Effect of Temperature and Soluble Solids Content on the Viscosity of Beetroot (Beta vulgaris) Juice Concentrate

The study investigates the viscosity of clarified beetroot juice as dependent on temperature and soluble solids content. Rheological research was carried out using a rotational rheometer with a system of coaxial cylinders. Flow curves were obtained in the temperature range from 10 to 60°C and at the soluble solids content of 50° to 67.1°Bx. The concentrate under study showed a Newtonian behaviour. Dynamic viscosity ranged from 5.2 to 320 mPa·s and depended on soluble solids content and temperature of measurement. The effect of temperature was described using an Arrhenius equation. Activation energy values were between 24.68 and 39.96 kJ/mol. The effect of soluble solids content was described employing a power-law function and an exponential function. In addition, two equations were proposed to describe the combined effect of temperature and soluble solids content on the viscosity of beetroot juice concentrate.     

Assessment of variables effects on sugar cane juice clarification by carbonation process

This paper reports a study of sugar cane juice carbonation and the evaluation of variables effects such as pH, carbonation time and temperature on industrially relevant parameters for the quality of sugar cane juice. Three different batches of sugar cane juice were evaluated using a complete two‐level factorial design with central point performed in triplicate. From results in this work, it can be seen that the higher sucrose concentrations and lower percentage of total soluble solids and reducing sugars were obtained in clarified juices with the maximum values for pH, time and reaction temperature (9.5, 60 min and 80 °C). The temperature favoured the removal of starch, phosphate and turbidity. Colour removal reached a maximum of 88–93% among the batches. The optimum clarification condition using carbonation procedure can be achieved between 20 and 40 min, at pH values between 8.0 and 9.5 and temperature condition at 80 °C.     

RHEOLOGICAL BEHAVIOR OF POMEGRANATE (PUNICA GRANATUM L.) JUICE AND CONCENTRATE

The rheological behavior of pomegranate juice (Punica granatum L.), prepared from fresh pomegranates, was studied as a function of solids concentration in the range 17.5–75°Brix at 10–55C, using a controlled stress rheometer. Concentration methods did not influence flow behavior. There were no significant differences (P > 0.05) between viscosity and activation energy values for the pomegranate juices concentrated by different methods. The juices exhibited Newtonian behavior regardless of the concentration method. The effect of temperature was described by an Arrhenius‐type equation with an activation energy in the range 5.34–32.2 kJ/mol depending on concentration. An exponential model described better the effect of the soluble solids on the viscosity and E_avalues. A simple equation was proposed for describing the combined effect of temperature and soluble solids content on the juice viscosity.     

Evaluation of enzymatic treatment of peach juice using response surface methodology

BACKGROUND: This work aimed to assess peach juice clarification using enzymatic treatment. The enzymatic hydrolysis was performed to reduce the juice viscosity and pulp content, and consequently to increase juice extraction. The hydrolysis conditions were optimized by the response surface methodology, where the influence of temperature, amount and type of enzyme and time of reaction were investigated. RESULTS: Two commercial pectinase preparations (AFP L3 and ULTRA SP WOP from Novozymes) as well as a cellulase (R10 from Onozuka) were tested. The hydrolysis using Pectinex AFP L3 (Novozymes) at 25 °C for 60 min presented the best results of pulp (48%) and viscosity (68%) reduction. CONCLUSION: Physical and chemical analyses showed that the enzymatic treatment is effective for reduction of peach pulp viscosity, pulp content and turbidity and does not influence other juice parameters such as pH, total acidity, vitamin C and soluble solids. Copyright © 2007 Society of Chemical Industry     

VISCOSITY REDUCTION AND PREVENTION OF BROWNING IN THE PREPARATION OF CLARIFIED BANANA JUICE1

Experiments were conducted to determine the effects of commercial enzyme preparations on viscosity reduction and filterability of banana juice, and the effectiveness of various anti-browning treatments on clarified juice. Two different combinations of pectinase, cellulase and hemicellulase were more effective in reducing viscosity and improving filterability of both green and ripe banana purees than a pectinase, galactomannanase or cellulase after incubation periods of 3, 6 and 9 h. An alpha-amylase was not effective in reducing viscosity as compared to the control, even of green banana puree high in starch. Potassium metabisulfite (100 mg/L) was more effective in producing a light colored juice with stable color than two heating methods (heating whole, unpeeled bananas at 100°C for 11 min.; heating puree at 80°C for 1–2 min) and ascorbic acid (470 mg/L). Polyphenoloxidase was active in the clarified juices treated with ascorbic acid and the control, and both darkened over time. Sensory analysis indicated that all the juices had similar banana flavor intensity.     

Molecular Weight Cut-off of Ultrafiltration Membranes and the Quality and Stability of Apple Juice

The quality and stability of apple juice clarified using 10,000 (10K), 50K, 100K, and 500K daltons molecular weight cut-off (MWCO) hollow fiber membranes were examined . Ultrafiltered juice was tested for initial stability, starch presence, pH, total acidity, total solids, soluble solids, turbidity, browning, Hunter color, total phenols, and sensory attributes. Turbidity, browning, total phenols, and sensory color were different depending upon the MWCO used. Samples were stored at 18°C and 43°C for 6 months and evaluated monthly. At 18°C, there were no significant changes but initial differences due to membranes remained. At 43°C, the increase in turbidity, browning, and chroma, as well as the decrease in lightness and hue with time, were significant. Reaction rates were all the same independent of the MWCO except for chroma.     

EFFECT OF SOLUBLE SOLIDS AND TEMPERATURE ON ASCORBIC ACID DEGRADATION IN LEMON JUICE STORED IN GLASS BOTTLES

Lemon juice at concentrations of 9°, 20°, 30°, 40° and 50°Brix was stored at 10°, 20° and 36°C for 16 weeks and sampled regularly for total soluble solids (TSS), pH, titratable acidity and ascorbic acid. No significant differences were found in the first two of these factors as a function of storage time. There was a small but significant decrease in citric acid concentration over 16 weeks. Ascorbic acid loss was greater at higher temperatures; at a constant temperature, the loss was smaller as TSS increased. Ascorbic acid degradation data fitted zero-, first- and second-order models equally well at all five TSS. Rate constants in 9°Brix juice were significantly higher than those for the other four concentrations at all three temperatures. E_a values of 47.8 and 24.1 kJ mol^?1 were calculated for ascorbic acid degradation in 9° and 20°Brix juices. The effect of temperature far outweighed the effect of TSS on ascorbic acid degradation. Over the 16-week storage period, maximum retention of ascorbic acid (95.7%) was obtained in the 50°Brix lemon juice concentrate stored at 10°C.     

EFFECT OF HYDROCOLLOIDS ON APPARENT VISCOSITY AND SENSORY PROPERTIES OF SELECTED BEVERAGES1

The effects were studied of low concentrations of 5 selected hydrocolloids (xanthan, hydroxypropylcellulose, sodium alginate, and carboxymethylcellulose of low and medium viscosity types) on viscosity and sensory properties of 3 commercial beverages: tomato juice, orange drink and soluble coffee. Tomato juice and orange drink were tested at 0° and 22°C, while coffee was tested at 22° and 60°C by 11-14 highly trained judges. Apparent physical viscosity was determined with a Brookfield uiscometer. Due to precipitate formation, it was not possible to test sodium alginate in orange drink nor hydroxypropylcellulose in coffee at 60°C. Without exception, increasing the hydrocolloid concentration significantly depressed (P < 0.001) the flavor and aroma intensities of all beverages a t both test temperatures. Taste effects were specific for the gumlbeverage combinations. In general, gums depressed the sourness and saltiness of tomato juice, the sourness of orange drink and the bitterness of coffee. Both physical and oral viscosities increased with gum concentration and decreased with temperature. Positive synergism was displayed by gums in tomato juice and orange drink. Excellent correlations (r > 0.9) were obtained between sensory and physical viscosities.     

THERMOPHYSICAL PROPERTIES OF PINK GUAVA JUICE AT 9 AND 11°BRIX

The effect of temperature on the conservation of pseudoplastic characteristics and on the physical properties of pink guava juice (Psidium guajava L.) variety Beaumont: B‐30 with two different total soluble solids (9°Brix and 11°Brix) was investigated. It was found that the juice exhibits pseudoplastic behavior in the range of shear rate between 40 to 160 s^?1 and within pasteurization temperature of 60–90C. While the flow behavior index (n) and density (p) increased, consistency coefficient (K), thermal conductivity (k) and specific heat capacity (C_p) decreased with increasing temperature. The linear regression equations or models for flow behavior index, consistency coefficient, density, thermal conductivity and specific heat capacity were determined with correlation coefficients ranging from 0.75 to 1.00.     

Effect of Thermal Treatment on the Rheological Pattern and Composition of Dry Bean Flour Soluble Extracts

Dry bean flour samples with 14% (dry basis) moisture content were exposed to thermal treatment, in sealed cans, at 50°, 70°, 80°, and 90°C, for various periods. The rheological pattern and composition of their soluble extracts, obtained at pH 10, were determined. Soluble extracts decreased in viscosity with time of treatment, up to a time dependent on temperature, where viscosity became constant. Soluble protein decreased with time of treatment. During the first step of dry bean flour heat treatment, soluble solids other than protein, were constant, then began to increase, promoting viscosity constance in spite of soluble protein decrease.     

Influence of milk pre-heating conditions on casein–whey protein interactions and skim milk concentrate viscosity

The viscosity of concentrates (50–55% total solids) prepared from skim milk heated (5 min at 80 or 90 °C) at pH 6.5 and 6.7 was examined. The extent of heat-induced whey protein denaturation increased with increasing temperature and pH. More denatured whey protein and κ-casein were found in the serum phase of milk heated at higher pH. The viscosity of milk concentrates increased considerably with increasing pH at concentration and increasing heating temperature, whereas the distribution of denatured whey proteins and κ-casein between the serum and micellar phase only marginally influenced concentrate viscosity. Skim milk concentrate viscosity thus appears to be governed primarily by volume fraction and interactions of particles, which are governed primarily by concentration factor, the extent of whey protein denaturation and pH. Control and optimization of these factors can facilitate control over skim milk concentrate viscosity and energy efficiency in spray-drying.     

STUDIES ON PRESERVATION OF SUGARCANE JUICE

ABSTRACT

The variety CoP 92226 was selected for preparing sugarcane juice beverage on the basis of yield and sensory attributes from eight promising varieties of sugarcane. Sugarcane juice beverage samples were prepared by pasteurizing the sugarcane juice at 70°C for 10 minutes and adding citric acid (40 mg/100 ml), ascorbic acid (40 mg/100 ml) and potassium metabisulphite (150 ppm). Samples of sugarcane juice beverage were stored at room (30±5°C) and refrigeration (4±2°C) temperature in pre-sterilized glass bottles and analyzed for physico-chemical, microbiological and sensory attributes at every 15 days interval for 90 days. The pH, total soluble solids and total sugars decreased, whereas, titratable acidity and reducing sugars increased significantly (P<0.01) during storage. An appreciable increase in total plate counts and yeast and mold counts were observed, however, no coliforms, were detected in sugarcane juice beverage during storage. The changes in different attributes were significantly (P<0.01) higher at room temperature as compared to refrigeration temperature. The sugarcane juice beverage having citric acid and potassium metabisulphite showed minimum changes in sensory qualities during storage, both at room and refrigeration temperature. An acceptable quality beverage of sugarcane juice with satisfactory storage stability for 90 days at room as well as refrigeration temperature could be prepared.     

HEAT-INDUCED GELATION AND PROTEIN-PROTEIN INTERACTION OF ACTOMYOSIN1

Natural actomyosin (NAM) and “crude” actomyosin formed gels yielding maximum strengths (from back extrusion force) at pH 5.0 and 5.5, respectively. At pH 6.0, NAM gels had a least protein concentration endpoint (LCE) value of 6 mg/ml. Gel strength increased exponentially with an increase of NAM concentration from 3.75–10 mg/ml. With constant time (30 min)-temperature heating, NAM gel forces increased by 20.5% (NS, P>0.05) in the 30–80°C range. Arrhenius plots of NAM interaction in solution and in gelation at pH 6.0 indicated two different reaction mechanisms within the temperature zones above and below approximately 35°C for solutions and 40°C for gels. Similarity of interaction slopes above the 35–40°C region suggested one reaction mechanism for NAM molecular aggregation in solution and gelation.     

RHEOLOGY OF MULBERRY PEKMEZ

The rheological behavior of mulberry pekmez (concentrated mulberry juice, °Brix = 72.0) with different solid contents (62.8, 55.8 and 46.0) was studied over the temperature range of 10, 20, 30, 40, 50 and 60C using a Controlled Stress Rheometer. Mulberry pekmez was found to exhibit Newtonian behavior. The effect of temperature can be described by means of Arrhenius equation. The activation energies for flow of samples vary from 53.11 to 12.73 kJ/mol depending on soluble solid contents. The effect of soluble solids on viscosity can be described by an exponential equation. The best model to describe the combined effects of temperature and soluble solids content on viscosity is η= 3.40 X 10^-10 exp (0.12C + 3723/T).     

EFFECT OF MALTING TEMPERATURE AND TIME ON ENZYME DEVELOPMENT AND SORGHUM WORT PROPERTIES

The effect of malting temperature and time on enzyme development and wort properties of an improved Nigerian sorghum cultivar (Ex-Kwara) were investigated. Malting was carried out at two temperature regimes, 20°C and 25°C for eight days. Parameters evaluated included α- and β;-amylase development, hot water extract (HWE), soluble extract, fermentability, fermentable extract, viscosity, filtration rate, reducing sugars, α;-amino nitrogen and total soluble nitrogen (TSN). For virtually all the parameters studied, germination at 25°C produced higher values on the 4th day after which temperature appeared to have little influence. α;-Amylase development continued throughout the germination period while β;-amylase peaked on the 6th day. Optimal values of total soluble nitrogen (TSN) were recorded at both 25°C and 20°C at the 6th and 8th day of germination respectively .     

EFFECTS OF PHOMOPSIS PEACH ROT ON PULP LOSSES AND PUREE QUALITY

The effects of a Phomopsis sp. on four peach (Primus persica) cultivars and three fruit maturities were evaluated for pulp losses and quality changes of peach puree. Fruits were inoculated with 2 mm × 2 mm of agar with Phomopsis mycelium and incubated at room temperature (24 to 26 C) for 3 days. The early-maturing cultivar Goldilocks had higher susceptibility to Phomopsis than the late maturing Babygold 8. Mature fruit had a slightly higher degree of susceptibility to Phomopsis than less mature fruit, except for Goldilocks, which showed equal susceptibility at all maturity stages. Pulp losses, percentage of decayed tissue, titratable acidity, Howard mold counts, soluble solids (SS), SS/acid ratio, viscosity, pH and changes in color were variable among cultivars and maturities. Puree made with 1% or more Phomopsis-decayed tissue may be unacceptable because of a high (16–75%) mold count.     

EFFECTS OF PROCESSING TIME AND TEMPERATURE ON THE QUALITY COMPONENTS OF CAMPBELL GRAPE JUICE

Campbell grape juice was processed at different temperatures (60, 70, 80 and 90C) and different times (30, 45 and 60 min), and evaluated for quality components and sensorial properties. The grapes were crushed, added with enzyme, heated, and pressed; then the juice was cold stabilized, filtered and pasteurized. The samples showed an increase in pH and a decrease in titratable acidity. Sugar/acid ratio and total soluble solids increased until 80C then decreased when 90C was reached. A slight increase in L* and b* values and a decrease in a* color values were also shown. Significant differences were mostly observed between processing temperatures than between processing times. Increasing processing temperature enhances the total phenolics, total anthocyanin and total flavonoid contents, and % radical scavenging activity of the juice until 80C but declined when the temperature reached 90C. Sensory evaluation showed that the preferred time–temperature combination for processing Campbell juice is between 70 and 80C for 30–45 min.

PRACTICAL APPLICATIONS

Campbell Early ( V. labrusca B.) is one of the major table grapes in Korea and overproduction of this grape variety in Korean market calls for an alternative product in which excess grapes can be utilized. This study is focused on the determination of the effects of processing time and temperature on the quality components of Campbell grape juice. The results can be a guide to have a processing method that can be used in producing Campbell grape juice with good sensory properties and high bioactive compounds     

Formation of acid‐precipitated soy protein–dextran conjugates by Maillard reaction in liquid systems

The conjugation reaction between soybean acid‐precipitated protein (SAPP) and dextran in liquid systems via the initial stage of the Maillard reaction was studied. Functional SAPP–dextran conjugates were prepared in 80% ethanol‐reacting system at 50 °C for 6 h, along with 95% ethanol‐reacting system at 60 °C for 24 h. The covalent attachment of dextran to SAPP was confirmed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and gel filtration chromatography.Compared to the classical dry‐heating, the reaction time of glycosylation in the two ethanol systems was largely shortened. Emulsifying activity of SAPP–dextran conjugates obtained by dry‐heating incubation and in ethanol was similar at pH 7.0 and10.0, significantly higher than that of SAPP–dextran mixture or SAPP alone. In addition, SAPP–dextran conjugates obtained in 80% ethanol‐reacting system for 6 h were completely soluble after heating at 90 °C for 20 min. The impact of various processing conditions on the formation of SAPP–dextran conjugates was investigated. This study provides important guidance to create protein–polysaccharide conjugates at mild temperatures in liquid systems.     

Effect of Temperature on the Serum Viscosity of Tomato Juice

Tomato juice was canned and exposed to processing temperatures of 82°C., 102°C and 112°C. Serum viscosity was measured after 30, 60, and 120 min at each temperature. Heat treatment affected serum viscosity. A temperature of 82°C applied for 2 hr resulted in a 17-30% loss of serum viscosity depending on the cultivar. Treatment at 112°C applied for 2 hr caused 67-82% loss, again depending on the cultivar.     

Tomato Product Quality from Transgenic Fruits with Reduced Pectin Methylesterase

Juice from transgenic tomato (Lycopersicon esculentum cv Rutgers) fruits with reduced levels of pectin methylesterase (PME) activity due to the expression of a PME antisense gene exhibited improvement in quality. The percentage increase in juice from transgenic fruits over that of juice from wild type Rutgers ranged between 5.1–5.3 for total solids, 3.8–6.1 for soluble solids, 70–80 for efflux viscosity, 180–220 for serum viscosity and about 50 for precipitate weight ratio. Time of harvest had no effect on quality of juice. Ketchup prepared from transgenic fruit juice had a lower Bostwick value, reduced serum separation and high serum viscosity compared to ketchup from parental Rutgers.