Structural Stability of Fresh and Frozen-Thawed'Valencia'(C. sinensis) Orange Juice

Valencia orange juice was subjected to different freezing rates and different storage times to study the effects of those treatments on the structural and dispersion properties of the insoluble particles. Examination with an electron microscope revealed that the juice contained plastids, mitochondria, oil droplets and cell walls. Fragments consisting mainly of vesicular membranes were present both before and after freezing and thawing. A slow freezing rate resulted in plastids with various degrees of disintegration. Separation of insoluble particles from the juice serum increased with increasing frozen storage time and was especially apparent at slower primary freezing rates. A decrease in color intensity and deterioration in appearance is related to longer storage time and to slower primary freezing rates.     

High pressure processing of Australian navel orange juices: Sensory analysis and volatile flavor profiling

Navel orange juices subjected to high pressure processing (HPP) and temperature treatment (TT) were stored at 4 and 10 °C for up to 12 weeks to establish the shelf-life of such products. The processed juices and a control juice, stored at − 20 °C, were assessed by a trained sensory panel and a consumer acceptance panel at 0, 1, 2, 4, 8 and 12 weeks or until such time that the juices were considered unfit for consumption. Untreated juice stored at 4 °C was similarly assessed for up to 2 weeks and untreated juice stored at 10 °C was assessed for up to 1 week. The volatile components of corresponding juices were isolated by SPME and the extracts were analyzed by GC–MS. Twenty key aroma compounds were selected for quantification and these data were used to monitor the change in volatile content of the juices during storage. The study showed that the odor and flavor of the HPP juice was acceptable to consumers after storage for 12 weeks at temperatures up to 10 °C. However, only the TT juice stored at 4 °C was acceptable after the same length of storage.

Industrial relevance

Orange juice is a sensitive product subject to a high microbial load that can tolerate only moderate heat treatment without the destruction of the product’s delicate aroma and flavor characteristics. High pressure processing at moderate pressures and storage at refrigeration temperatures have been evaluated as means of maximizing microbial inactivation while maintaining consumer acceptability of the product. The sensory and analytical data presented demonstrate that high pressure processing with refrigeration can extend the shelf-life of orange juice while maintaining consumer acceptability.     

Mathematical Modeling of Microbial Growth in Packaged Refrigerated Orange Juice Treated with Chemical Preservatives

ABSTRACT Microbial flora of refrigerated orange juice was analyzed during storage at 10 °C and the effects of the following factors were discussed: 1) the previous washing process of the orange peel, 2) the different levels of the added preservatives (citric acid, ascorbic acid, potassium sorbate, sodium benzoate), 3) the gaseous permeabilities of the packaging film. Gompertz equation was applied to model molds and yeasts growth for the different treatments and packaging conditions. The washing procedure with sodium hypochlorite extend 2–3 d the storage life of the juice (time to reach microbial counts of 10⁶ CFU/ml) in both packaging films. The use of organic acids and potassium sorbate or sodium benzoate (1.66–6.94 mM) led to storage life values > 11 d in polyethylene and > 20 d in the low gaseous permeability film, maintaining good sanitary conditions.     

Changes in carotenoids including geometrical isomers and ascorbic acid content in orange–carrot juice during frozen storage

Fruits and vegetables are highly perishable foods, which explains the need to apply preservation techniques, such as freezing. The aim is to combine shelf life extension with maintenance of sensory and nutrient characteristics. The stability of orange–carrot juice stored at –40 °C for 132 days was studied. The ascorbic acid and carotene contents and the influence of storage time were analysed. Carotenes were identified and quantified by liquid chromatography and ascorbic acid was determined by differential pulse polarography. The initial concentration of ascorbic acid was 27.09 mg/100 ml and decreased by 4.1% during the storage period. Vitamin A activity in the orange–carrot juice increased during the period studied, fitting a linear model (R²=0.87). Of the 14 carotenes identified, only antheraxanthin and the mixture of 9-cis-violaxanthin and neoxanthin decreased in concentration during the storage period.     

Organic acids in orange,grapefruit and cherry juices quantified by high-performance liquid chromatography using neutral resin or propylamine columns

Malic and citric acids were measured in orange and grapefruit juices by h.p.l.c. using a neutral resin column. Low levels of succinic acid (<0.01%) present in some samples required the use of a propylamine column, which was also used for succinic and malic acids in sweet cherry juice. All samples required preliminary separation on ion exchange columns to remove interfering substances. Either refractive index or ultraviolet (206 nm) detectors can be used for analyses after purification.     

Radio frequency electric fields processing of orange juice

The non-thermal process of radio frequency electric fields (RFEF) has been shown to inactivate bacteria in apple juice at moderately low temperatures, but has yet to be extended to inactivate bacteria in orange juice. An 80 kW RFEF pasteurizer was used to process pulp-free orange juice at flow rates of 1.0 and 1.4 l/min. Escherichia coli K12 in orange juice was exposed to electric field strengths of 15 and 20 kV/cm at frequencies of 21, 30, and 40 kHz. Ascorbic acid (Vitamin C) content and color of the juice before and after treatment were analyzed. Electrical energy costs were calculated using the measured voltage and current. An energy balance was performed using the inlet and outlet temperatures. Processing at an outlet temperature of 65 °C reduced the population of E. coli by 3.3 log relative to the control. Increasing the treatment time and temperature and decreasing the frequency enhanced the level of inactivation. Varying the electric field strength over the range of conditions used had no effect on the inactivation. No loss in ascorbic acid or enzymatic browning was observed due to RFEF processing. The electrical energy determined using the voltage and current was 180 J/ml. This was in good agreement with the energy calculated using the temperature data. The electrical cost was $0.0026/l of orange juice. The results provided the first evidence that the RFEF process inactivates bacteria in orange juice at moderately low temperatures.

Industrial relevance

The RFEF process has been shown to inactivate E. coli in apple juice at moderately low temperatures, but has yet to be extended to inactivate bacteria in orange juice. An RFEF pilot plant pasteurizer was used to process orange juice at rates of up to 1.4 l/min. RFEF processing reduced the population of E. coli by 99.3% at 60 °C and a hold time of 3 s, whereas conventional heating at the same conditions had no effect on the E. coli. This work demonstrated that the non-thermal RFEF process can be extended to inactivate bacteria in orange juice.     

Polyphenol oxidase activity,phenolic acid composition and browning in cashew apple (Anacardium occidentale, L.) after processing

This study describes the extraction and characterisation of cashew apple polyphenol oxidase (PPO) and the effect of wounding on cashew apple phenolic acid composition, PPO activity and fruit browning. Purification factor was 59 at 95% (NH₄)₂SO₄ saturation. For PPO activity, the optimal substrate was catechol and the optimum pH was 6.5. PPO K_m and V_max values were 18.8 mM and 13.6 U min⁻¹ ml⁻¹, respectively. Ascorbic acid, citric acid, sodium sulphite and sodium metabisulphite decreased PPO activity, while sodium chloride increased PPO activity. Wounding at 2 °C and 27 °C for 24 h increased PPO activity but storage at 40 °C reduced PPO activity. Gallic acid, protocatechuic acid and cinnamic acid (free and conjugate) were identified in cashew apple juice. Cutting and subsequent storage at 40 °C hydrolysed cinnamic acid. 5-Hydroxymethylfurfural content in cashew apple juice increased after injury and storage at higher temperatures, indicating non-enzymatic browning.     

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.     

Stability of lipids and proteins in leaf protein concentrates.

Although freeze-dried leaf protein concentrate (l.p.c.) contains as much as 15–20% of lipids in which linolenic acid (60%) is the predominating component fatty acid, it appears to be unexpectedly stable when stored under ordinary conditions, i.e. at room temperature and exposed to air. Linolenic acid, in the form in which it occurs in l.p.c. is less prone to destruction than in the form of total lipid isolate, or in the form of more conventional linolenic-containing vegetable oils. Rates of disappearance of linolenic acid and also loss of protein quality as judged by dye-binding capacity, on heat treatment appear to follow a progressive trend as temperature is increased, without displaying a well-defined order of reaction. With increasing temperatures, increased moisture levels result in an increase in the rates of both lipid and protein transformations. In heat treatments involving temperatures below 100°C, the presence of the lipid fraction does not affect protein transformation. At higher temperatures, when the lipid itself undergoes substantial oxidation, protein quality as judged by dye-binding capacity is considerably affected.     

Benefits of thermosonication in orange juice whey drink processing

This study aimed to evaluate the effect of short-time heat-treatment (HTST, 90 °C/20 s) and thermosonication (TS) at temperatures of 70, 80, and 90 °C (TS70, TS80, and TS90) on the quality parameters of orange juice whey drinks. Formulations with different orange juice/reconstituted whey proportions were subjected to sensory analysis, and the ideal formulation was established through survival analysis (31% whey, 69% orange juice). This formulation showed approval of 75% of the consumers, which is considered satisfactory. It was processed by HTST or TS and evaluated for the microbial counts, rheological parameters, color, physical properties (differential scanning calorimetry and time-domain nuclear magnetic resonance), volatile compounds, and bioactive compounds. TS-treated orange juice whey drinks showed a higher microbial inactivation (>1 log cfu/mL increase) and microbial stability during 21 days of storage (2.9, 4, and 1.1 log cfu/mL lower counts for aerobic mesophilic bacteria, yeasts and molds, and lactic acid bacteria, respectively). Furthermore, it showed higher antioxidant (>15% increase), anti-hypertensive (>24% increase), and anti-diabetic (>30% increase) activities and lowered ascorbic acid degradation (>8%). Finally, it showed lower viscosity (decreases in consistency index >46.9 Pa.sⁿ) and an improved volatile profile (presence of maltol and butanoic acid, ethyl ester). The effects were more pronounced at 80 and 90 °C. TS is a promising technology for treating orange juice whey drinks.Industrial relevanceThermosonication can be used in the processing of orange juice whey drinks, resulting in better microbial inactivation, increased shelf-life, and improved functional properties and physical parameters compared to conventional processing. In this sense, this research's findings contribute to the utilization of non-conventional technologies by the dairy industry.     

Chemical Changes during Storage of an Alcoholic Orange Juice Beverage

Chemical stability of a pasteurized, noncarbonated, alcoholic orange juice beverage, (8% ethanol and 30% reconstituted Valencia frozen concentrated orange juice), was investigated. It was hot-filled into clear glass bottles under nitrogen and subjected to 14-wk storage at 4, 25, and 40°C. pH, °Brix, titratable acidity, and % alcohol remained constant throughout storage. Accumulation of furfural and darkening paralleled ascorbic acid degradation. The beverage exhibited 25 times more browning at 40°C and 9 times more at 25°C than at 4°C after 14-wk. d-Limonene decreased at all temperatures. Nitrogen headspace slightly improved stability at 40°C. Time and temperature were most significant in storage and long-tem shelf-life could only be achieved with refrigeration.     

水杨酸处理结合冰温贮藏对吊干杏采后品质的影响

以吊干杏为试材,采用2.0 mmol/L的SA（Salicylic acid,SA）浸泡处理杏果10 min,以蒸馏水处理作为对照,将处理后的杏果贮藏于（4~6）℃和（?1.5~?1）℃下,研究水杨酸处理结合冰温贮藏对吊干杏采后保鲜效果的影响。结果显示,与冷藏（4~6）℃相比,冰温（?1.5~?1）℃贮藏49 d的吊干杏腐烂率与失重率较低,营养物质含量更高,过氧化氢含量与超氧阴离子生成速率处于较低水平,体现较高的抗氧化酶活性,膜质受损程度较轻。与冷藏组相比,2 mmol/L SA处理可显著抑制冷藏和冰温贮藏期间吊干杏果实腐烂率和失重率的上升（P<0.05）;显著延缓硬度、可溶性固形物、抗坏血酸和可滴定酸含量的下降（P<0.05）;显著抑制超氧阴离子生成速率、过氧化氢含量、丙二醛含量及细胞膜透性的上升（P<0.05）;并显著提高贮藏后期超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶及过氧化物酶的活性（P<0.05）。结果表明,冰温贮藏较普通冷藏更有利于维持吊干杏较好的采后品质;2 mmol/L SA处理可有效延缓冰温和冷藏期间吊干杏品质的下降,尤其对冰温贮藏吊干杏各指标的影响更为明显。     

Effect of some physical factors on the viability of third-stage Gnathostoma binucleatum larvae

To diminish the risk of transmission to humans of advanced third-stage larvae (A3L) of Gnathostoma binucleatum in fish foods, we evaluated the effects of some physical factors on larval viability. A3L protected within fish meatballs were subjected to freezing, refrigeration, boiling, dry heat, and immersion in lemon juice. By freezing, larvae were killed in 48 h, by refrigeration after 30 days, by boiling in 4 min, and by broiling for 60 min. By lemon juice immersion (pH 2.5), encysted larvae were killed after 5 days and nonencysted larvae in 7 h. Results show that freezing fish at -10 to -20°C for 48 h, or cooking fish by frying, boiling, or broiling, will prevent transmission of G. binucleatum. Furthermore, results dispel the popular myth that lemon juice kills encysted larvae in fish.     

Quantitative analysis of styrene monomer in foods. A limited East Australian Survey

The levels of styrene monomer in foods packaged in polystyrene containers were determined by a headspace gas chromatography (g.c.) method and two reversed phase high-performance liquid chromatography (h.p.l.c.) methods. A total of 146 samples were analysed from Victoria and New South Wales which included yoghurt, cream, cheese, dessert, ice cream, egg white, onion dip and margarine. The highest level of styrene found was 0.1 mg kg^?1 in yoghurt. About 85% of all yoghurt samples were found to have values less than 0.05 mg kg^?1. The lowest values of styrene obtained were for margarine samples, of which more than 90% contained less than 0.010 mg kg^?1. The estimated limits of detection of the h.p.l.c. methods for all products except margarine were 0.005 mg kg^?1. The h.p.l.c. detection limit for margarine and the g.c. method for yoghurt were estimated to be 0.01 mg kg^?1.     

Preservation of mango juice by freezing and canning

In this work the preservation of mango juice by freezing and canning was compared. The following results were obtained: The loss of ascorbic acid during the preparation of canned mango juice is mainly due to the processing steps other than retorting which had the least harmful effect. The retention of ascorbic acid and carotene after canning and freezing was nearly the same. Both freezing and canning caused no marked changes in the pectin content. The inactivation of the pectin methylesterase was more obvious after canning than after freezing. Reducing sugars slightly increased after freezing and canning, while the acidity and pH showed no appreciable changes. The chemical constituents except the sugars of the commercial samples were lower than those of the experimental samples. During storage, the percentage retention of ascorbic acid and carotene were lower when pasteurization was not included, and in canned samples they were higher in the experimental juice than in the market samples. Pectin content showed no changes in all cases studied. The activity of pectin methylesterase slightly decreased in frozen samples, while it was a small increase in case of canned juices. During storage the microbial count of frozen and canned samples decreased when storage progressed. The addition of water and sugar during manufacturing of commercial samples did not help to obtain a product with good storage stability. There was a significant difference between the characteristics of frozen pasteurized and non pasteurized mango juice. It seems very important to pasteurize mango juice before storage in a frozen form.     

Effect of Storage on Anthocyanin Degradation in Black Mulberry Juice and Concentrates

Anthocyanins present in fruits and vegetables are receiving increased attention because of their potential antioxidant activity but are very susceptible to degradation during processing and storage. Effect of storage on kinetics of anthocyanin degradation and hydroxymethylfurfural (HMF) formation in black mulberry juice and concentrate was determined during 8 months of storage at temperatures of 5°, 20°, 30°, and 40 °C. The monomeric anthocyanin degradation was in accordance with the first-order reaction kinetics and the activation energies of anthocyanin degradation in black mulberry juice and concentrate were found as 56.48 and 49.75 kJ mol^?1, respectively. HMF formation in black mulberry juice and concentrate increased linearly with storage time and temperature and followed zero-order reactions. The activation energies of HMF formation in black mulberry juice and concentrate were found as 75.70 and 104.11 kJ mol^?1, respectively. The losses of antioxidant activity for black mulberry juice and concentrate during storage at different temperatures were in the ranges of 4.87–16.01 and 4.47–33.57 %, respectively. Antioxidant activity in black mulberry juice and concentrate was correlated with total monomeric anthocyanins.     

Kinetics of anthocyanin degradation and polymeric colour formation in black carrot juice concentrates during storage

The changes in anthocyanins (ACNs) and polymeric colour of black carrot juice concentrate (BCJC) samples were monitored during storage at ?23, 5 and 20 °C for 319 days and at 30 °C for 53 days. While ACN degradation was fitted to a first‐order reaction model, polymeric colour formation was fitted to a zero‐order reaction model during the storage. Half‐life periods for ACN degradation in BCJCs were 603, 137 and 29 days at 5, 20 and 30 °C, respectively. The reaction rate constants for polymeric colour formation were 0.0207, 0.1435 and 0.5581%/days at 5, 20 and 30 °C, respectively. HPLC‐MS analyses of BCJC showed that cyanidin‐3‐galactoside‐xyloside‐glucoside‐ferulic acid (56%) was the major ACN, followed by cyanidin‐3‐galactoside‐xyloside (19%) and cyanidin‐3‐galactoside‐xyloside‐glucoside‐sinapic acid (10%). Cyanidin‐3‐galactoside‐xyloside‐glucoside‐ferulic acid was the most stable ACN in BCJC at storage temperatures. BCJCs should be kept at sub‐freezing temperatures to minimise ACN degradation.     

Malolactic fermentation in sea buckthorn (Hippophaë rhamnoides L.) juice processing

Malolactic fermentation (MLF) traditionally used in winemaking was applied to sea buckthorn to reduce the high sourness of the berry juice. Chemical and microbiological aspects, as well as sensory properties of the juice during MLF were studied in order to develop an optimal process. In 1:1 water diluted juice with malic acid content of 15 g/l and pH 2.8, efficient conversion of l-malic acid to l-lactic acid was achieved with direct inoculation of unadapted Oenococcus oeni at a cell density of 10⁹ CFU/ml. The rapid malic acid degradation was performed by non-growing bacterial cells without loss of sugars, vitamin C, or pulp oil. More than 50% of the initial malic acid was metabolized to lactic acid and CO₂ already in 12 h of fermentation and a significant decrease in sourness and astringency was noticed. In 24 h fermentation, pH value was increased to 3.1 and only 3 g/l malic acid remained in the juice. Prolonged fermentation had only minor effect on malolactic reaction, but off-flavor of the juice began to increase.     

冷冻预处理对刺葡萄榨汁品质的影响

冷冻预处理有利于提高葡萄榨汁出汁率,但冷冻预处理对葡萄榨汁后汁液的品质影响目前尚不清晰。将葡萄果粒在-30℃条件下冷冻至中心温度-21℃,解冻后榨汁作为试验组,将果粒4℃条件贮藏后榨汁作为对照组,研究冷冻预处理对刺葡萄汁花色苷、色差、总糖、总酸等指标的影响。结果表明,葡萄汁在4℃条件下贮藏30天后,对照组与试验组中的花色苷含量、色差、总糖、总酸含量差异均不显著。说明冷冻预处理对刺葡萄汁品质不会产生不良影响。     

Separation of fructose,glucose and sucrose in fruit by high performance liquid chromatography using UV detection at 190 nm

Fructose, glucose and sucrose were separated by high performance liquid chromatography (h.p.l.c.) on a 5 μm amine column and detected by absorbance at 190 nm. The procedure quantified these sugars in orange juice and in carambola fruit, but preliminary ion exchange column chromatography was necessary before satisfactory h.p.l.c. results could be obtained. The method is sensitive to 1.2 μg of fructose or 9 μg of glucose or sucrose.