CHANGES IN FLAVOR ATTRIBUTES DURING RIPENING OF FERMENTED SAUSAGES

Production of flavor-related compounds (amines and short-chain fatty acids) was followed throughout the ripening of a fermented sausage, and related to populations of two spoilage microorganisms (pseudomonds and Brochothrix thermosphacta) and lactic acid bacteria (LAB). Changes in pH, acidity, degree of oxidation and water activity were observed. Although spoilage microorganisms were present through ripening to 30 days, no off-odor was detected. The antibacterial activity of LAB, including Lactobacillus plantarum, was caused by a lower pH, as well as lactic acid, bacteriophage, and bacteriocin-like compounds synthesized by the strain. The concentration of short-chain fatty acids, mainly acetic acid, increased toward the end of the study time as a consequence of microbial metabolism. Putrescine and cadaverine, produced by Bacillaceae, increased during the first six days of storage, remaining constant through 30 days of ripening. Tyramine, a metabolic product of lactic acid baceria decreased after 24 days of storage.     

CHANGES IN QUALITY ATTRIBUTES OF LONGAN JUICE DURING STORAGE IN RELATION TO EFFECTS OF THERMAL PROCESSING

Longan juice is accepted gradually by consumers due to its unique succulent, sweet and aromatic flavor. The effects of thermal processing (91C, 20 min) on quality related attributes (color, translucency, total soluble solids, total acidity, reducing sugars, ascorbic acid, phenolic compounds, protein and pectin) of longan juice during storage at low temperature were investigated. The heat-treated longan juice had a higher translucency and lower concentrations of pectin, phenolic compounds and proteins of longan juice, compared with the nonheat-treated juice. Furthermore, the thermal processing maintained higher concentrations of total soluble solids and total acidity but a lower ascorbic acid concentration. However, the thermal processing had no significant effects on reducing sugar concentration. Overall, the thermal processing maintained effectively color appearance and nutritional attributes such as total soluble solids and total acidity of longan juice during storage at low temperature. These results suggest that the thermal processing exhibits a potential for quality maintenance of longan juice.

PRACTICAL APPLICATIONS

Browning and turbidity are the major factor to influence quality of fruit juice during storage. Thermal processing is generally applied to improve quality and extend shelf life of fruit-related products. In this study, application of thermal processing exhibited potential for quality maintenance of longan juice in terms of evaluations of color, translucency and concentrations of total soluble solids, total acidity, reducing sugars, ascorbic acid, phenolic compounds, protein and pectin. The information obtained from this study could be used as a guideline for designing thermal processing to control the quality of longan juice.     

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.     

EVALUATION OF TIME-TEMPERATURE RELATED QUALITY CHANGES IN ICE CREAM DURING STORAGE

The keeping quality of vanilla-flavored ice cream was investigated during 21 weeks of storage. Ice cream samples at 4 different temperature treatments were evaluated for 3 attributes by 14 judges using a deviation-from-reference scale. Sampling tools and presentation containers were designed to provide uniform samples and serving temperatures without melting. The ice cream kept at a variable storage treatment showed a trend toward becoming less firm and darker in yellow than the other samples from the 86th day of storage onward. Differences in creaminess, hardness, and vanilla flavor were noticed in ice cream after 170 days of storage. A commercial time-temperature indicator was used to monitor temperature exposure; but, since indicator response was slower than published, no correlations could be made with quality changes.     

鲜食核桃贮藏中脂肪酶活性及油脂酸价变化

对贮藏中影响鲜食核桃脂肪酶活性与油脂酸价的因素进行了研究。发现贮藏温度、包装袋有无对脂肪酶活性影响显著（P〈0．05），缝合线紧密度对脂肪酶的活性影响不显著，贮藏温度、缝合线紧密度、包装袋有无对油脂酸价的影响显著（P〈0．05），核桃油脂酸价随着脂肪酶活性的增大而上升。     

延(边)黄牛发酵牛肉干贮藏期间品质研究

对发酵牛肉干与传统牛肉干在贮藏期间品质进行研究.发酵牛肉干分别用泡菜汁、植物乳杆菌作为发酵剂.将乳酸菌发酵牛肉干、泡菜发酵牛肉干和传统牛肉干真空包装后放入4℃冰箱中贮藏6个月,每个月对其细菌菌落总数、一般营养成分(水分含量、粗蛋白含量、粗脂肪含量、粗灰分含量)及嫩度进行测定.结果表明:3种牛肉干细菌菌落数均未超标;水分有所下降,灰分、蛋白质和脂肪含量相对升高;发酵牛肉干能明显改善牛肉干嫩度.     

CHANGES IN THE RESPONSE TO GIBBERELLIC ACID OF BARLEY ENDOSPERM SLICES DURING STORAGE

Endosperm slices representative of freshly harvested as compared with stored barleys produce relatively little α-amylase when treated with gibberellic acid (GA). The response is improved by suitable storage, by heating or by procedures which increase oxygen supply to the aleurone cells. No difference could be detected in the response to GA of the dehusked corns of the two types of barley. It appeared that the outer coverings of the freshly harvested barley restrict the permeability to oxygen to a greater extent than those of stored barley, possibly because of higher microbial activity.     

QUALITY CHANGES OF FRESH-CUT HONEYDEW MELONS DURING CONTROLLED ATMOSPHERE STORAGE

Quality, physiology, and microbial population were monitored with honeydew cubes held in air or controlled atmosphere (CA) of 2% 0₂+ 10% CO₂ at 5C and 4%0₂+ 10% CO₂ at 10C. The CA was beneficial in maintaining quality of honeydew cubes. Quality deteriorated rapidly with concomitant increase in respiration rate during the latter half of the 6-day at 10C or 10-day at 5C shelf-life. The shear force of samples was maintained by CA at 10C, but the visual quality was poor when that benefit was still noticeable. At 5C, an effect ofCA was not noted because the low temperature did not allow the shear force to decrease. The bacterial population was less on honeydew cubes held in CA than in air. Modified atmosphere with these gas mixtures would be beneficial in maintaining quality and retarding microbial growth on honeydew cubes, but strict temperature control is essential to avoid anaerobic respiration.     

冷藏鲜肉中腐败乳酸菌的分离及鉴定

利用稀释平板法从冷藏3 d的肉样品中共分离出60株疑似乳酸菌菌株,经过2次划线分离,然后进行革兰氏染色、镜栓、过氧化氢酶试验、明胶液化试验、硝酸盐还原试验和H2S检验,得到36株乳酸菌.将分离出的这36株乳酸菌,经过形态学和生理生化鉴定,确定他们属于5大类,即清酒乳杆菌,13株;马里乳杆菌,8株;消化乳杆菌,7株;口乳杆菌,4株;未知乳杆菌,4株.     

QUALITY ATTRIBUTES, PECTOLYTIC ENZYME ACTIVITIES AND PHYSIOLOGICAL CHANGES DURING POSTHARVEST RIPENING OF NECTARINE

The postharvest ripening at 20C and 90–95% RH for 10 days of ‘Armking’ nectarine grown in a greenhouse was investigated over two seasons. Firmness, titratable acidity, ascorbic acid, pH and maturity index were all adequate to stablish the rate of ripening. However, soluble solids content and reducing and non-reducing sugars showed no significant changes. It took about 10 days for very early ripening fruit (100 g weight and 82 N firmness) and 6 days for normal early ripening fruits (115 g weight and 46 N firmness), both harvested at preclimacteric stage, to become eating ripe (near 20 N). Total weight loss and decay after 10 days was approximately 11%. During ripening there was a temporal coincidence among higher rates of ethyleneproduction, higher pectinmethylesterase (PME) and polygalacturonase (PG) activities, lower firmness and acidity and higher maturity index. PME and PG activities increased during ripening, with a highly negative linear correlation between activities of the two enzymes and firmness. In very early ripening fruit, PME activity was more closely related to softening than PG, whereas in normal early ripeningfruit, PG activity was slightly more closely linked to the loss offirmness than PME.     

DEAN QUALITY: CHANGES IN HPLC PROFILES OF ACETIC ACID-EXTRACTABLE PROTEINS DURING STORAGE1

Samples of black beans (Phaseolus vulgaris L. cv. Orfeo) either dried in the field or by using heat treatment were stored for 3, 6 and 9 months under normal (15°C, 35% RH) and extreme conditions (30°C, 85% RH) to produce cotyledon hardness. After storage the cotyledon proteins were extracted with 5M acetic acid solution and the clarified extracts were analyzed by reversed-phase HPLC. The two drying procedures did not affect the HPLC chromatographic data. Samples that showed a gradual increase in cotyledon hardness showed quantitative and qualitative changes in HPLC chromatograms. Overall extractability of proteins was reduced in samples stored for nine months under high temperature and high humidity.     

FLAVOR AND QUALITY CHANGES IN SWEET ONIONS DURING STORAGE AT ROOM TEMPERATURE

Flavor and quality parameters of onions (Allium cepa ‘Walla Walla Sweet’) were monitored for up to 7 weeks following harvest. Shelf-life of bulbs harvested earlier in the season was shorter than that of onions harvested 3 weeks later. Soluble solids of inner scales and average pyruvate, 3,4-dimethyl thiophene and disulfides content increased during the 4 week shelf-life at 22C of the onions harvested in June. These increases resulted in the final contents to be comparable to those of onions harvested on July 2, 1992, which were relatively stable. The pyruvate concentration was comparable to that of a mild, nonpungent onion. Correlations between pyruvate, thiophene and soluble solids were not significant. The relationship between 3,4-dimethyl thiophene, disulfides and onion flavor is discussed.     

凤梨南瓜乳酸发酵保健饮料的研制

以凤梨、南瓜为主要原料，研制发酵型乳酸饮料，用正交试验确定其最佳工艺条件为：凤梨汁：南瓜汁=1：2．混合发酵剂用量为6％，发酵时间为24h。产品具有风味独特、酸甜适口、营养丰富的特性。     

ACID PH PRODUCED BY LACTIC ACID BACTERIA PREVENT THE GROWTH OF BACILLUS CEREUS IN BOZA, A TRADITIONAL FERMENTED TURKISH BEVERAGE

The growth and survival of Bacillus cereus, a known pathogen commonly found in cereals, during lactic acid fermentation of boza, a traditional Turkish cereal beverage, was studied. In the boza base inoculated with both the starter culture and B. cereus, the acidity developed to pH 2.6 and 0.8% titratable acidity after 72 h; the growth of B. cereus was reduced from 3.9 log cfu/mL to 1 log cfu/mL within 72 h. The control boza base to which starter was not added had a pH of 3, titratable acidity of 0.8%. The B. cereus in this boza base to which no starter culture was added dropped to 1 log cfu/mL after 72 h. No strains of lactic acid bacteria were found to produce bacteriocins antagonistic to B. cereus. Low pH and acidity were found to be the major factors inhibiting growth of B. cereus in boza.     

CHANGES IN SOYMILK QUALITY AS A FUNCTION OF COMPOSITION AND STORAGE

ABSTRACT

Three soymilk products formulated with different concentrations of fat, sugar and starch were evaluated for changes in their physical properties and volatiles profile over time (3 months) under different temperatures (4, 22 and 38C) of storage. Samples were tested for pH, color, viscosity and volatile flavor changes. The pH and color of the soymilks decreased significantly during the first month of storage and then remained stable over time. Color and viscosity of the soymilk products were affected by both the soymilk composition and storage treatment. The high‐fat soymilk sample (product C) had the whitest color (lower ΔE) and the lowest viscosity. Storage at 38C negatively affected the color. The viscosities of the soymilk products stored at 4C were the lowest among the treatments. The major volatiles identified in all soymilk products were hexanal, heptanal, octanal, nonanal, hexanol, 1‐octen‐3‐ol, benzaldehyde, 2‐pentyl furan and 2‐ethyl furan. The intensities of the volatile compounds in the soymilk products increased during the first weeks of storage, particularly when stored at 38C. The intensities, however, decreased gradually over time. Among the three formulated soymilk products, the sweetened sample (product B) gave the lowest flavor intensities under all three temperatures of storage. Overall, storage at 4C and addition of sugar preserve best the soymilk quality.

PRACTICAL APPLICATIONS

Soy products are well appreciated for their nutritional and potential health benefits. Soy beverage consumption is increasing among North American consumers because of improvements in soy beverage quality and processing technologies. There is, however, a demand for new value‐added soy‐based drinks with improved “functional” (health‐benefiting) properties. Soy beverage could be an excellent carrier for “functional” or “nutritive” ingredients such as minerals, vitamins and omega 3 oils; however, addition of such ingredients may affect the stability of the product and requires the development appropriate of technologies for their incorporation. Results from this project provide new knowledge on the storage stability and quality of three different soy product formulations. The information could be useful in the establishment of optimal conditions for processing of functional soy beverages, for use by the food industry.