EFFECT OF ANTIBROWNING TREATMENT ON COLOR AND FIRMNESS OF FRESH-CUT PEARS1

A 30‐second dip in a solution of 4‐hexylresorcinol, isoascorbic acid, N‐acetylcysteine, and potassium sorbate prevented browning of fresh‐cut ‘Anjou’ and ‘Bartlett’ pears (Pyrus communis L.) for 9 days at 5C in air, regardless of initial ripeness. Firmness of pears did not change in response to chemical treatments or time in storage, except that pears slices initially < 25 N, quite ripe, generally became translucent and excessively soft during storage. Firmness of the 5‐mm thick slices was measured by puncturing to 2.5 mm using a 4 mm diameter cylindrical probe and by a three‐point bending test. A puncture test was more suitable (and more convenient) than bending for measuring firmness of the slices. Color (L*, a*, and b*) and transmittance through the slices in the visible and near infrared range (400 to 1900 nm) were measured. The a* value was more sensitive to browning and less affected by ripeness and storage than transmittance at specific wavelengths or the overall absorbance in the visible range.     

大豆异黄酮的热水提取及其纯化工艺的优化

研究了热水从大豆胚芽中提取异黄酮的工艺，方法简便、可行且提取率、纯度满足实验要求；并采用HPLC法对提取液中异黄酮组分进行鉴定。经大孔树脂纯化、乙酸乙酯萃取三次后，异黄酮纯度超过60％。     

EFFECT OF VARIOUS DRYING METHODS ON TEXTURE AND COLOR OF TOMATO HALVES

Tomatoes were pretreated with osmotic solutions (NaCl and sucrose) at different concentrations and then dried using hot air (75C, 1.5 m/s), a vacuum (55C, 75 kPa) or hot-air drying followed by microwave treatment (400 W, 10 s). The effects of pretreatment and drying method on the drying kinetics were examined. A puncture test and scanning electron microscopy were used to analyze the effects of these processes on texture and microstructure. Hunter values ( L, a, b ) were used to measure color. Measurements showed that two osmotic solutions, S₃ (40% sucrose, 5% NaCl) and S₄ (40% sucrose, 10% NaCl), performed better, reducing drying times and having a positive effect on microstructure, but an adverse effect on hardness. Apart from the type of process, dehydration reduced firmness and collapsed the structure of tomato halves. The subsequent microwave treatment then caused further damage, especially on the surface of the dried samples, but enhanced their color when combined with appropriate osmotic treatment.

PRACTICAL APPLICATIONS

This study shows that the color and structural changes of tomato during drying can be reduced using appropriate procedure. This may find application in the production of dried tomato with better appearance and lower drying cost.     

QUALITY OF FROZEN SHRIMP THAWED BY RECIRCULATING AIR VERSUS WATER IMMERSION

The quality of shrimp thawed using a constant temperature thawing chamber compared with running water was studied. Shrimp thawed in room temperature air was used as the control. Shrimp thawed using the thawing chamber had lower drip loss, higher yield and moisture content than shrimp thawed by running water. However, the differences were not statistically significant. There were also no significant differences in press juice and shear force between control and shrimp thawed using either thawing method. Shrimp thawed using the thawing chamber had lower aerobic bacterial counts than either control or shrimp thawed using running water. Shrimp thawed using the thawing chamber did not exceed ?1C throughout the thawing experiment, and microbial growth during thawing was also avoided. Results indicated that the thawing chamber has potential for the foodservice industry to produce uniformly thawed products under sanitary conditions.     

可见分光光度法测定马蹄皮中总黄酮的含量

建立测定马蹄皮中总黄酮含量的光谱分析方法.以40%乙醇为溶剂,微波辅助提取马蹄皮中的总黄酮.以芦丁为标准样品,以NaNO2-Al(NO3)3-NaOH为显色剂,采用可见分光光度法在510 nm测量波长测定马蹄皮中总黄酮含量.回归方程A=0.0105 C+0.0014,相关系数R2=1,黄酮浓度在8.41 mg/L～82.88 mg/L范围内服从比耳定律.测定结果显示,马蹄皮中总黄酮的平均含量为1.59%,重现性试验RSD=1.38%(n=6),平均回收率99.6%(RSD=0.799%,n=6),精密度试验RSD=1.64%(n=6).     

BLANCHING OF WHITE POTATOES BY MICROWAVE ENERGY FOLLOWED BY BOILING WATER

SUMMARY —Small white potatoes were heated with microwave energy followed by boiling water to determine the penetration of heat, inactivation of peroxidase and firmness of the potatoes. Treatments consisted of heating potatoes with microwave energy for 0.5, 1, 1.5 and 2 min followed by boiling water for 0, 1, 2, 3, 4 and 5 min. Temperature measurements were made at depths of 0.75 and 1.5 cm using tubers with a mean radius of 1.95 cm. Peroxidase inactivation was measured along the radius of a slice removed from the equatorial region. Firmness was determined by the ALLO-Kramer shear press. Potatoes, when heated by microwave energy, became hot first at the core with a heat gradient developing toward the periphery. Boiling water produced a heat gradient from the periphery toward the core. Consequently, the tissue located about midway of the radius was subjected to the least amount of heat. The minimum time required to completely inactivate peroxidase and the firmness values of the potato tissue at the time of enzymatic inactivation were as follows: 1.5 min microwaves and 3 min boiling water, 119 lb shear force; and 2 min microwaves and 2 min boiling water, 124 lb shear force. Peroxidase was not completely destroyed when the potatoes were subjected to energy for 1 min or less followed by heating in boiling water up to 5 min.     

柿子皮多酚物质的提取和除臭效果的研究

探讨了柿子皮多酚物质的提取工艺条件及多酚的除臭效果,研究结果确定最终工艺为提取温度为45℃、提取时间为90min、料液比为1:16、丙酮浓度为50%.提取物经过处理所得3个样品对三甲胺,氨水,吲哚有较好的除臭效果,效果最好样品的除臭率为32.17%～36.12%.对甲醛除臭效果不明显,除臭率最高只有3.9%.在一定时间范围内,除臭效果随添加剂量的增加和时间的延长而增强.     

RESIDUAL GAS VOLUME EFFECT ON QUALITY OF RETORT POUCH WET-PACK PEARS

Wet pack pears in retort pouches were studied for six months. Four selected residual gas volumes [10, 15, 20 and 30 cubic centimeters (cc)] were used to determine the influence of residual gas volume on physicochemical and sensory attributes. Three storage temperatures (4.4, 26.7 and 37.8C) were used to carry out an accelerated shelf‐life study. Residual gas of 30 cc promoted faster darkening and higher ascorbic acid degradation than the rest of the volumes studied (α≤ 0.01). No significant effect of residual gas volume was found on any other attribute analyzed. Temperature accelerated the consumption of remaining oxygen in the pouches, degradation of ascorbic acid, formation of 5‐hydroxymethyl‐2‐furaldehyde (HMF) and 2‐furaldehyde, and softening of pears. Calculated activation energies (E_a) for HMF and 2‐furaldehyde formation, ascorbic acid, and color degradation were 35, 31.1, 29.8, and 10.4 kcal/mol, respectively. Residual gas volume of 20 cc was the maximum volume studied that accomplished the desired shelf‐life for this product.     

EFFECTS OF PEEL ADDITION AND STORAGE ON QUALITY OF GOLDEN APPLE (SPONDIAS CYTHEREA SONN) HOT SAUCES

Fresh, frozen or brined golden apple puree (Spondias cytherea) was utilized in hot sauces. The effects of puree, fruit peel addition, and storage on quality of sauces was investigated. Base formulation, (%) consisted of golden apple puree (50), water (25), vinegar (10), peppers (6), sucrose (4) aromatic spices (2), citric acid (1.1) sodium chloride (1.0), xanthan gum (0.8) and sodium benzoate (0.1). Processing of hot sauces was at85–90C for15–20 min followed by hot‐filling into glass bottles. Fruits were acceptable in 20% brine up to 6 weeks at28–31C. Physico‐chemical quality of sauces varied due ( >P <0.05) to fruit puree. Sensory quality did not vary (< P >0.05) in sauces with 0% or 5% peel, however, sauces of 100% peel were more yellow ( P <0.05), had lower total soluble solids ( P <0.05) and were less acceptable ( P <0.05). The shelf‐life of sauces was at least 90 days at28–31C or 5C.