Alighourchi Hamidreza, Barzegar Mohsen, Sahari Mohammad Ali, Abbasi Soleiman
Department of Food Science and Technology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran.
Iran J Microbiol. 2014 Feb;6(1):51-8.
Pomegranate fruit is a rich source of bioactive compounds. The serious concern over unprocessed fruit juices is microbial contamination, which effectively inactivated by thermal processing, but it significantly affects juice functional compounds. Therefore, the effect of gamma irradiation and ultrasonic on inoculated microbial to pomegranate juices was studied.
Two pomegranate cultivars were purchased from the Agricultural Research Center of Saveh, and their juices were extracted by a manual device and immediately centrifuged. Then the studied microorganisms were re-suspended in sterile pomegranate juices. The juices were continuously sonicated at amplitude levels of 50, 75 and 100% and times of 0, 3, 6, 9, 12 and 15 min at temperature of 25 ± 1 °C. Irradiation treatment was also carried out at various doses of 0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3 kGy.
The results showed that lower amplitude levels (50 and 75%) did not inactivate E. coli and S. cerevisiae significantly (<1.5 log reduction), while at 100% amplitude level for 15 min, their population reduced by 3.47 and 1.86 log cfu/mL, respectively. Gamma irradiation treatment at 1 kGy also reduced E. coli by 6.66 log cfu/mL, whereas at 3 kGy it reduced S. cerevisiae by 5.08 log cfu/mL.
The low-dose gamma irradiation could potentially inactivate the studied microorganisms compared to the sonication, which had less destructive effects on their populations. Further research is needed to determine the effect of these methods on other fruit juices for industry purposes.
石榴果实富含生物活性化合物。未加工果汁面临的严重问题是微生物污染，热处理虽能有效灭活微生物，但会显著影响果汁中的功能化合物。因此，研究了γ射线辐照和超声处理对接种于石榴汁中微生物的影响。
从萨韦农业研究中心购买了两个石榴品种，用手动装置提取果汁并立即离心。然后将研究的微生物重悬于无菌石榴汁中。在25±1℃下，将果汁在振幅水平为50%、75%和100%以及时间为0、3、6、9、12和15分钟的条件下连续超声处理。还进行了不同剂量（0、0.5、1.0、1.5、2.0、2.5和3千戈瑞）的辐照处理。
结果表明，较低的振幅水平（50%和75%）对大肠杆菌和酿酒酵母的灭活效果不显著（减少量<1.5个对数），而在100%振幅水平下处理15分钟，它们的数量分别减少了3.47和1.86 log cfu/mL。1千戈瑞的γ射线辐照处理使大肠杆菌数量减少了6.66 log cfu/mL，而在3千戈瑞时，酿酒酵母数量减少了5.08 log cfu/mL。
与超声处理相比，低剂量γ射线辐照可能会灭活所研究的微生物，且对微生物数量的破坏作用较小。为了工业目的，还需要进一步研究这些方法对其他果汁的影响。
