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。     

EFFECT OF TEMPERATURE ON VISCOSITY OF FRUIT JUICES AND PUREES

SUMMARY: The viscosities of selected fruit juices and purees were measured with a coaxial-cylinder viscometer in the temperature range 20–70°C. Depectinized apple juice and Concord grape juice were Newtonian fluids at all concentrations and their viscosity decreased considerably at higher temperatures. Cloudy apple and orange juices changed from Newtonian to pseudoplastic at concentrations higher than 50 and 20° Brix. respectively. Temperature had a smaller effect on viscosity of cloudy juices than of clear juices. The apparent viscosity of fruit purees (pseudoplastic fluids) decreased slightly at higher temperatures. The activation energy for flow increased with the juice concentration and decreased with the presence of suspended particles in the fruit product. The data and conclusions are useful in the design and operation of efficient food-processing equipment.     

VACUUM-PUFF FREEZE DRYING OF TROPICAL FRUIT JUICES

SUMMARY— A study was made to develop high Quality juice powders from four tropical fruits. Guava and mango puree, passion fruit and pineapple juice were dehydrated in a vacuum-puff freeze-drying process. Sucrose in amount (25–40%) approximating nectar formulations was mixed with single-strength juice or puree samples, blended 2 min, and frozen. Freezing temperatures of various samples were measured in a constant temperature bath of −21.6°F. Samples initially frozen in blast freezers at −40°F or 0°F with 0.25–1.0 lb/ft² were vacuum-puffed and freeze dried on aluminum trays at 50μ Hg and 120–130°F shell temperature for 6–9 hr to 1–2% moisture. Puffing was affected by (1) rapid freezing of the juice-sucrose mixture; (2) artificially entrapping some gas in the mixture before freezing; (3) changing the pressure or temperature in the chamber to effect gas expansion; and (4) increasing the mixture viscosity to limit bubble sizes. Results of drying over 160 different samples showed that: (1) added sucrose to give a 40° 5° Brix in the mixture resulted in a stable 'puffed' structure; (2) several permissible calcium salts and silica at 0.1–0.5% (w/w) added to the mixture before drying, improve the free-flowing properties of the dried product. Process variables are discussed and typical sample compositions given.     

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.     

枇杷果酒加工工艺的研究进展

从酵母菌种、果汁处理、酒精发酵的控制、下胶和澄清等方面,阐述枇杷果酒加工工艺的研究进展.     

SENSORY AND PHYSIO‐CHEMICAL PROPERTIES OF MEMBRANE FILTERED APPLE JUICES1

Shelf‐stable apple juices were prepared using two ceramic and four polymeric tubular membranes of varying pore sizes and evaluated using color matching and triangle tests. Juices from 9 kDa and 20 kDa membranes were different in color and aroma/flavor from the other membranes, the characteristics of which did not differ from each other. A full sensory profile was obtained for experimental juices produced using a 0.02 μm ceramic membrane and from commercial pasteurized apple juice. Experimental juices were prepared from fresh and stored apples with and without ascorbic acid. Twelve judges evaluated color; cooked/caramelized, appley, fruity and green aromas and seven flavor attributes (cooked/caramelized, appley, fruity, green, sweet, sour, astringence). Analysis of variance and principal component analysis revealed that membrane filtered juices lacked the cooked/caramelized aroma and had a green flavor compared with the commercial apple juice. Membrane filtered juices prepared from freshly harvested apples had less appley and fruity aroma and flavor, but were more sour and astringent than juices prepared from stored apples. Ascorbic acid treatment significantly reduced the yellow color and increased the astringence of juices.     

PSYCHOPHYSICAL AND PSYCHOMETRIC EVALUATION OF COMMERCIAL APPLE JUICES

Psychophysical and psychometric relationships of five commercial apple juices were evaluated. Sugar content of apple juices ranged from 9.6 to 10.6%, acid content from 0.40 to 0.51% and phenolic content from 0.12 to 0.23%. Sweetness intensity (log) correlated with sugar content (r = 0.92), sourness intensity (log) with acid content (r = 0.93) and sugar-acid ratio (r = 0.92), and bitter/astringent taste (log) with phenolic content (r = 0.95) and the acid content (r = 0.91). The expected correlation between sweetness intensity and sugar acid ratio was absent. Preference (like/dislike) scores for thefive brands of apple juices were significantly different at p < 0.05 and ranged from 5.70 to 7.90. Preference did not correlate with any chemical contents, ratios or sensory intensities. Preference for apple juice was adequately described by multivariate equations combining aroma intensity either with sugar content (r²= 0.91) or sweetness intensity (r²= 0.99).     

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。     

罗汉果甜甙V含量分布及与果实密度和水溶物含量关系

通过常规提取法提取罗汉果植株各部位的水溶性成分,并采用高效液相色谱法测定烘干后罗汉果叶、茎、薯块甜甙V的含量,实验结果表明各部位甜甙V的含量各不相同,分别为0.011%,0.002%,0.006%,三者的甜甙V含量关系为叶>薯块>茎.同时通过对不同质量不同体积罗汉果中水溶物和甜甙V的含量测定,初步揭示了干罗汉果果实密度与水溶性物质含量的关系.实验结果表明,干罗汉果的密度越大,其水溶性物质的含量越大,果实中甜甙V的含量也越大.     

EFFECT OF PRESERVATION WITH SACCOGLOTTIS GABONENSIS ON THE BIOCHEMISTRY AND SENSORY ATTRIBUTES OF FERMENTING PALM WINE

Fresh palm‐wine, from Raphia hookeri was treated with different amounts of Saccoglottis gabonensis. The alcohol content, refractive index, assimilation of sugars and assimilation of nitrates were mcnitored (for 4 days) in treated samples and untreated controls (containing no S. gabonensisj. Fermentation rates were monitored by determining CO₂ production as well as pH and tit ratable acidity changes within the same period. Sensory attributes of fresh and treated palm wine were compared. Sensory evaluation studies were carried out on (1) The fresh palm wine, (2) Palm‐wine stored for 4 days at ambient temperature (27C‐29C) and (3) Palm‐wine stored for 30 days at ambient temperature. Treatment with S. gabonensis led to increased alcohol content and CO₂ production with lower sugar content (sucrose, glucose and maltose) and pH, than in control samples. There were no significant variations in the refractive indices of treated and untreated samples. CO₂ production decreased with each successive fermentation day in both treated and untreated samples. Panelists preferred the sensory properties of fresh palm‐wine to that of palm‐wine treated with S. gabonensis. However, by the second day the sensory characteristics of treated palm‐wine was preferred. Until the 4th day, the color and taste of treated palm‐wine ‐was acceptable while the untreated samples became unacceptable. By the 30th day both treated and untreated palm‐wine samples became unacceptable.     

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).