As a group, carbohydrates are quite heterogeneous, differing in primarystructure (ring size and shape), degree of polymerization (mono vs. oligo vs.polysaccharides), macromolecular characteristics (linear structure vs. branchedcompact structure), linkage (i.e.,αorβglycosidic linkage, linkage position),and charge (see Chapter 1 for more detailed coverage of carbohydrate structure).The physical and chemical differences give rise to disparate properties,including solubilities, reactivities, and susceptibility to digestive enzymes.From an analytical perspective, the simplest situation is where there isonly one type of carbohydrate present in a sample with minimal interferingcompounds — measuring glucose oligomers in corn syrup, for example. Inthis case the disparate reactivities of sugars based on structure (e.g., ketoseor hexose forms), charge, and type (e.g., glucose vs. arabinose) do not presenta problem. It is the case most often though, especially with raw materials(e.g., seeds, cereal grains) and food products (ice cream, baked goods), thatvarious types of carbohydrates are present in a sample with other compoundsincluding lipid solubles, proteins, and minerals. The heterogeneityof this group of compounds can make analyzing the total carbohydratecontent of a sample quite complex.
đang được dịch, vui lòng đợi..
