【作者】 刘凤霞；

【导师】 廖小军；

【作者基本信息】 中国农业大学 ， 农产品加工及贮藏工程， 2014， 博士

【摘要】 本研究以芒果为原料,首先对芒果制汁品种适宜性进行筛选,结合超高压(High hydrostatic pressure, HHP)和蒸汽热烫技术研究不同处理对芒果关键内源酶和品质的影响,从而开发HHP芒果汁加工新工艺,并对HHP和高温短时(High temperature short time, HTST)芒果汁品质进行了系统研究。主要结果与结论如下：(1)四个芒果品种间的β-胡萝卜素、Vc、多酚、抗氧化活性(DPPH, FRAR)、糖、酸、挥发性成分、颜色、内源酶活性等都存在差异,运用主成分分析法可将四个品种很好的分开。其中,“台农一号”中总酚含量最高、抗氧化活性最高、葡萄糖、果糖含量最高、糖酸比最低、PPO和POD酶活性最低、挥发性成分种类最多。因此选择“台农一号”作为适宜制汁品种进行加工工艺开发。(2)HHP结合蒸汽热烫1min处理可有效钝化芒果中PPO和POD酶,解决了HHP不能完全钝酶的问题；且热烫后芒果中Vc、类胡萝卜素及糖含量变化不显著,总酚及抗氧化活性显著上升,总色差△E<2,表明该条件能在钝酶的同时有效地保持芒果的原有品质。(3)HHP (300MPa/15min、400MPa/5min、500MPa/2.5min、600MPa/1min)和HTST(110℃/8.6s)处理可以有效的杀灭芒果中的微生物,保证安全性。HHP处理后未热烫芒果中Vc、总类胡萝卜素、糖含量变化不显著,总酚及抗氧化活性显著上升；而热烫芒果经HHP处理后上述变化不显著。HTST处理后芒果中Vc、总酚、糖含量及抗氧化性变化同HHP处理,总类胡萝卜素含量变化不显著,但HTST处理中的高温引起了β-胡萝卜素的异构化,样品的总色差△E最大。HHP和HTST处理后,芒果浆的表观粘度均显著变大,触变性均减小,贮存模量G’和损耗模量G”均有增大的趋势,上述变化在HTST处理的样品中更显著。(4) HHP (600MPa/1min)结合蒸汽热烫1min和HTST(110℃/8.6s)处理后,芒果汁中菌落总数小于2个对数,霉菌酵母小于1个对数,符合国家卫生标准,且贮藏16周过程中未见微生物生长。(5)HHP和HTST处理后芒果汁中的Vc、异Vc钠、总酚、总类胡萝卜素、蔗糖含量及抗氧化活性无显著变化,而葡萄糖和果糖含量显著下降；在4和25℃贮藏16周后,Vc、异Vc钠、总酚、总类胡萝卜素及抗氧化活性、蔗糖均有不同程度的下降,而葡萄糖和果糖含量逐渐提高；较零级和一级动力学模型,联合动力学模型可以更好地拟合贮藏期间芒果汁中Vc、异Vc钠、总酚、总类胡萝卜素和糖含量的变化。芒果汁中对抗氧化活性起主要作用的是总酚和异Vc钠,抗氧化活性与异Vc钠(R=0.780-0.989)和总酚(0.785-0.968)含量呈显著正相关。(6) SPME-GC-MS指纹图谱技术可有效地用于比较分析HHP和HTST处理对芒果汁挥发性成分的影响。分析结果表明,HTST处理后可能促进芒果汁中氨基酸和不饱和脂肪酸的降解,导致芒果汁中二甲基硫醚和丙酮含量显著高于未处理和HHP处理芒果汁。感官评定结果也表明,HHP芒果汁风味优于HTST处理芒果汁。更多还原

【Abstract】 With combination of high hydrostatic pressure (HHP) and steam blanhcing, the effects on inactivation of key enzymes and qualities of mango were studied, and the processing conditions of mango juice were optimized. Furthermore, effects of HHP and high temperature short time (HTST) on qualities of mango juice were comparatively investigated. The main results were shown as follows:(1) The present study demonstrated that different mango cultivars presented different physico-chemical and antioxidant characteristics, including β-carotene, Vc, polyphenols, anti-oxidant activity, sugars, organic acids, volatile compounds, color and enzyme activity. The four mango cultivars were well separated by principal component analysis (PCA), and each cultivar presented a distinctive characteristic which can be significant predictors in differentiating mango cultivars. Of the four cultivars selected in this study, Tainong No.1had higher content of total phenols, fructose and glucose, higher antioxidant activities (using DPPH, FRAP assay), more volatile compounds, lower sugar/acid ratio, lower PPO and POD activity. Thus, Tainong No.1was selected for processing optimization of mango juice.(2) The combination of HHP and steam blanching treatments can effectively inactivate PPO and POD in mango. After blanching treatment, total phenols and anti-oxidant activity were significantly increased, while the content of Vc, carotenoids and sugars was not changed, and total color difference (AE) was below2(without visible changes), indicating that the blanching condition used in this study can be a good choice in canmercial practice to extend the shelf life and maintain the quality of mango product.(3) This study indicated that no natural microorganisms were detected in un-blanhced and blanched mango pulp after HHP treatments at300MPa/15min,400MPa/5min,500MPa/2.5min, and600MPa/1min and HTST treatment at110℃/8.6s. For un-blanhced mango pulp, HHP significantly increased the content of total phenols and anti-oxidant activity, while had no effects on the content of Vc, carotenoids and sugars. Similar changes were found in HTST-treated mango pulp in Vc, total phenols, sugars and anti-oxidant activity. HTST treatment had no effects on total carotenoids content, but can cause β-carotene isomerization. HTST-treated samples had highest AE. Moreover, HHP and HTST treatments increased the viscosity, storage modulus and loss modulus of un-blanched and blanched mango pulp, which were more significant in HTST-treated samples.(4) Immediately after HHP or HTST treatment and during16weeks storage, counts of TAB were less than2.00logi0CFU/mL, and counts of Y&M were less than1.00log10CFU/mL, which met the requirements of Chinese Drink Standard GB10789-2007and indicated that mango juice was microbiologically safe in this study.(5) Glucose and fructose decreased significantly, while Vc, sodium erythorbate, total phenols, total carotenoids, sucrose and anti-oxidant activity changed insignificantly after HHP or HTST treatment. After16weeks storage at4and25β, there were significant decrease in Vc, sodium erythorbate, total phenols, total carotenoids, sucrose and anti-oxidant activity, and significnat increase in glucose and fructose in mango juice. Kinetic data of changes in Vc, sodium erythorbate, total phenols, total carotenoids, and sugars during storage fitted well into a combined model for both HHP-and HTST-treated samples. The main contributors to the total antioxidant capacity in mango juice were total phenols and sodium isoascorbate, whihc were positively correlated to the changes in antioxidant capacity regardless of storage temperature, with R being0.780-0.989for sodium isoascorbate and0.785-0.968for total phenols.(6) Headspace SPME-GC-MS fingerprinting could be a useful tool in screening the different effects of distinct processing technologies on volatile of food fraction to uncover different process-induced chemical changes in processed mango juice. HIST processing seems to enhance the formation of dimethyl sulfide and acetone, due to thermal degradation of amino acid and unsaturated fatty acid. From sensory evaluation, HHP treated mango juice showed better flavor property compared to HTST treated mango juice.更多还原