Teresa Delgado

Effect of hot air convective drying on the fatty acid and vitamin E composition of chestnut (Castanea sativa Mill.) slices

The aim of the present work was to study the effect of hot-air drying on the quality of chestnut slices, regarding fatty acid and vitamin E composition. Chestnut slices of two varieties, Longal and Judia, were dried in a tray dryer at 50xa0°C, for 1, 2, 4, 6, 8 and 10xa0h. Concerning fatty acids, at beginning both varieties presented significant different contents in C16:0, C18:0, C18:1, C18:2cc, C20:0 and C20:1, being C18:2cc the most abundant. Concerning vitamin E, both varieties had similar γ- and δ-tocopherol contents; however, after 10xa0h of drying their concentrations decreased in Longal (19.2 and 14.4xa0%, respectively). It was also in slices of Longal variety that a significant decrease was observed in C18:0 (15.0xa0%), C18:1 (19.4xa0%), C20:0 (14.3xa0%) and C20:1 (11.1xa0%) after 10xa0h of drying, suggesting this variety to be a little more heat sensible than Judia. Even though some variation on lipid composition was observed along drying of chestnuts, the variety showed to have a higher effect than the drying process itself. Thus, hot air convective drying seems to be an interesting process to apply in the future to this nut in order to produce a healthy snack, not causing potential losses from a nutritional point of view.

Comparison of different drying methods on the chemical and sensory properties of chestnut (Castanea sativa M.) slices

The aim of this work was to determine the effect of hot-air convective drying (D), osmotic dehydration (OD), osmotic dehydrationxa0+xa0drying (ODxa0+xa0D) and freeze-drying (FD) on chemical and sensorial characteristics of chestnut slices. Proximate composition, sugars, organic acids and lipid profiles were determined along 60xa0days of storage. Immediately after production, D and FD samples had similar proximate compositions, both with higher fat and protein contents than the osmodehydrated ones, the latter with increased sucrose contents. FD was the method that better preserved starch, amylose, ascorbic and citric acid molecules at day 0, while D originated samples with higher glucose and fructose contents. Along storage, the major variations were observed on organic acids: ascorbic acid decreased on all methods, while fumaric acid increased. Only small variations were observed on the fatty acids and vitamin E profiles and amounts. All samples presented similar and good overall sensorial acceptance with the exception of D. FD was the method that better preserved the sensorial characteristics until 60xa0days of storage, while D only preserved freshness until 15xa0days and ODxa0+xa0D until 30xa0days. In general terms, the most adequate and accepted preservation methods to apply to chestnuts would be FD and ODxa0+xa0D.

Hazelnut (Corylus avellana L.) cultivars and antimicrobial activity

Publisher Summary This chapter appraises the nutritional properties of hazelnuts, focusing on its antimicrobial activity. Hazelnuts are highly nutritious because of their high fat content. They contain protein (10-20%) and oil (>50%), which are the major constituents. The most important fatty acids in hazelnuts are the monounsaturated and polyunsaturated fatty acids, MUFAs and PUFAs, respectively. The presence of MUFAs and PUFAs, notably the ω-3 and ω-6 fatty acids, is considered more desirable in terms of nutritional quality than the saturated fatty acids, and because of their possible health benefits, as there is evidence that an MUFA-rich diet can lower the risk of coronary heart disease and may have a preventive effect against atherosclerosis. Hazelnut kernels also contain essential amino acids—for example, arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, and valine—with arginine and leucine being the most abundant. Non-essential amino acids also exist in hazelnut kernels, with glutamic acid/glutamine found in the greatest quantity, followed by aspartic acid/asparagine, and alanine. Hazelnuts also contain vitamins. The predominant soluble vitamins are vitamins B1, B2, B6, niacin, ascorbic acid, and folic acid. Extracts of different C. avellana parts, such as leaves and fruits, and of different varieties show the ability to inhibit the growth of different important pathogenic microorganisms. The consumption of these fruits, beyond other important biological properties, may promote human protection against infections, explaining their wide use in traditional medicine and showing their great potential as a source of bioactive substances.

Osmotic dehydration effects on major and minor components of chestnut (Castanea sativa Mill.) slices

The effect of osmotic dehydration (OD) conditions (temperature, time and sucrose concentration) on some nutritional parameters, soluble sugars, organic acids, fatty acids and vitamin E composition of chestnut slices was studied. Temperature at 60xa0°C and contact time of 7.5xa0h decreased significantly both protein (in 20 and 15%) and fat (in 25 and 20%) contents when compared to 30xa0°C and contact time of 2.5xa0h, simultaneously with the incorporation of sugars from the osmotic medium. An increase in temperature from 30 to 60xa0°C and contact time from 2.5 to 7.5xa0h also changed amylose percentage from 12 to 17xa0g/100xa0g of starch, suggesting modifications on starch conformation. Concerning organic acids, an increase in temperature from 30 to 60xa0°C induced thermal degradation of citric (54% of loss), malic (36% of loss) and ascorbic (23% of loss) acids. Temperature and sugar concentration did not affect significantly fat composition, particularly PUFA, the main fatty acid class, while contact times of 7.5xa0h led to the partial oxidation of linolenic acid (17% of loss when compared to 2.5xa0h). A 50% decrease was also observed on vitamin E content when temperature increased from 30 to 60xa0°C. Thus, OD might cause changes on the chemical composition of chestnut slices, requiring low temperature and contact times to avoid loss of important bioactive components such as ω-3 fatty acids (ex. linolenic acid) and vitamin E.

Organic acid profile of chestnut (Castanea sativa Mill.) as affected by hot air convective drying: Drying influence on chestnut organic acids

ABSTRACT The objective of the present work was to evaluate the effect of hot air convective drying on the organic acid profile of chestnut. An extractive method, with internal standard, followed by HPLC-UV was validated, allowing the quantification of malic, ascorbic, citric, and fumaric acids with good precision and accuracy. Fresh chestnuts presented differences between varieties. The thermal process caused equivalent losses of ascorbic acid on both varieties, but higher losses of malic acid in Longal. Furthermore, fumaric acid contents increased on both varieties. Therefore, hot air convective drying affected the organic acid composition of chestnut slices, and this effect was varietal dependent.