Quality of Freeze Concentrated Orange Juice

Pasteurized Valencia and Temple orange juices concentrated to 45°Brix by freeze concentration retained their fresh juice flavor. Direct steam infusion heating to inactivate enzymes allowed more rapid heating than indirect heating and successfully lowered juice peel oil during vacuum cooling. Except for considerable pulp reduction of feedstream juices, there were few differences from normal citrus juice recovery procedures for freeze concentration. Since the product retained most of the aroma constituents of fresh juice, careful handling and high quality feed juice prior to freeze concentration was much more important than for evaporation. Fresh juice freeze concentrated to 45°B, then pasteurized at temperatures of 80°, 97° and 111°C had reduced sucrose (up to 25%) as the temperature increased to 111°C.     

Process optimisation of the bitter gourd (Momordica charantia) concentrated juice preparation for a freeze‐dried powder

Bitter gourd (Momordica charantia), a commonly consumed vegetable in South Asia, eastern‐South Asia, China, Japan, Korea peninsula, Caribbean Sea isles etc., is used as an adjunct in the management of diabetes mellitus. In this study, in order to find the effective ways of producing bitter gourd freeze‐dried powder, the concentrated juice of bitter gourd was produced through enzymatic process (EP), ultra filtration (UF), reverse osmosis and vacuum concentration technology. Results indicated that total saponins, total sugar and pH value in bitter gourd juice were almost unchanged after EP and after UF (P ≥ 0.05). However, UF decreased the turbidity and improved transmittance of juice (P < 0.05). When compared with the vacuum concentration alone, the combined process of reverse osmosis followed by vacuum concentration had 3.33 folds of production efficiency and 1.725 times of vitamin C content in concentrated juice. With freeze‐drying microscope system, the eutectic point of the freeze‐dried product of bitter gourd juice was detected to be ?37.5 °C, which was important to optimise lyophilisation parameters. The freeze‐drying microscope system was more accurate than the conventional electric resistance method in detecting the eutectic point of freeze‐dried product.     

蔗汁冷冻干燥工艺条件实验

采用正交实验方案 ,研究蔗汁冷冻干燥过程中入料锤度、装料厚度、冻结速度的交互作用对冻干时间的影响 ,发现装料厚度的影响最大 ,认为采用较高的入料锤度和合理的装料厚度对降低蔗汁冷冻干燥的生产成本有所帮助。     

苦瓜汁的真空冻干

为了对苦瓜汁进行真空冷冻干燥,首先通过简单的电阻装置测定了苦瓜汁的共晶点与共融点。然后按照一定的升温程序对苦瓜汁进行了冻结与升华干燥,并得到了苦瓜汁的真空冻干曲线。最后对真空冻干苦瓜粉与鲜苦瓜汁所含的Vc、矿物质、蛋白质、苦瓜总苷等指标进行了对比,结果表明,真空冷冻干燥能较好地保持苦瓜的生物活性与特征。     

Concentration of apple and pear juices in a multi-plate freeze concentrator

In this article we will examine the process for concentration of apple and pear juices as well as concentration of sugar solutions modelling pear juice (simulation fluid) using a descending film multi-plate freeze concentrator. It has been determined in advance the freezing point of those fluids in the working concentration and temperature intervals. In addition, different parameters were studied to allow tracking of the process of freeze concentration, such as ice accumulation, variation of the content of soluble solids in the solution and in the ice removed, ice production and energy consumption. The apple and pear juices tested showed similar behaviour, while the mixture of sugars used for simulation showed better behaviour, due perhaps to the absence of foam in the process and to the quicker formation of ice. It has been obtained concentrations of 30.2 and 30.8 °Bx with the apple and pear juices, respectively, and up to 32.7 °Bx with the simulation fluid.Industrial relevanceThe clarified juices usually are concentrated on an evaporation stage. In this stage the juice is subjected to high temperatures that cause undesirable reactions, such as non enzymatic browning and destruction of nutritive compounds. The freeze concentration is a technology that allows eliminating water from the juices at temperatures below the water’s freezing point, what allows obtaining products of better quality. In this work has been applied this technology to concentrate apple and pear juices, obtaining promissory results.     

Estimation of the freezing point of concentrated fruit juices for application in freeze concentration

In freeze concentration operations the fluids remain at temperatures below 0 °C. For a good study of this concentration operation is very important to know the values of freezing point. The aim of this work was to establish a model that predicts the freezing point of fruit juices at various concentrations within the range of interest for freeze concentration (10-40 °Brix). The model proposed relates the freezing point of a juice with the concentrations of main sugars present in the juice: sucrose, glucose and fructose. The freezing point of apple juice, pear juice and peach juice was determined experimentally at various concentrations, and experimental results were well correlated with model calculations.     

RETENTION OF D-LIMONENE DURING FREEZE DRYING OF ORANGE JUICE

Retention of d-limonene during freeze drying of citrus juices from several sources was investigated as a multi-phase problem. Reconstituted to 25 and 10° Brix, commercial frozen concentrates show high retention (between 90 and lOO%), whereas fresh-squeezed juice shows a relatively low retention (about 30%), comparable to that found previously for synthetic emulsions. Retention data for pasteurized fresh juice after substantial agitation and for never-concentrated, commercial pasteurized juices show an intermediate value (between 60 and 70%). Presence and stability of cloud are shown to correlate closely with improved d-limonene retention in commercial frozen concentrates. On this basis, a simple model is developed which predicts the retention level for this type of juice in the asymptotic region. The results for the other types of juice studied are interpreted with the aid of microscopic determinations of oil droplet size and the model derived for synthetic emulsions.     

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.     

QUALITY CHANGES DURING STORAGE IN KOREAN CLEAR PEAR JUICES CONCENTRATED BY THREE METHODS

Pears of Shingo variety were coarsely ground, and subjected to heat treatment by HTST (high temperature short time) and pectinase treatment to produce a cloudy pear juice. The pear juice was then treated with Viscozyme, gelatin and bentonite, and filtered through an ultrafiltration membrane to produce a clear pear juice. The clear pear juice was concentrated to 3 to 5 fold by vacuum evaporation, freeze concentration, and reverse osmosis methods. The concentrates were diluted to 10° Brix and stored at 4C for 15 days. The single strength juice was evaluated for color, turbidity, heat stability, and sensory preference at 5 day intervals during storage. The pear juice concentrated by the three methods showed only small differences in quality. While the clear pear juice with added ascorbic acid had no quality changes at 4C after 15 days' storage, that without the addition of ascorbic acid resulted in some deterioration in browning, turbidity and heat stability after 10 days' storage. There were small, but significant flavor differences among clear pear juices concentrated by evaporation, freeze concentration and reverse osmosis.     

果汁冷冻浓缩过程中冰晶形成规律的研究

本研究测定了橙汁和菠萝汁的冰点曲线,并以此探讨在果汁冷冻浓缩时水分冻结率的变化规律。结果表明,果汁在开始冻结的温度附近结冰率变化最大;以后逐渐减慢。橙汁和菠萝汁的最大冰晶生成区分别是-0.8～-7.9℃和-0.7～-6.7℃。冷却介质温度越低,冰晶的生长速度越快,但最终冰晶尺寸越小。当介质温度为-10℃左右时,可获得较大的冰晶尺寸。本文也研究了搅拌作用及果汁预处理因素对冰晶生长的影响。     

Better lime purification of sugar beet juice obtained by low temperature aqueous extraction assisted by pulsed electric field

Purification of the sugar beet juices obtained by novel low temperature extraction (at 30 °C) assisted by pulsed electric field (PEF) and conventional high temperature extraction (at 70 °C) was done by the method of lime-carbon dioxide treatment. The total concentration of lime used for the purification was varied from 6 to 15 kg of CaO/m³ of the juice. Filtration properties of the juices of first carbonation, as well as purity and coloration of the final thin juices, were compared. It was observed that purification of the juice extracted at 30 °C results in faster filtration of the juice of first carbonation and lower coloration of the final thin juice as compared to the juice obtained by means of purification of the juice extracted at 70 °C. It suggests that the quantity of CaO required for the efficient juice purification may be decreased from 15 kg/m³ (for the juice extracted at 70 °C without PEF treatment) to approx. 8 kg/m³ (for the juice obtained by PEF-assisted extraction at 30 °C).     

Enhancement of phenolic compounds content and antioxidant activity of strawberry (Fragaria × ananassa) juice by block freeze concentration technology

The aim of this study was to evaluate the effects of freeze concentration of strawberry juice on content of total phenolic, anthocyanins content and antioxidant activity of the concentrated fluid and the ice obtained. An increase in the values of phenolic content was observed in the concentrate fraction for all the freeze concentration stages (five stages). The process efficiency presented a reduction when compared with the first stage, and however, the average efficiency remained around 65% in all the stages. The concentration of pelargonidin‐3‐O‐glycoside present in samples was increased in all stages. Furthermore, the antioxidant activity of the concentrated fluid of each stage, measured by DPPH and ABTS methods, was significantly higher in comparison with the juice feed. Also, antioxidant activity can be correlated with the content of pelargonidin‐3‐O‐glycoside presented in the strawberry juice. Freeze concentration can be considered a good alternative for improving the antioxidant activity of strawberry juice.     

Effect of mixing time, freeze-drying and baking on phenolics, anthocyanins and antioxidant capacity of raspberry juice during processing of muffins

BACKGROUND: Consumption of baked products constitutes an important part of a daily breakfast considering that people are continually grabbing meals on the go. Among baked products, muffins rank third in breakfast products and attract a broad range of consumers. Incorporation of red raspberry juice into muffins can add value to the product while preserving health benefits to the consumer. The purpose of this study was to evaluate the effect of mixing time, freeze‐drying and baking on the phenolic and anthocyanin contents and antioxidant capacity of raspberry juice during the preparation of muffins. RESULTS: Freeze‐drying of raspberry batters reduced their phenolic content and antioxidant capacity regardless of mixing time. Non‐freeze‐dried raspberry batter mixed for 5 min had the highest phenolic content (0.88 mg gallic acid equivalent g^?1 dry matter (DM)). Non‐freeze‐dried raspberry muffins had the highest antioxidant capacity (0.041 µmol Trolox equivalent g^?1 DM). Freeze‐dried raspberry batters mixed for 5 and 10 min had the highest anthocyanin content (0.065 mg cyanidin‐3‐glucoside g^?1 DM). Baking reduced the anthocyanin content of both non‐freeze‐dried and freeze‐dried raspberry muffins. CONCLUSION: Despite the reduction in valuable compounds, muffin is a vehicle for the delivery of these compounds. Copyright © 2012 Society of Chemical Industry     

Effects of Juice Matrix and Pasteurization on Stability of Black Currant Anthocyanins during Storage

The effects of juice matrix and pasteurization on the stability of total phenols and especially total and individual anthocyanins were examined in black currant (BC) juice and mixtures with apple, persimmon, and peach juices at 4 °C and 20 °C. Total phenol content decreased in all juices at both temperatures but there was a trend to lower levels in unpasteurized over pasteurized juices. Differences in the decline of total anthocyanins between pasteurized and unpasteurized juices varied according to the juice type and the storage temperature. At 4 °C storage, anthocyanins declined in all juices according to pseudo 1st‐order kinetics and there were only small differences in the rates between pasteurized and unpasteurized juices. However, at 20 °C, although pasteurized and unpasteurized BC juices and pasteurized mixed juices followed pseudo 1st‐order kinetics, there was a different pattern in unpasteurized mixed juices; a rapid initial decline was followed by a slowing down. The effect of the added juice on anthocyanin decline was also different at either temperature. At 4 °C, the anthocyanins decreased faster in mixed juices than BC juice alone, but at 20 °C, at least in pasteurized mixed juices, the decline was similar or even slower than in BC juice; there were only small differences among the 3 mixed juices. At 20 °C, in pasteurized and unpasteurized BC juices, the rate of decrease was essentially the same for all 4 individual anthocyanins but in the mixed juices the 2 glucosides decreased significantly faster than the 2 rutinosides.     

Quantitative bioactive compounds assessment and their relative contribution to the antioxidant capacity of commercial orange juices

Dietary recommendations for healthy eating include the consumption of fruit juices whose health effects are ascribed, in part, to carotenoids, phenolic compounds and vitamin C. These bioactive compounds have been implicated in the reduction of degenerative human diseases, mainly due to their antioxidant potential. Orange juice is characterized by substantial accumulation (apart from ascorbic acid) of flavonoids and carotenoids. Commercial orange juice is the main human dietary source of antioxidant compounds in developed countries. The qualitative and quantitative determination of carotenoid, flavonoid and vitamin C content of Spanish commercial orange juices was achieved by high‐performance liquid chromatography. The health‐related properties of bioactive compounds contained in orange juice are based on their antioxidant activity. The antioxidant capacity of these juices was assessed by 2,2‐diphenyl‐1‐picrylhydrazyl stable radical scavenging and was compared with a freshly squeezed orange juice. In addition, the relative contribution of the different bioactive compounds to the antioxidant activity of orange juices was calculated. Total vitamin C was found to be the major contributor to the antioxidant potential of the orange juices studied, followed by flavonoid and carotenoid compounds. Ascorbic acid, total vitamin C and β‐cryptoxanthin content correlated positively with the free‐radical scavenging parameters. No significant differences, in terms of antioxidant capacity, were found between commercial traditional pasteurized orange juices and freshly squeezed orange juice. Copyright © 2003 Society of Chemical Industry     

OPTIMIZATION OF GUAVA JUICE AND POWDER PRODUCTION

Enzyme treatment of guava puree was optimized for yield and clarity by first determining the most effective concentration, then varying both incubation time and temperature. Application of Pectinex Ultra SP-L® was optimal using 700 ppm enzyme for 1.5 h at 50C. Clarified guava juice was clearer (89.6%) when prepared using ultrafiltration (MW cut-off 40–60 kDa) rather than plate and frame filtration (82.8%); however, the latter was higher in both soluble solids and ascorbic acid. Clarified guava juice powders were made using freeze-drying, spray drying and tunnel drying. The freeze-dried product had superior quality; however, the spray-dried product was stable and may be more economical. Sensory panelists ranked the cloudy juice prepared from aseptic guava puree highest, and there were no significant differences between the juices from pasteurized, clear nectar, freeze-dried puree powder or juice powder.     

Impact of enzymatic treatment on chemical composition,physicochemical properties and radical scavenging activity of goldenberry (Physalis peruviana L.) juice

Tropical pulpy juices play an important role in nutrition as an excellent base for low‐calorie and dietetic products. Goldenberry (Physalis peruviana L.) is one of the most promising exotic fruits and many interesting functional products could be developed from these berries. In this work we are reporting, for the first time, on the chemical composition and some physicochemical parameters of the goldenberry fruit juice. We have also investigated how some of these properties are affected by enzymatic treatment and pasteurisation. By enzymation, not only is the yield of juice increased, but also the macro‐ and micro‐components. Application of enzymes, moreover, leads to juices with higher pulp content, higher acidity and higher total soluble solids. On the other side, enzyme‐treated juices were characterised by lower alcohol‐soluble solids and pH values. Water‐ and fat‐soluble bioactives were estimated in appreciable amounts in the juice. The antioxidative potential of different processed juices was assessed by means of bleaching of the stable 1,1‐diphenyl‐2‐picrylhydrazyl radicals and the resulting values were correlated with each of the antioxidant compounds. The results obtained can be considered very satisfactory and the juice could be widely appreciated when compared with other products commonly available on the market. The data are helpful for the optimisation of goldenberry juice production. It was the purpose to present a comprehensive assessment of the goldenberry juice and to address the potential for its delivery in functional drinks. Copyright © 2006 Society of Chemical Industry     

Microencapsulation of Lactobacillus rhamnosus GG by Transglutaminase Cross‐Linked Soy Protein Isolate to Improve Survival in Simulated Gastrointestinal Conditions and Yoghurt

Microencapsulation is an effective way to improve the survival of probiotics in simulated gastrointestinal (GI) conditions and yoghurt. In this study, microencapsulation of Lactobacillus rhamnosus GG (LGG) was prepared by first cross‐linking of soy protein isolate (SPI) using transglutaminase (TGase), followed by embedding the bacteria in cross‐linked SPI, and then freeze‐drying. The survival of microencapsulated LGG was evaluated in simulated GI conditions and yoghurt. The results showed that a high microencapsulation yield of 67.4% was obtained. The diameter of the microencapsulated LGG was in the range of 52.83 to 275.16 μm. Water activity did not differ between free and microencapsulated LGG after freeze‐drying. The survival of microencapsulated LGG under simulated gastric juice (pH 2.5 and 3.6), intestinal juice (0.3% and 2% bile salt) and storage at 4 °C were significantly higher than that of free cells. The survival of LGG in TGase cross‐linked SPI microcapsules was also improved to 14.5 ± 0.5% during storage in yoghurt. The microencapsulation of probiotics by TGase‐treated SPI can be a suitable alternative to polysaccharide gelation technologies.     

Effect of pulsed electric fields pretreatment on juice expression and quality of chicory

This study investigates the effects of pulsed electric fields (PEF) and freeze thawing (FT) pretreatments on juice yield and quality from chicory by pressing (P). The four different modes (P, PEF-P, FT-P and P-PEF-P) were compared. The effects of pressing mode, PEF conditions, cossettes size on the juice yield, and total soluble matter (°Bx), conductivity, pH, turbidity in expressed juices were evaluated. The pressing kinetics for different modes were also investigated. For studied modes, the highest juice yield and kinetic rate were obtained for FT-P mode, the lowest was P mode. PEF-P and P-PEF-P modes resulted in the same juice yield, an increase of 9% higher than P mode. A 600 V/cm of intensity and 0.2 s duration were optimal PEF conditions with desired energy consumption. Moreover, cake mixing and relative small-sized cossettes allowed improving juice yield assisted by PEF-P mode. Quality analysis showed that expressed juice from smaller cossettes by PEF-P mode has lower turbidity and higher inulin content.     

Evaluation of different methods for the production of juice concentrates and fruit powders from cactus pear

The present work aimed both at improvement and extension of a previously developed process for the production of cactus pear juice. The total yield was increased by 10% through processing whole instead of peeled fruits and by further optimisation of pulp enzymation. As an alternative to HTST pasteurisation, cross-flow microfiltration was applied for non-thermal cactus pear juice preservation. Juice concentrates and fruit powders were produced by rotary evaporation and freeze drying at laboratory scale and compared to products obtained at pilot plant-scale applying a three-stage column evaporator and spray drying, respectively. To monitor process-related quality changes, the resulting products were characterised in terms of colour and selected quality parameters. For both juice concentrates and fruit powders, initial colour characteristics were retained. In addition to betanin isomerisation, C₁₁-epimerisation of proline-betaxanthin was demonstrated to be a valuable indicator of the respective heat treatment applied. Whereas no adverse reactions were observed during juice production, non-enzymatic browning and HMF formation were found after concentration at pilot plant-scale and freeze drying, respectively.

Industrial relevance

Although cactus pear meets all requirements for food colouring purposes, no attempt has been made so far to exploit this potential. The feasibility of processing cactus pear juice into concentrates and fruit powders was demonstrated in this study. In contrast to single-strength juice, concentrates and powders are easier to handle during transportation and storage and also open further fields of application that may promote cactus pear fruit processing at industrial scale in the future.