Hydrothermal hydrolysis of sweet chestnut (Castanea sativa) tannins

Abstract

Sweet chestnut tannins were treated with subcritical water at temperatures from 120 to 300 °C for reaction times of 15, 30 and 60 min. A great influence of temperature and reaction time on the product yield was noticed. Spectrophotometric methods were used to determine the total tannins, phenols and carbohydrates contents and antioxidant activity. Furthermore, vescalin, castalin, vescalagin, castalagin, 1-O-galloyl castalagin, gallic, ellagic and ferulic acids were analysed by HPLC. The results obtained from hydrothermal hydrolysis were compared to results from acid hydrolysis. Finally, the reaction parameters of the hydrothermal hydrolysis process were optimized aimed at obtaining a product with a high concentration of ellagic acid. The optimal conditions for obtaining the highest concentration of ellagic acid of 29.55 % were 250 °C and 5 min. The concentration of ellagic acid in tannin extract obtained by acid hydrolysis was 8.19 %.

Subcritical Water Extraction of Chestnut Bark and Optimization of Process Parameters

“…Observing the results, it can be concluded that yield decreases when increasing the temperature and time, because at higher temperatures and longer extraction times the hydrothermal degradation of water soluble compounds and their conversion to water insoluble products takes place. This is in agreement with the results of our previous work [ 1 ], where hydrolysis of chestnut tannins was studied and it was observed that secondary reactions of water-soluble fraction to char and gases were obvious at temperatures higher than 150 °C. For lower temperatures (150 and 200 °C), a higher solvent–solid ratio (30 mL/g) gives higher extraction yields, while at 250 °C, a higher yield was obtained for a lower solvent–solid ratio (10 mL/g).…”

“…The experimental results show that the yield of ellagitannins decreases when the temperature increases, while at a temperature of 150 °C, it increases from 10 to 35 min and then decreases. Ellagitannins are not stable and are hydrolyzed at high temperatures under subcritical conditions into ellagic acid [ 1 ]. In our previous work, where the hydrothermal hydrolysis of chestnut tannin extract [ 1 ] was studied, it was observed that the content of ellagitannins was the highest when sweet chestnut tannins were treated by subcritical water at 120 °C.…”

“…Biomass represents the natural source of valuable components which could found application in many industries. The chestnut tree is the source of many important compounds [ 1 ]. Besides their seeds, used for fresh consumption and for preparation of chestnut purée, marron-glacé and chestnut flour [ 2 , 3 , 4 ], chestnut trees are also used for the construction of furniture, agronomic utensils, and cooperage [ 5 ].…”

Behaviour of Low Molecular Weight Compounds, Iron and Copper of Wine Spirit Aged with Chestnut Staves under Different Levels of Micro-Oxygenation

“…The toasted wood (oak and chestnut) commonly used in enology comprises hydroxybenzoic acids (C 6 -C 1 ), such as gallic acid and syringic acid, as well as ellagic acid, a dilactone that has origin on the hydrolytic release of 6,6’-dicarbonyl-2,2′,3,3′,4,4′-hexahydroxybiphenyl units (HHDP) from ellagitannins [ 42 ]. They exist in the wood in the free form or conjugated, and also derive from the thermal degradation of gallotannins, lignin and ellagitannins, respectively, during the heat treatment in cooperage [ 43 ].…”

Antioxidant activity and phenolic composition of wine spirit resulting from an alternative ageing technology using micro-oxygenation: a preliminary study

“…Ellagic acid provided by the wood is closely related to the thermal degradation of ellagitannins during the heat treatment in cooperage (Gagić et al, 2019). Oxidation and hydrolysis of ellagitannins in the liquid medium (Karvela et al, 2008;García-Estévez et al, 2017) can also give rise to ellagic acid.…”