Properties of Orange Juice with Supercritical Carbon Dioxide Treatment

The effects of supercritical CO₂ (SC-CO₂) on the microbiological, sensory (taste, odour, and colour), nutritional (vitamin C content), and physical (cloud, total acidity, pH, and °Brix) qualities of orange juice were studied. The CO₂ treatment was performed in a 1 litre capacity double-walled reactor equipped with a magnetic stirring system. Freshly extracted orange juice was treated with supercritical CO₂, pasteurised at 90°C, or left untreated. There were no significant differences in the sensory attributes and physical qualities between the CO₂ treated juice and freshly extracted juice. The CO₂ treated juice retained 88% of its vitamin C, while the pasteurised juice was notably different from the fresh juice and preserved only 57% of its vitamin C content. After 8 weeks of storage at 4°C, there was no microbial growth in the CO₂ treated juice.     

Malic Acid as a Source of Carbon Dioxide in Cucumber Juice Fermentations

The degradation of malic acid to lactic acid and CO₂ during fermentation of cucumber juice was investigated. This malolactic reaction was the major source of CO₂ when cucumber juice was fermented by Lactobacillus plantarum. It may also be an important CO₂ source in controlled cucumber fermentations. In addition to CO₂ production, the degradation of malate served to buffer the fermentation and increase sugar utilization. The pH after 7 days’fermentation was 2.8 when 13 mM malic acid was present in the juice and 4.1 with 135 mM malic acid. In the same fermentations, 52% of the sugars were degraded with the low malic acid concentration while complete sugar utilization was observed with the highest malic acid level.     

Extraction of Annatto Seed Pigment by Supercritical Carbon Dioxide

Operating pressures ranged 3000–7000 psi and temperatures 40–55°C. Maximum solubility of pure bixin was 0.003 and of annatto seed pigment 0.26 mg/g CO₂. Analyses of annatto seed pigment from supercritical carbon dioxide extractions showed only α-and β-bixin present. Only bixin was extracted from mixed samples consisting of bixin and norbixin. No thermal degradation product was detected in samples extracted within the temperature range we used. Increased temperature resulted in increased pigment/g CO₂ at all pressures. Isothermal increases in pressure did not increase pigment/g CO₂. Efficiency of annatto pigment extraction was increased in the presence of an oil.     

Influence of Fluid Concentration on the Elevation of Boiling Point of Blackberry Juice

The rise in boiling point of blackberry juice was experimentally measured at soluble solids concentrations in the range of 9.4 to 58.4°Brix and pressures between 4.9?×?10³ and 9.0?×?10⁴ Pa (abs.). Different approaches to representing experimental data, including the Dühring's rule, a model similar to Antoine equation and other empirical models proposed in the literature were tested. In the range of 9.4 to 33.6°Brix, the rise in boiling point was nearly independent of pressure, varying only with juice concentration. Considerable deviations of this behavior began to occur at concentrations higher than 39.1°Brix. Experimental data could be best predicted by adjusting an empirical model, which consists of a single equation that takes into account the dependence of rise in boiling point on pressure and concentration.     

Changes in Muscadine Grape Juice Quality During Cold Stabilization and Storage of Bottled Juice

Muscadine grapes (Vitis rotundifolia, Michx.) of two cultivars (Noble and Carlos) were washed and extracted. The resulting juice was cold stabilized for 0, 7 and 60 days at 2°C, then treated, bottled, pasteurized and stored at 2°C and 24°C for 0, 4, 8, and 12 months. Carlos juice was lower in phenols and pH and higher in acidity than Noble. The high total anthocyanins and phenols in the Noble juice caused a significant loss in pigment during cold stabilization. Dilution of juice with 40% water and adjustment of the sugars was beneficial to flavor and color of Carlos, yet 40% dilution was too high for Noble juice. Treatment of either juice with CaCO₃ increased pH and decreased acidity. During 12 months storage, the Carlos juice became darker due to browning, while the Noble juice became lighter by losing pigment, especially at 24°C.     

MASS TRANSFER IN PACIFIC HAKE (Merluccius australis) PACKED IN REFRIGERATED MODIFIED ATMOSPHERE

The objective of this research was to develop, and experimentally validate a fully mathematical model, to predict mass transfer phenomena in Pacific Hake (Merluccius australis) packed in refrigerated modified atmosphere. A mathematical model to predict mass transfer of CO₂, O₂, N₂ and water vapor was developed and validated. The diffusion model was developed utilizing Fick's second law, considering fish fillet as an infinite slab and applied to Pacific Hake (lean fish species) under refrigeration conditions. CO₂ diffusivity of Pacific Hake was determined by an inverse procedure at OC and resulted in a value of 5.19 × 10^?10 [m²/s] that is in accordance with values reported in the literature. However, postmortem variations of pH could affect solubility and diffusivity of CO₂ in fish muscle.     

Kinetics of Deterioration of Pineapple Concentrate

Pineapple juice concentrate undergoes reactions leading to color formation and quality loss. Kinetics were studied calorimetrically, spectrally and by chemical analysis. Two exothermic processes occurred between 40° and 80°C, one independent of, and one dependent on O₂ concentration. The rate of the O₂ independent reaction decreased exponentially with time, (sucrose hydrolysis). The rate of the O₂ dependent process was constant with time, complex, and not defined. Heat producing reaction rates were not altered by concentrations of major sugars/organic acids. Development of color occurred later than heat production. Color development had a complex dependence on solids and 0₂ concentration, and correlated with initial rate of 5–hydroxymethylfurfural (HMF) formation. CO_z, decrease in titratable amines and amino acids, and loss of reducing agents accompanied color development. Heat and color production and chemical changes correlated with sensory quality.     

Inactivation of yeasts in grape juice using a continuous dense phase carbon dioxide processing system

The effects of dense phase CO₂ processing parameters, including temperature (25 and 35 °C), CO₂ concentration (0, 85 and 170 g kg⁻¹) and pressure (6.9, 27.6 and 48.3 MPa), on yeast survival and sensory properties of grape juice were investigated. The dense phase CO₂ process resulted in more than a 6 log reduction in yeast population. As the CO₂ to juice concentration, temperature and pressure increased, the inactivation rate increased. CO₂ in the supercritical state was more effective in inactivating yeast than in the subcritical state. The process did not cause detectable flavor degradation. Dense phase CO₂ processing can be an effective non‐thermal alternative process for pasteurization of grape juice. Copyright © 2005 Society of Chemical Industry     

Cross-flow Microfiltration with Gas Backwash of Apple Juice

Cross-flow microfiltration (MF) was applied for clarification of commercially pressed depectinized apple juices and pectin containing artificial apple juice suspensions under continuous low pressure inlet conditions (35 kPa - 209 kPa). Periodic gas backwash (air or N₂) removed solids from exteriors of 0.2 μm cut-off hollow fiber polypropylene membranes. Flux and nephelos turbidity units (NTU) of filtrates for both commercial juices and artificial juices were evaluated. Commercial juices after vacuum filtration and MF had 100–110 L/m²/hr flux during 2 hr operation. Low pectin (1%) artificial juices had ～70 L/m²/hr flux during 1.5 hr. NTUs of filtrates from all treatments were <0.69. All filtrates were commercially sterile.     

Apparent solubility of lycopene and β-carotene in supercritical CO2, CO2 + ethanol and CO2 + canola oil using dynamic extraction of tomatoes

Lycopene and β-carotene were extracted from freeze-dried tomatoes (skin + pulp) with pure SC CO₂ and SC CO₂ + 5% w/w co-solvent at 40 °C, 400 bar and flow rates of 0.5 and 1.2 L/min. The apparent solubility of lycopene and β-carotene in the multicomponent complex system was determined from dynamic extraction experiments using a laboratory-scale supercritical extraction system. Solubility of pure lycopene and β-carotene in SC CO₂ (binary system) was reported in the literature to be of the order of 10⁻⁶ mole fraction. The apparent solubility of lycopene extracted from tomatoes with SC CO₂ (multicomponent complex system) under the same conditions was almost one order of magnitude smaller. The apparent solubility obtained using oil as a co-solvent was higher than that obtained with ethanol as a co-solvent or pure SC CO₂. The differences in solubility are mainly due to the polarity of the co-solvent and the impact of the tomato matrix in the multicomponent complex system.     

Application of Phenolic Extracts from Selected Plants in Fruit Juice

Plant phenolics have gained considerable interest in recent years for their potential effects against food related microorganisms. In the present study, phenolic extracts from the leaves of three plants namely Moringa oleifera, Morus indica, and Mentha spicata were prepared by a mixture of methanol/acetone/water. The UV spectra of extracts were recorded and contents of total phenolics determined. The extracts were incorporated in pineapple juice and their solubility and stability were studied. In addition, the acceptability of treated juice samples was sensory evaluated. The solubility of M. indica and M. oleifera extracts was found to be more than that of M. spicata. The two extracts were also stable in the pH environment of pineapple juice when stored at 4°C for two weeks. The pineapple juice treated with M. indica extract was more acceptable compared to that of M. oleifera, according to sensory evaluation. Therefore, the effect of addition of phenolic extract from M. indica on the shelf life of pineapple juice stored at 4°C was investigated by monitoring the changes in titrable acidity and sensory parameters for 8 weeks. Results indicated that the extracts of natural phenolic compounds can be used to improve the quality and safety of foods.     

Kinetic Parameter Estimation for Quality Change during Continuous Thermal Processing of Grapefruit Juice

Reaction order, activation energy (E_a) and average rate constant (k_av) were evaluated by dynamic modeling for color degradation of grapefruit juice during thermal processing. Simulated aseptic conditions were: 85–135°C, 40–175 set processing time, and average velocities 5–30 cm/set. Quality was assessed by nonenzymatic browning index (NEBI) and S-hydroxymethyl-furfural (HMF). Average values for reaction-order and energy of activation were: 0 and 21.4 kcal/g-mol (NEBI) and 0.3 and 23.2 kcal/g-mol (HMF), respectively. These values were compared with those contained in the deformed ellipsoid which define the 90% joint confidence interval of all possible parameter combinations. Based on initial and final concentrations, the method can predict effects of processing on liquid foods.     

苹果汁中糖和氨基酸的美拉德反应动力学模拟研究

在苹果汁的热加工过程中,美拉德反应对其质量的影响是极其重要的.为了能控制象美拉德反应这样复杂的反应,必须对其进行定量研究.本文通过对苹果汁中主要糖和氨基酸的美拉德反应动力学模拟.阐述了苹果汁中非酶褐变的美拉德反应机理,应用反应动力学原理,定量地描述反应的变化和预测反应随时间-温度的变化规律.     

Thermal Degradation Kinetics of Pigments and Visual Color in Watermelon Juice

Thermal degradation of total carotenoids, lycopene and visual colour of watermelon juice was studied at 50–90°C up to 5 h. Total carotenoids content in fresh watermelon juice was reduced from 4.568 to 0.929 mg/100 g, lycopene from 4.403 to 0.82 mg/100 g and Hunter ‘a × b’ value from 251.66 to 89.59 when heated at 90°C for 5 h. First order model explained the degradation behaviour of total carotenoids, lycopene and Hunter ‘a × b’ value evident from correlation coefficient (R²) higher than 0.93. The dependence of degradation rate constant of total carotenoids, lycopene and Hunter ‘a × b’ value on temperature was adequately explained by Arrhenius equation. The activation energies for total carotenoids, lycopene and Hunter ‘a × b’ value were 24.19, 26.46, and 55.47 kJ/mol, respectively. Total carotenoids and lycopene were correlated with Hunter ‘a × b’ value with R² > 0.99 indicating that visual colour may be used to predict lycopene and total carotenoids contents in watermelon juice.     

橙汁模拟体系非酶褐变产物及评价标准

以橙汁中糖、氨基酸、抗坏血酸、柠檬酸为变量构建不同的非酶褐变模拟体系,通过研究体系贮藏期间3-羟基-2-吡喃酮（3-hydroxy-2-pyrone,3OH2P）、5-羟甲基糠醛（5-hydroxymethylfurfural,5-HMF）、糠醛（furfural,2-F）3 种褐变产物的变化,确定褐变产物的可能来源;通过分析比较褐变度（A420 nm）、褐变指数（browning index,BI）、总色差值（ΔE）3 种非酶褐变评价标准的相关性,确定不同评价标准是否有一致性。结果表明：果糖降解是生成5-HMF的主要途径,3OH2P来源于抗坏血酸的降解,糖能促进2-F的生成;在含糖的模拟体系中,A420 nm、BI、ΔE相互之间均呈显著正相关（P＜0.05）,这3 种评价标准具有一致性;然而在不含糖的体系中,A420 nm与BI、ΔE均无显著相关性（P＞0.05）,这3 种评价标准存在差异性。     

Physicochemical Characterization of Pure Persimmon Juice: Nutritional Quality and Food Acceptability

Technological process for production of non‐astringent persimmon (Diospyros kaki Thunb. cv. “Rojo Brillante”) juice was described. The degree of fruit ripening expressed as color index (CI) varied between 12.37 and 16.33. Persimmon juice was characterized by determining physicochemical quality parameters as yield, total soluble solids (TSS), pH, titratable acidity (TA), organic acids, and main sugars. A thermal treatment of 90 ºC for 10 s was effective in controlling naturally occurring microorganisms for at least 105 d of storage without significantly affecting production of soluble brown pigments (BPs) and 5‐hydroxymethyl furfural (5‐HMF), total phenolic compounds (TPC), antioxidant capacity and acceptability of juice by panelists. Storage time affected all and each of the above parameters, reducing BPs, TPC and antioxidant capacity but increasing 5‐HMF content. Refrigerated storage enhanced the acceptability of the juices. This information may be used by the juice industry as a starting point for production of pure persimmon juices.     

红枣果汁果渣与果酒果渣膳食纤维功能特性的比较研究

为了探究红枣果汁果渣与果酒果渣膳食纤维功能特性的差异,以红枣果汁果渣和果酒果渣为原料制备膳食纤维,通过测定膳食纤维的持水力、膨胀力、溶解性、持油力、阳离子交换能力以及吸附胆固醇、胆酸钠、葡萄糖能力,评价红枣果汁果渣与果酒果渣膳食纤维的功能特性。结果表明:红枣果酒果渣膳食纤维的持水力、膨胀力、溶解性、持油力、阳离子交换能力以及吸附胆固醇、胆酸钠、葡萄糖能力均显著高于果汁果渣膳食纤维(P<0.05),且随发酵天数延长,红枣果渣膳食纤维的功能特性均逐渐增加。发酵8 d时,果酒果渣膳食纤维持水力、膨胀力、溶解性、持油力、阳离子交换能力以及吸附胆固醇、胆酸钠、葡萄糖能力较果汁果渣膳食纤维分别提高了1.10、1.11、1.75、1.39、2.03、1.49、1.10和1.83倍,表明发酵有助于提高红枣果渣膳食纤维的功能特性。     

Quality Enhancement of UF-clarified Pear Juice using Adsorbent and Weak-base Resins at Different Temperatures

ABSTRACT: The efficiency of polymeric adsorbent (PA) and weak‐base anion (WBA) resins at different temperatures to improve the quality of UF‐clarified pear juice was investigated. UF‐clarified and partially concentrated pear juice was passed through PA and then through WBA resins at 23, 30, and 50 °C. Treated juice samples were analyzed for pH, titratable acidity, color, phenolics, minerals, sugars, and organic acids. Treated juice showed 85% reduction in both color and titratable acidity. There was also a significant reduction (P < 0.05) in the content of polyphenolics and organic acids. No significant changes (P > 0.05) in the nutritional value were detected. Temperatures higher than 23 °C did not significantly (P > 0.05) improve the efficiency of the resins tested.     

Flavor, Aroma, and Compositional Changes in Strawberry Juice Concentrate Stored at 20° C

Strawberry juice concentrate (68°Brix) was stored at 20°C for 0–6 days. Samples were analyzed for changes in taste, aroma and color degradation, and these changes were related to composition change. Astringent taste, musty/moldy and pungent aromas and brown color developed rapidly over 6 days. This decrease in quality was accompanied by CO₂ production and a decrease in free amino acids, while reducing sugar and titratable acidity concentrations remained stable.     

Effects of Commercial-scale Pulsed Electric Field Processing on Flavor and Color of Tomato Juice

Effects of commercial‐scale pulsed electric field (PEF) processing on the flavor and color of tomato juice during storage at 4 deg;for 112 d were studied. Tomato juice was prepared by hot break at 88°C for 2 min and then thermally processed at 92° for 90 s or PEF processed at 40 kV/cm for 57 μs. The PEF‐processed tomato juice retained more flavor compounds of trans‐2‐hexenal, 2‐isobutylthiazole, cis‐3‐hexanol than thermally processed or unprocessed control tomato juice (P < 0.05). PEF‐processed juice had significantly lower nonenzymatic browning and higher redness than thermally processed or control juice (P < 0.05). Sensory evaluations indicated that the flavor of PEF‐processed juice was preferred to that of thermally processed juice (P < 0.01).