THE EFFECT OF EDIBLE FILM ON OIL UPTAKE AND MOISTURE RETENTION OF A DEEP-FAT FRIED POULTRY PRODUCT

The recent trend in reducing the fat content in fried foods is leading to the development of low-fat products using batter and breading formulations from protein and other hydrocolloids. The functionality of many of these edible ingredients on moisture retention and fat barrier properties during deep-fat frying is not clearly understood. The objective of this study is to evaluate the effectiveness of hydroxypropyl methylcellulose edible film coating on chicken balls for moisture retention and fat reduction during deep-fat frying. Two sizes (35 and 47 mm) of uncoated and coated chicken balls were fried in peanut oil at 175C for five different frying periods ranging from 30 to 180s for small and 30 to 300s for large balls. The moisture and fat content from the surface layer and core were determined. In comparison to the control, moisture retention up to 16.4% and fat reduction up to 33.7% were observed.     

木薯淀粉/壳聚糖可食性复合膜对鲜切菠萝蜜的保鲜研究

主要研究不同的被膜对鲜切菠萝蜜的保鲜效果。分别用壳聚糖、木薯淀粉制成不同的涂膜液对鲜切菠萝蜜进行涂膜处理。在3℃±1℃的条件下贮藏，涂膜后的鲜切菠萝蜜可溶性固形物、总糖、淀粉、总酸、VC的变化均小于对照组，抗菌性能优于对照组。对鲜切菠萝蜜的保鲜作用就不同的膜成分而言，壳聚糖膜的保鲜效果最佳，木薯淀粉-壳聚糖复合膜的保鲜效果优于木薯淀粉膜。     

EFFECTS OF MOISTURE,SUCROSE, NaCl,AND ARABINOXYLAN ON RELAXATION IN WHEAT DOUGH AS MEASURED BY DMTA

The effects of sucrose, NaCl, and arabinoxylan on the α-relaxation of wheat doughs with different water contents were investigated using Dynamic Mechanical Thermal Analysis (DMTA). DMTA measurements were made at the heating rate of 2°C/min from at least 30°C below the observed onset of the α-relaxation (glass transition) to at least 30°C above the transition. The glass transition temperature, T_g , was taken from the onset temperature of the decrease in storage modulus (G′). The frequencies used were 0.1, 1, and 5 Hz and amplitude was 16 μm. The storage modulus, G′, showed α-relaxation in all doughs with added ingredients. Added ingredients decreased the glass transition temperature of dough. The T_g of doughs with different ingredients decreased with increasing water content of doughs over the whole a_w range used (0.113–0.753). Also, the T_g increased with increasing frequency.     

EFFECT OF GAMMA RADIATION ON WHEAT STARCH AND ITS COMPONENTS

SUMMARY– Studies on the susceptibility of irradiated wheat starch, amylose and amylopectin to alpha- and beta-amylolysis reveal that they are more susceptible to enzyme actions, compared to their unirradiated controls; however, irradiated amylose seems to be comparatively more vulnerable. From irradiated starch, series of oligosaccharides of the maltose series are discernible, while glucose appears only above 200 Krad dose level. Quantitative analysis of the radiolytic breakdown products of starch reveal that at high dose levels (1 Mrad) maltose, maltotriose and maltotetrose are the main products. Results on the separation of radiolytic breakdown products suggest they resemble those produced by alpha-amylolysis of starch.     

变性淀粉及谷朊粉对面团特性的影响研究

研究淀粉及变性淀粉、谷朊粉对面团特性的影响。结果显示：在面粉中，按4％的比例添加马铃薯变性淀粉，对面团的稳定时间、弱化度及抗张强度等均有显著的影响（P〈0．01）；添加6％木薯变性淀粉，面团抗张力增加26、6％；添加3％的谷朊粉，面团形成时间及稳定时间均有较大增加。木薯原淀粉及其变性淀粉等对面团的特性影响不大。     

CONTROLLED ATMOSPHERE STORAGE AND EDIBLE COATING EFFECTS ON STORAGE LIFE AND QUALITY OF TOMATOES

Tomatoes at pink stage maturities were coated with Semperfresh^TM edible fruit coating which is composed of sucrose esters of fatty acids, sodium carboxymethyl cellulose and mono-diglycerides of fatty acids. One group of coated and uncoated tomatoes were stored at 23 × 2C under air atmosphere, another group was stored at 12C under air atmosphere and third group was stored at 12C, 93–95% RH in a controlled atmosphere (CA) containing 3% CO₂, 3% O₂ and 94% N₂. Samples of tomatoes were analyzed for firmness, weight loss, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene to examine changes in quality during storage. Semperfresh^TM edible fruit coating was found to be significantly effective at both storage temperatures (23 × 2C and 12C) in air to delay changes in firmness, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene. Semperfresh^TM fruit coating reduced fruit weight loss as compared to fruit without coating but the difference between coated and uncoated tomatoes was not significant. Shelf-life of pink tomatoes was increased 3 days at 23 × 2C and 6 days at 12C in air by coating. CA storage delayed compositional changes in tomatoes significantly as compared to air storage of coated and uncoated tomatoes. CA storage also had a significant potential for reducing weight loss and microbial spoilage. Tomatoes were stored 40 days in CA. Coated and uncoated tomatoes exhibited the same results in CA.     

EFFECTS OF TEMPERATURE AND MOISTURE CONTENT ON THE VISCOELASTIC BEHAVIOR OF COWPEAS

The viscoelastic parameters of cowpeas (Vigna unguiculata) were studied at different temperature and moisture content combinations. Cowpeas were tested at temperatures of 25°, 45° and 70°C and moisture contents of 13.9, 19.6 and 22.4% dry basis on an Instron Universal Testing Machine using stress relaxation techniques. The response of cowpeas was characterized by two Maxwell bodies in parallel without the incorporation of a residual spring. The relaxation curves (uniaxial modulus versus time) were used to calculate temperature and moisture shift factors, which subsequently led to the construction of a single master response curve. Cowpeas are both thermo-rheologically and hydro-rheologically simple biological materials.     

EFFECTS OF CORN MEAL, VITAL WHEAT GLUTEN, HIGH AMYLOSE STARCH AND EXTRUSION PARAMETERS ON TECHNOLOGICAL PROPERTIES OF WHEAT-BASED EXTRUDED BREADING

A wheat‐based extruded breading was produced using a Brabender single‐screw laboratory scale extruder (model GNF 1014/2) and applied to chicken nuggets. Response surface methodology was applied to study and optimize the effects of formulation and extrusion parameters on pick up, texture, solid loss, oil absorption and adhesiveness of fried coated nuggets. An optimized extruded breading was produced at 160C, 27% moisture content, 15% vital wheat gluten, 8% high amylose starch and 30% corn meal. The product showed pick up of 29.87%, adhesiveness of 100%, texture of 166.1 g, oil absorption of 2.97% and solid losses of 0.0885 absolute. The product presented similar values of pick up and adhesiveness, better texture, lower oil absorption and higher solid loss during deep‐frying, compared with commercial breadings. Acceptance test showed that the product had better overall appearance and fairly similar texture, compared with the commercial ones.     

淀粉基脂肪模拟物的性质及代脂研究

以玉米淀粉为原料，在不同条件下对其进行酸水解制取脂肪模拟物。并对得到的不同DE值（糖液中的还原糖含量占干物质百分率）的玉米淀粉基脂肪模拟物进行性质研究。扫描电镜观察结果表明，样品具有2μm-6μm的粒径；x-粉末衍射图表明，样品保留了A型特征峰。以其中一种脂肪模拟物为代表，作为脂肪替代品加到奶油中进行代脂研究，结果表明所制得的玉米淀粉水解产物可作为脂肪模拟物用于奶油中。     

EFFECTS OF OHMIC PRETREATMENT ON OIL UPTAKE OF POTATO SLICES DURING FRYING AND SUBSEQUENT COOLING

The effect of ohmic pretreatment on the oil uptake of potato slices during frying and subsequent cooling was investigated. The treated potato slices were heated by either directly sandwiching the slices between two electrodes or by heating them in a 0.11% salt solution. The treatment was carried out using an alternating current field of 35.5 V/cm. Results of this study indicate that oil uptake during frying and subsequent cooling of potato slices was decreased by the ohmic pretreatment without involving a liquid medium (direct sandwiching). However, when the ohmic pretreatment was carried out in a liquid medium, the effect was not evident. This might be due to water absorption during the treatment, which increased initial moisture content as well as porosity of the treated samples.     

淀粉糊化和回生的研究

对淀粉糊化和老化现象进行了论述，着重介绍了其影响因素，并概述了淀粉糊化和老化的测定方法。