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P2-154 Microbial Reduction of Dried Laver (Porphyra tenera) and Identification of Resistant Bacteria after Electron Beam Treatment

Tuesday, August 2, 2016
America's Center - St. Louis
You Jin Kim, Kyungpook National University, Daegu, Korea, The Republic of
Hui Su Oh, Kyungpook National University, Daegu, Korea, The Republic of
Min Ji Kim, Kyungpook National University, Daegu, Korea, The Republic of
Jeong Hoon Kim, Kyungpook National University, Daegu, Korea, The Republic of
Jae Baek Goh, Kyungpook National University, Daegu, Korea, The Republic of
In Young Choi, Kyungpook National University, Daegu, Korea, The Republic of
Mi-Kyung Park, Kyungpook National University, Daegu, Korea, The Republic of
Introduction: Laver (Porphyra tenera) is one of the most favorite brown seaweeds in Korea, containing essential amino acids, vitamins, and fiber. Since dried laver is contaminated by manufacturing process, new microbial reduction method is required to ensuring its safety.

Purpose: This study investigated the effect of electron beam (EB) treatment on the microbial reduction of dried laver and identified EB–resistant bacteria from the treated dried laver.

Methods: After EB treatment of 4 kGy and 7 kGy, the numbers of total bacteria and EB-resistant bacteria were measured using tryptic soy agar (TSA) and mannitol salt agar (MSA), respectively. The morphological and biochemical characteristics of each isolated EB–resistant bacterium was investigated using gram-staining, catalase test and salt tolerance test. These bacteria were identified by using 16S rDNA sequence analysis.

Results: Compared to the number of total bacteria in the control group, the total bacterial number after EB treatment of 4 kGy and 7 kGy was significantly decreased to (5.4 ± 0.5) × 104 CFU/g and (1.1 ± 0.6) × 104 CFU/g, respectively. With the increases of EB dosage, the number of red colony was almost the same whereas yellow colony was significantly decreased to (3.3 ± 1.2) × 103 CFU/g and 0 CFU/g for 4 kGy and 7 kGy, respectively. All red and yellow colonies were gram-positive cocci, catalase–positive and resistant to TSA media containing 5% NaCl. From the result of 16S rDNA sequence analysis, yellow and red colonies were identified as either Micrococcus flavus or M. luteus with 99% similarity for yellow colony, and Deinococcus proteolyticus and D. piscis with 99% and 97% similarity for red colony, respectively.

Significance: This study demonstrated that EB treatment was an effective method in the reduction of total bacterial number except for some of EB-resistant bacteria.

Back to: Poster Session 2 – Low-water Activity, Laboratory and Detection Methods, Epidemiology, Produce, Pre-harvest, Dairy and Beverages, Food Defense, General Microbiology
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