金针菇真空冷冻干燥及其蜜饯加工条件的优化

讨论了新鲜金针菇的不同预处理方法及其真空冷冻干燥和蜜饯加工条件的优化。结果表明，预处理采用柠檬酸和抗坏血酸混合液进行护色处理，并用0．5％氯化钙溶液硬化处理；真空冷冻干燥优化条件：物料厚度选定在1cm～1．5cm之间，真空度达65Pa，冷阱温度为-50℃，物料温度为-25℃。时间20h～30h；蜜饯加工采用真空渗糖，其产品质量明显优于未经过优化的产品。     

EGG QUALITY AS AFFECTED BY STORAGE AND HANDLING METHODS

The quality and shelf-life of fresh eggs were studied under simulated climatic conditions as found in Kuwait. Three groups of eggs (unwashed, washed, and washed and oil treated) were used. The treated eggs were stored at 5°, 25°, 37° and 42°C. Internal and external quality and sensory evaluation of the eggs stored up to 75 days were determined. The quality of the unwashed and washed eggs stored at 37°C and 42°C deteriorated rapidly while the wash and oil treatment extended shelf-life but decreased in quality to C over a period of time. The percent weight loss in the oil treated eggs at all temperatures was about 0.6% while the washed and unwashed lost more depending upon the temperature and storage time. All parameters studied for interior quality showed that oil treated eggs were significantly better than untreated eggs even at 42°C. Sensory evaluation on boiled eggs indicated that changes in flavor and overall quality for untreated eggs stored at high temperatures were obvious while little change in texture was observed. It was concluded that under Kuwaiti conditions eggs should be oil treated directly after collection and stored at or below 25°C so that the quality and shelf-life can be extended significantly.     

正交法优化微波提取茶多酚的工艺

对微波提取工艺方法进行改进,并在利用正交法优化常规水提取茶多酚工艺的基础上,进一步优化了微波提取茶多酚的提取工艺.最终确定:常规水提取的最佳提取工艺为:液固比30:1,温度85℃,时间80 min,在此工艺条件下茶多酚提取得率为8.781 9%;微波提取最佳工艺为:液固比25:1,微波功率750W,提取时间14 min,按此工艺进行了重复性验证试验得到茶多酚的平均提取得率为9.603 5%,RSD为0.858 0%.结果表明:在各自最佳工艺条件下,微波提取较常规水提取提高了9.355 6%,而且大大缩短了提取时间,提取结果稳定性极好.     

A COMPREHENSIVE EVALUATION OF EGG AND EGG REPLACERS ON THE PRODUCT QUALITY OF MUFFINS

ABSTRACT

Five muffin formulations, liquid whole egg, dry whole egg, and three commercial egg replacers, which partially replaced egg in the formulations, were evaluated to determine differences in product qualities caused by egg and egg replacers. The products were prepared following the same procedure and other ingredient compositions, except for egg or egg replacer used in the formulation. Physical product characteristics and sensory properties of the samples were evaluated. It was found that egg, as an ingredient in the muffin formulation, is critical to obtain expected product quality characteristics. None of the commercial egg replacers produced acceptable quality muffins at 100% replacement. Partial replacement of egg with commercial egg replacers changed product characteristics altering moisture retention, bulk volume, color, texture and flavor. Some of these differences, however, were not readily detected by the sensory panelists.

PRACTICAL APPLICATIONS

This study comprehensively evaluated the effects of egg and egg replacers on final product quality, when used in pilot‐scale muffin production. An array of tests were conducted on samples prepared according to respective ingredient manufacturers' recommendations – partially replacing egg with commercial egg replacers – to objectively evaluate the differences in quality and sensory attributes. The functionalities of each ingredient (egg replacer) in muffin formulations were interpreted based on the results obtained. The observations and results of this study would be important in selecting appropriate ingredients for muffin formulations to obtain desired product qualities.

     

EFFECTS OF BAKING PARAMETERS ON THE WHITE LAYER CAKE QUALITY BY COMBINED USE OF CONVENTIONAL AND MICROWAVE OVENS

The effects of combined conventional and microwave oven baked white layer cake characteristics were studied. Two types of commercially milled wheat flour, white (A) and whole wheat (B), were used. The modified white layer cake making method was used for conducting the cake baking trials. The conventional baking times (8 or 11 min), microwave power (400 or 600 W) and microwave baking time (30, 40, or 50 s) were chosen as baking parameters. Conventional baking was applied to form the cake crust before baking with the microwave oven used to form the crumb of the cakes. The performance of combination baking was compared with the performance of conventional baking. The volume, bake loss, internal factors, and crust color of cakes were evaluated as quality characteristics. The bake losses of cakes using the combination of short oven times and low microwave power for selected microwave times were smaller than the bake losses of the control cakes for both flours. Long oven times and low microwave power increased the specific volume of cakes. Cakes baked from flours A and B exhibited similar internal properties. Oven time significantly affected the crust color of cakes made with flour A. The crust color of cakes made with flour B was similar to the crust color of control cakes. Using a combination of conventional and microwave baking produces cakes with qualities equivalent to the qualities of cakes produced with conventional baking.     

CHANGES IN QUALITY OF DEHYDRATED KIBBLED ONIONS DURING STORAGE

SUMMARY— Dehydrated kibbled onions. of the Egyptian variety, containing 4-5% moisture, were stored under different conditions and their keeping quality as influenced by storage variables determined. 3 packaging materials, namely cans, polyethylene and Saran pouches were used. Samples were stored at temperatures of 15, 25 and 35°C at 44% relative humidity for 39 wk. Temperature of storage was found to have the largest effect on product quality. The can package was found to be superior to the flexible pouches; however, Saran pouches could be used under certain conditions. Moisture content increased significantly in polyethylene pouches at all temperatures, but in Saran pouches only at 25° C Absorbance of onion extracts, as measure of browning, increased significantly with storage temperature and to a smaller extent due to packaging materials. Products in polyethylene deteriorated most, while the difference between Saran- and can-packed products was small. A similar trend in results was found in tristimulus color determinations. All products stored at 15° C and those in cans at 25°C were found to be of good organoleptic quality. The pyruvic acid development potential could not be used as a sensitive indicator for determination of product quality.     

THE EFFECT OF AIR-DRYING, FREEZE-DRYING AND STORAGE ON THE QUALITY AND ANTIOXIDANT ACTIVITY OF SOME SELECTED BERRIES

The aim of this study was to analyze the effects of air-drying and freeze-drying and subsequent storage of dried products on the content of polyphenols, anthocyanins and the antioxidant properties of selected berry fruits. The material was raspberry ( Rubus ideaus L. ), strawberry ( Fragaria ananassa Duch ) and bilberry ( Vaccinum myrtillus ). Despite exposure to atmospheric oxygen, the stored freeze-dried fruit retained the properties of the raw material better than the air-dried product. In the case of the latter, there were considerable differences in the retention of total polyphenolic and anthocyanin content as well as antioxidant properties in the three fruit species examined. In particular, bilberry maintained a high polyphenol and anthocyanin content and high antioxidant potential despite the greatest losses of these compounds.

PRACTICAL APPLICATIONS

Consumer demand for food with health-promoting qualities is increasing. The food industry has intensified its efforts to provide high quality, semi-processed products that fulfil this requirement. The results presented in this work indicate that even after long-term storage and despite exposure to atmospheric oxygen, freeze-dried berries retain the antioxidant properties of the raw material to a very high degree. Therefore, lyophilisates can satisfy this particular need. Air-dried berries are much less stable during long-term storage. The dynamics of the changes occurring during the storage of both kinds of product are presented in detail.     

果蔬片微波干燥特性及最佳工艺研究

通过对利用微波干燥香蕉片的研究，揭示了微波干燥果蔬片的失水特性。同时，进行四因素三水平的正交实验以及二因素三指标的二次正交回归实验，得出各指标的回归方程，并进行参数优化，从而得到最佳工艺条件：前期发射功率为900W、前期时间2min、后期发射功率397W、后期时间11．3min。     

预处理对冻干黄豆芽品质的影响

主要研究了几种不同的预处理对黄豆芽冻干产品品质的影响.发现,黄豆芽可以不经漂烫处理;而经20%的麦芽糊精、饱和β-环糊精溶液浸泡1h可明显提高产品品质.     

THE STABILITY OF BIOCHEMICAL,MORPHOLOGICAL AND BREWING PROPERTIES OF YEAST CULTURES MAINTAINED BY SUBCULTURING AND FREEZE-DRYING

Yeasts in the National Collection of Yeast Cultures showed substantial variation in biochemical and morphological properties following maintenance by conventional subculturing for prolonged periods. Variation was greatly diminished in yeasts maintained by freeze-drying. Although the initial viability of cultures immediately after freeze-drying had not always been high, only a very small subsequent decrease in viability has been detected after storage for periods of between 10 and 20 years. Detailed study of the properties of brewing yeasts following prolonged storage in the freeze-dried state showed that brewing performance remained unchanged.     

EVALUATION OF EFFECTS OF SOAKING AND PRECOOKING CONDITIONS ON THE QUALITY OF PRECOOKED DEHYDRATED PEA, LENTIL AND CHICKPEA PRODUCTS

Peas, lentils and chickpeas were blanched and soaked in water, then cooked with four different cooking methods and dehydrated in a convection tray dehydrator. Color, splitting and butterflying rate; firmness; and rehydration rate were evaluated. Dehydrated yellow and green peas produced by soaking at 22C for 9 h and 82C for 4 h in 0.07% NaHCO₃ solution, and followed by precooking at 110C for 10 min had the best quality with respect to firmness, splitting and butterflying rate. Dehydrated chickpeas produced by soaking at 22C for 9 h and 82C for 3 h in 0.07% NaHCO₃ solution, and followed by precooking at 110C for 10 min had the best quality. Dehydrated lentils produced by soaking at 22C for 2 h and 82C for 20 min in 0.07% NaHCO₃ solution, and followed by precooking at 106C for 10 min had the best quality.

PRACTICAL APPLICATIONS

Traditionally, soaking and cooking of peas, lentils and chickpeas (PLCs) takes one a long time. It is desirable to manufacture dehydrated precooked PLCs to provide convenience for the users. The objective of this study was to investigate the quality of precooked dehydrated PLCs as affected by processing. The fundamental cooking characteristics of PLCs obtained in this study are very useful for the food industry.