石榴浓缩清汁产业化技术研究

介绍了石榴浓缩清汁产业化生产工艺、加工技术及相应的产品质量标准.选用目前国际先进设备,采用此项加工技术,可生产营养损失少、具有天然风味的石榴浓缩清汁.     

RHEOLOGICAL PROPERTIES OF OIL-IN-WATER EMULSIONS FORMED WITH MILK PROTEIN CONCENTRATE

The rheology and the microstructure of emulsions stabilized with milk protein concentrate (MPC) were investigated using different MPC and oil concentrations. Steady‐shear tests showed that the emulsions were Newtonian at low oil concentrations (<20 wt%), whereas they were pseudoplastic and thixotropic at high oil concentrations (>20 wt%). Dynamic rheological measurements demonstrated that these emulsions behaved as weak gels, as indicated by relatively high values of G′ to G″. The rheological behavior of these emulsions was consistent with bridging flocculation mechanisms, whereby more than one droplet is shared by adsorbed casein aggregates/micelles. This was confirmed by confocal microscopy, which showed that these emulsions were aggregated.     

HTCA—丙酮溶液流变行为与可纺性关系的研究

用气压式毛细管流变仪研究了高温法二醋酸纤维素（ＨＴＣＡ）—丙酮纺丝溶液的非牛顿指数ｎ，结构粘度指数△η和粘液活化能△Ｅη与可纺性的关系．结果表明，ｎ值的增大和△η的减小有利于改善ＨＴＣＡ—丙酮溶液的可纺性，但难以作为可纺与不可纺的判据．而△Ｅη能较好地表征ＨＵＣＡ—丙酮溶液的可纺性，△Ｅη值越高．流动性和可纺性越差，实验表明△Ｅη高于８０ＫＪ／ｍｏｌ时．其溶液不可纺．在ＨＴＣＡ—丙酮溶液中加入１０—１５％左右的助溶剂Ｄ，可提高丙酮的溶解能力，使ｎ值增大，△η和△Ｅη降低，从而改善了可纺性。     

RHEOLOGICAL AND PHYSICOCHEMICAL BEHAVIOR OF FORTIFIED YOGURT, WITH FIBER AND CALCIUM

Yogurt systems were prepared from whole milk, adding 50 mg of calcium/100 mL of yogurt, and three levels of fiber from two wheat‐bran sources. In comparison with a plain yogurt, the presence of fiber and calcium augmented the consistency, diminished the syneresis and the pH was higher. Fiber increased the consistency, and all the formulated samples exhibited a non‐Newtonian response. During 3 weeks of storage time, the consistency reduced (from 2.0 to 0.32 Pa·s ⁿ ), syneresis increased (from 20 to 48%) and pH decreased (from 4.5 to 4.2) as a function of the system formulation.     

RHEOLOGICAL PROPERTIES OF SINGLE-CELL PROTEIN CONCENTRATE: DOPE FORMATION AND ITS FLOW BEHAVIOR

SUMMARY –Protein solution was made with single-cell protein (SCP) concentrate obtained by alkali extraction of Torula dried yeast. The minimum coagulation temperature for the dope was determined. The dope containing 10–25% of the extracted protein having a pH range of 9–12 was subjected to viscosity measurement at a temperature lower than the coagulation temperature. The optimum protein content of the SCP concentrate dope for spinning seems to be in the range of 15–20% At pH 9, the dope attained maximum viscosities without gelation.     

RELATIONSHIP BETWEEN RHEOLOGICAL BEHAVIOR AND BOSTWICK MEASUREMENT DURING MANUFACTURE OF KETCHUP

ABSTRACT

The Bostwick consistometer remains an integral part of assessing the consistency of tomato products. For instance, the consistency of lots of tomato paste are designated at the factory by their Bostwick measurement; tomato ketchup is produced to meet Bostwick ranges given in U.S. Standards for Grades. This work addresses the blending of tomato pastes, at different Bostwick readings, for use in the remanufacture of ketchup. For both blends and ketchup, the Bostwick measurement was correlated to rheological parameters measured by two methods: a single‐point method and rotational viscometry. The correlations between the Bostwick measurement and the viscosity were compared with the theoretical prediction based on gravity current flow. The results illustrate that the relationship between the Bostwick measurement and (K/ρ)^?1/(2n+3) provides a means to predict the Bostwick length from at‐line or in‐line viscosity measurements.

PRACTICAL APPLICATIONS

The results of this work provide a means to predict the Bostwick length from at‐line or in‐line viscosity measurements. Specifically, the quantitative relationships presented in the article allow in‐line process control schemes to improve final product quality.

     

RHEOLOGICAL BEHAVIOR AND PHYSICOCHEMICAL CHARACTERISTICS OF GOLDENBERRY (PHYSALIS PERUVIANA) JUICE AS AFFECTED BY ENZYMATIC TREATMENT

Goldenberry (Physalis peruviana) juice was prepared and enzymatically treated with two dosages (300 and 600 ppm) of Pectinex Ultra SP‐L, then, the juice was concentrated to 30 and 40°Brix. Rheological properties of juices were studied at a wide range of temperatures (5 to 100C) and shear rate range from 0.3 to 100/s using Brookfield Digital Viscometer. The Herschel–Bulkley, Casson and Bingham rheological models were applied to describe the rheological properties of different juices. These properties are key parameters required to solve food industry problems in numerous areas such as quality control, evaluation of consumer acceptance and texture. The results indicated that juice concentrates behave as non‐Newtonian fluids (pseudoplastic) and have a definite yield stress. The Bingham and Casson, plastic viscosity, yield stress, consistency index and flow index decreased with increasing enzyme dosage and temperature. The effect of temperature on the viscosity described by means of an Arrhenius‐type equation. The activation energy for viscous flow depends on the total soluble solids. Moreover, sensory evaluation for juices was carried out. In consideration of industrial utilization, detailed knowledge on the rheological and physicochemical characteristics of cape gooseberry juice is of major importance.     

FLOW BEHAVIOR OF CLARIFIED ORANGE JUICE AT LOW TEMPERATURES

This paper presents a study of the rheological behavior of clarified and depectinated orange juices, with different soluble solid contents, at temperatures just above their freezing point. The rheological behavior of depectinated and clarified orange juice was determined for a wide range of soluble solid contents (10–65.8° Brix) and temperatures ( − 15 to 30C). The results indicated that the samples behave like a Newtonian fluid. The effect of temperature on the juice can be described with an Arrhenius-type equation. It was found that the activation energy for viscous flow was in the range of 9.4 to 59 kJ/mol, depending on the concentration. The effect of the soluble solid content can be described by an exponential-type equation. Finally, an equation in which dynamic viscosity depends on temperature and soluble solids content gives the following expression: η =  1  ×  10 ^{- 15} exp(0.12C  +  9021/T), where T in Kelvin, C in °Brix, and viscosity in mPa·s.

PRACTICAL APPLICATIONS

It is necessary to know the relationship between viscosity with temperature and concentration, since knowledge of these parameters is of vital importance in the manipulation, calculation and design of all those unit operations during the process, mainly those based on heat and quantum transfer.     

Volatile composition and sensory quality of Spanish pomegranates (Punica granatum L.)

BACKGROUND: Pomegranate is highly valued for its health‐promoting effects. Fruits of nine pomegranate cultivars were analysed for volatile compounds, antioxidant activity and quality parameters, including maturity index and CIEL*a*b* colour. Volatile compounds were isolated from fresh juices using hydrodistillation; extracts were analysed using gas chromatography/mass spectrometry. Fruit colour was influenced by cultivar and grouping of cultivars according to their taste (sweet, sour‐sweet or sour), with sweet fruits having more intense red colour and higher lightness values. RESULTS: A total of 18 compounds were found in pomegranate aroma profiles, including monoterpenes, aldehydes, alcohols, monoterpenoids and linear hydrocarbons. The most abundant compound were trans‐2‐hexenal, 3‐carene, α‐terpinene and α‐terpineol. The total concentration of volatiles ranged from 1.7 to 10.9 g kg^?1. Overall consumer liking of pomegranate juices was associated with the presence of monoterpenes such as α‐pinene, β‐pinene, β‐myrcene, limonene and γ‐terpinene. The presence of aldehydes such as hexanol, hexanal and cis‐3‐hexenol was correlated with poor overall consumer liking. CONCLUSION: Fruits from the cultivar Mollar de Elche 2 were those most suited for juice processing because they had the highest total concentration of volatiles, which was related to high overall consumer liking, intense and acceptable fresh pomegranate odour and flavour (high scores of satisfaction degree), medium intensity of red colour and low sourness. Copyright © 2010 Society of Chemical Industry     

Anthocyanin and organic acid profiles of pomegranate (Punica granatum L.) juices from registered varieties in Turkey

This is the first study to analyse the profiles of anthocyanin (ACN) and organic acid (OA) and some physico‐chemical properties of pomegranate juices (PJs) obtained from nine registered varieties in Turkey. HPLC analyses revealed that there were significant differences between ACN contents (28–447 mg L^?1) and profiles (P < 0.01). The PJs contain maximum six ACNs, 3‐glucosides and 3,5‐diglucoside of delphinidin, cyanidin and pelargonidin. The major OA in PJs was citric acid (66–74%), followed by malic (6–12%), succinic (5–19%), nonidentified (0–14%) and tartaric acids (0.1–3.7%). Amongst individual OAs, citric acid had the most significant effects on TA (r = 0.9761), pH (r = 0.9208) values and sourness of PJs. As different from literature, results of this study revealed that malic acid contents of authentic PJs could be higher than 1.5 g L^?1. Consequently, ACN and OA profiles could be successfully used in quality control because all PJs have their own typical ACN and OA profiles.