THERMAL DIFFUSIVITY MEASUREMENTS of WHEAT FLOUR and WHEAT FLOUR DOUGH

A simple technique was used to measure thermal diffusivity of whole wheat flour and whole wheat flour dough at various levels of moisture and temperatures. the experimental values showed good agreement with the calculated values. It was found that thermal diffusivity of dough increases with moisture and temperature below 60C, but above 60C its value decreases. This is attributed to physico-chemical changes, e.g., starch gelerinization and protein coagulation. Due to these changes swelling and softening of dough occur, which reduce the ability of dough to diffuse thermal energy, thus lowering the value of the thermal diffusivity. Based on the experimental value of wheat dough at various moisture levels and temperatures, the following equation is proposed: α= (7.957 − 0.6346 M + 0.217 T + 0.008 M²− 0.00176 T²− 0.00051 M × T) × 10-7     

小麦碾皮制粉面粉品质的测定与分析

用布勒实验磨对同一种小麦获取的碾皮麦和未碾皮麦分别制粉,并对两种面粉进行品质测定．实验表明：小麦碾皮制粉工艺制取的面粉品质优于传统制粉工艺制取的面粉．     

小麦面粉中戊聚糖的化学分析测定法

将面粉试样与12％的盐酸溶液共沸，使样品中的戊聚糖水解，生成戊糖，戊糖脱水生成糠醛，再蒸馏出糠醛，并用四溴化法测定蒸馏出的糠醛含量，据此换算得出戊聚糖含量。     

SENSORY AND PHYSICAL PROPERTIES OF MUFFINS MADE WITH WAXY WHOLE WHEAT FLOUR

ABSTRACT

The quality of muffins made with different amounts (0, 15, 30, 45 and 60%) of waxy whole wheat flour (WWWF) blended with conventional whole wheat flour were characterized. High amounts of WWWF blends produced darker but acceptable crust color. WWWF formulations had a softer crumb on day 0 and day 4, but greater firmness after 16 days storage. Samples did not differ in springiness on day 0, but a slight decrease occurred in all samples, and WWWF samples were slightly less springy after 16 days. Proton (¹H) NMR showed two distinct relaxation times, indicative of water migration from the crumb of the muffin to the crust. Sensory evaluation showed high overall likability, except for muffins made with 60% WWWF. The 60% muffins had lower volume than all other formulations. Results show that 15–30% WWWF produces a softer, moister muffin, but this advantage is lost after 8–16 days storage.

PRACTICAL APPLICATIONS

This study shows that 15–30% waxy whole wheat flour blended with conventional whole wheat flour produces softer and moisture whole wheat muffins, with good consumer acceptability. Muffins with WWWF remained softer for 4–8 days, but were firmer than control after 16 days storage. Waxy whole wheat flour also adds additional fiber, so its inclusion in blends with conventional whole wheat may help in the development of higher fiber products with a softer and moister crumb.

     

制粉工艺的新创意(2)--1000t全八辊磨生产工艺的设计与实践

介绍了郑州金苑面业有限公司采用包括全八辊磨粉机、小麦色选机、卧式撞击磨、前路大量出粉工艺等多项新设备、新技术，自行设计、安装、调试的1000t全八辊磨机面粉生产线投入运行后与常规四辊磨制粉工艺相比，取得了单位产量高、面粉灰分低、资金投入省、动力消耗少、经济效益好等多项经济技术指标的成功范例，为制粉工业和制粉工艺的发展走出了一条新的路子。     

COMPARATIVE STUDY OF CHEMICAL COMPOSITION AND PHYSICOCHEMICAL PROPERTIES OF DEFATTED WHEAT GERM FLOUR AND ITS PROTEIN ISOLATE

Chemical composition and physicochemical properties of defatted wheat germ (WG) flour (DWGF) and protein isolate (DWGPI) were evaluated to determine their potential as food ingredients. Protein content of DWGF was 31.42% while that of DWGPI was 84.18%. Comparison of the amino acid composition to the Food and Agriculture Organization/World Health Organization reference pattern indicated that DWGF and DWGPI had well‐balanced amino acid profiles. Both of them were relatively rich in lysine, whereas cystine was lacking. The main mineral constituents of DWGF were potassium, magnesium and calcium, while sodium was the dominating element in DWGPI as a result of salt extraction. Concentrations of potassium, magnesium, calcium, manganese and zinc in DWGPI were significantly decreased because of alkaline extraction compared to those in DWGF. The elements copper and iron were higher in DWGPI than in DWGF. Total flavonoid content of DWGF was about 0.35 g rutin equiv/100 g, whereas that of DWGPI was lower (about 0.24 g rutin equiv/100 g). Compared to soybean protein isolate, DWGPI was easily digested by pepsin in vitro, while DWGF was comparatively indigestible. Nonreduced and reduced sodium dodecyl sulfate‐polyacrylamide gel electrophoresis analyses seem to show that interpolypeptide S‐S bonds were absent in the structure of WG proteins. DWGF and DWGPI shared four groups of bands: (1) 85–70 kDa; (2) 55–50 kDa; (3) 47–40 kDa; and (4) below 20 kDa.     

PHYSICAL and THERMAL PROPERTIES of GORGON NUT

Bulk density, true density, angle of repose, coefficient of friction on metal surfaces, specific heat, thermal diffusivity and conductivity of gorgon nut were determined using standard techniques for different sizes of nuts at moisture contents and temperatures ranging from 15 to 60% (dry basis) and 25 to 55C, respectively. the physical properties varied quadratically with moisture content. Specific heat increased with moisture and temperature but decreased with the size of the nut; whereas, the thermal diffusivity showed a reverse trend. Thermal conductivity increased with moisture content but did not follow any trend with temperature within the range of the study. the physical and thermal properties data at various moisture contents and temperatures were used to develop equations for different sizes of gorgon nuts.     

BLACK TIP DISCOLORATION IN INDIAN RICE. EFFECT OF EXTENDED MILLING ON MILLING CHARACTERISTICS, CHEMICAL COMPOSITION AND COOKING QUALITY

Extended milling of rice decreased the incidence of mycoflora and reduced black tip discoloration but reduced the head rice yield and kernel weight. Protein content, ash, reducing sugars, nonreducing sugars and free fatty acids increased whereas amylose decreased significantly with the increase in the number of discolored grains. Discolored rice required significantly less time to cook, showed decreased water uptake, reduced kernel elongation and losses. Cooking time decreased; water uptake, elongation in cooked rice and gruel solid loss increased with an increase in the degree of milling. Correlation coefficients between the different variables were calculated.     

PHYSICAL, CHEMICAL AND SENSORY QUALITY OF MICROWAVE-BLANCHED SNOW PEAS

Snow peas were blanched using four methods [conventional boiling water (BW); steam (ST); microwave (MW); and microwave blanched in heat sealable bags (MWB)], then held frozen at (～18C) for four weeks. Immediately after blanching, MWB‐blanched snow peas retained more reduced ascorbic acid (RAA; 72%), than other treatments. Blanching treatment had no effect on lightness [L* value). With the exception of BW‐blanched peas, blanching significantly altered color. After frozen storage, MWB‐ and MW‐blanched samples both contained about 26 mg/100 g RAA, significantly more RAA than other treatments. MWB‐blanched peas generally had as high or higher sensory appearance, aroma, flavor, texture and general acceptability scores than other treatments. These results imply that blanching snow peas in a heat‐sealable microwave bag, prior to frozen storage, produces a product of equivalent sensory quality and superior nutritional quality compared with more conventional blanching methods.     

MOISTURE ADSORPTION BEHAVIOR OF BISCUITS FORMULATED USING WHEAT, OATMEAL AND PASSION FRUIT FLOUR

Moisture adsorption isotherms from a new biscuit considered as functional food were determined using a gravimetric static method at 25 and 40C and over a range of relative humidity from 0.112 to 0.903. The biscuit had 2.5, 3.3, 10.0 and 31.0% of ash, fiber, protein and fat, respectively, and 4.7% moisture content. The equilibrium moisture content of the biscuit (kg/kg) increased when the storage temperature at any given water activity ( A _w) was reduced. The experimental data were analyzed using different models, namely Guggenheim–Anderson–de Boer (GAB) (three-parameter relationships), Henderson and Oswin (both models with two parameters), which exhibited a sigmoid shape at the studied temperatures. The maximum isosteric heat of sorption was 21.6 kJ/mol, which exponentially decreased when the moisture content was increased. The GAB model was found to be the most suitable for describing the adsorption characteristics at the temperature and A _w range studied, according to the relative error and the coefficient determination.

PRACTICAL APPLICATIONS

This article describes the characterization of moisture adsorption behavior of a new biscuit considered as functional food. In general, the sorption behaviors of several foods have been studied extensively; nevertheless, a reduced number of published articles about biscuit sorption isotherms are found in the literature. The experimental data reported in this article may be important for the scientific community of the food science and technology. Isosteric heat of sorption is important for the determination of the binding strength of water to the food, as well as the amount of water present in the food.