PEELING AND THE PHYSICAL AND CHEMICAL PROPERTIES OF KIWI FRUIT

Hand peeling of kiwi fruit has some disadvantages such as difficulty during peeling, increase of loss in weight and nutritional value. Peeling of kiwi fruits with alkali (NaOH) was investigated. Some chemical (acidity, pectin, and chlorophyll) and physical properties (Hunter color value and weight loss) of the fruits were determined after selected alkali peeling methods were used. Peeling methods at 80, 90 or 100C temperatures; in 13, 18 or 23% of NaOH solutions and for 3, 4 or 5 min durations were tested and compared with hand peeling. Weight (fruit tissue) loss in hand peeling was higher than alkali peeling. Peeling with alkali was easier. Nutritional value (ascorbic acid content) of alkali peeled fruits was higher than hand peeled kiwi fruit. Because of less weight loss, better green color and high pectin content the method including 15% of NaOH solution at 95C for 4 min was selected as most advantageous peeling method.     

EXTRACTION OF ACID-SOLUBLE COLLAGEN FROM GRASS CARP (CTENOPHARYNGODON IDELLA) SKIN

Grass carp is a freshwater fish species widely known by consumers over the world. Its skin has abundant collagen which has many healthy effects. Four variables (acetic acid concentration, temperature, time, solvent to material ratio) were taken to investigate their effects on the extraction efficiency of collagen from grass carp skin. From the results obtained, each of them showed a significant role in the extraction. The yield of collagen increased with the increase of acetic acid concentration to 0.5 M, and thereafter decreased. Elevation of temperature during extraction could also lead to the increase of collagen yield. However, when the temperature was above 20C, a negative effect was observed. The yield of collagen increased with the extension of time, especially when the time was shorter than 24 h. A positive relation was also observed between solvent to material ratio and yield of collagen.

PRACTICAL APPLICATIONS

Grass carp is widely consumed over the world for its delicious taste and healthy effect. A large amount of collagen exists in the skin tissues. Development of collagen from grass carp skin can bring added value for the fish processing industry. In this work, extraction of collagen from grass carp skin was investigated and effects of acetic acid concentration, temperature, time and solvent to material ratio on the extraction efficiency were determined. The results indicated that the above variables were influential for the extraction process. It is important to define the level of these variables in practical application so that the extraction efficiency can be improved, and a time-saving, cost-efficient process can be obtained.     

IMMUNOLOGICAL AND CYTOPATHOGENIC PROPERTIES OF LISTERIA MONOCYTOGENES ISOLATED FROM NATURALLY CONTAMINATED MEATS

Meat products have been implicated as the potential source of Listeria monocytogenes infection in humans. Here, we investigated the incidence of this organism in raw beef and poultry meat products and assessed their biochemical, immunological and cytopathogenic properties. Forty meat samples (20 beef and 20 poultry) were analyzed and the isolates were tested for sugar fermentation, hemolysin production, phospholipase activity, serotype profile, abilities to react with Listeria- specific monoclonal antibodies (MAbs) EM-7G1 and C11E9, and cytotoxic effects on hybridoma Ped-2E9 cells. Thirteen (6 beef and 7 poultry) meat samples (32.5%) were positive for L. monocytogenes. A total of 276 Listeria isolates were obtained, of which 182 (66%) were confirmed to be L. monocytogenes, 80 (29%) were L. innocua, 12 (4.3%) were L. welshimeri and 2 (0.7%) were identified as L. grayi. Fifty six percent of the L. monocytogenes isolates were serotype 4, while 42% were serotype 1, and 2% were untypeable. All but two L. monocytogenes isolates were hemolytic and phospholipase positive (99%). In the ELISA assay, MAb C11E9 showed reaction with L. monocytogenes isolates from all 13 positive meat samples (100%), while MAb EM-7G1 reacted positively with 12 of 13 positive meat samples (92.3%). Hemolysin-positive L. monocytogenes isolates were cytopathogenic to Ped-2E9 cells, while hemolysin-negative strains showed no effect. This study demonstrated that 32.5% of commercially purchased raw meat products were contaminated with cytopathogenic L. monocytogenes strains, and could be a potential source for infection in susceptible populations if these meats were not processed or cooked properly.     

EVALUATION OF THE PHYSICAL,CHEMICAL AND SENSORY PROPERTIES OF JERKY PROCESSED FROM EMU,BEEF, AND TURKEY1

Three jerky formulations were prepared from beef top round, turkey breast, and various emu cuts (inner mid drum, inner outside drum, oyster, and fan fillet). The meat sources were sliced, cured, smoked, and dried. All treatments were evaluated for palatability traits, shear force and chemical properties. No significant difference was found in the sodium or ash levels among the three treatments. Beef jerky had the highest percentage fat followed by emu, and then turkey (p < 0.05). Emu jerky was the toughest, chewiest, and most desirable as evaluated by a trained and consumer sensory panels. The production of emu jerky may be of particular interest to the emu industry to increase profits by utilizing less desirable cuts and opening a new market for the meat obtained from the emu. The information provided by this study can be utilized by emu producers and product marketers for the advancement of the emu industry.     

CHEMICAL AND PHYSICAL PROPERTIES OF PLASTIC FAT PRODUCTS SOLD IN MALAYSIA

Five domestic and four imported Malaysian plastic fat products and their separated high melting point triacylglycerols (HMG) were analyzed for their chemical and physical characteristics. Chemical characteristics consisted of fatty acid (FA) and triacylglycerol (by TG carbon number) composition. Physical characteristics encompassed dropping and softening points, solid fat content, polymorphic crystal habit and DSC melting and crystallization patterns. β crystal habit was related to high levels of 16 or 18 carbon fatty acids in the HMG and high levels of TG48 or TG54 which are β tending. Domestic products contained very low levels of trans fatty acids; they were blends of natural fats such as palm oil, palm kernel and milk fat. Levels of the individual fats in the blends were estimated by means of FA and TG composition analyses. The content of solid fat, determined by the AOCS method, was much lower than that obtained by the IUPAC method. Texture at 23C of products, as determined by penetrometer test of the original materials, was similar for all products.     

棉籽蛋白提取工艺及其主要理化性质研究

对棉籽蛋白的提取工艺条件进行研究,并对所提取的蛋白的等电点、变性温度及分子量分布等主要理化特性进行探讨.结果表明,棉籽蛋白提取的最佳工艺条件为:pH值10,温度40℃,料液比10:1,浸提时间60min,此时蛋白质的提取率为755%;所提棉籽蛋白的等电点在5.00左右,变性温度为67.23℃,SDS-PAGE电泳图谱中主要有9条蛋白谱带,所对应的亚基相对分子量,从上至下依次约为55400、46600、36400、29100、27300、24200、18200、16300、14600u.     

两种干酪在成熟过程中理化性质变化

对鹰嘴豆复合干酪与牛乳干酪成熟过程中的理化性质变化进行研究.通过对比试验,得出以下结论:两种干酪在成熟过程中水分含量均呈下降趋势,复合干酪的水分含量高于牛乳干酪;脂肪、蛋白质含量和酸度均呈缓慢增加趋势,复合干酪的脂肪、蛋白质含量及酸度均低于牛乳干酪.     

QUALITATIVE AND QUANTITATIVE EVALUATION OF POMELO MATURITY USING MULTIVARIATE COMBINATION OF CHEMICAL AND PHYSICAL PROPERTIES

The present study reports the use of multivariate data analysis in combining physical and chemical properties for qualitative and quantitative evaluation of pomelo maturity. Pomelos of "Thong Dee" variety were harvested at four stages of maturity: immature, early mature, late mature and over-mature. The categories of maturity were classified with discriminant analyses on all variables and only nondestructive variables. The accuracy of classification using nondestructive variables (80.0%) was comparable to that using all variables (85.0%). For the estimation of the ratio of soluble solids content to acidity designated as a maturity measure, partial least squares regression models were developed based on either all remaining variables or nondestructive variables. The predictive performances by the two models were not significantly different. The acoustic response characterized by the third resonant frequency was shown to be the most important variable in qualitative and quantitative assessment of pomelo maturity.

PRACTICAL APPLICATIONS

The results of the current study present a number of nondestructive parameters that are associated with pomelo maturity. They can be used to develop an on-line grading machine for pomelos.     

THE PHYSICAL PROPERTIES OF MILK FATS OF DIFFERENT CHEMICAL COMPOSITIONS

A series of milk fats of different fatty acid composition has been obtained by supplementing the diet of the dairy cow with tallow, a mixture of palm oil/palmitic acid or soya oil. The melting behaviour of the milk fats has been studied using the differential scanning calorimeter. Dietary soya oil yielded a butterfat which was fairly soft (50 per cent of the crystalline material melting at 8^oC), whilst palm oil/palmitic acid gave a relatively hard butterfat (50 per cent of the crystalline material melting at 18-3^oC), with the product derived from feeding tallow intermediate between these extremes, but closer in its behaviour to the butterfat obtained by feeding palm oil/palmitic acid. In order to eliminate the effect on the melting behaviour of milk fat triglycerides having non-random structures, thermograms were also obtained for samples of the experimental butterfats after they had been inter-esterified. The results suggest that, for the milk fats having the compositions used in this work, melting behaviour is dominated by the proportion of palmitic acid present.     

PHYSICAL,CHEMICAL AND SENSORY PROPERTIES OF SUGAR‐FREE JELLY*

The increase in diabetes and obesity has increased the demand for sugar‐free/low‐calorie products. Three jelly formulations were prepared using sucralose, low‐methoxyl pectin and maltodextrin with either xanthan gum or locust bean gum (LBG) used singly or in combination and stored at 4C or 43C for shelf life evaluation. Jelly treatments were evaluated for chemical, physical and sensory properties. The combination of xanthan gum and LBG significantly reduced syneresis compared with either gum used singly. The combination of xanthan gum and LBG resulted in significantly higher firmness and springiness values than using xanthan gum or LBG alone. The overall acceptability, aroma, taste, texture, spreadability and sensory attributes for no sugar‐added grape jelly averaged 5.8–6.4 in a 9‐point hedonic scale consumer acceptance study.