KINETICS OF OSMOTIC DEHYDRATION IN ORANGE AND MANDARIN PEELS

The nutritional and health properties of some citrus peel components such as pectin, flavonoids, carotenoids or limonene make interesting developing processing methods to obtain peel stable products, maintaining its quality attributes, increasing its sweetness and improving its sensory acceptability. In this sense, osmotic dehydration represents a useful alternative by using sugar solutions at mild temperature. Kinetics of osmotic treatments of orange and mandarin peels carried out at atmospheric pressure and by applying a vacuum pulse at the beginning of the process were analysed at 30, 40 and 50C, in 65 °Brix sucrose, 55 °Brix glucose and 60 °Brix rectified grape must. Vacuum pulse greatly affected mass transfer behavior of peels due to the greatly porous structure of albedo. So, PVOD treatments greatly accelerate the changes in the product composition in line with an increase in the peel sample thickness. In osmotic processes at atmospheric pressure, sample impregnation occurs coupled with osmotic process, but much longer treatments are required to achieve a reasonable concentration degree which assures sample stability. Low viscosity osmotic solutions seems recommendable in order to promote both diffusional and hydrodynamic transport, in vacuum pulsed pretreatments at mild temperatures.     

CAROTENOIDS IN JUICE OF SHAMOUTI ORANGE

SUMMARY— More than 50 carotenoids were isolated from the juice of Shamouti orange (Citrus sinensis [L] Osb.) using a combination of column and thin layer chromatography. In addition to carotenoids usually found in citrus, others not previously detected in common orange varieties were identified. These include γ-carotene, rubixanthin, the new ketones sinthaxanthin and its OH-derivative, as well as lutein 5,6-monoepoxide. The dial-polyol fraction was most predominant yielding about 70% of the total carotenoids. It was established that low pigmentation of Shamouti orange juice is due to its low total carotenoid content rather than the absence of colored carotenoids.     

FLAVOR AND CHEMICAL COMPARISON OF PASTEURIZED AND FRESH VALENCIA ORANGE JUICES1

Freshly extracted Florida Valencia orange juice was heated at 98C for 11 s to produce lightly heated juice, and for 37 s to produce heavily heated juice. Sensory panels detected a flavor difference between the fresh, unheated juice and the heavily heated juice. Analyses of these two juice samples by headspace gas chromatography (GC) showed no significant qualitative or quantitative differences. GC analyses of methylene chloride extracts of juices and of residues from distillation of the juices showed only one detectable difference in each case. Extracts of the whole juices showed one GC peak, which was significantly larger in the heavily heated juice, identified as the potential off flavor compound, octanoic acid. Extracts of the high-boiling distillation residue showed one unidentifed late-eluting GC peak which appeared only in the heavily heated juice. These findings supplement previous reports that more severe pasteurization conditions than required for juice processing cause detectable flavor changes in heated juice.     

SHELF-LIFE AND MICROBIAL GROWTH KINETICS OF FRESH CITRUS JUICES: SHAMOUTI ORANGE

The paper deals with the shelf-life and endogenous microbial growth kinetics of freshly squeezed unpasteurized Shamouti orange juice. Microbial and organoleptic data was evaluated for seven temperatures (range of 2.0 to 14°C). Microbial lag-time was more sensitive to temperature change in the lower range (E _a = 42.4 Kcal/mol). The effect of temperature on growth rate was quite moderate in the lower range but in the order of 12.1 Kcal/mol at the upper end. Organoleptic data kinetics indicated that unpasteurized Shamouti juice can maintain its initial quality for 4 days if kept a 2°C and about 2 days if kept at 7°C. The kinetics data (both microbial and taste) was used successfully for the prediction of microbial growth and for taste deterioration under variable time-temperature conditions (i.e., simulation of cold chain path).     

STABILITY OF ASCORBIC ACID IN ORANGE JUICES AFTER INITIAL USE AT HOME BEGINS

Ascorbic acid (AA) stability in orange juices, both fresh and commercially packaged in different types of containers (Tetrabrik, glass and tin), was studied. The purpose was to ascertain how well AA is retained once use at home has commenced. The AA levels of the orange juices were measured at 0, 1, 3, 5, 67, 24, 48, 72 and 168h following squeezing in the case of fresh oranges and for commercially packaged juices following opening of the container. Storage was at 4 or 25C. Fresh juice was stored in an open jar; packaged juice in the container in which it came. When stored 7 days at 4C, retention ranged from 93.8 to 95%.     

市售橙汁类饮料总抗氧化活性的比较

比较市售橙汁类饮料的总抗氧化活性。采用ABTS法对11种市售橙汁类饮料的总抗氧化活性进行测定，并分析其总抗氧化活性与所含抗坏血酸、多酚类以及类胡萝卜素的关系。结果：100％橙汁的总抗氧化活性比调配得到的橙汁类饮料要高，调配得到的橙汁类饮料由于添加了VC和β-胡萝卜素也具有较高的抗氧化活性。样品总的抗氧化活性与多酚类的含量之间存在着较好的相关性，说明多酚类物质可能是市售橙汁类饮料的主导抗氧化活性成分。     

柑橘类果汁中柠檬苦素的含量及其性质研究

对市售13种柑橘类果汁柠檬苦素含量进行测定,并研究柠檬苦素的抗氧化活性、抗菌活性和抗肿瘤活性。结果毒明,不同柑橘类果汁中柠檬苦素含量有显著差别;柠檬苦毒对猪油具有抗氧化作用,能够抑制枯草芽孢杆菌的萌发和生长,并在体外能显著抑制人胃癌细胞的生长,作用时间与存活率呈负相关,且呈一定剂量关系。研究结果为开发柠檬苦素功能食品添加剂提供了理论依据。     

COLOR AND VITAMIN C CONTENT IN MANDARIN ORANGE JUICE AS AFFECTED BY PACKAGING MATERIAL AND STORAGE TEMPERATURE

Mandarin orange (Citrus reticulata) juice was packed in two different non-transparent cartons made of polyethylene, cardboard and (1) aluminum foil (Tetrapak ^® ) or (2) ethylene vinyl alcohol copolymers (Pure-pak ^® ) and was stored at 4C or room temperature (25  ±  3C). During the shelf life of these juices (35 days), changes in the headspace gas composition, vitamin C and CIEL*a*b* color coordinates were evaluated. In addition, a consumer panel evaluated the sensory color of the juices. Mandarin orange juices darkened and ascorbic acid content decreased with storage time. Type of carton and storage temperature played a predominant role in determining the final juice quality, with Tetrapak ^® carton providing the juice with the best quality (intense orange color and high vitamin C content and consumer preference) throughout their shelf life.

PRACTICAL APPLICATIONS

This study was a clear example of how research can help real food companies in selecting the right materials for their production lines. In this particular case, the results presented show how Tetrapak^® packaging led to a final mandarin orange juice of higher quality compared to Pure-pak^® packaging. Therefore, citrus processing companies have some scientific data comparing the behavior of these two types of non-transparent cartons. Besides, the companies manufacturing these cartons also have some information about their materials and can use it to improve them.     

膜分离技术在果蔬汁生产中的应用

介绍了膜分离技术在果蔬菜汁澄清，脱苦，浓缩等方面的应用，探索了利用膜联合过程生产高品质质果蔬汁的实际可能性。     

纳他霉素在柑桔防腐保鲜中的应用

本研究分离了导致柑桔腐败的重要菌种,采用直接喷雾法将不同浓度的纳他霉素悬浮液作用于柑桔并和未经纳他霉素处理的柑桔进行比较,通过相关指标测定,确定大量桔青霉和少量的酵母菌是导致柑桔腐败变质的主要病菌,在温度为18℃～22℃、湿度为58%～65%的环境条件下纳他霉素的最佳作用浓度为300mg/L～400mg/L.