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Impact des procédés de déshydratation sur les transferts de matière et sur les mécanismes de dégradation de l’acide ascorbique et des composés phénoliques de la pomme. Application à six variétés de pommes de table ou à cidre

Abstract : A regular consumption of fresh or processed fruit is widely acknowledged for its beneficial effect on health. Polyphenols, which are naturally present in fruit, generate an increasing interest from nutritionists, manufacturers and consumers because of their antioxidant properties and their potential role in the prevention of certain cancers and cardiovascular diseases. Apple is naturally rich in polyphenols and its regular consumption makes it very interesting in terms of daily intake. Nevertheless, studies on the impact of processing on their behaviour are scarce. In this thesis, two processes, dehydration-impregnation by soaking (DIS) and convective drying, have been studied separately and combined. Several cultivars of dessert apples (Belchard ®, Royal Gala and Reinette grise of Canada) and cider apples (Avrolles, Guillevic and Marie Ménard) were selected, through three consecutive years. For each process, dehydration and degradation kinetics of ascorbic acid and different classes of polyphenols were followed, antioxidants being measured by HPLC-UV-DA; two temperatures (45 and 60 °C) were tested in DIS. Changes in sugars concentrations during DIS (fructose, glucose and sucrose) were also measured by HPLC-RI. Having set up the analytical methods for quantifying ascorbic acid and phenolic compounds on products enriched in sucrose, these compounds were monitored as a function of processing time. During DIS, a significant impact of the crop year was observed on mass transfer, larger than the cultivar's one. Temperature accelerates mass transfers and has a negative impact on the retention of antioxidants. However, the results reveal significant differences between polyphenols and ascorbic acid behaviours. The loss of ascorbic acid is very rapid, mainly due to oxidation and leaching with water. Concerning polyphenols retention differs with their chemical structure. Procyanidins, polymerized compounds which can bind with cell walls polysaccharides, undergo very little loss. On the opposite, hydroxycinnamic acids, preferential substrate of the polyphenol oxidase with a low molecular weight, record higher loss. By comparison, convective drying better preserves ascorbic acid and phenolic compounds, without any difference due to their chemical characteristics. In addition, apple cultivar showed little impact on mass transfer. When combined to convective drying and even if it only represented 10% of the total processing time, DIS lead to about half of the final losses in polyphenols. Differences observed between compounds were similar to those already described for DIS. The impregnation of sucrose may nevertheless be interesting to mask the astringency of procyanidins and improve the taste of dried apples.
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Submitted on : Monday, March 9, 2015 - 8:58:13 PM
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  • HAL Id : tel-01128571, version 1

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Emilie Devic. Impact des procédés de déshydratation sur les transferts de matière et sur les mécanismes de dégradation de l’acide ascorbique et des composés phénoliques de la pomme. Application à six variétés de pommes de table ou à cidre. Ingénierie des aliments. Institut des Sciences et Industries du Vivant et de l’Environnement, 2010. Français. ⟨tel-01128571⟩

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