AN ENDO-POLYGALACTURONASE IN CUCUMBER FRUIT1

A homogenous endo-polygalacturonase (EC 3.2.1.15,) has been isolated from mature pickling cucumbers. This is the first report of an endo-polygalacturonase in cucumbers. The enzyme was purified by three chromatography steps on Sephadex cation exchangers. The molecular weight is 35,000 daltons. With polygalacturonic acid as the substrate at an ionic strength (μ) of 0.15, the pH optimum is 5.6. The enzyme is not active atμ= 0.027. Maximum activity occurred atμ= 0.2. The half-life of the enzyme is 1.2 min at 70°C in pH 5.2, 0.1 M acetate buffer. An inhibitor, isolated from the sericea lespedeza, which inhibits polygalacturonases from fungal sources, also inhibits the cucumber enzyme. This enzyme may be involved in tissue breakdown during the latter stages of fruit development.     

METHOD FOR DETERMINATION OF FIRMNESS IN CUCUMBER SLICES1

A punch and die assembly was adapted to the Instron UTM for deter-mination of firmness of mesocarp and endocarp tissues in cucumber slices. A cylindricalpunch 0.315 cm diameter (0.200 to 0.635 cm diameter tested) and a cucumber slice thickness of at least 0.48 cm were found to be suitable for the method developed. Penetration force was about five times greater for mesocarp than endocarp in 4 to 5 cm diameter cucumbers. Mesocarp and endocarp were firmer near the stem end than near the blossom end of cucumbers. Force readings also declined for both tissues with increase in fruit diameter from about 2 to 6 em. Single slices taken from the center of 20 cucumbers and punched once each at specified locations in the mesocarp and endocarp provided sufficient sampling to limit the coefficient of variation to about 5%. The correlation coefficient between sensory analysis for firmness and puncture force readings of fermented cucumber slices was 0.88.     

INFLUENCE OF THE SKIN ON PUNCTURE PROPERTIES OF CHILLED AND NONCHILLED TOMATO FRUIT

The puncture properties (firmness, toughness) of tomato skin and its influence on the overall puncture properties of mature-green fruit during ambient temperature (22C) ripening or chilled (5C) storage were estimated from the difference between whole fruit puncture force-deformation behaviour and that measured with the skin removed. Although the firmness of the skin of nonchilled fruit did not change significantly (p > 0.05) over 28 days of ripening, its contribution to overall puncture firmness increased from about 25 to 70%. Both skin toughness and its contribution to overall puncture toughness doubled within the first week of ripening of nonchilled fruit. The firmness of chilled fruit skin decreased (p > 0.05) only after 16 days of storage, but its contribution to overall puncture firmness remained constant at 25–30%. Both the toughness of the skin of chilled fruit and its contribution to overall puncture toughness remained constant during storage. Possible artifacts in the measurement of puncture properties of chilled fruit are discussed. The results are consistent with a toughening of tomato skin during early stages of ripening of nonchilled fruit that somewhat compensates for a rapid reduction in pericarp tissue integrity, and with an increase in firmness or rigidity of tomato skin and underlying tissue(s) during chilled storage of fruit.     

ZJS88－1型杏仁软皮脱皮机的研制

杏仁是人们喜爱的营养保健食品，杏仁软皮的脱除是杏仁加工中要解决的关键问题。本文论述了杏仁软皮的摩擦脱除机理，介绍了ＺＪＳ８８－１型杏仁软皮脱皮机柔性硬摩擦装置及脱皮机结构材点。生产试用及其机器性能测试结果表明：该脱皮机结构合理，性能良好，并适用于类似食品的脱皮加工，具有较广的使用价值。     

果蔬保鲜膜的保鲜机理与研究进展

综述果蔬保鲜膜的保鲜机理,介绍果蔬保鲜膜先后出现的硅窗调气薄膜、微孔果蔬保鲜膜、可食性果蔬保鲜膜、抗菌保鲜膜的主要性能、特点及其应用现状,并简要分析果蔬保鲜膜今后的发展趋势。     

LIPIDS IN SUBCUTANEOUS TISSUES AND LONGISSIMUS MUSCLES OF FEEDLOT AND GRASS-FED EWES1

Subcutaneous and intramuscular lipids from feedlot-and grass-fed ewes were studied to determine if diet would influence fatty acid composition of these older animals. Subcutaneous lipid of ewes from the feedlot-fed group contained more 4-methyl branched acids, less iso and anteiso branched acids, less stearic acid and more octadecenoic acid than grass-fed ewes. Only small amounts of medium chain acids (10–15 carbons) were noted in longissimus muscle lipids from both dietary groups and essentially all of them were in the triglycerides. Lipids in longissimus muscle of feedlot ewes contained more monounsaturated and less polyunsaturated acids and this was due to higher levels of triglycerides in longissimus lipid of feedlot-fed ewes. Approximately three times as much high melting stearic acid was present in subcutaneous lipid of both dietary groups of ewes as has been noted in subcutaneous lipid of lambs. Reduction of high melting stearic acid in mutton fat by a short grain feeding period should make mutton more acceptable.     

高效液相色谱法测定蜜饯中食用合成色素

建立了蜜饯中食用合成色素（柠檬黄、苋菜红、胭脂红、日落黄、亮蓝）的高效液相色谱测定方法，采用C18（4.6mm×200mm，5μm）色谱柱，甲醇和乙酸铵为流动相，流速为1．0mL/min，柱温30℃，梯度洗脱程序为：甲醇＋0．02mol／L乙酸铵，6％～40％甲醇，2．8％／min；40％～60％醇，2．5％／min；60％甲醇，3min；6％甲醇，7min；检测波长：0min～5．5min，430nm；5．51min～8．0min，520nm；8．01min-10．0min，510nm；10．01min-13min，480nm；13．01min-20min，600nm。确定了蜜饯中合成色素的前处理方法。本方法具有灵敏度高，干扰少，色素回收率高的优点。     

MINERALS AND XENOBIOTIC RESIDUES IN THE EDIBLE TISSUES OF WILD AND POND-RAISED LOUISIANA CRAYFISH1

The popularity of Cajun cuisine has promoted the consumption of Louisiana crayfish, Procambarus clarkii. Tail meat and hepatopancreatic tissues of crayfish captured from two locations in the Atchafalaya River Basin and four open ponds were analyzed separately for xenobiotic metal and mineral composition using an inductively coupled plasma emission spectrometer (ICP) and chlorinated hydrocarbons by gas chromatograph (GC) with electron capture detector. Less than 3 mg/kg of toxic xenobiotic metals were found in the tail meats and less than 5 mg/kg in the hepatopancreatic tissues. Mineral concentrations were similar to those reported for other crustacean species. Occasional trace amounts of DDD and DDE were found present in tissue samples.     

DISTRIBUTION OF OCHRATOXIN A IN CHICKEN TISSUES AND EGGS

The kinetics of distribution of ochratoxin A (OA) in chicken tissues was studied. Day-old chicks were fed a starter diet alone or containing 1 ppm OA. After 5 weeks, all chicks were intubated with 50 μg ³H-OA per chick. The highest level of radioactivity was found in kidney and liver 8 hr after intubation. Peak levels of OA in kidney, liver and breast were found to be 12, 4, and 0.2 ppb, respectively. Over 90% of the radioactivity was eliminated 48 hr after intubation. Moreover, when laying hens were fed a diet containing 0.5 or 5.0 ppm of OA for 2 weeks, the highest levels of OA were found in the kidney (124 ppb) and liver (80 ppb) also. Levels of OA in breast, leg and eggs of laying hens were found to be 8, 7, and 2.8 ppb, respectively.     

A COMPARISON OF FRUIT OF HIGHBUSH AND RABBITEYE BLUEBERRY CULTIVARS1

In 1986, 1988 and 1989, fruit from highbush blueberry (Vaccinium corymbosum L., cvs Collins, Bluecrop, and Herbert) and rabbiteye blueberry (V. ashei Reade, cvs Climax, Tifblue, and Menditoo) grown at the same location were compared for size, raw product quality, storage, and sensory attributes. Compared with rabbiteye blueberry fruit, fruit of highbush cvs were generally larger in size, volume, and surface area and higher in titratable acidity, higher Hunter color attributes of ‘L’, ‘a’, ‘b’, and chroma, protein, P, Ca, Mg, Mn, Fe, Cu, B (dry wt. basis), and higher in decay and water loss after 3 weeks storage at 7 C. Rabbiteye fruit, compared with highbush fruit, were generally higher in pulp pH, percent soluble solids, percent dry matter, seed weight per fruit, weight per seed, fruit height/width ratio, periderm dry weight per fruit, periderm wt. per surface area (in mg/cm²), sugar:acid ratio, firmness (as shear), and in sensory seediness. Fruit soluble solids, dry matter, hue, titratable acidity, pulp pH, and firmness of both species were influenced by weather (years).     

COMPOSITION OF THE LIPIDS OF CUCUMBER AND PEPPERS

SUMMARY— Cucumber and green peppers contain 103 mg and 400 mg total lipid per 100g raw vegetable tissue. The neutral lipids, phospholipids and glycolipids comprise 39, 49 and 15% of the cucumber lipids and 82, 2 and 16% of the pepper lipids respectively. The neutral lipids of both were composed mainly of glycerides. In the peppers the triglycerides accounted for 60% of the total lipids. Cucumber, had less glycerides but contained several unidentified sterols. Phosphatidylcholine was the major class in both vegetables accounting for 46 and 76% of the phospholipids of cucumber and pepper respectively. Palmitic, linoleic and linolenic acids were the principal fatty acid components. The lipids of peppers were very rich in linoleic acid (70%) whereas those of the cucumbers contained relatively more linolenic acid.     

THE CYTOCHEMICAL LOCALIZATION OF PEROXIDASE IN TOMATO FRUIT CELLS1

The localization of peroxidase activity a t the ultrastructural level in tomato fruit (Lycopersicon esculentum Mill cv. Walters) has been accomplished using the diaminobenzidine histochemical reaction. In immature tomato fruit the peroxidase activity was most prominent at the inner surface of the tonoplast, although some cell wall activity was observed. However, in mature tomato fruit most of the peroxidase activity was localized in the cell wall. No activity was found in organelles or in the cytoplasm of either immature or mature fruit. The significance of these observations is discussed in relation to the physiological role of the enzyme in fruit ripening.     

TEXTURE AND STRUCTURE OF CRISPY-PUFFED FOOD PRODUCTS PART II: MECHANICAL PROPERTIES IN PUNCTURE

A puncture test was used to describe the mechanical and textural behavior of crispy-puffed food extrudates. Four criteria were identified from the force-time curves: (1) the average puncturing force, F_m, (2) the spatial frequency of structural ruptures, N_wr, (3) the average specific force of structural ruptures, f_wr, and (4) the crispness work, W_c. The discriminating power of these criteria was shown through the effects of moisture content and recipe composition in the extrusion-cooking process. Relationships between puncture criteria were also studied. The effect of water activity showed that the force related criteria described well the mechanical behavior of expanded extrudates.