Carbohydrate and lipid composition of vegetables, and bioavalability assessed in a rat model: Impact different cultivation systems

Summary

Environmental as well as cultivation factors may greatly influence the chemical composition of plants. The main factors affecting chemical composition of foodstuff is level and type of fertilizer (conventional and organic cultivation systems), location or soiltype and year of harvest. Organic foods are defined as products which are produced under controlled cultivation conditions characterized by the absence of synthetic fertilizers and very restricted use of pesticides.
Dietary carbohydrates constitute a major fraction of most feedstuffs and can be divided according to glycosidic linkage into sugars (mono- and disaccharides), oligosaccharides, starch and non-starch polysaccharides (NSP). The bulk of disaccharides and starch will be broken down by the action of pancreatic and mucosal enzymes in the small intestine, while there are no enzymes capable of cleaving some types of oligosaccharides and NSP. A fraction of starch (resistant starch) may also pass the small intestine undegraded either because the starch is physically inaccessible, the starch has a structure that resist amylolysis or the starch is retrograded after heat treatment. Lignin is not a carbohydrate but is tightly associated to cell wall polysaccharides. The term dietary fibre (DF) is used for cell wall and storage NSP and lignin. Adequate intake of dietary fibre are generally accepted as linked to health benefit into a protective role in large bowel cancer, diabetes, coronary heart disease and the issue of faecal bulking.
Linoleic (C18:2 n-6) and α-linolenic (C18:3 n-3) are essential fatty acids, which cannot be synthesized in the mammalian organism, and therefore must be supplied in the diet of animals and man. These fatty acids are precursors for the important longer chain higher polyunsaturated fatty acids of the n-6 and n-3 families. Although fats are essential part of the diet, but if consumed in excess, they may exert negative effects on human weight change.
Potatoes, carrots, peas, green kale, apple, and rapeseed were grown by three different cultivation strategies, i.e. organic (ORG), conventional (CON), or semi-organic (ORG+) farming system. Each ingredient was treated as for application for human consumption: potatoes, mature, soaked peas and kale were boiled and raw carrots and apples were shredded, and the food was then freeze-dried and packed into airtight bags. Rapeseed oil was produced from the air-dried rapeseeds of the three cultivation treatments, and the residual was discarded.
The carbohydrate fraction of the ingredients except rapeseed oil was analysed into: starch, sugars, oligosaccharides and all its constituents and lignin. Likewise the dietary lipids of all ingredients were extracted and the long-chain fatty acids determined by GLC.
The ingredients were mixed with a standard synthetic mixture and were formulated to meet the NRC requirements for rats and used in a balance experiments for measuring the bioavalability of the ingredients.
Carbohydrate and lignin were predominant dietary constituents with value from 584 g/kg DM in kale to 910 g/kg DM in potatoes. Triacylglycerol was the major lipid class in pea with 82 % of total fatty acids in contrast to apple with only 35 % of fatty acids of the ether extract.