A simple model of paprika carotenoid oxidation by oxygen in the air (Varón et al., 1997, 2000) has been proposed for the theoretical interpretation of equation (6). This model also confirms that the first-order kinetic of colour loss is really a pseudo-first-order kinetic since, at a given temperature, (A) is only constant if the concentration of the oxygen in contact with the paprika can be considered constant, which is reasonable to suppose in ordinary storage conditions.
The results obtained in this study show that the paprika obtained from the Ocal variety plants cultivated in greenhouse have greater initial colour (A0). It can be seen that in conditions 1 and 3 (Table 15.7), the curves of the graphs obtained from the experimental data both from the field and greenhouse cross, while in conditions 2 and 4 (Table 15.7) they do not, since the time needed for this to happen is longer than the experimental period (214 days). This means that while the greenhouse-cultivated plants produce a paprika of greater initial colour, its colour loss is also greater. In addition, although the greenhouse paprika suffers a greater loss of colour, in conditions 2 and 4 it continues to have more colour than that obtained from field cultivated peppers throughout the experimental period. Thus, the paprikas obtained from greenhouse-grown peppers and kept for less than 200 days in conditions 2 and 4 maintain higher levels of extractable colour during storage (Figure 15.3). In conditions 1 and 3, extractable colour in one or other of the paprikas is greater according to the number of days of storage. For example, after storage for about 25 days in condition 1 and 70 days in condition 3, the extractable colour of paprikas obtained from fruit cultivated in the open air is greater than that for greenhouse-cultivated peppers, regardless of the initial value of the former.
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