Onions were not selected for the study due to the [i]Allium[/i] cultivars being at any greater risk of spoilage through microbial growth than other vegetables. The decision was based on onions being one of the most popular vegetables in the world, sold in considerable numbers.
The study considered how the packaging of vegetables, like onions, can optimize the conditions for promoting the length of time vegetables can be kept for before they start to go ‘off’ and become inedible. Food that goes off may become discoloured or lose its physical structure. There is also a loss of taste and nutrients. This happens as a result of either bacterial or fungal growth. With onions this effect is accelerated if the onions are pre-prepared (such as being sliced.)
The study was led by Dr. Eva Almenar. In a research note, Dr. Almenar describes the process: “We focused on ready-to-use onions, which have grown to become one of the five most commonly sold vegetables in the last decade.”
She then added: “We’ve found a package and sanitizer combination that led to diced onions being acceptable for purchase after two weeks of storage.”
The key to this was finding the best combination of packaging, controlling the atmosphere within the packaging, and the choice of disinfectant agent. It was found that the packaging that could best hold atmospheric conditions of higher levels of carbon dioxide and correspondingly low levels of oxygen, worked best.
In addition to the atmospheric controls, the most efficient chemical disinfectant was found to be a diluted concentration of bleach (or sodium hypochlorite.) These conditions repeatedly showed that sliced or diced onion could remain ‘fresh’ for a period of up to two weeks. The study included an end of shelf-life taste test. Here the aroma and flavour were reportedly satisfactory.
Trials will take place using other types of vegetables, and looking into creating packaging made from renewable resources, such as protein derived from egg whites.
The research has been published in the International Journal of Food Microbiology. The research paper is titled “Interactions between sanitizers and packaging gas compositions and their effects on the safety and quality of fresh-cut onions (Allium cepa L.).”
