CHANGES IN QUALITY ATTRIBUTES OF LONGAN JUICE DURING STORAGE IN RELATION TO EFFECTS OF THERMAL PROCESSING

Longan juice is accepted gradually by consumers due to its unique succulent, sweet and aromatic flavor. The effects of thermal processing (91C, 20 min) on quality related attributes (color, translucency, total soluble solids, total acidity, reducing sugars, ascorbic acid, phenolic compounds, protein and pectin) of longan juice during storage at low temperature were investigated. The heat-treated longan juice had a higher translucency and lower concentrations of pectin, phenolic compounds and proteins of longan juice, compared with the nonheat-treated juice. Furthermore, the thermal processing maintained higher concentrations of total soluble solids and total acidity but a lower ascorbic acid concentration. However, the thermal processing had no significant effects on reducing sugar concentration. Overall, the thermal processing maintained effectively color appearance and nutritional attributes such as total soluble solids and total acidity of longan juice during storage at low temperature. These results suggest that the thermal processing exhibits a potential for quality maintenance of longan juice.

PRACTICAL APPLICATIONS

Browning and turbidity are the major factor to influence quality of fruit juice during storage. Thermal processing is generally applied to improve quality and extend shelf life of fruit-related products. In this study, application of thermal processing exhibited potential for quality maintenance of longan juice in terms of evaluations of color, translucency and concentrations of total soluble solids, total acidity, reducing sugars, ascorbic acid, phenolic compounds, protein and pectin. The information obtained from this study could be used as a guideline for designing thermal processing to control the quality of longan juice.     

UNDERSTANDING ULTRAFILTRATION PERFORMANCE WITH MOSAMBI JUICE IN AN UNSTIRRED BATCH CELL

Ultrafiltration (UF) of sucrose and pectin solutions, their mixtures and enzymatically treated mosambi (Citrus sinensis [L.] Osbeck) juice has been performed on a batch unstirred membrane cell. Thin film composite polyamide membrane of molecular weight cut‐off 50,000 was used. The sucrose solution's permeate flux declined marginally, but for the pectin solution, it decreased rapidly over time. The sucrose–pectin mixture exhibits a flux decline similar to that of the pectin solution. The gel‐type pectin layer over the membrane's surface governs the flux decline of the sucrose–pectin mixture. The nature of the flux decline and the values of the permeated total soluble solids of enzymatically treated mosambi juice show similar behavior as compared with that of the UF of the sucrose–pectin mixture. The permeate of the enzyme‐treated mosambi juice contains almost all the soluble solids and acids (in terms of citric acid) with a remarkable improvement in juice clarity.     

高压均质对NFC水蜜桃浊汁稳定性及品质的影响

本文采用高压均质技术,探究了均质压力（20~40 MPa）及次数（1~2次）对NFC水蜜桃浊汁的混浊度、离心沉淀率、粒径、Zeta电位等稳定性指标和pH、TSS、总酸、固酸比、还原糖、色泽、总酚、V_C等品质指标的影响。结果表明:高压均质（30~40 MPa/1、20~40 MPa/2）可有效提高NFC水蜜桃浊汁的稳定性,离心沉淀率较未处理组下降13.49%~24.22%,平均颗粒粒径由1853.67 nm降至501.10~665.27 nm,绝对Zeta电位值显著提高（P<0.05）。随着均质压力及次数的增加,浊汁中可溶性果胶含量上升,而残存果胶甲基酯酶活力逐渐降低。高压均质后,浊汁色泽显著改善,L*值升高,褐变指数BI值下降（P<0.05）;30 MPa/1下,品质保持最佳,总酚、V_C含量较未处理组显著提高（P<0.05）,而pH、TSS、总酸和固酸比无变化（P>0.05）;随着均质次数增加,pH、TSS、总酚和V_C含量显著降低（P<0.05）,品质下降。高压均质处理可有效提高NFC水蜜桃浊汁稳定性、抑制褐变,并提高总酚、V_C等营养物质含量。     

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.     

Microfiltration and Ultrafiltration Comparison for Apple Juice Clarification

Unpasteurized raw apple juice processed by microfiltration (MF) or ultrafiltration (UF) was evaluated for quality and the methods compared for process efficiency. Juice permeate was analyzed for total solids, soluble solids, color, turbidity, pH and acidity. Apple juice processed by MF was significantly (p < 0.05) darker, more turbid, contained higher total and soluble solids than juice processed with UF, and was preferred by a taste panel. MF processed more permeate per unit time than UF under similar operating conditions with no noticeable difference in power consumption (watt-hr/L).     

响应面优化酶法加工火龙果清汁工艺条件的研究

利用酶法加工火龙果清汁,考察了酶解温度、酶、底物、时间对火龙果清汁加工工艺的影响,在单因素的基础上,通过响应面试验对酶法加工火龙果清汁的工艺进行优化.结果表明适宜的工艺条件为酶解pH值5、温度53.09℃、时间6.16h、酶添加量0.07％,在该工艺条件下出汁率可达94.71％,其清汁具有红龙果特有的色泽和香味,可溶性固形物含量基本保持不变,总酸含量有所提高,基本不含果胶.     

热处理对采后琯溪蜜柚果实汁胞粒化的影响及其与细胞壁代谢的关系

汁胞粒化是柚类果实采后主要的品质劣变现象。本实验以琯溪蜜柚果实为材料,研究热处理对果实贮藏期间品质的影响,探讨其抑制汁胞粒化的作用和适宜处理条件,并探究该抑制作用与细胞壁中木质素和细胞壁多糖代谢的关系。分别以35、42、49、56 ℃热水对琯溪蜜柚果实进行喷淋处理,根据果实冷藏期内汁胞粒化指数、水分质量分数、可溶性固形物和可滴定酸质量分数变化筛选较优处理温度,并评价该温度处理对果实汁胞木质素质量分数、木质素合成酶活力、细胞壁多糖含量及其降解酶活力的影响。结果表明：与其他处理相比,42 ℃热水处理15 min能够较好地延缓琯溪蜜柚果实贮藏期间汁胞粒化指数升高和水分质量分数降低,维持汁胞可溶性固形物和可滴定酸质量分数;与对照组相比,42 ℃热水处理抑制了汁胞中苯丙氨酸解氨酶、肉桂醇脱氢酶和过氧化物酶活性,减缓了木质素质量分数增加;并且抑制了纤维素酶、果胶甲酯酶、多聚半乳糖醛酸酶和β-半乳糖苷酶的活性,延缓了纤维素和半纤维素含量的升高、共价结合态果胶含量降低、离子结合态果胶和水溶性果胶含量的增加。因此,42 ℃热水喷淋处理可有效延缓采后琯溪蜜柚果实汁胞粒化等品质劣变现象,其减缓汁胞粒化的作用可能与木质素合成相关酶和细胞壁多糖降解酶活性受抑制,延缓汁胞木质化、纤维化和果胶降解,使细胞壁组分和结构得到较好的维持有关。     

THE EFFECT OF ENZYMATIC MASH TREATMENT, PRESSING, CENTRIFUGATION, HOMOGENIZATION, DEAERATION, STERILIZATION AND STORAGE ON CARROT JUICE

The enzyme preparation Pectinex Smash XXL was employed to macerate the carrot pulp, the effect of enzymatic mash treatment (EMT), pressing, centrifugation, homogenization, deaeration, sterilization and storage on carrot juice was investigated. As compared with the control sample, an increase of juice yield, total soluble solid (TSS) and carotenoids in carrot juice was close to 20%, 1% and 26 mg/kg, respectively, after EMT. The EMT also increased the color parameters CIEL*, a*and C*values in carrot juice. However, it significantly decreased the viscosity from 2.54 to 2.09 mPa·s. The centrifugation resulted in a significant decline in turbidity from 240.33 to 187.33 NTU and a significant increase in the color parameters in carrot juice. After homogenization, the turbidity and the carotenoids in carrot juice were significantly reduced from 187.33 to 161.67 NTU and from 61.87 to 58.76 mg/kg, respectively. The turbidity and carotenoids in carrot juice decreased during storage, and all the color parameters had a closer relationship with storage temperature and time; higher storage temperature and longer storage time caused greater loss of color.     

超高压处理对猕猴桃汁品质的影响

本实验主要探讨了热敏性纯猕猴桃汁经100～500 MPa超高压处理后品质的变化情况.考察的指标有果汁色泽、黏度、pH、单宁、总酸、果胶、总VC、蛋白质以及可溶性固形物,并与未经超高压处理的果汁对照品进行了比较.实验结果表明,超高压处理能较好保持果汁原有的品质和风味,但有些现象还需要进一步从理论上探讨.     

Surface pasteurization of fresh pomelo juice vesicles by gaseous chlorine dioxide

This study developed an in-package pasteurization method that released gaseous chlorine dioxide (ClO₂) triggered when moisture vapor from the fresh produce interacted with a ClO₂ precursor. The samples were placed in sealed containers (750 ml) containing mixtures (0.1–1.0 g) of sodium chlorite and citric acid powders (1:1) and treated for up to 15 min at 25°C. Our results showed that, production of gaseous ClO₂ was linearly correlated with the reaction time (R²>0.95) with mean concentrations in the range of 1.70 – 8.66 mg/L. The gaseous ClO₂ treatments for 15 min significantly reduced Escherichia coli and fungi populations on pomelo juice vesicles with reductions of 6 and 2 log CFU/g, respectively. Perchlorate and chlorite in samples were not detected, and chlorate was only detected when the mean ClO₂ concentration was over 4.09 mg/L. The treatments did not significantly affect total soluble solids, total acids, pectin and malondialdehyde contents, and color of pomelo juice vesicles. The contents of ascorbic acid, naringin, and limonin, and bitterness score decreased with the increase of mean ClO₂ concentrations. Overall, our results demonstrate an effective nonthermal approach for microbial inactivation while maintaining the quality of fresh pomelo juice vesicles.     

PHYSICOCHEMICAL AND SENSORY PROPERTIES OF MUSCADINE GRAPE JUICE AND CONCENTRATES

Juices from bronze and red muscadines were concentrated by low-temperature vacuum evaporation. Half of each of the lots was treated with a mixture of pectinolytic and cellulolytic enzymes and the other half untreated. Red juice was higher in soluble solids and Brix-to-acid (BTA) than bronze, but pH, acid, and viscosity were similar. When concentrated to 68° Brix, the BTA was the same regardless of juice type. Enzyme treated samples were not different from their nontreated counterparts, except for slightly higher pH of treated red juice. Hue angle for bronze concentrate shifted from about 100 to 78 while chroma increased. Hue for the red juice shifted from about 40 to 95, while chroma remained constant. Fructose and glucose were the major sugars with sucrose averaging less than 1%. Panelists rated the bronze reconstituted juices lower in color intensity, aroma intensity, sweetness, acidity, and flavor than the single-strength juice. However, the red reconstituted juices were rated higher in color intensity than their single-strength counterparts. Panelists rated reconstituted juices higher when reconstituted with essence recovered plus water than with water only.     

不同发酵菌及酶处理的蜜桃酵素体外抗氧化活性比较

以蜜桃为原料,利用不同菌发酵和不同酶预处理蜜桃制备蜜桃酵素,探究不同菌发酵和酶处理对蜜桃酵素发酵和活性的影响。不同菌发酵的蜜桃酵素的p H值和可溶性固形物含量在发酵初期下降较快,发酵20h后期趋缓;而清除O2·^-和DPPH·的能力在发酵初期提升较快,发酵50 h后趋缓。发酵60 h后,各组的可溶性固形物含量由5.00°Brix降至约3.60°Brix;酵母菌发酵蜜桃酵素清除O2·^-和DPPH·的能力都较高,分别为43.70%和38.25%。蜜桃酵素感官评定得分高低对应发酵菌依次为:酵母菌、双歧杆菌-7菌和10菌、乳链球菌-5菌、植物乳杆菌。两种果胶酶和纤维素酶1.5L能显著增加蜜桃浆液的可溶性固形物含量;酶解预处理能够提高蜜桃浆液本身的O2·^-和DPPH·的能力。果胶酶处理可以得到澄清的蜜桃酵素液,且能提高蜜桃酵素的风味,其中经果胶酶SPL处理的蜜桃酵素的香气和滋味最优。     

响应面法优化超声辅助凹土-壳聚糖澄清姜汁工艺

以凹土和壳聚糖为原料负载后作为复合澄清剂,在单因素实验的基础上,以姜汁透光率为考察指标,研究超声处理对姜汁澄清效果的影响,通过响应面法对姜汁澄清工艺进行优化,并以色泽、透光率、可溶性固形物含量、总酚含量、姜辣素含量、蛋白质含量为指标,对比了超声辅助凹土-壳聚糖澄清法与其他澄清方法对姜汁澄清效果及品质的影响。结果显示,超声辅助凹土-壳聚糖复合澄清剂澄清姜汁的最佳工艺条件为:超声时间10 min、超声温度54℃、超声功率160 W。在此优化条件下,姜汁的透光率达96.78%±0.56%以上。对比不同澄清方法发现,超声辅助凹土-壳聚糖澄清法所得澄清姜汁色泽浅、透光率高、姜辣素含量最高,且差异显著(P<0.05);而影响姜汁稳定性的总酚含量及蛋白质含量最低,与其它三种方法差异显著(P<0.05);可溶性固形物含量与其它方法相比差异性甚小。     

不同制汁工艺对绿芦笋汁理化成分和抗氧化活性的影响

以绿芦笋为材料,研究了直接破碎制汁、热烫后破碎制汁、热烫后破碎经纤维素酶处理制汁、冷冻芦笋解冻后破碎制汁四种工艺对绿芦笋汁理化成分和抗氧化活性的影响。结果表明:热烫处理能保护芦笋汁的色泽,提高VC的稳定性;纤维素酶处理能提高芦笋汁的可溶性固形物、总糖及总黄酮含量及其抗氧化活性;热烫和纤维素酶处理均能降低芦笋汁中的可溶性蛋白和总酚含量。      

Effect of UV–Vis Irradiation on Enzymatic Activities and Physicochemical Properties of Four Grape Musts from Different Varieties

The influence of ultraviolet–visible irradiation on some quality attributes (pH, soluble solids content, color parameters, absorption spectrum, vitamin C, total acidity, total phenolics, formol index, and total and reducing sugars) and polyphenol oxidase, peroxidase, and pectinmethylesterase activities of fresh grape juices was investigated. Grape juice was made from two varieties of white grapes (Victoria and Dauphine) and two varieties of pink grapes (Emperor and Red Globe). Each juice was irradiated for 140 min with a high-pressure mercury lamp of 400 W that emits in a range between 250 and 740 nm. Polyphenol oxidase was not completely inactivated during irradiation, reducing only 80% of its initial activity in juices from white grapes and only 50% in those from pink grapes. On the contrary, peroxidase was completely inactivated. A slight or nonexistent variation was observed in most of the measured physicochemical parameters, showing high stability during irradiation. Only vitamin C and color had a significant variation, with an average decrease of 30% for vitamin C in all varieties and a more important variation of color parameters in the pink varieties than in the white ones.     

蟠桃品种用于加工鲜榨汁的适宜性评价

为研究不同蟠桃品种的鲜榨汁加工适宜性,本实验对北京平谷地区的7 个蟠桃品种的理化与营养指标（pH值、总酚含量、抗坏血酸含量、蛋白质含量、可滴定酸含量、可溶性固形物含量（soluble solids content,SSC）、固酸比、果胶含量）和加工品质指标（单果质量、L*、a*、b*值、褐变度、出汁率、黏度）进行了测定,并从色泽、气味和风味三方面进行感官评价。通过相关性分析、主成分分析和聚类分析法筛选出了SSC、出汁率、果胶含量、a*值和蛋白质含量5 个核心品质评价指标。通过层次分析法得出：SSC和出汁率的权重值为0.32,果胶的权重值为0.18,a*值和蛋白质的权重值分别为0.11和0.07。对7 个蟠桃品种的鲜榨汁品质综合评价表明：瑞蟠21的鲜榨汁品质最好,其次为瑞蟠20、瑞蟠4和瑞蟠19,而巨蟠、瑞蟠2和瑞蟠3的鲜榨汁品质较差。     

THE USE OF PULSED ELECTRIC FIELDS IN PRODUCING JUICE FROM PAPRIKA (CAPSICUM ANNUUM L.)

Investigations were conducted on the impact of pulsed electric field (PEF) treatment on yield and some quality parameters of juice from paprika and results were compared to the results of juice obtained from enzymatically treated or untreated paprika mash. Paprika was comminuted mechanically after which the mash was subjected to either PEF (electric field strength = 1.7 kV/cm, pulse number = 30 and specific energy input per pulse = 0.5 kJ/kg) or a pectolytic enzyme preparation treatment. The extent of cell disintegration after the different pretreatments was monitored through cell disintegration index (Z_p) measurement prior to juice extraction through pressure (10 MPa for 4 min). Some quality parameters (pH, soluble solids (°Brix), total dry matter, color, total carotenoids as β-carotene and vitamin C) of the resultant juice samples were determined. PEF and enzyme treatments resulted in about 10% and 9% increase in juice yield, respectively. Juice from PEF treated paprika compared well in quality with enzyme treated or the untreated. And in some cases such as in color (redness, a value) of the juice, PEF treated had values (+ 18) higher than enzyme treated having + 15.5 and also in the amount of β-carotene extracted into the juice PEF treated juice had more than 60% as compared to about 44% from enzyme treated juice. The pH value for enzyme treated juice was lower than the others.     

高压微射流技术对红枣汁理化性质的影响

以红枣汁为研究对象,研究高压微射流对红枣汁理化性质的影响。将红枣汁分别采用不同压力（40、80、120、160、200 MPa）和不同处理次数（1、2、3、4 次）处理,分析高压微射流处理对红枣汁的ζ电位、平均粒径、色差、透光率、非酶褐变程度和可溶性固形物含量的影响。结果表明：在不同压力条件下的红枣汁的平均粒径、可溶性固形物、澄清度、非酶褐变程度和色差值有显著性差异（P＜0.05）,160 MPa条件下处理4 次的红枣汁平均粒径最小,是对照组平均粒径的16.8%;160 MPa条件下处理2 次的红枣汁透光率达到最佳,为77.6%;120 MPa条件下处理4 次的红枣汁可溶性固形物含量达到最高,较对照组增加了29.6%;160 MPa条件下处理1 次的红枣汁非酶褐变程度最低,与对照组之间差异性不显著性（P＞0.05）,160 MPa条件下处理1 次的红枣汁色差值L*最大。不同处理次数的红枣汁之间的电位有显著性差异（P＜0.05）。表明高压微射流可以改善红枣汁的理化性质,能够为消费者提供高质量的果汁。     

Cloud stabilization in citrus beverages by low methoxyl pectin

Cloud in citrus beverages containing 40–65% total soluble solids (TSS) is stabilized by the addition of 0.05–0.1% ammonia deesterified low methoxyl pectin (LMP) containing 4.5% methoxyl, and 2–6 mg of calcium per 100 g of the beverage. The concentration of LMP and calcium required decreased as the TSS increased. The stabilization of cloud is based on the principle that calcium added at concentrations much lower than that required for gel formation results in considerable increase in the viscosity of the LMP solution. Heat inactivation of pectin esterase (PE) in the juice is not essential for cloud stabilization.     

Studies on the effects of blanching time, evaporation time, temperature and hydrocolloid on physical properties of chili (Capsicum annum var kulai) puree

Thermal processing of chili (Capsicum annum var Kulai) and canning in the form of puree is an alternate process of producing a product with extended shelf-life while retaining its favorable qualities. Red chili was subjected to blanching treatment at different temperatures and times in a steam-jacketed kettle. Test samples were removed, cooled, drained and tested for enzyme activity (peroxidase and lipoxygenase). The model of response surface methodology was introduced to investigate the effects of time, temperature and amount of pectin on the physical properties of chili puree subjected to the evaporation process. Pectin was used as a thickening agent to enhance the viscosity of the puree. A complete inactivation of the enzymes was obtained with the blanching temperature of 100 °C for 6 min. First-order reaction kinetics fitted adequately to predict color loss and pectin was found to improve the viscosity and total soluble solids of the puree.