Amylopectin interactions

The reactivity of fish lipids and proteins depends on variety of both the level of oxidation and reaction conditions. PULA interact more easily and form stronger bonds with proteins and starches than other FA. DHA is preferentially bound. Fresh lipids are more reactive than oxidized lipids. The interactions of fish lipids with amylose are different than those with amylopectin. The effect of heating and freezing on lipid-protein, lipid-amylose, and lipid-amylopectin interactions is also different (Bienkiewicz and Kolakowska, 2001a,b). The interactions of lipids with other food components create new products attributes and also affect the properties of fats, particularly their extractability and availability in the human organism. 

It is commonly believed that it is amylose that forms complexes with hpids, but complexation, which occurs concomitantly with the endothermic gelatinization, has been identified and provided evidence of the existence of amylopectin-lipid interactions (Ehasson, 1994). Apparent starch amylose content correlated well with enthalpies of amylose-lipid complexes (Villwock et al., 1999). Lipids are most likely to complex with amylopectin to the extent they do with amylose. The interaction depends on the amylose amylopectin ratio. If amylose is present, the first interaction is that between amylose and lipids, followed by a lipid-amylopectin interaction. This is a mixture of B- and V-pattem starches. The best complexes are formed by 100% amylopectin poorer complexes occur in a 50% solution due to the presence of amylose (Gudmudsson and Eliasson, 1990). 

Amylopectin interacts more effectively with amylose and, thus, generates greater viscosity and gel strength. When the amylose content of the starch increases, the viscosity and gel strength of the starch paste also increase. Amylose alone and high-amylose maize starch, produce strong though films. 

Starch pastes may be dried to films, especially for nonfood applications, such as adhesives and coatings for paper sheets or textile fibers. The desired technical properties are plasticity, strength, water solubility, response to humidity, transparency and gloss. They result from the type of paste texture, clarity and gelling, which arc consequences of amy-lose-amylopectin interactions. Only starches from waxy com, potato or other root and tuber crops exhibit the desired properties, wdiereas native cereal starches are not so well suited in this respect because of their short texture and rapid setting to gels, which favors insolubility, turbidity and brittleness. Drawbacks of most native starches are ... 

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

In a current rheological study [296], the galactoxyloglucan from Hymenia courbaril was mixed with starch containing 66% amylose and with waxy corn starch (amylopectin). The gel mixtures showed, under static rheological conditions, an increase in paste viscosity compared to those of the polysaccharides alone. Dynamic rheometry indicated that the interactions resulted in increased thermal stability of the gel formed in comparison to that of the starch alone. 

Maltese cross (Blanshard, 1979). The crystallinity of starch is caused essentially by amylopectin pol)Tner interactions (Banks and Greenwood, 1975 Biliaderis, 1998 Donald, 2004 Hizukuri, 1996). An illustration of currently accepted starch granule structure is given in Fig. 5.5. It is believed that the outer branches of amylopectin molecules interact to arrange themselves into "crystallites" forming crystalline lamellae within the granule (Fig. 5.5 Tester et al., 2004). A small number of amylose polymers may also interact with amylopectin crystallites. This hypothetical structure has been derived based on the cluster model of amylopectin (Hizukuri, 1986 Robin et ah, 1974 Fig. 5.1). 

Amylopectin Amylopectin is similar to amylose except that the glucose chain has branches. These branches involve linkages at the -CH2OH position ( 6), which makes them a 1 —> 6 linkages. Amylopectin is water-soluble it also interacts with iodine to form a reddish-purple complex. Typically, amylopectin is ten times the size of an amylose molecule. Digestion requires (3-amylase (1 4 linkages) and a second... 

Glycogen, animal starch, is similar to amylopectin, but it features more branching and tends to have a higher molecular weight. Glycogen occurs in the liver and muscle tissue. It interacts with iodine to produce a red color. 

Starch (20 mg, dry basis) in water (10 mL) is heated at certain temperatures in sealed tubes for 30 minutes. The tubes are then cooled to room temperature and centrifuged. Supernatant is withdrawn and its amylose content is determined according to the method of Williams et al. (1970). The value of amylose leaching reflects the association of amylose, and interactions between amylose and amylopectin in the starch. 

The characteristics of the isolated biopolymers depend on their structure. Cellulose and amylose are linear polymers, whereas amylopectin, pectin and hemicelluloses are branched polymers. Pectin and amylopectin contain carboxylic groups, which make interactions with water molecules very important. Amylose has a helix structure, whereas the cellulose molecule looks like a ribbon. The interactions with water and other neighbouring molecules are therefore different. 

Interaction of these mutants further clarifies the biosynthetic pathway. For example, the wx mutant is epistatic to all other known maize endosperm mutants and no amylose accumulates (Table 3.6). Mutants such as sh2, bt2 and sit cause major reductions in starch accumulation, but when in combination with wx, the starch produced is all amylopectin.271 In the double mutant ae wx, wx prevents the production of amylose and ae reduces the degree of branching, resulting in the accumulation of a loosely-branched polysaccharide.88 The su mutant is epistatic to du, su2 and wx relative to accumulation of phytoglycogen, but ae and sh2 are partially epistatic to su, causing a marked reduction in the su stimulated phytoglycogen accumulation (Table 3.6). The addition of du or wx to ae su partially overcomes the ae inhibitory effect, and phytoglycogen accumulates. 

Until recently, the location and state of amylose within granules was one of the most important questions remaining to be answered. Three main hypotheses for the location of amylose within starch granules have been put forward. The first hypothesis is that amylose is laid down tangentially to the radial orientation of amylopectin in order to minimize the amylose-amylopectin helical interactions.142 There is,... 

In summary, therefore, substantial information regarding the location and state of amylose has been obtained. Individual amylose chains are believed to be randomly located in a radial fashion among the amylopectin molecules. The concentration of amylose (and lipid) increases towards the surface of the granule, with smaller (leach-able) amylose chains predominating near the surface. Amylose chains are believed to be in a single helical state, although a small proportion may be involved in lipid complexes.147 Some of the larger (non-leachable) amylose chains may be involved in double helical interactions with amylopectin.159... 

Do double helical interactions between amylose and amylopectin chains occur within the granule ... 

Amylose is synthesized by granular-bound starch synthase, whereas amylopectin is synthesized by soluble starch synthase (Chapter 4).334,339 Because amylose is synthesized by the granular-bound starch synthase in a progressive manner,340 the amylose molecule is likely confined in the granule and has little opportunity to interact and form double helices with other starch molecules to facilitate branch formation. Branching reactions do occur on some amylose molecules, but at a much lower frequency than with amylopectin, and result in slightly branched amylose molecules. 

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