Air drying and colour characteristics of chestnuts pre-submitted to osmotic dehydration with sodium chloride

Sweet Chestnut (Castanea sativa Mill.) Nutritional and Phenolic Composition Interactions with Chestnut Flavor Physiology

The European chestnut (Castanea sativa Mill.), is an environmentally and economically important species in Europe, mainly for fruit production. The chestnut fruit is well-known for its nutritional properties, namely its high concentration of carbohydrates (starch) and its low-fat content, as well as being one of the few fruits that do not contain gluten. Due to its chemical and nutritional characteristics beneficial to health, the sweet chestnut is a food recommended at different levels. The biochemistry of the mouth and nose of a human being is very complex. However, understanding the different interactions between the biochemistry of our sensory organs and food helps us to comprehend certain concepts, such as flavor and how it is involved in the sensory evaluation of the chestnuts. For the selection of high-quality products, it is necessary to develop reliable methods both from a qualitative and sensory point of view, and chestnut is a fruit with unique sensory characteristics that can be used in various gastronomic dishes, from main courses to desserts.

Chestnut Drying Is Critical in Determining Aspergillus flavus Growth and Aflatoxin Contamination

Chestnut drying is used to prevent postharvest losses and microorganism contamination during storage. Several studies reported the contamination by aflatoxins (AFs) produced by Aspergillus spp. in chestnuts. The effect of drying temperatures (from 30 to 50 °C) was evaluated on the growth of A. flavus and the production of aflatoxins in chestnuts. The influence of the treatment on the proximate composition, the total phenol content and antioxidant activity of chestnuts was considered. Fungal colonization was observed on the nuts dried at 30, 35, and 40 °C; the incidence was lower at 40 °C. The highest concentrations of AFB₁ and AFB₂ were produced at 40 °C. No aflatoxins were detected at 45 or 50 °C. At 40 °C A. flavus was under suboptimal conditions for growth (a_w 0.78), but the fungus was able to synthesize aflatoxins. As the temperatures applied increased, the total phenol content increased, while the antioxidant activity decreased. A drying treatment at 45 °C for seven days (a_w 0.64) could be a promising method to effectively control both the growth of aflatoxigenic fungi and the production of aflatoxins. This study provides preliminary data useful to improve the current drying conditions used in chestnut mills, to reduce both fungal growth and aflatoxin production.

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 60 °C and contact time of 7.5 h decreased significantly both protein (in 20 and 15%) and fat (in 25 and 20%) contents when compared to 30 °C and contact time of 2.5 h, simultaneously with the incorporation of sugars from the osmotic medium. An increase in temperature from 30 to 60 °C and contact time from 2.5 to 7.5 h also changed amylose percentage from 12 to 17 g/100 g of starch, suggesting modifications on starch conformation. Concerning organic acids, an increase in temperature from 30 to 60 °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 7.5 h led to the partial oxidation of linolenic acid (17% of loss when compared to 2.5 h). A 50% decrease was also observed on vitamin E content when temperature increased from 30 to 60 °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.

Osmotic Dehydration of New Zealand Chestnuts with and without Shell and Pellicle

Osmotic dehydration offers an alternative to air-drying for reducing moisture content at ambient temperature. Of four different solutes investigated, 22% (mass basis) sodium chloride (NaCl) and 60% (mass basis) sucrose solutions were the most successful, with each achieving approximately a 10% reduction in wet basis moisture content after 8 h without significant detrimental side effects, although NaCl solutions cause noticeable darkening in the pits on the surface of the chestnuts. The presence of the shell and pellicle did not significantly affect the dehydration rate. Osmotic dehydration by NaCl or sucrose prior to mechanical shell removal produced a small increase in efficiency of the shell removal process.

Osmotic dehydration of fruits and vegetables: a review

The main cause of perishability of fruits and vegetables are their high water content. To increase the shelf life of these fruits and vegetables many methods or combination of methods had been tried. Osmotic dehydration is one of the best and suitable method to increase the shelf life of fruits and vegetables. This process is preferred over others due to their vitamin and minerals, color, flavor and taste retention property. In this review different methods, treatments, optimization and effects of osmotic dehydration have been reviewed. Studied showed that combination of different osmotic agents were more effective than sucrose alone due to combination of properties of solutes. During the experiments it was found that optimum osmosis was found at approximately 40 °C, 40 °B of osmotic agent and in near about 132 min. Pretreatments also leads to increase the osmotic process in fruits and vegetables. Mass transfer kinetics study is an important parameter to study osmosis. Solids diffusivity were found in wide range (5.09-32.77 kl/mol) studied by Fick's laws of diffusion. These values vary depending upon types of fruits and vegetables and osmotic agents.