Volume 3, Issue 3

Jam is an intermediate moisture food containing fruit pulp, pectin, sugar and acid. The effect of sugar and pectin concentration, pH, shear rate and temperature on the time dependent rheological properties of pineapple jam was studied using a rheometer. Pineapple jam exhibited thixotropic behavior. Shear stress of the pineapple jam at a particular time of shearing depended on the shear rate, temperature and composition. Weltman, Hahn, and Figoni and Shoemaker, models were applied to describe the time dependent flow properties of pineapple jam. Hahn model described adequately the rheological characteristics of pineapple jam.

This study aims at developing a kinetic model for the degradation of trypsin inhibitor (TI) in horse gram (Dolichos biflours) subjected to a defined set of processing conditions. The study was carried out in isothermal conditions over a temperature range of 60-120° C. The degradation of TI followed first order kinetics. It was adequately modeled by the Arrhenius equation. Using the time temperature data of the nonisothermal heating process encountered in three different cooking methods viz. open pan, pressure cooking and cooking in a recently developed and patented fuel-efficient 'EcoCooker', and the kinetic data obtained under isothermal temperature conditions, a mathematical model has been developed to predict the degradation of TI in these three modes of cooking.

Breadmaking experiments were undertaken to investigate the effect of addition of selected fully hydrogenated palm oil-based emulsifiers (DATEM, SSL and DMG) on the baking performance of open top white breads in terms of volume, oven spring, weight, density, color, crumb texture and shelf life using the strong and weak flours. The bread samples were prepared using straight dough method with standardized formulation for every experiment except varying six usage levels of emulsifier from 0.0% (control sample) up to 1.25% based on flour weight. The properties of bread were objectively measured and quantitatively analyzed using analysis of variance (ANOVA) with 5% significance level. Emulsifier performed most effectively at a usage level of 0.50% of flour weight. DATEM was effective as volume and oven spring improver while SSL was effective in improving crumb texture. As overall, emulsifier added breads had larger volume, higher oven spring, lower weight and density, whiter color, finer crumb texture and longer shelf life compared to control breads. The improvement in baking performance with added emulsifier was more prominent for the strong flour compared to weak flour.

The present study is part of a project aimed at producing bambara groundnut (Voandzeia subterranean) flours for the preparation of koki (a steamed cooked paste). The flours were produced from the black (BBG) and white (WBG) varieties by the combined processes of soaking, drying, dehulling and milling. Some physicochemical characteristics of the flours were evaluated and the effects of flour particle size, salt concentration and pH on their functional properties were investigated. Significant varietal influence was indicated on the proteins and carbohydrates with the WBG variety showing high level of proteins (19.7%) and the BBP variety the highest carbohydrate content (61.7%). It was equally observed that an increase in NaCl tends to induce a reduction in the water absorption capacity (WAC), foam capacity and emulsion properties. The emulsion and foam capacities were observed to be at their minimum values within the pH range 2 and 4.

Rheological characteristics of commercial creams were investigated at different freeze-thaw conditions. This study was carried out to determine the effect of the freeze-thaw treatment on rheological behaviour and the activation energy in different commercial creams. Freeze-thaw treatment was made at different times of frozen storage within a range from 0 to 6 weeks. For each freezing cycle, the sample was submitted to rheological measurements within range of temperature between 20 and 40° C. A rotational, concentric cylinder viscosimeter Viscotester VT550 (Germany) type Searle was used in this work. The apparent viscosity is defined as the ratio of shear stress and shear rate, which was varied between 17.8 and 445 s-1. The Power Law or Oswaltd Waele model describes well the rheological behaviour of the analyzed samples. Furthermore, in all cases sample viscosity increased when was exposed to freeze-thaw treatment with respect to the not treated sample. And other hand, the activation energy has high values; hence there is clear evidence that the rheological behaviour presents a high dependence with the temperature.

The influence of different cooling techniques (dry ice/ice packs) and storage temperature (-2°C/3°C) to prolong the shelf life of Arctic charr (Salvelinus alpinus) fillets were evaluated by sensory analysis, physical methods, chemical and microbial analysis. The effects of storage temperature were stronger than of different cooling agents. Superchilling (-2°C) of fillets packed with dry ice resulted in 6 days extension of shelf life compared to chilling (3°C). The use of dry ice parallel to superchilling prolonged shelf life for 1 day compared to fillets stored with ice packs. No negative effects on quality of the fillets where detected that could be linked to cell destruction caused by partial freezing or to sour taste, caused by absorption of CO2 gas in fish flesh.

Litchi pulp was treated with various concentration levels of hydrolytic enzymes viz. pectinase (0-0.133%w/w), cellulase (0-0.266%w/w) and hemicellulase (0-0.20%w/w) for different durations (30-150 min) at 45°C. The effect of enzyme treatment conditions was studied on yield, clarity, apparent viscosity and total soluble solids (TSS) of juice obtained from the pulp. The optimum process conditions were determined by employing a second order central composite rotatable design in combination with response surface methodology. Yield, clarity and TSS of juice were found to increase and apparent viscosity was found to decrease significantly by enzymatic treatment. The optimum conditions for enzymatic treatment of pulp obtained after a 2 sided desirability function with the responses juice yield, clarity and TSS to be maximized and viscosity to be minimized were 0.076% (w/w) pectinase, 0.138% (w/w) cellulase, 0.107% (w/w) hemicellulase and incubation time of 106.5 min. The predicted values for juice yield, clarity, viscosity and TSS under optimized conditions were 77.19 %, 93.53%, 1.359mPa s and 19.68°brix which showed a good agreement with the experimental values under the same set of conditions.

In this study, quality of Man-tou, the Chinese traditional steamed bread during storage was studied. Values for water retention capacity, total water solubles, soluble starch, and soluble amylose and amylopectin of Man-tou decreased with storage time. Results showed that hardness, chewiness and gumminess of Man-tou increased, while, springiness cohesiveness and resilience decreased along with prolonged storage time (p<0.05). Sensory evaluation results showed that all sensory rating of Man-tou, including softness, stickiness, cohesiveness, elasticity, taste and total score, dropped drastically within 24 h of storage time (p<0.05). Differential Scanning Calorimeter (DSC) was used to determine crystalline structure of amylopectin in Man-tou, and the value for enthalpy of crystallization was found increased with storage time. Amylopectin crystallization was significantly associated to Man-tou firming (p<0.01).

The effects of cooking and milling of grains from 14 maize cultivars on the characteristics of fine flours were studied in a factorial experimental design. Wet milling significantly increased (P<0.05) fine flour (<400 microns) yields, water absorption capacity at 90°C, solubility index at 25°C, swelling capacity at 95°C and least gel forming concentration. Fine flour composition and functionality were variety dependant. Maize cultivars producing similar fine flours in terms of functionality were classified into three groups: ATP SR-Y, ADV NCRE, CMS 9015, and 88094M131Exp124 for group 1; CMS 8704, CMS 8501, CMS 8806, PDY and ASPY for group 2; and the last group comprising K9351, 87036Exp124, CMS 2019. The specific functional properties maize cultivars should be taken into account in the formulation of pre-cooked weaning food from fine flours.