RHEOLOGICAL BEHAVIOUR OF CLARIFIED MANGO JUICE CONCENTRATES

The rheological behaviour of clarified mango juice was measured at temperatures 15–85C and concentrations 15–66 °Brix, using a rotoviscometer. Mango juice free of pectin and pulp behaves as a Newtonian fluid. The effect of temperature can be described by an Arrhenius-type equation. The activation energy for viscous flow was in the range of 1.64–8.44 kcal/g-mol, depending on the concentration. The effect of concentration was modelled better by an exponential relationship than a power-law relationship. Simple equations are proposed for describing the combined effect of temperature and soluble solids content on the juice viscosity.     

HACCP在猕猴桃果汁饮料生产中的应用

将HACCP体系应用于猕猴桃果汁饮料的生产中，根据生产工艺流程，对各工序的生物、化学、物理危害进行分析，并确定了4个关键控制点，制定了HACCP计划表，为保证猕猴桃果汁饮料的质量安全提供了依据。     

RHEOLOGICAL BEHAVIOUR OF SHEARED JAMS. RELATION WITH FRUIT CONTENT

Eight samples of jam were sheared to destroy gel structure and their flow behaviour was analysed in a concentric cylinder viscometer. Jams were prepared from 4 different fruits—strawberry, peach, plum, and apricot—at 50% and 30% fruit content approximately. Flow of sheared jam showed time dependence, which could be quantified by the Weltmann model and which was eliminated by shearing samples for 8 min at 300 rpm. Casson's yield stress values were obtained at two ranges of shear rates: 0.08–1.01 s⁻¹ (O₀₁) and 2.58–387.30 s⁻¹ (o₀₂). o₀₂ values were about double the o₀₁ values. Flow was adequately described by the Herschel and Bulkley model, introducing either of the yield stress values (o₀₁ or o₀₂). Significant differences were found for some of the rheological parameters studied (Weltmann A and B constants, o₀₁, o₀₂, K₁, and n₁) between samples containing 50% and 30% fruit. These results demonstrate the role played by fruit particles in the rheological behaviour of this type of product and suggest the possibility of using rheological parameters as indices of fruit content in jams.     

RHEOLOGICAL BEHAVIOUR OF INFANT FOODS

The rheological properties of four different infant foods were studied. Flow of all samples showed time dependence, which was qualitatively evaluated and quantitatively described by the Weltman and Hahn models. Rheological data were obtained at a constant shear rate of 57.6 s⁻¹. These foods showed coefficients of thixotropic breakdown between 4.34 Pa. s and 16.69 Pa. s. Values of the Hahn equation parameter were: p from 1.25 to 1.93 Pa and a from 0.019 to 0.031 s⁻¹. The results showed that the Weltman equation was better than the Hahn equation in describing the thixotropic behaviour of these foods. After eliminating time dependency, flow was adequately described by the Herschel-Bulkley model.     

RHEOLOGICAL BEHAVIOUR OF COCOA DISPERSIONS

The steady-shear viscosities of cocoa mass and cocoa suspensions were measured over a wide range of temperature and cocoa powder content. The effects of gasification, moisture and lecithin contents were also investigated. The viscosity of cocoa mass followed the Quemada or the Casson model. Both viscosity and yield stress decreased with increasing temperature. Degasification also lowered the viscosity and yield stress. The viscosity of concentrated cocoa suspension increased with increasing powder content and exhibited shear-thinning behaviour, and followed the Kreiger and Dougherty model. While the relative intrinsic viscosity was nearly constant, the maximum volume fraction increased with increasing shear stress or shear rate. Addition of moisture in suspension increased the viscosity due to partial gelation of starch; while addition of lecithin decreased the viscosity due to the lesser number of flocs in the suspension.     

ACID-SOLUBLE NUCLEOTIDES OF JUICE VESICLES OF CITRUS FRUIT

Nucleotides from fruit of "Orlando" tangelo (Citrus reticulata x C. paradisz) and "Hamlin" and "Pineapple" sweet oranges (C. sinensis) extracted with perchloric acid, were separated by anion-exchange chromatography using formic acid:aqueous ammonium formate as the eluting solvent. Tentative identification of the various fractions was made by comparing the retention time of unknowns with standards fractionated by the same procedure and by adsorption spectral analyses. With the use of these methods, acid-soluble nucleotides were found to be present in appreciable quantities in mature fruit. Those in concentration that could be tentatively identified were CMP, AMP, CDP, UMP, ADP, CTP, GDP, UDP and ATP. The latter was further assayed by the luciferin-luciferase method. The possible significance of the nucleotides to fruit quality was discussed.     

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.     

ALCOHOL-INSOLUBLE CONSTITUENTS OF JUICE VESICLES OF CITRUS FRUIT

SUMMARY– The texture of the edible portion of citrus fruit is determined by the characteristics of the juice vesicles and their insoluble constituents. Alcohol-insoluble solids (AIS) of the juice vesicles of several varieties of oranges, grapefruit and tangerines were studied at different stages of maturity. The protein content of the AIS as determined by the Kjeldahl method was found to decrease with fruit maturity, although total amount per fruit tended to increase. Polysaccharides were separated by extracting the AIS with alkali of various concentrations. Each fraction after hydrolysis was analyzed for the monomers both by paper chromatography and gas chromatography of the silylated derivatives. Galactose, arabinose and traces of glucose were found in fractions associated with galacturonic acid, and xylose, arabinose and glucose in different proportions were found in the hemicellulose and cellulose fractions. Traces of rhamnose and other uronic acids also were detected.     

HACCP在果汁饮料生产中的应用

探讨了HACCP在果汁饮料加工中的具体应用。并对果汁饮料生产过程环节可能造成的潜在危害进行物理、化学和生物分析，确定关键控制点、临床范围、监测体系和校正措施，将生产过程的危害因素降到最低限度，从而提高产品质量。     

超滤法澄清西番莲果汁的研究

以寻求提高西番莲原汁超滤时的渗透通量为目的，用国产芳香聚酰胺膜平板超滤器进行试验，对超滤操作条件，果汁预处理，膜的清洗进行研究。结果表明，西番莲原汁超滤时渗透通量最高的操作压力为0．15MPa，最佳进料速度为22mL/s，操作温度为室温；原汁经海藻酸钠—碳酸钠澄清剂预处理后可以明显增大渗透通量；超滤处理后。原汁的西番莲固有滋味和品质得到较好保留。采用超滤澄清法生产高质量的西番莲原汁是可行的。     

FLOW BEHAVIOUR OF CONCENTRATED ORANGE JUICE*

Abstract Orange concentrate, at the 60-65° Brix concentration level, is a non-Newtonian fluid with yield stress and time dependent behaviour. While recovery from low-rate shear is reversible, shear at high rate causes irreversible destruction of the viscous structure. Part of this effect is due to disintegration of pulp particles. Pulpless concentrate (serum) is also non-Newtonian, but yield stress and time dependent behaviour are present only when pectin concentration is high. Depectinized serum is Newtonian. The effect of temperature on flow properties of all three types of material was studied.     

壳聚糖对山楂汁澄清效果的研究

旨在研究壳聚糖对山楂汁澄清的效果。试验结果表明，壳聚糖的用量为0．13～0．19g／100mL、温度为40～70℃、pH3.0～3.5，保温时间为40～50min的工艺条件澄清山楂汁，透光率可达90％以上，且清汁中可溶性固形物含量保持不变。通过正交试验，得出壳聚糖对山楂汁澄清处理的最适工艺参数：温度40℃，用量0．15g／100mL，pH3．3，时间40min。     

果汁保健酸奶的研制

采用水提法得到了枸杞子和红枣有效成分的提取液,研究果汁保健酸奶的生产配方和最佳生产工艺.得出生产果汁保健酸奶的最佳工艺条件为:90℃～95℃、5 min高温杀菌牛乳,接种量按奶液体积比的3%,在42 ℃下培养3.5 h,分别加奶液质量6%的蔗糖、6%的枸杞汁、6%的红枣汁及0.2%的黄原胶作为稳定剂.     

RHEOLOGICAL BEHAVIOUR OF BUTTER AT SMALL DEFORMATIONS

Thirteen continuously churned commercial butter samples were evaluated for rheological properties at small deformations. The methods performed included dynamic experiments in shear and compression, stress relaxation in shear and static compression at 5–20C each. Linear viscoelastic behaviour was observed up to a critical strain of 0.001. The structure breakdown due to shear strains between 0.001 and 0.01 was found to be fully recoverable. No qualitative differences in the rheological behaviour were observed between the samples. Temperature-induced variations were mainly ascribed to changes in the solid fat content. Correlations between selected rheological measures in the linear viscoelastic region (i.e., complex modulus G* [Pa], relaxation modulus G(t) | _t ≃ 0[Pa], and modulus of deformability M_D[Pa]) were found to be causal and only slightly affected by the solid fat content.     

枸杞鲜果果汁灭菌温度的选择

生产加工果汁,灭菌是必要的步骤.对不同温度下枸杞鲜果果汁的颜色变化及其多糖和类胡萝卜素的含量变化进行研究,确定鲜枸杞果汁生产加工的最佳灭菌温度.结果表明:在所测温度范围内(80℃～100℃),果汁颜色随温度升高逐渐变浅;β-胡萝卜素含量随温度升高趋于降低;多糖含量随温度升高先升后降.最终确定,生产加工枸杞鲜果果汁的最佳灭菌温度在80℃左右.     

RHEOLOGICAL BEHAVIOUR OF BUTTER AT LARGE DEFORMATIONS

Eleven traditionally produced butter samples were evaluated for rheological properties at large deformations by lubricated and nonlubricated uniaxial compression with varying sample geometries and compression rates, by stress relaxation in shear and creep experiments in compression at 5–20C each. Compression forces required to deform cylindrical samples in nonlubricated conditions were higher than in lubricated cases. Correction of shape changes in nonlubricated stress-strain curves resulted in good agreement with lubricated experiments at low compression rates up to stress maxima or yielding. As frictional forces were relatively smaller at high deformation rates, lower stresses were obtained in nonlubricated conditions. Samples with higher height/diameter ratios showed more pronounced stress maxima. A biaxial extensional viscosity, η be , was computed for nonbrittle, soft samples. Typical slopes in logarithmic plots of viscosity against strain rate were approximately -1. At strains of about 0.01 creep compliance depended on compression stress. The average ratios of recovered to initial instantaneous compliance were between 0.31 and 0.59, and increased with sample temperature. A calculated ηBE from creep compression showed fair agreement with ηBE from static compression experiments. At comparable strains, a conversion of creep compliance to the stress relaxation modulus by an approximate method showed a good fit of experimental results.     

PHYSICOCHEMICAL AND SENSORY PROPERTIES OF MUSCADINE GRAPE JUICE AND CONCENTRATES

Juices from bronze and red muscadines were concentrated by low-temperature vacuum evaporation. Half of each of the lots was treated with a mixture of pectinolytic and cellulolytic enzymes and the other half untreated. Red juice was higher in soluble solids and Brix-to-acid (BTA) than bronze, but pH, acid, and viscosity were similar. When concentrated to 68° Brix, the BTA was the same regardless of juice type. Enzyme treated samples were not different from their nontreated counterparts, except for slightly higher pH of treated red juice. Hue angle for bronze concentrate shifted from about 100 to 78 while chroma increased. Hue for the red juice shifted from about 40 to 95, while chroma remained constant. Fructose and glucose were the major sugars with sucrose averaging less than 1%. Panelists rated the bronze reconstituted juices lower in color intensity, aroma intensity, sweetness, acidity, and flavor than the single-strength juice. However, the red reconstituted juices were rated higher in color intensity than their single-strength counterparts. Panelists rated reconstituted juices higher when reconstituted with essence recovered plus water than with water only.     

果汁非酶褐变的机制及控制措施

本文阐述了果汁非酶褐变的机制：焦糖化反应、美拉德反应、抗坏血酸氧化分解和多元酚氧化缩合,并对目前常用的抑制果汁非酶褐变的方法进行了综述.     

树脂在现代果汁加工中的应用

树脂的发展经历了沸石、磺化媒、磺化酚醛树脂、凝胶聚苯乙烯、聚丙烯酸到大孔离子交换树脂和吸附树脂的过程。现在，树脂在工业生产、生化医疗、环境保护、食品制造，还有国防军事、原子能研究等很多方面都有应用。随着一些新型树脂的问世，它的用途越来越广泛，详细介绍了树脂在果汁加工中的应用。