热杀菌结合冷藏改善绿芦笋汁的贮藏稳定性研究

为研究热杀菌处理对绿芦笋汁贮藏稳定性的影响,通过121℃、3min(F03min)处理绿芦笋汁,并置于(4±1)℃条件下冷藏,定期测定其各指标(菌落总数、色泽、可溶性蛋白、总糖、总酚、总黄酮、VC含量与DPPH自由基清除能力)的变化。结果表明:F03min热杀菌处理可将芦笋汁中的固有微生物完全杀死,且在芦笋汁冷藏的120d均无微生物生长;F03min杀菌处理结合冷藏可有效抑制绿芦笋汁贮藏期间L*和a*值的上升,延缓可溶性蛋白、VC、总酚和DPPH自由基清除能力的下降,维持总糖和总黄酮含量的稳定,保持绿芦笋汁的贮藏稳定性,有效延长绿芦笋汁的贮藏货架期,使其冷藏期延长至120d。     

贮藏温度对绿芦笋汁色泽稳定性的影响

研究了不同贮藏温度(常温25℃和冷藏5℃)条件下,绿芦笋汁的色泽、叶绿素、类胡萝卜素、Vc、总酚、还原糖和氨基酸含量的变化,以探究贮藏温度对绿芦笋汁色泽稳定性产生的影响。结果表明:叶绿素的化学降解是绿芦笋汁贮藏期间色泽变化的主要原因,Vc、总酚和还原糖含量的降低也促使了芦笋汁色泽的变化,而氨基酸与芦笋汁的色泽无显著相关性。5℃贮藏显著抑制了绿芦笋汁叶绿素、Vc、总酚和还原糖含量的降低,抑制了类胡萝卜素含量的上升,从而有效地保护了芦笋汁的绿色,维持了绿芦笋汁色泽的稳定性。     

蓝莓渗透脱水和流化床干燥过程中理化变化的研究

蓝莓在高果糖浆(70±1°Brix)和不同渗透温度(45、55、65℃)条件下,不同的渗透液温度处理对蓝莓VC的损失有不同影响,其中以渗透液温度65℃处理对VC的含量影响最大,45℃下渗透脱水VC的损失最少。在5±1℃贮藏时蓝莓干中的花色苷比在22±1℃贮藏时稳定性好。光照使蓝莓干在贮藏过程中总花色苷残留率迅速下降,而暗箱贮藏使蓝莓干在贮藏过程中总花色苷残留率下降缓慢。     

包装容器对绿芦笋汁货架期品质的影响

绿芦笋汁采用121℃、3min杀菌处理后,分别灌装于预先杀菌处理的玻璃瓶和聚对苯二甲酸乙二醇酯(PET)瓶中,于(4±1)℃冷藏,通过测定绿芦笋汁贮藏期间色泽、叶绿素、类胡萝卜素、维生素C、总酚和还原糖含量的变化,以探究不同包装容器对绿芦笋汁贮藏期间品质的影响。结果表明:玻璃瓶包装可有效延缓绿芦笋汁冷藏期间色泽亮度的上升和绿色的受损,抑制类胡萝卜素含量的上升,从而有效地保护绿芦笋汁的绿色,维持绿芦笋汁色泽的稳定性,在贮藏结束时L*值为56.15,a*值为-1.27,总叶绿素含量为5.584mg/L;玻璃瓶装绿芦笋汁的维生素C、总酚和还原糖含量的降低受到显著抑制,尤其是维生素C含量在贮藏3个月时仍为0.204mg/m L,保留率为82.93%,总酚和还原糖的保留率分别为52.74%、64.58%,而PET瓶装绿芦笋汁的维生素C、总酚和还原糖的保留率分别为28.05%、43.68%和58.67%。由此,玻璃瓶包装可有效维持绿芦笋汁冷藏期间的货架品质。     

减压对金铃大枣贮藏过程中生理生化变化的影响

在(-1±0.5)℃的条件下,以常压贮藏为对照,进行金铃大枣的减压贮藏实验。在贮藏过程中,测定了枣果的VC含量、可溶性固形物(TSS)含量、多聚半乳糖醛酸酶(PG)活性、丙二醛(MDA)含量及相对电导率,研究了减压贮藏对枣果生理生化变化的影响。结果表明,减压贮藏可以显著抑制枣果的成熟和衰老,但对保持枣果VC含量的效果不显著。     

MAP结合低温贮藏对高成熟度鲜枣的保鲜效果

研究了以不同体积分数混合的O2、CO2、N2进行气调包装,在(0±0.5)℃贮藏条件下对着色面积在75%以上的全熟鲜枣(Ziziphus zizyphus)品质的影响。结果表明,经过60d的贮藏,不同体积分数的气调包装均能有效抑制全熟鲜枣果实衰老和营养物质损失,能不同程度地延缓果实中MDA(丙二醛)含量的上升和硬度的下降;降低质量损失和乙醇积累量;减缓鲜枣果实中TA(可滴定酸)含量的下降和颜色变化以及还原糖含量的上升;可有效地防止VC、cAMP(环磷酸腺苷)和总黄酮等营养物质的损失;同时能够较长时间保持果实鲜亮的颜色。其中以气体体积分数为5%O2、2%CO2、93%N2的气调包装对全熟鲜枣的保鲜效果最好。     

壳聚糖涂膜对‘红宝石无核’葡萄保鲜效果的影响

研究壳聚糖涂膜对葡萄低温贮藏品质的影响。以‘红宝石无核’葡萄为研究材料,用不同浓度(0.5%、1%、1.5%)的壳聚糖水溶液涂膜葡萄,以用蒸馏水处理的果实作为对照(CK),低温贮藏,测定贮藏期间葡萄果实失重率、可滴定酸(TA)、可溶性固形物(TSS)、VC、丙二醛(MDA)等的变化。结果表明,1%壳聚糖涂膜可以有效降低‘红宝石无核’葡萄在贮藏期内水分散失速度,减少TA和VC的损失,并抑制MDA的在果实中的积累。试验表明,壳聚糖涂膜是一种有效的葡萄保鲜方法,有着较好的应用前景。     

氯吡苯脲处理和质量损失对猕猴桃品质和电学特性的影响

为探明氯吡苯脲（1-(2-chloropyridin-4-yl)-3-phenylurea,CPPU）处理和贮藏过程中质量损失对不同品种 猕猴桃品质和电学特性的影响,以生长期使用20 mg/L CPPU处理幼果的‘秦美’、‘海沃德’猕猴桃为试材,在 室温下贮藏,比较不同质量损失和CPPU处理对‘秦美’、‘海沃德’果实品质指标和电学参数的影响。结果表 明：猕猴桃CPPU处理和贮藏过程中的质量损失都会导致果实品质显著下降,质量损失对‘秦美’猕猴桃品质下降 影响更大,CPPU处理对‘海沃德’猕猴桃品质下降影响更大。在选定的24 个频率中,CPPU处理和未处理的‘秦 美’、‘海沃德’的特征频率分别为3 980、2 510、251、631 kHz,对应的敏感电参数为并联等效电感（Lp）。可 基于果实VC含量与Lp的回归方程实现CPPU处理猕猴桃的无损检测,从而区分猕猴桃是否使用了CPPU。质量损失 率与电学特性无显著相关性,无法建立数学模型实现猕猴桃新鲜度的无损检测。     

壳聚糖-海藻酸钠双层修饰VC脂质体的稳定性及其强化水蜜桃汁的生物学评价

壳聚糖(CH)和海藻酸钠(AL)两种多糖通过静电相互作用,层层自组装修饰在包裹了维生素C的传统脂质体(liposomes,LPs)表面,形成新型多聚物运载体系(polyelectrolyte delivery system,PDS),研究其在长期贮藏过程中的泄漏动力学;以VC溶液为对照,将LPs、过滤PDS(filtered PDS)、未过滤PDS(non-filtered PDS)分别添加入水蜜桃汁以营养强化VC,研究果汁在贮藏过程中的稳定性变化和生物学功效。结果表明,PDS中的VC泄漏较未修饰脂质体(LPs)的慢,泄漏过程符合Peppas模型;添加未过滤PDS和过滤PDS的营养强化水蜜桃汁较其他组的色差变化较小,pH值更稳定,在30 d贮藏期间微生物生长不明显。多糖双层修饰的脂质体(PDS)比未修饰的传统脂质体(LPs)具有更好的缓释作用,在保护果汁的营养成分和维持饮料体系的稳定性上效果更显著。     

青梅汁浓缩过程中非酶褐变的研究

非酶褐变是青梅汁加工和贮藏过程中发生褐变的主要原因。研究青梅汁浓缩过程中不同添加剂对果汁非酶褐变的影响,结果表明:添加青梅汁质量0.005%的异抗坏血酸钠对果汁浓缩过程具有显著的防褐变效果。同时,研究添加不同添加剂对青梅汁浓缩前后果汁颜色变化与其VC、总糖和总酚含量变化相关系数R2,结果表明:青梅汁浓缩过程中非酶褐变主要是由酚类物质的氧化缩合引起,VC的氧化、美拉德反应和焦糖化反应对果汁颜色劣变影响不大。     

Loss of rutin and antioxidant activity of asparagus juice caused by a pectolytic enzyme preparation from Aspergillus niger

We found that a commercial pectolytic enzyme preparation from Aspergillus niger (pectinase AN) contained laccase activity that decreased rutin content and antioxidant activity of asparagus juice. This research investigated the effects of pH, temperature, and concentration of pectinase AN on pectinase AN’s laccase activity to decrease rutin content and antioxidant activity of asparagus juice. Asparagus juice was incubated with pectinase AN at different pHs (3.2, 4.5 and 5.8), temperatures (25, 37, and 50 °C) and enzyme concentrations (0.1%, 0.5% and 1%). Rutin content and antioxidant activity of samples was determined by HPLC and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) free radical method, respectively. The rate of loss of rutin and antioxidant activity of asparagus juice was smaller at pH 3.2 than at pH 4.5 and pH 5.8, smaller for 0.1% pectinase AN than 0.5% and 1% pectinase AN. The rate of loss of rutin of asparagus juice was greater at 25 °C than at the other two temperatures. Pectinase AN can decrease rutin content and antioxidant activity of asparagus juice at the selected conditions. But rutin content and antioxidant activity of asparagus juice produced using pectinase AN could be less decreased at pH 3.2 and 0.1% of enzyme with less than 2 h of incubation time. This information was helpful for juice industry to produce juices with high antioxidant activity using pectinase AN.     

草莓清汁加工过程中的VC损失及保护研究

主要研究了不同加工工艺对VC的影响，加工过程易造成草莓清汁中VC损失，EDTA及醋酸对VC具有明显的保护作用，特别是0．5％的EDTA和0．5％的醋酸以0．5：15的体积比混合使用时，保护效果尤佳；草莓预处理中宜选用0．05％的KMnO4溶液，打浆时间为1min，这样可明显减少VC的损失。同时对贮存工艺进行了研究，得出了最佳贮存工艺参数。     

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.     

Comparing the impact of high pressure,pulsed electric field and thermal pasteurization on quality attributes of cloudy apple juice using targeted and untargeted analyses

The impact of low-oxygen spiral-filter press technology combined with thermal pasteurization (TP), pulsed electric field (PEF) and high pressure processing (HPP) on cloudy apple juice quality was investigated immediately after the treatments and after 3 weeks of storage at 4 °C. Based on equivalent levels of microbial safety and desired shelf-life, low and high processing intensities were selected: TP (72 °C/15 s; 85 °C/30 s), PEF (12.5 kV/cm, 76.4 kJ/L; 12.3 kV/cm, 132.5 kJ/L), and HPP (400 MPa/3 min; 600 MPa/3 min). High intensity thermal treatment resulted in a bright, yellowish color which was maintained during storage. PPO and POD activities were largely reduced by high intensity PEF and TP yet showed high resistance to HPP. The highest vitamin C content was provided by fresh juice followed by PEF-treated juices. Due to oxidative degradation reactions, vitamin C of all treated samples significantly decreased during storage. Immediately after processing, high cloud stability values were obtained in all samples; however, cloud stability decreased during storage particularly for HPP juices with high residual PME. No significant changes were observed in pH, titratable acidity, organic acid and sugar content which also corresponded to sweet and sour taste. Results from untargeted volatile profiles showed that esters increased after PEF and were better retained after HPP. Contrary to TP treatment where ester degradation reactions occurred together with the formation of off-flavors. Most of the volatiles decreased during storage which could be linked to oxidation and ester hydrolysis reactions.Industrial relevanceBeing one of the most popular fruit juices consumed worldwide, cloudy apple juice can still undergo quality changes such as color degradation, cloud loss (fast sedimentation) and flavor changes during processing and storage. This study evaluates the potential of low-oxygen spiral-filter press in combination with different preservation technologies to obtain a maximal quality of cloudy apple juice. Results showed that high intensity thermal pasteurization can effectively inactivate quality-degrading enzymes, therefore it is useful to obtain an optimal cloudy apple juice product in terms of color and cloud stability. Although HPP has minimal impact on aroma of the juice, shelf-life of the juice may be limited due to incomplete enzyme inactivation. In the case of PEF treatment, thermal effects may contribute to maintain apple juice quality.     

混浊苹果汁储藏过程中色泽稳定性的研究

通过HPLC等方法分析果汁中酚类和VC等物质在储藏中的变化,发现混浊苹果汁在储藏中发生的非酶褐变主要是由酚类的氧化聚合而引起,可通过低温储藏加以控制。聚原花色素、表儿茶素、绿原酸和VC的损失以及果汁的褐变随储藏时间的延长和温度的升高而加剧。果汁颜色变化先快后慢,L值降低,a值升高,b值变化较小。氨基酸也参与了褐变反应,但Maillard反应不显著。缩合单宁的平均聚合度随储藏时间的延长和温度的升高而变大。粒径分析表明储藏过程中有新的颗粒产生。     

Acid adaptation and temperature effect on the survival of E. coli O157:H7 in acidic fruit juice and lactic fermented milk product.

In this study, two strains of Escherichia coli O157:H7, (ATCC 43889 and ATCC 43895) were acid adapted at pH 5.0 in tryptic soy broth (TSB) for 4 h. Commercial products of mango juice (pH 3.2), asparagus juice (pH 3.6), Yakult--a diluted milk fermented drink (pH 3.6), and low-fat yoghurt (pH 3.9) were inoculated with acid-adapted or nonadapted cells of E. coli O157:H7. Survival of the inoculated E. coli O157:H7 in these commercial food products during storage at 25 or 7 degrees C was examined. It was found that although survival of the acid-adapted and nonadapted E. coli O157:H7 ATCC 43895 in asparagus juice during storage at 7 degrees C did not show marked difference, in general, acid adaptation and low temperature enhanced the survival of E. coli O157:H7 in both the commercial fruit juices tested. On the contrary, acid adaptation reduced the survival of both the strains of the test organism in Yakult and low-fat yoghurt stored at 7 degrees C. Besides, E. coli O157:H7 ATCC 43895 survived longer than ATCC 43889 in all the products examined, regardless of the storage temperature and acid adaptation.     

超高压与热杀菌对刺梨汁贮藏期品质影响的比较

本实验对比了超高压（500 MPa、10 min）和传统热杀菌（90 ℃、15 min）对刺梨汁处理前后及4 ℃、30 d贮藏期内微生物、理化指标、色泽、活性成分等的影响。结果表明,两种处理使刺梨汁菌落总数均小于1.0（lg（CFU/mL））,贮藏结束时,超高压与热处理组菌落总数分别为1.83（lg（CFU/mL））和2.60（lg（CFU/mL））;两种处理均使刺梨汁L*值显著上升（P＜0.05）,热处理刺梨汁褐变度显著高于超高压处理（P＜0.05）,表明超高压能更好地保持刺梨汁原有的色度;贮藏期间b*值呈现下降趋势;与热处理相比,超高压处理能更好地保持刺梨汁中的总酚、VC水平及超氧化物歧化酶（superoxide dismutase,SOD）活力。贮藏结束时,超高压组总酚、VC质量浓度、SOD活力及抗氧化活性的保留率分别为93.32%、52.80%、64.49%、93.96%,热处理组总酚、VC、SOD活力与抗氧化活性的保留率分别为81.68%、28.35%、41.65%、93.30%。综上,超高压处理相较于传统热处理在保持刺梨汁品质特性与抗氧化物质方面有显著优势,可作为一种新型刺梨汁饮料加工技术。     

高压脉冲电场和热处理对蓝莓汁品质的影响

以蓝莓汁为原料,比较了高压脉冲电场（PEF）杀菌和热力杀菌处理对蓝莓汁中微生物和理化指标的影响,以及不同处理的蓝莓汁在贮藏期间的品质变化规律。结果表明：PEF可以有效杀灭蓝莓汁中的微生物;PEF杀菌对蓝莓汁色泽参数影响程度小;杀菌处理后,贮藏期内PEF处理和热处理对蓝莓汁的还原糖、总酸、可溶性固形物含量、总酚含量影响较小,PEF处理较热处理能更好地保持蓝莓汁中的VC和花青素含量。     

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.     

储藏过程中百香果汁非酶褐变的研究

百香果汁在储藏过程中易发生非酶褐变,影响其品质。研究了储藏期间同非酶褐变相关的物质的变化规律及其与褐变的关系。结果显示,总糖、还原糖、氨基态氮和VC均随储藏温度升高或储藏时间延长而减少,褐变度及5-HMF含量则随储藏温度升高或储藏时间延长而增加,总酚含量变化不显著。因此,VC的氧化分解及Maillard反应是导致百香果汁储藏过程中非酶褐变的主要原因。