Application of Electron Beam Technology on Freeze-Dried Berries for Fungal Decontamination

Abstract

Safety, quality, and sensory perception of foods are of paramount importance for food preservation. This study explores the combination of freeze-drying technology with electron beam processing (eBeam) processing to create a low microbial bioburden of food without compromising food quality. The hurdle approach in food processing and preservation operates by combining two or more techniques to extend food shelf life. Freeze-drying and eBeam processing are non-thermal processes that have complementary effects for food preservation. The purpose of this study was to understand the antimicrobial effects of eBeam processing on a freeze-dried berry medley. Freezedried berry medley consisting of strawberries, blackberries and raspberries was exposed to specific doses of eBeam radiation (3, 5, and 10 kGy) to isolate fungi that were resistant to these eBeam doses. The isolates that survived the eBeam processing were identified (Aspergillus sp., Penicillium sp., Cladosporium sp.) using Internal Transcribed Spacer (ITS) sequencing and their D10 values were determined. A dose validation study was then performed on the freeze-dried berries to show that 15 kGy was sufficient to eliminate all fungal spores/mycelia in the freezedried berry product. Quality attributes of the berries were analyzed for changes due to eBeam processing using multidimensional gas-chromatography – olfactometry – mass spectrometry (MDGC-O-MS). Four (4) volatile compounds showed significant increases (P < 0.05) by the eBeam treatment; 2-butenal, 3-methyl butenal, ethyl acetate, 2-furancarboxaldehyde. One (1) volatile compound showed significant decrease (P < 0.05) by the eBeam process; alpha pinene. Color attributes were tested for any changes due to eBeam processing using a colorimeter; no significant color changes were observed (P < 0.05) for L*, a*, or b* values of each individual berry except for the a* value of strawberries. Minimal changes to freeze-dried berry medley were observed with eBeam processing between 0 to 15 kGy.