Fruit & Vegetable Magazine

Features Production Research
Keeping potatoes fresh


March 3, 2009
By Public University of Navarre

Topics

March 3, 2009 — From the harvest to marketing, vegetable products
suffer damage produced by the triggering of a series of processes that
tend to negatively affect the quality of, in this case, the potato.

March 3, 2009 — From the harvest to marketing, vegetable products suffer damage produced by the triggering of a series of processes that tend to negatively affect the quality of, in this case, the potato.

This tendency can be modulated by a number of control techniques for the surrounding conditions of the products, mainly the storage temperature, the relative humidity and the composition of the surrounding atmosphere.

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The study of the effects of the composition of the atmosphere surrounding the processed potato was the objective of the PhD thesis defended by Ignacio Ángel Angós Iturgaiz at the Public University of Navarre in Spain. His work concluded that an atmosphere rich in carbon dioxide (CO2) and with high concentrations of oxygen (O2) enhances the quality of the minimally processed potato given that these factors slow down the loss processes of water and nutrients, and its change of colour (going a brown colour). This thesis was defended at the Department of Food Technology of the Higher Technical School of Agricultural Engineers. Angós, agricultural engineer and researcher currently undertaking work at the ALITEC research group at the Public University of Navarre.

“Employment of atmospheres rich in CO2 and high concentrations of O2 in the enhancement of quality characteristics of minimally processed cv. Monalisa refrigeration-stored potato” is the title of the thesis in which Angós analyzed the effect these gases have in maintaining the respiratory physiology of a number of physical-chemical properties on the quality of the product (slices of minimally processed potato of the Monalisa variety stored under refrigeration at four degrees Celsius over a period of 14 days).

No new gas was introduced during the trials (basically oxygen, nitrogen and carbon dioxide), limiting the modifications to changes in the percentages of the gases. Efforts were focused on marking out the combinations of gases that maximized the characteristics of quality with greater precision. In this way, the qualitative effect of the CO2 on the respiration of the product under study began to be evaluated by means of the technique of passive modification of atmospheres.

Based on this study, the role of CO2 in the respiratory metabolism of the product remains to be determined, and which will enable a series of studies to be initiated under various controlled atmospheres consistent in O2 and CO2 mixtures in variable concentrations. In these studies, the potentiality of the different gaseous combinations to reduce respiratory rates and to minimize colour changes and textural characteristics of the raw material was determined and the guidelines for the final part of the research set out.

Thus, the proportion of oxygen was raised to 80 per cent, compared to the 20.9 per cent in the atmosphere we normally respire, while CO2 – with a residual presence, was increased to 20 per cent. This combination is the one that obtained the optimum results, given that, in these proportions, all the processes of degradation of the minimally processed potato – from its processing to its end of useful life – are slowed down. During the period – a maximum of 14 days – in which the potato was refrigerated at a temperature of four degrees Celsius, the loss of water, nutrients and texture was slower, as was the onset of discolouration.