Analysis Of Browning Cause In Passion Fruit Spray Power In Processing

As a kind of typical subtropical fruit of Guangxi, passion fruit tastes delicious with a unique flavor and has bioactive substances such as flavonoids and alkaloids in it, which make passion fruit as fruit as well as medicine. So just making juice is not a good way to process passion fruit, which is very popular in our country at present. As we all known, making fruit powder is one of the main way to process fruit and vegetable products, because it’s advantage in storage and usage. This paper has researched on the problem of enzymatic browning and non-enzymatic browning during fruit powder processing, to provide theoretical support in sphere of passion fruit powder processing. Studies as following:1. In each paragraph of the passion fruit powder processing (beating, concentration, sterilization, spray), the fruit powder has severe browning and color change. The rate of L*(light), a*(red and green), b*(yellow and blue), each reduced by24.91%,92.32%,59.22%. Comparing passion fruit spray powder and puree, reducing sugar, amino nitrogen, ascorbic acid, total phenolic and carotenoid each reduced by14.07%,29.22%,75.66%,67.36%,41.59%. Therefore, during passion fruit powder processing, colors changed tremendously. The browning has related to Maillard browning, Vc auto-oxidation reaction, phenolic polymerization carotenoid degradation.2. The acid content of passion fruit puree is3.04g/100g, pH is2.8. It is high acid and low pH fruit, which makes the activity of polyphenol oxidase (PPO), peroxidase (POD) very low, respectively0.944U/g-min,4.185U/g-min. and enzymatic browning difficult to occur. Phenols are substrates for enzymatic browning, but after the heat treatment by50℃for20mins, the total phenolic content and browning index was no significant difference at50℃(P<0.05). The phenomena above illustrated that the passion fruit puree was not easy to enzymatic be browning, therefore non-enzymatic browning is the main cause for browning of passion fruit spray drying.3. Study on color dynamics of concentrates puree and sterilization puree in different temperature and residence time shows that, the rate of L*, a*, b*decreases with the increase of heated temperature and heating time in processing, the chromatic aberration ΔE value and browning index rising, and product color, turn to dark yellow. The b*value changes most quickly. B*value can be one of the fruit browning index. Concentrated puree and sterilization puree at different temperatures, the ΔE change faster than the browning index. ΔE at90℃changes of50℃respectively4.2times and6.04times. ΔE is better demonstration of changes in the value of non-enzymatic browning. Build kinetics model of color can guide and predict the machining process the change of puree color on different process residence time. Activation energies for nonenzymatic browing of concentrates puree and sterilization puree were34.1054and42.8784kJ/mol. Concentrates puree has the higher activity of nonenzymatic browning. The equations:(1) lnk=10.777-34.1054/RT and (2) lnk=13.637-42.8784/RT.4. Study on substance dynamics of concentrates puree and sterilization puree in different temperature and residence time shows that the degradation rate of total phenols, ascorbic acid and carotenoids with prolonged residence time and temperature while faster. Concentrates puree its ascorbic acid at different temperatures is changing fast, about5.71times50℃, the sterilization puree’s ascorbic acid is also changing fast, about4.33times of50℃. Correlation analysis concluded that the main factor affecting passion fruit puree of non-enzymatic browning is ascorbic acid, total phenol, carotene change. Ascorbic acid and total phenol combined impact of b*values change.5. Preparation passion fruit pulp spray powder by taking four different processing technology, which are direct spray(SD1), spray after pulp sterilization(SD2), spray after pulp concentration(SD3), spray after pulp concentrate and sterilization(SD4). The highest rate range of ascorbic acid was75%-79%, and rate range of total phenols was55%-61%. SD2was the most suitable processing condition. The change of carotene content in SD2and SD3were the main factors affecting the AE, the change of total phenol content in SD4was the main factor affecting the ΔE, and the total phenolics and carotenoids has synergy effect on ΔE.