EFFECT OF HIGH PRESSURE PROCESSING ON THE TEXTURE OF SELECTED FRUITS AND VEGETABLES

Prepared fruits and vegetables were subjected to high pressure processing at 100–400 MPa for 5–60 min in an isostatic press and their influence on product texture was evaluated. Pressure had a dual effect on product texture characterized by an initial loss in texture, ascribed to the instantaneous pulse action of pressure, followed by a more gradual change as a result of pressure-hold. The extent of the initial loss and the subsequent partial recovery were pressure dependent with the former more prominent at higher pressures and the latter at lower pressures. The pressure treated samples were generally brighter in color somewhat resembling the appearance of mildly heat treated samples. For all vegetables pressure treated at 100 MPa for 60 min, the initial loss in texture was totally recovered during the pressure hold yielding an overall texture firmer than that of the raw product. There was no recovery of texture during the standing period at atmospheric pressure after the pressure treatment.     

EFFECT OF STORAGE AND DACUS INFECTION OF OLIVE FRUITS ON THE QUALITY OF THE PRODUCED VIRGIN OLIVE OIL

Olives from three different locations ( Olea europaea cv. Koroneiki), uninfected or infected by the insect Dacus oleae, were collected and stored at 15°2C for 21 days. Samples were taken at 0, 3, 7, 10, 12, 14, 17 and 21 days following collection. Moisture and oil content of olive fruits and the quality parameters of the extracted virgin olive oil were evaluated. Analytical parameters determined were titratable acidity, peroxide value and the specific extinction coefficients at 232 nm (K₂₃₂ and 270 nm (K₂₇₀). Regression equations and best fitting curves between examined parameters and time were evaluated. Olive oil from fly infected olives had higher initial values and a higher rate of increase of the parameters measured. The only parameter affecting oil quality was K₂₇₀. Maximum storage time within legal limit for K₂₇₀ was 16 days for fly uninfected and 10 days for fly infected olives.     

EFFECT OF A HIGHWAY'S TRAFFIC ON THE LEVEL OF LEAD AND CADMIUM IN FRUITS AND VEGETABLES GROWN ALONG THE ROADSIDES

Samples of fruits (grapes, pomegranates, and tomatoes), and vegetables (onions, potatoes, and spinach) were collected directly from randomly selected commercial farms along the Tripoli-Zawiya major road, at the appropriate harvest seasons, during the period of May through November 1988. The objective was to determine the extent of contamination of the crops with toxic heavy metals, lead and cadmium, from traffic emissions. For the purpose of comparison, similar crops were collected, within the same periods, from farms in Waddy Al-Rabia, far away from any major road.
The samples were dry-ashed, and analyzed using flameless Atomic Absorption Spectrophotometer (AAS).
The statistical analyses of the experimental data showed that the major road contributed significantly (P < 0.05) to higher concentrations of lead in all the crops examined; and also cadmium in all the crops except in potatoes. Vegetable crops were found to have higher contents of these two metals than the fruits. Substantial amounts of these metals could be removed by washing the samples with triple distilled water.     

YEAST AND ITS EFFECT ON THE FLAVOUR OF ALCOHOLIC BEVERAGES*

Sensory examination of an aroma model consisting of alcohols, fatty acids, esters and aldehydes, in concentrations estimated in whisky, has proved that—in addition to vicinal diketones—esters predominate as components influencing the aroma, but also some fatty acids exercise a most marked influence. Furthermore, some people possess a good ability to smell certain compounds whereas others cannot smell them as well, but detect other compounds more easily. Within the group of more than 100 identified aroma components, mainly the same substances appear in the volatile aroma fraction of beer, wine and distilled beverages. In view of this, it seems evident that the raw materials utilized for the production of the beverages contribute to no more than a limited extent towards the aroma composition. The aroma components which are most noticeable are produced by the yeast during fermentation, and the nature of the final aroma first and foremost depends upon the kind of yeast used, and upon the fermentation conditions. Although the yeast for the most part produces the same aroma components also In different beverages, considerable variation may occur in the quantities of aroma components even in beverages of the same type. The structure and function of the plasma membrane selectively regulate the uptake of different compounds from the medium into the yeast cell, and the release of the metabolites from the cell into the medium. In this sense, the lipid composition of the plasma membrane and its lipolytic enzymes may possess a decisive importance. The activity of the lipolytic enzymes present in the plasma membrane must be controlled by some regulatory mechanism. If this is the case, the permeability of the plasma membrane can be modified, e.g., by activation of the phospholipases, with consequent degradation of membrane phospholipids. Consequently, it is likely that one of the functions of the lipolytic enzymes present in the plasma membrane is that of participation in the transport processes by changing the permeability properties of the plasma membrane.     

草莓粉非酶褐变的抑制及抗结块性研究

对草莓粉非酶褐变的抑制及抗结块性进行了研究,结果表明：添加适量的亚硫酸氢钠、采用内置干燥剂的阻湿阻氧好的保鲜袋包装、在低温低湿条件下贮藏,对草莓粉非酶褐变具有很好的抑制作用;添加硬脂酸镁1.0%、微晶纤维素0.5%、硅胶0.5%,对草莓粉具有很好的抗结块作用.     

粥化酶及其在果蔬加工中的应用研究

研究了粥化酶的粗酶特性及其在果蔬加工中的应用，并比较了粥化酶与其它果蔬加工用酶在苹果加工中的应用效果。研究结果表明粥化酶作用的最佳条件符合果蔬加工的要求，它能够不同程度的提高果蔬的出汁率及其澄清度；与其它果蔬加工用酶相比粥化酶具有作用效果好，价格便宜的优点     

植物提取物用于果蔬防腐保鲜研究进展

致腐菌是诱发果蔬采后病害,造成果蔬在货架期间和贮藏过程腐败变质的主要原因.主要从植物提取物对果蔬采后致腐菌的抑制作用,不同提取方法对致腐菌的抑制效果,提取物用于果蔬防腐保鲜效果三个方面概述了植物提取物在果蔬防腐保鲜上的研究进展.     

EFFECT OF LIGHT SOURCE ON ACCEPTABILITY OF CITRUS FRUITS

The effect of three commonly used light sources on the color acceptability of oranges, lemons and limes was investigated. The color of the oranges under incandescent (INC) and metal halide (MH) lights was more preferred (P<0.05), by the panelists than when presented under fluorescent (FL). The main reason was the dull orange color seen under FL light. Relative luminance data, collected via a fiber optic probe connected to a photo diode array, demonstrated the reason to be insufficient red light reflected from oranges presented under FL. The yellow lemons were also preferred more under INC and MH than under FL: the latter resulted in a greenish tinge appearance. The color of the limes was more preferred under INC light than under FL, but preferred equally to the product presented under MH.     

乙醇处理对桃果实贮藏期间POD、PPO活性的影响

以“大久保”和“绿化9”桃果实为试材,研究了在10℃±2℃和2℃±2℃贮藏条件下,不同浓度的乙醇蒸汽处理(1mL/kg、2mL/kg、4mL/kg)对桃果实POD、PPO活性的影响。结果表明“,大久保”用4mL/kg浓度的乙醇在10℃±2℃下处理3d,“绿化9”用4mL/kg浓度的乙醇在2℃±2℃下处理5d,有效提高了桃果实POD的活性,加强了机体的抗氧化系统,保持膜的完整性,减少冷害发生,同时抑制了果实PPO活性,减少果实褐变和腐烂病的发生,延长了贮藏期。     

树脂法提取纯化草莓色素的研究

研究以草莓为原料、用大孔树脂提取和纯化草莓色素的工艺条件.试验结果表明,最佳的工艺条件是:提取液为0.1 mol/L的盐酸溶液;最佳树脂是AB-8树脂;最佳吸附条件是:50℃,pH=1.5的条件下吸附,吸附流速为1 BV/h;最佳解吸条件是:用pH=1.5时,50%的乙醇在室温条件下洗脱,洗脱流速为0.5 BV/h.