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Food Structure

Abstract

During fat digestion (lipolysis) a number of physiochemical events can be seen directly by light microscopy. Hydrolysis of emulsified fat droplets bylipases at pHs above about 6.5 proceeds with the formation of visible product phases that may include both crystalline as well as liquid crystalline phases. The crystalline phase is primarily calcium-fatty acid soap and its formation is favored by high calcium concentrations, alkaline pHs, and inhibited by low pH and monoglycerides. The formation of liquid crystalline product phases are favored by low calcium-concentrations. monoglycerides and lipid saturated bile salt solutions. Both phases are solubilized by bile salts but the crystalline phase to a much lesser degree. Colored and fluorescent hydrophobic solutes that a re dissolved in long cha in triglyceride appear to flow directly into the liquid crystalline product phases where they can be codispersed with the digested lipid by bile salts. Measurements of the shrinking diameters of digesting fat droplets show that enzyme activity on individual droplet~ falls rapidly during lipolysis. This suggests that lipase molecules a re physically displaced from the substrate interface during lipolysis and dispersed in the product phases.

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