Microbiological changes and severity of decay in apples stored for a long-term under different storage conditions

Abstract

© 2016, Lithuanian Institute of Agriculture. All rights reserved. Apples occupy most of the Latvian vegetable market, nevertheless there is a lack of good quality locally grown apples. Using advanced storage technologies, such as storage in controlled atmosphere in ultra low oxygen (O 2 ) (ULO) and elevated carbon dioxide (CO 2 ) conditions, as well as pre-treatment of fruits with 1-Methylcyclopropene (1-MCP) will substantially improve the quality of fruits and globally assist apple growers to distribute more qualitative and safe fruits on the local market. The aim of the study was to ascertain the causes of apple decay that occurred during storage under different conditions. Two apple storage technologies were tested in this study: cold storage under conventional conditions + 1-Methylcyclopropene treatment and controlled atmosphere – 2.0% CO 2 , 1.0% O 2 (ULO1) and 2.5% CO 2 , 1.5% O 2 (ULO 2 ) conditions. After apple storage for six months the following microscopic fungi were isolated: Penicillium expansum (30.44%), Monilinia fructigena (26.08%), Neofabraea alba (21.73%), Colletotrichum acutatum (13.04%), Botrytis cinerea (8.69%) in cold storage, while P. expansum (35.26%), Colletotrichum acutatum (23.57%), Neofabraea alba (11.76%), B. cinerea (11.76%), M. fructigena (11.76%) and Fusarium avenaceum (5.89%) were isolated from fruits that prior to storage were pre-treated with 1-MCP. Apples that had been stored under ULO1 conditions predominantly were contaminated with: N. alba (33.34%), M. fructigena (26.69%), B. cinerea (13.33%), P. expansum (6.66%), F. avenaceum (6.66%), Phomopsis/ Diaporthe eres (6.66%) and Mucor circinelloides (6.66%), while under ULO 2 : N. alba (33.33%), M. fructigena (33.33%), F. avenaceum (16.67%) and P./D. eres (16.67%). Diversity of microscopic fungi, which were isolated from differently stored and decayed apple samples, was quite similar, though with insignificant difference. For instance, microscopic fungus F. avenaceum was not found only in cold storage kept fruits, while microscopic fungus of the genus P./D. eres was identified when apples were stored under ultra low oxygen conditions.