Industrial Processing of Chestnut Fruits (Castanea sativa Mill.) - Effects on Nutrients and Phytochemicals

Determining the composition of bioactives in foods, both nutrients and non-nutrients, is essential in understanding how processing can modify potential health benefits. The effects of industrial processing, on the composition of fibre, starch, free sugars, antioxidant vitamins (C and E), carotenoids and phenolics were determined in fruits (kernels) from four Portuguese cultivars of Castanea sativa. The chestnut fruit industrial processing is divided into four major stages: harvest, post-harvest storage (during 3 months at +/- 0 degrees C), industrial peeling (by flame or fire - "brulage" - at temperatures of 800 to 1000 C during 1 to 2 s in a rotary cylindrical oven) and freezing (tunnel with a CO2 flow at -65 degrees C during 15 to 20 min). Data are presented for each bioactive at each stage of the industrial processing. The focus of this work was on the Portuguese cultivars 'Judia', 'Longal', 'Martainha' and 'Lada'. The bioactives selected for analysis can influence both organolepetic and nutritional properties of the chestnut fruits. Starch and hemicelluloses are the predominant polysaccharides but free sugars, mainly sucrose (saccharose), were also present. The fibre and free sugars contents increased during industrial processing, while the interaction cultivar x processing stage had the greatest influence on the starch content. Vitamin C and vitamin E (predominantly delta-tocopherol) were present in the fruits with lower levels of carotenoids (lutein and lutein esters). The contents of vitamin C and carotenoids were negatively affected during industrial processing. Various phenolics, mainly gallic and ellagic acids and lower levels of ellagitannins, were also identified. The presence of significant amounts of these bioactives clearly shows that chestnuts are a health-positive food.