The potato is a leading human staple diet in the world, with only maize, wheat and rice ahead of it. Its importance as a food is due to its nutritive value, being rich in carbohydrates and for its vitamin C, potassium and phosphorus content. The pattern of consumption has changed over the past few years, in tandem with changes in society and it is increasingly common for the potato to get to homes, not as a fresh product, but processed in some form or other.
These latter products are known as fourth range products where fresh vegetables and fruit are cut up and canned/bottled before sale.
From the harvest to their 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.
The study of the effects of the composition of the atmosphere surrounding the processed potato was the objective of the PhD thesis defended by Mr Ignacio Ángel Angós Iturgaiz at the Public University of Navarre. 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. Mr Angós, agricultural engineer and researcher currently undertaking work at the ALITEC research group at the Public University of Navarre.
Combinations of gases
"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 this thesis, in which Mr Angós analysed 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 4º C 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 maximised 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 minimise 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%, compared to the 20.9% in the atmosphere we normally respire, while CO2 – with a residual presence, was increased to 20%. 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 4ºC, the loss of water, nutrients and texture was slower, as was the onset of discoloration.
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