Influence of gamma radiation treatment on microbial contamination, quality indicators and anthocyanin content in dark raisins

Abstract

One of the most promising and gentle methods for reducing the number of microorganisms in food and agricultural raw materials is treatment with ionizing radiation. The work aimed to evaluate the effect of antimicrobial treatment with gamma radiation on quality indicators and anthocyanin content in dark raisins. The object of the study was dark raisins produced in Uzbekistan. The studied samples were analyzed according to quality indicators (organoleptic, moisture, color) and microbiological indicators (total microbial contamination, yeast content, mold, and coliform bacteria). The main groups of microorganisms isolated from the surface of raisins were also identified using MALDI-TOF mass spectrometry. The anthocyanin content of the samples was measured by pH differential spectroscopy. Studies have shown that when dark raisins are irradiated in the dose range from 1.5 to 9 kGy, there is a significant decrease in the number of main sanitary-indicative microorganisms. It has been established that the optimal dose for suppressing microflora is 4-6 kGy. Microbial contamination of raisins is mainly caused by molds of the genera Mucor, Rhizopus, and Aspergillus and yeasts of the genera Candida and Phomopsis. As a result of treatment with ionizing radiation, a decrease in the content of anthocyanins by 1.5-2 times was noted. At the same time, no changes in the color, taste, and presentation of raisins were established. Treatment of dark varieties of raisins with gamma radiation can be recommended as an alternative to chemical treatment.