration of raw and roasted corn semolina at 30, 50 and 70 °C shows that raw semolina absorbs more water, has higher equilibrium moisture content and hydration rate constant values than roasted semolina. The rate of hydration is linearly related to average moisture content. Hydration rate index (HRI), defined as the change of hydration rate constant per unit change in hydration temperature (Δk/ΔT), is determined for raw and roasted semolina. The activation energies for raw and roasted semolina are 10.6 and 7.7 kJ mole−1, respectively. Studies on the volume increase and leaching loss of semolina at 30–100 °C show that hydration temperatures above 70 °C markedly increase the per cent volume increase and the leaching loss. These two values are higher for raw semolina than roasted samples.

Optimization of culture conditions for growth of the green alga Haematococcus pluvialis

The effects of light intensity, inoculum volume, sodium nitrate and carbon dioxide concentrations on the growth of Haematococcus pluvialis were investigated using response surface methodology (RSM). All the four variables exhibited significant effects on growth and can be related (r ≥ 0.926, P ≤ 0.01) by a second-order polynomial consisting of linear, quadratic and interaction terms. The total quadratic effect (P ≤ 0.01) dominates over the total linear effect (P ≤ 0.01) but the role of interaction terms (P ≤ 0.10) is marginal. The optimum values of these variables were: carbon dioxide 1.54%, sodium nitrate 1.06 g/l, inoculum volume 24.97% and light intensity 2.42 klux; the predicted maximum value for the yield of biomass was 0.51 g/l (dry weight).

A Comparison of Selected Quality Attributes of Flours: Effects of Dry and Wet Grinding Methods

Studies were conducted on the selected quality attributes of rice flour obtained by dry and wet grinding methods. Raw and parboiled rice have been dry ground at a moisture content of 12%, while wet grinding is performed at 30%. The functional properties of ground samples and doughs made out of the flours were characterized. The damaged starch contents in the dry ground rice flour were 21.5 and 22.6% for raw and parboiled samples, respectively; whereas, these were only 8.7 and 9.5% for wet ground samples. The dry ground rice flour formed sticky dough having high stickiness values but it was less cohesive in nature compared to those of wet ground samples. The doughs made from wet ground rice were more adhesive than the dry ground samples; the former was suitable for forming extrusion processing for preparing various convenience foods like pasta and noodles.

A RESPONSE SURFACE APPROACH FOR THE PRODUCTION OF NATURAL PIGMENT ASTAXANTHIN FROM GREEN ALGA, HAEMATOCOCCUS PLUVIALIS: EFFECT OF SODIUM ACETATE, CULTURE AGE, AND SODIUM CHLORIDE

ABSTRACT The effect of sodium acetate, sodium chloride and Haematococcus pluvialis culture age on biomass yield, astaxanthin content and astaxanthin production was investigated using response surface methodology in a batch mode of cultivation. An orthogonal experimental design, with three variables (at five coded levels of −1.682, −1, 0, 1 and 1.682) and three response functions, was employed to study the effect of the individual variable on the response functions. The response functions correlated well (r≥0.98, p≤0.01) with these variables by second order polynomials consisting of linear, quadratic and interaction terms. The effect of culture age dominated over the sodium acetate and sodium chloride concentrations. Optimum conditions for achieving high astaxanthin content (>1.4%w/w) and astaxanthin production (13 mg/L) were found to be with 31–50 mM sodium acetate and 0.55–0.63% (w/v) of sodium chloride.

Effect of Hydrocolloids on Quality of Proso Millet Cookie

The absence of gluten in proso millet offers difficulty to shape the dough for the preparation of products. The effects of hydrocolloids like gum acacia, guar gum, xanthan gum, carboxymethylcellulose (CMC) and hydroxypropylmethylcellulose (HPMC), and the thermal treatment of proso millet flour and doughs on cookie-making quality were studied. The product attributes that were determined included the sensory and textural properties of the product and compared them with the wheat cookie. Thermal treatment, as well as the addition of hydrocolloids markedly, changed the product qualities. Xanthan and guar gum-added doughs exhibited high instrumental adhesiveness and sensory stickiness which were undesirable for obtaining the appropriate shape of a cookie. The product made from untreated proso millet flour (PMF) showed the highest mass per unit piece followed by the refined wheat flour (RWF) product; the lowest mass and soft texture were displayed by the products made from the CMC and HPMC. The principal component analysis of the results indicated that untreated PMF and RWF products were placed in the opposite quadrants to behave in a different manner. The sensory quality of the product prepared with untreated PMF was inferior to that of the control sample and was not acceptable to sensory judges. The HPMC- and CMC-added products were distinctly different with respect to their volatile quality as per the e-nose analysis. The treated PMF with gum acacia-added product had the similar odour characteristics and were closely associated with firmness and overall quality to match the wheat product and also were best suited for dough-handling purpose.

Effect of raw material characteristics on the properties of fried rice–blackgram dough

The dough, comprising a mixture of rice and blackgram, is shaped in a forming extruder followed by deep frying to obtain a crisp snack. Although it is a popular product in several oriental countries, the details of the role of raw materials and processing conditions are not known. Two different flour mixes obtained from rice and blackgram were studied to investigate the influence of the raw material on product characteristics. Fine particles in one flour mix (70 µm) had a high water-holding capacity (1.7 g/g) and gave product with low fat content (∼16%), but had an undesirable hard texture coupled with a floury mouth feel. On the contrary, coarse particles (113 µm) in another flour mix with a low water-holding capacity (1.5 g/g) produced a snack with higher fat content (26–30%) with a desirable crisp texture. Addition of fat and the use of coarse flour can avoid bursting of the product during frying, which is a common problem associated with frying of such products while using fine flour. A mechanism for frying rice–blackgram dough strands has been proposed.

Bioactives-retained non-glutinous noodles from nixtamalized Dent and Flint maize

Nixtamalization is a well-known pre-treatment technique in the tortilla industry. Nixtamalized maize (nixtamal) is known for its modified physicochemical as well as nutritional attributes. In the present study, two types of nixtamalization processes (traditional and ecological) were employed for the development of whole-grain-maize-based noodles using Dent and Flint maize genotypes. Results showed that ecological nixtamalization had resulted in better cooking and textural qualities of noodles compared to the one prepared traditionally. Dent maize noodles from traditional and ecological nixtamalization had lower retention of phenolics (40 and 64%, respectively) whereas, Flint maize noodles retained 50 and 66% phenolics, respectively. Dent maize noodles had undergone phenolics loss of 5-6% on cooking while those of Flint maize lost only 2%. Ecological nixtamalization maintained the pH of the cooking liquor within an acidic-neutral range and yielded noodle with higher retention of phenolics whereas, the traditional process negatively affected the antioxidant compounds and their properties.