Insoluble fibre

The data confirmed that gels can be obtained for all the extruded fibres. However, a slight decrease in G with the frequency can be observed indicating that they did not behave as true viscoelastic solids. Indeed they contain some insoluble fibres embedded in the network and it is a composite gel rather an ideal gel. 

When dietary fibre became a nutrition issue it was assumed that the insoluble fibre such as bran was the most beneficial subcomponents. It now appears that soluble fibres can lower blood cholesterol while insoluble fibre such as wheat bran merely speeds up the transit of food through the gut. Developments in this area are awaited. 

Fibre drinks, containing both soluble and insoluble fibres (non-starch polysaccharides). These drinks add bulk to the diet and increase stool weight (a low stool weight is associated with an increased risk of bowel cancer and gall stones). Fibre also binds cholesterol (a risk factor for heart disease), thus reducing its adsorption from the intestine. To support a claim, the quantity of drink consumed in a day must provide at least 3 g of fibre, i.e. one-sixth of the recommended daily allowance of 18 g. 

Insoluble fibre binds water, making the faeces softer and bulkier, aiding defecation. 

Addition of more insoluble fibre to the diet increases the bulk of the faeces, the rate of movement of gut contents and lowers intracolonic pressure. A normal transit time for food through the gut is approximately 20-48 hours, but many individuals have a transit time in excess of 72 hours. 

Western diets are generally high in refined foods and low in fibre content. Fibre may be insoluble, for example cellulose, or soluble, for example pectin from plants. Insoluble fibre binds water, increases the bulk of the faeces and increases rapidity of transit through the intestine. Soluble fibre slows absorption of cholesterol and reduces blood cholesterol concentration. 

Chau, C. F., Wang, Y. T., and Wen, Y. L. (2007a). Different micronization methods significantly improve the functionality of carrot insoluble fibre. Food Chem. 100,1402-1408. 

Huang, Y.-L., Sheu, F., Lee, M.-H., and Chau, C.-F. (2008). Effects of particle size reduction of insoluble fibres by micron technology on various caecal and faecal indices. ]. Sci. Food Agric. 88,435-441. 

Figure 14.6. Hydrolysis of Pinus radiata chips (Clark et al., 1989). Enz)Tnatic digestibihty and the overall carbohydrate survival are improved by the addition of SO2 during presteaming. The water-insoluble fibre yield after washing decreases with increasing SO2, while its digestibility (defined as the yield of glucose after 72 hr, expressed as a percentage of the theoretical yield) increases with increasing amounts of SO2. ft is clear that most benefits from using SO2 are achieved with a SO2 level of about 2-3%.

The AUC of a single 500-mg oral dose of amoxicillin was found to be 12.17 mierograms/mL per hour in 10 healthy subjeets on a low fibre diet (7.8 g of insoluble fibre daily) but only 9.65 mierograms/mL per hour when they ate a high fibre diet (36.2 g of insoluble fibre daily) a difference of about 20%. Peak serum levels were the same and occurred at 3 hours. The clinical relevance of these changes is likely to be minimal. 

Digestibility has been shown to be related inversely to the content of acid detergent insoluble nitrogen (ADIN), which reflects the part of the food nitrogen that is bound closely to insoluble fibre. The digestible imdegradable protein content (DUP) of a food is calculated thus ... 

A.M. van Bennekum, D.V. Nguyen, G. Schulthess, H. Hauser, and M.C. Phillips, Mechanisms of cholesterol-lowering effects of dietary insoluble fibres Relationships with intestinal and hepatic cholesterol parameters, Br. J. Nutr, 94 (3), 331-337, 2005. 

Insoluble fibre Lignin and non-starch polysaccharides in plant cell walls (cellulose and hemicellulose). 

Cellulose represents a significant proportion of non-starch polysaccharides in foods (Table 4.20) and forms the so-called insoluble fibre (Table 4.21). Fruits and vegetables contain around 1-2% of cellulose, cereals and legumes 2-4%, wheat flour contains only 0.2-3% of cellulose, depending on the milling process (Table 4.19), because a large proportion of cellulose is found in the bran that contains 30-35% of cellulose. Cellulose also forms about 40-50% of wood mass, 80% of linen fibres and 90% of cotton fibres. 

Xyloglucans are present in small amounts in monocotyledon plants (monocots) that include some vegetables (e.g. onion, garUc and asparagus) and, especially, cereals. The greater portion of the xyloglucans is a component of insoluble fibre. 

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