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.     

RHEOLOGICAL PROPERTIES OF CLOUDY AND CLARIFIED JUICE OF MALUS FLORIBUNDA AS A FUNCTION OF CONCENTRATION AND TEMPERATURE

The rheological behaviour of cloudy and clarified juice of Malus floribunda was studied as a function of solid concentration, in a range of 45–70 Brix, at nine temperatures (5–50C). Cloudy and clarified juices are slightly thixotropic at 65–70 Brix and 5–10C. At lower concentrations and higher temperatures the thixotropy is low and can easily be eliminated by shearing. The power law model was applied to fit the pseudoplastic behaviour depending on the concentration level. Cloudy juice has pseudoplastic behaviour for concentrations higher than 45 Brix. Clarified juice is pseudoplastic at 65 Brix for temperatures lower than 25C and Newtonian at higher temperatures and for solid concentrations lower than 60 Brix. The activation energy for flow evaluated with the Arrhenius-Guzman equation, increases with solid concentration and ranged from 10.8 to 3.45 kcal gmol⁻¹ for cloudy juice and 15.3 to 7.9 kcal gmol⁻¹ for clarified juice. A nonlinear correlation accounting for temperature and concentration effects on the consistency coefficient was identified.     

Rheological properties of Josapine pineapple juice at different stages of maturity

The rheological behaviour of Josapine pineapple juice with at various maturity stages was studied at a wide range of temperature (5–65 °C) and concentration (4–14 °Brix) using a rotational rheometer as the measuring system. The results show that josapine pineapples juice demonstrated a Newtonian behavior and is influenced by maturity stage, temperature and concentration. The Arrhenius typed equation successfully describe the effect of temperature on the viscosity, on the other hand, the effect of concentration can be described better using exponential equation. Finally, an equation describing the combined effect of temperature and concentration on viscosity at different stages of maturity was successfully developed.     

Thermal resistance of Alicyclobacillus acidoterrestris spores in different heating media

The aim of this work was to study the influence of temperature (85, 90, 95 and 100 °C), total soluble solids (SS: 10 and 20°Brix or % by weight of sucrose) and pH (3.5 and 4.0) on decimal reduction time ( D- value) of the Alicyclobacillus acidoterrestris strain DSM2498 spores in apple juice, orange juice and malt extract broth (MEB). The effects of SS and pH on D -values and z- values in each media were insignificant ( P  > 0.05). In apple juice, orange juice and MEB, z- values of A. acidoterrestris for pH 3.5 and pH 4.0 were 12.2 ± 1.3–14.2 ± 3.2 °C, 11.2 ± 0.3–9.4 ± 0.0 °C and 11.9 ± 0.8–10.3 ± 0.4 °C, respectively. z- values of apple juice, orange juice and MEB samples with SS = 10°Brix and SS = 20°Brix were 14.1 ± 3.2–12.2 ± 1.3 °C, 10.2 ± 0.7–10.5 ± 1.1 °C and 11.3 ± 1.5–10.9 ± 0.2 °C, respectively. However, D -values of all samples were affected by temperature significantly ( P  < 0.01). Average D -values of apple juice, orange juice and MEB were 101.2 ± 14.7, 34.4 ± 7.9, 20.3 ± 4.9 and 4.3 ± 1.3 min for 85, 90, 95 and 100 °C. This study demonstrated that A. acidoterrestris spores exhibited high resistance to thermal processing applications. pH and SS of the media did not affect thermal resistance.     

EFFECT OF CONCENTRATION ON THE RHEOLOGY AND SERUM SEPARATION OF TOMATO SUSPENSIONS

The °Brix value of the tomato concentrate, from which tomato suspensions were prepared, was shown to have a large effect on the resulting apparent viscosity and storage modulus. The apparent viscosity of a tomato suspension prepared from a 30 °Brix tomato concentrate was only 35% of that of a suspension prepared from a 4.9 °Brix juice, both standardized on the same water unextractable solids (WUS) (0.65%) and total tomato solids (TS) level. After homogenizing the difference in apparent viscosity was only about 10–15%. A similar trend was found for the dynamic moduli. The decrease in rheological parameters of the nonhomogenized suspensions is probably partly related to the decrease in diameter of the tomato particles due to the concentration process. Moreover, microscopic fracture of the cellulosic, microfibrillar network of the cell wall plays a part. Serum separation of diluted nonhomogenized tomato suspensions was higher if made from a concentrate that was concentrated to a higher °Brix value. This phenomenon is discussed in terms of variations in uniaxial compression of the network in the diluted tomato suspensions caused by gravitational force.     

RHEOLOGICAL BEHAVIOUR OF KIWI FRUIT JUICE CONCENTRATES

The rheological behaviour of diluted kiwi concentrates (22.5–63.0 °Brix) over the temperature range 4 to 70C, was studied. The values below 55.7 °Brix fit the power law while above 55.7 °Brix fit the Herschel-Bulkley equation. Maximum and minimum consistency index values were 62225 and 16 mPa. s ⁿ . Concentrates showed a yield stress at 55.7 °Brix, from 5 to 11 Pa, and 63.0 °Brix, from 19 to 53 Pa. Yield stress was correlated with temperature by means of a linear equation. Arrhenius activation energies were in the range of 28.97 to 33.89 kJ/mol. The average value of the flow behaviour indexes varied from 0.85 (sample at 22.5 °Brix) to 0.59 (sample at 63.0 °Brix). Simple equations are proposed to describe the combined effect of temperature and soluble solids content on consistency index and rheological behaviour index.     

THIXOTROPY OF ORANGE CONCENTRATE AND QUINCE PUREE

Orange juice with pulp and pectins is thixotropic at soluble solids concentrations of 55 and 60 Brix in the range of temperatures from 0 to 20C and shear rate from 7.2 to 57.6 s⁻¹. Quince purée is thixotropic at soluble solids concentrations of 12.3 to 28 °Brix in the range of temperatures between 0 to 20C and shear rate from 7.2 to 57.6 s⁻¹. The thixotropic behaviour of orange juice and quince purée increases with increasing concentration and decreasing temperature and they can be described by the kinetic model proposed by Figoni and Shoemaker (1983):

The thixotropic structure of orange juice was destroyed by applying a shear rate of 57.6 s⁻¹ for 5 min, and for quince purée for 10 min. Quince purée shows a greater thixotropic character than orange juice, because it has a higher content of fiber, pulp and pectins and also because it shows a microscopic structure consisting of long particles and heterogeneous fibers.     

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.     

Rheological behaviour of apple juice and pear juice and their concentrates

This paper reports the rheological behaviour of apple juice and pear juice. The effect of temperature on this behaviour for concentrated apple juice and pear juice of 71°Brix and 70°Brix, respectively, is examined and equations are given to describe the change in viscosity with temperature within the temperature range 5–60°C. The rheology of apple juice and pear juice of different soluble solids concentrations at 25°C is likewise reported with equations to relate the change in viscosity with concentration within the concentration range studied. In all these cases these juices are Newtonian in behaviour.     

DEVELOPMENT AND PROCESS OPTIMIZATION OF RED RADISH CONCENTRATE EXTRACT AS POTENTIAL NATURAL RED COLORANT

Red radish concentrate extracts produced from two radish cultivars, red-skinned cv. Fuego and red-fleshed cv. Chinese Red Meat, were evaluated as potential sources of natural colorants. Unit operations were developed and optimized. Anthocyanins were extracted using a modified abrasive peeler or a hammermill for cultivars Fuego and Red Meat, respectively. The anthocyanin extract was further purified by standard juice processing operations and concentrated by conventional evaporative technology and/or direct osmosis. Anthocyanin recoveries of 80–90% as compared to solvent/resin purification were obtained. Anthocyanins extracted from epidermal tissue resulted in juices with fairly low initial °Brix (1.3°), which facilitated juice concentration to levels of 17° Brix containing 400 mg anthocyanin/100 mL concentrate. Radish concentrate provided color similar to FD&C Red #40. Sensory analysis showed     

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.     

Progressive freeze concentration of orange juice in a pilot plant falling film

In the present study the cryoconcentration of orange juice was investigated, using a pilot plant unit for cryconcentration of liquids using a cold surface. The evolution in time of the concentration of solids in the juice and in the ice was analyzed during the process. It was found that the concentration of solids in the juice showed a linear increase in time at a rate of 0.75 °Brix/h until a final concentration of 28.8 °Brix. The concentration of solutes in the ice showed an exponential increase.Industrial relevanceThe freeze concentration allows dewatering orange juice at temperatures below the water's freezing point, which allows obtaining products of better quality. The freeze concentration is a technology that allows eliminating water from the juices at temperatures below the water's freezing point, which allows obtaining products of better quality. This work has applied this technology to concentrate orange juice, obtaining promissory results.     

Inactivation of Escherichia coli O157:H7, Salmonella typhimurium and Listeria monocytogenes in apple juice with gaseous ozone

This research was initiated to assess the efficacy of gaseous ozone for inactivation Escherichia coli O157:H7, Salmonella typhimurium and Listeria monocytogenes in apple juice. Juice samples with solids content of 18, 36, and 72 °Brix inoculated with a culture cocktail of three foodborne pathogens were treated with gaseous ozone at a flow rate of 3.0 L/min and an ozone generation rate of 0.10, 0.90, 3.51, and 5.57 g/h for 0.5, 1, 5, and 10 min, respectively. The inactivation kinetics of gaseous ozone on foodborne pathogens conformed to the Weibull model. The time required to achieve a 5 log reduction (t_5d) was estimated using the parameters of the Weibull model. The t_5d increased with increasing solids content of apple juice. The ozone generation rate did not impart a significant effect (p > 0.05) on t_5d. Gaseous ozone is effective at inactivating foodborne pathogens in apple juice but the efficacy is dependent on the solids content of the juice sample.     

浓缩苹果汁生产过程中cAMP分布规律研究

探究浓缩苹果汁生产过程中3’,5’-环磷酸腺苷（3’,5’-cyclic adenosine monophosphate,cAMP）含量的分布规律。利用HPLC方法测定水浸提和乙醇浸提两种不同方式处理榨汁后的苹果果渣的cAMP含量和浓缩果汁中cAMP的含量,分析不同稀释倍数、不同可溶性固形物含量的浓缩苹果汁cAMP变化规律,并利用cAMP分配系数（DCcAMP）描述榨汁过程中cAMP含量的分布规律。结果表明：榨汁后苹果果渣中cAMP含量为（63.444 1±2.323 6）μg/g,70 °Brix的浓缩苹果汁成品中cAMP含量为（58.611 3±1.349 3）μg/mL,30 °Brix的浓缩苹果汁半成品中cAMP含量为（12.018 3±0.583 9）μg/mL;建立了浓缩苹果汁中cAMP含量与可溶性固形物含量之间的关系方程为y= 0.808 5x-1.218 5;测定得到70 °Brix和30 °Brix浓缩苹果汁的DCcAMP分别为92%和19%。因此,在浓缩苹果汁生产过程中,cAMP更趋向于存在苹果果渣中,且浓缩工艺对cAMP有富集作用。     

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.     

Compositional variations and sensory acceptability of apple juice drink

Apple juice drinks containing 60% of Granny Smith or Jonathan juice, 8–14% soluble solids and Brix: acids ratios of 15:1 to 30:1 were assessed by a panel of twenty-five tasters. Sweetness and sourness increased with increasing levels of soluble solids and acidity respectively. Sourness showed little change with soluble solids at constant Brix: acid ratio but sweetness changed significantly. Intensity of flavour increased with soluble solids but the changes differed in the two types of drinks. Drinks having different soluble solids or Brix:acid ratios sometimes had similar flavour acceptabilities. Sweetness or lack of sourness, and intensity of flavour appeared to account for much of the flavour acceptability of the drinks. Equations for predicting flavour acceptance, based on Brix and Brix:acid ratios, were also developed.     

Optimisation of osmotic dehydration of 'Tommy Atkins' mango fruit

Osmotic dehydration of mango in sucrose solution as influenced by temperature (30–50 °C), immersion time (60–150 min) and solution concentration (40–60% w/w) was studied through response surface methodology. Responses of water loss and solid gain were fitted to polynomials, with multiple correlation coefficients ranging from 0.72 to 0.95, respectively. The fitted functions were optimised for maximum water loss and minimised incorporation of solids in order to obtain a product resembling non-processed fruit. Optimum conditions to obtain water removal >25% with solid uptake lower than 6% could be obtained using a 44% (w/w) sucrose solution concentration, temperatures up to 38 °C and immersion times up to 80 min.     

Effect of pretreatment conditions on physicochemical parameters of carrot juice

Carrot juice obtained by hydraulic press with wooden set-up was subjected to pretreatments (temperature, time and pH) prior to extraction process. Their effects on the most important quality parameters of carrot juice, such as beta-carotene, reducing sugars, pectin, vitamin C, viscosity, pH and acidity were studied. Response surface methodology was employed, where the experiment was carried out according to a central composite rotatable design. The variables ranges used were 61.50–98.50 °C (temperature), 124.55–595.45 s (time) and 2.31–6.69 (pH – concentration of citric acid). The results showed that beta-carotene extraction was significantly increased (52.9%) with these pretreatments in comparison to control samples. All the derived mathematical models for the responses were found to be fit significantly to predict the data. The responses were optimised by numerical method and were found to be 7190 μg per 100 g beta-carotene, 3.41% reducing sugars, 4.96 mg per 100 g vitamin C, 0.59% pectin, 1.64 × 10³ Ns m⁻² viscosity, 5.26 pH and 4.97% acidity at optimum input variables of 75.26 °C (temperature), 349.89 s (time) and 3.2 (pH). The desirability for all the responses was found to be 83.8%.     

NONENZYMATIC BROWNING IN CLARIFIED APPLE JUICE AT HIGH TEMPERATURES: A RESPONSE SURFACE ANALYSIS

The effect of temperature and soluble solids on nonenzymatic browning in clarified and concentrated apple juice was analyzed by response surface methodology. Color development at 20, 40 and 60 Brix and temperatures ranging from 70–90C were compared over a time range of 30–180 min. the browning reaction was found to be dependent on soluble solid content as well as on the reaction conditions such as temperature and time. the model combines the effect of temperature, soluble solids content and time on color change due to nonenzymatic browning.     

The influence of enzymatic treatment of mash on the analytical composition of apple juice

Five apple juices were produced on a pilot scale by crushing the fruit, treating the mash with pectolytic enzymes, pressing, extracting water from the pomace, pasteurization, treatment of the juice with enzymes, combined gelatin/silica sol fining and final ultrafiltration. The temperature of the mash treatment was either ambient or one of 30, 40, 50 or 60 °C, in order to test whether this led to different compositional changes in the corresponding juices. The main emphasis was put on detection of D -galacturonic acid as the indicator substance for the extent of the enzymatic treatment. In the pasteurized raw juices after pressing we found values from 226 to 398 mg L⁻¹. A distinct increase of the galacturonic acid levels could be observed during the clarification steps. Enzymatic juice treatment raised the concentrations to 580–720 mg L⁻¹. After ultrafiltration, final values of 790–1100 mg L⁻¹ were measured. Generally, the highest values were found in the 50 °C sample, which is the optimum temperature for pectinase activity. This was also true for the colloid concentrations and polyphenols. The influence of the temperature of the enzymatic mash treatment on other characteristic juice parameters like total titratable acidity, density, sugar, and minerals concentrations was low.