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Browsing by Author "Fernandes, Ana Ilídia de Sousa Sagres"

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  • Effect of storage conditions on the quality and food safety of hazelnuts and almond pastes
    Publication . Fernandes, Ana Ilídia de Sousa Sagres; Ramalhosa, Elsa; Correia, Paula
    Hazelnuts and almonds are nuts that are widely consumed worldwide. However, there are some problems with their preservation. The dissertation work developed in the present work is part of the ValNuts Project, in which it is intended to valorise dried nuts. The present work intends to study hazelnuts and almonds. In this sense, the effect of temperature (4, 25 and 35 oC) on hazelnut kernel storage over time (0, 3, 6, 9 and 12 months) was examined in terms of fatty acids, oxidative stability and microbiological parameters. Regarding the almond, it was proposed to prepare a paste, for which it was desired to determine the shelf life using an accelerated test. The temperatures tested were 4, 25, 45, 55 and 65 oC, over three months. The parameters evaluated were colour, water activity, moisture content, fat content and fatty acids profile, oxidative stability, microbiological parameters and sensory analysis. Concerning hazelnuts, after 12 months of storage, no significant differences were observed in fatty acid percentages. The induction times decreased after three months, remaining similar until 12 months. Nevertheless, no significative oxidation occurred along storage at 4, 25, and 35 oC. Thus, the temperatures at 4, 25 and 35 oC are not critical factors to consider in the storage of hazelnut kernels, considering the measured parameters. Some mycotoxins were determined in hazelnuts, such as beauvericin, bikaverin, 3-nitropropionic acid, citreohybridinol, flavoglaucin, quinolactacin A, abscisic acid, leecanoric acid, asperglaucide, asperphenamate, cyclo(L-Pro-L-Tyr), cyclo(L-Pro- L-Val), infectopyron and tryptophol; however, they were detected in low quantities. Regarding almond pastes, the brightness and hue decreased and the a* increased after three months at 65 oC, indicative of Maillard reactions. The aw values were constant over time (0.32 and 0.44). Concerning the storage time, the peroxide values increased after one month; however, applying high temperatures, such as 55 and 65 oC, did not cause a considerable increase in peroxide value after three months. Furthermore, high temperatures, such as 55 oC and 65 oC, did not cause very evident secondary oxidation. Concerning the microbiological counts, these were always <1.7 log CFU/g. On the contrary, the temperature of 65 oC negatively affected the sensory quality of the almond pastes after three months. As this temperature is high and it is uncommon to find it during storage, it is suggested that the almond pastes present a high shelf-life (> 6 months).
    2022Master thesis Open access Show more