TEXTURAL AND VISCOELASTIC CHANGES OF CANNED BISCUIT DOUGH DURING MICROWAVE AND CONVENTIONAL BAKING

Textural changes of canned biscuit wheat dough during microwave and conventional baking were described and contrasted using empirical methods. Drastic increases of specific volume and modulus of elasticity were observed in the beginning and the ending periods of both baking processes. Weight loss showed a significantly (p < 0.001) linear relationship with baking time for both baking methods, but the weight loss rate constant for microwave baking was 0.36%/s significantly (p<0.01) higher than conventional baking. Multi-dimensional Scaling showed that microwave baking for 50 s best resembles the textural characteristics of wheat dough under conventional baking for 10 min. Stress relaxation modeling indicated that microwave baking produced higher viscosity and modulus of elasticity values which translates into baked biscuits with undesirable tougher texture.     

USE OF THE FARINOGRAPH IN PREDICTING BAKING QUALITY OF UNCHLORINATED AND CHLORINATED FLOURS

The viscoelastic properties of six Coker 916 flours with different protein contents were analyzed along with their baking properties. The wheat grain was grown under different amounts of nitrogen, which resulted in the variation of protein content. A portion of each flour sample was chlorinated, and comparisons were made between viscoelastic properties and baking quality. The farinograph was used to link the data derived from the flour analysis with baking quality. The stability, mixing tolerance index (MTI) and peak time (PT) correlated significantly with baking performance and were also good predictors when testing quality of chlorinated flour. Chlorination increased the absorbency of the flour, which contributed to a firmer crumb and a stable baked product.     

EFFECTS OF MICROWAVE COOKING ON FISH QUALITY

Changes in tenderness, unit proteolytic activity, protein denaturation and fatty acid content of trout (Onchorhyncus mykiss) cooked in microwave oven for different time-power combinations were studied and the relationship between protein denaturation and textural changes was investigated. Trout was cooked in the microwave oven at 20, 40 and 60% powers for 10, 20, 30, 40 s. As a control uncooked fish was used. Proteolysis was controlled by using microwave energy. Texture degradation due to proteolytic enzymes was reduced as microwave power increased. As cooking time and/or power of the microwave oven increased, proteolytic activity decreased which was a sign of the increase in enzyme inactivation. A correlation was found between the variation of texture and proteolytic activity (r = 0.973). It was observed that proteolytic enzymes were effective especially on myosin. Most of the fatty acids were not destroyed during microwave cooking. The optimum cooking conditions in microwave oven were determined as 60% power for 20 s of cooking time.     

小麦加工品质与面包焙烤品质关系的研究

对目前小麦各项加工品质的评价指标及其与面包焙烤品质关系的研究进展进行了较为详细的介绍，分析了蛋白质含量、高分子量麦谷蛋白亚基组成、小麦淀粉含量、小麦粉脂类与面包烘焙品质的关系，以期推动我国小麦品种品质的研究与开发。     

EFFECTS OF WATER AND MICROWAVE ENERGY PRECOOKING ON MICROBIOLOGICAL QUALITY OF CHICKEN PARTS

Hot water precooked chicken parts were consistently lower in bacterial count than the microwave energy cooked samples. The surviving bacteria on the hot water cooked samples belonged to either the genus Micrococcus or the genus Staphylococcus. All colonies were nonpigmented. However, in addition to those bacteria found on the water cooked samples, pigmented staphylococcus and occasionally Gram positive rods were present on the microwave energy cooked samples. Precooking chicken parts in hot 3% polyphosphates solution resulted in an almost sterile product. Polyphosphates were more effective in controlling the growth of micrococcus and staphylococcus, which were the principle microbial flora found on the surface of fresh dressed chicken.     

MICROWAVE AND CONVENTIONAL BLANCHING EFFECTS ON CHEMICAL, SENSORY, AND COLOR CHARACTERISTICS OF FROZEN BROCCOLI

Broccoli (cv. Empress) obtained from a local supplier was blanched within 15 h of harvest. It was blanched by four methods in covered containers: conventional boiling water (1900 mL, 4 min) (BW), steam (300 mL water, 4 min) (ST), microwave heated in 1 L glass containers (60 ml water, 4 min, 700 W) (MW), and microwave heated in 1 L Seal-a-Meal^TM bags (45 ml water, 4 min) (MWB). Aliquots were frozen at -18C for 4 weeks. Fresh unblanched broccoli peroxidase activity ranged from 389 to 829 units/min; activity was essentially zero immediately after all blanching treatments. The highest reduced ascorbic acid (RAA) content occurred in fresh unblanched broccoli. Some peroxidase regeneration occurred during frozen storage. Immediately after blanching, all blanched broccoli had lower RAA content than control broccoli. MW-blanched broccoli retained the greatest amount of RAA and had appearance, visual color, texture scores, and chroma of florets and stems equivalent to ST-blanched broccoli. MW-blanched broccoli had flavor and general acceptability scores similar to BW-blanched broccoli. After 4 weeks in frozen storage, MW-blanched broccoli had the highest RAA content.     

酶制剂对国产面粉烘培品质的影响

主要研究4种酶制剂对国产面粉烘焙品质的影响.研究结果:国产面粉通过添加酶,使其烘焙品质有了明显改善,制作的面包比容、弹性、黏聚性增加;硬度和咀嚼度降低,经改良的国产面粉能制作出高品质面包.     

EFFECT OF COMMERCIAL ENZYMES ON THE BAKING AND KEEPING QUALITY OF A FAT REDUCED MUFFIN

Utilization of a protein-based fat substitute (100% replacement) in a muffin with and without added fungal protease, fungal amylase and/or bacterial amylase was compared with a full fat counterpart. The enzymes were evaluated independently and in combination with each other. Physical tests indicated no significant differences (P>0.05) among any of the variations in volume, crumb L and crust L and b values. The full fat muffin was significantly (P<0.05) more tender, lower in moisture, and more yellow of crumb when compared with the other variations. The 100% fat substituted muffin with enzymes, generally, had a lower moisture content, lower volume, decreased staling rate, and decreased crumb firmness when compared with the 100% fat substituted muffin without enzymes.     

NUTRIENT QUALITY OF SELECTED VEGETABLES PREPARED BY CONVENTIONAL AND COOK-FREEZE METHODS

Selected vegetables (spinach, broccoli, sweet potatoes, and collard greens) prepared in 2.27 kg (5 lb) quantities by boiling, were frozen and stored for six months at ?18°C. Zinc, iron, β-carotene, and ascorbic acid were determined on the raw vegetable immediately after cooking and after reheating in a microwave oven subsequent to 6 months frozen storage. The greatest nutrient loss occurred for water soluble nutrients during boiling. Nutrient comparison between cooked samples (conventional method) and samples microwaved after 6 months frozen storage (cook-freeze method) indicated that differences existed only in ascorbic acid content of spinach. Data indicated that vegetables prepared by cook-freeze, a method used by health care institutions, were generally equal in nutrient quality to conventionally prepared vegetables.     

THE USE OF MULTIVARIATE STATISTICAL ANALYSIS IN DETERMINING THE SENSORY QUALITY OF WHITE MONOVARIETAL WINES

A sensory study of monovarietal white wines (Chardonnay, Garnacha and Macabeo) from two Spanish regions (Aragón and Navarra) was carried out. Among the three varieties, Chardonnay wines made the best organoleptic impression. Linear correlation showed quality of taste and acidity were the attributes that correlated well with overall impression. Except for color, no attribute examined differed significantly by region. Factorial analysis, applied to the volatile components of Chardonnay, followed by stepwise regression, revealed that the quality of aroma was related to certain major and minor chemical sets. Scores for the quality of Chardonnay wines decreased under the influence of ethyl propanoate, l‐propanol, glycerine and 2,3 butanediol. Minor set, MN2, and major set, M1, were related to fruity and vegetable aromas. Those two chemical sets had a positive influence on the aromatic quality of Chardonnay wines.