Lab 3 Properties of starch.pdf - BIOL3201 Food Chemistry Lab 3 – Properties of starch Introduction Rice is a staple cereal crop in Southeast Asia It

Lab 3 Properties of starch.pdf - BIOL3201 Food Chemistry...

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BIOL3201 Food Chemistry Lab 3 Properties of starch Introduction Rice is a staple cereal crop in Southeast Asia. It is rich in starch which consists of amylose and amylopectin. There are different varieties of rice but they can generally be categorized into glutinous (waxy) and non-glutinous rice. The former contains a low amount of (<5%) or no amylose and high in amylopectin; it is a glucose polysaccharide high in Glycemic Index (GI) number (Larsen, 2017), which the glucose monomers are linked together by α(1 4) glycosidic bond with little α(1 6)-linkage branches. The latter contains a high amount of amylose that is generally 20-25% by dry basis in rice and some high-amylose rice grains contain up to 30%; it has lower GI number and higher molecular weight and consists of shorter α(1 4)- linked glucan chains highly branched through additional α(1 6)-linkage ( Widiastuti Setyaningsih, Saputro, Lovillo & Barroso, 2015 ). Objective The respective aims of Experiment 1 and 2 are to compare the textural difference of steamed dessert made from glutinous and non-glutinous rice flour and to determine the amylose content in both glutinous and non-glutinous rice flour. Methods Please refer to the lab manual. Results Experiment 1: Functional properties of starch in a food product The appearance of the steamed desserts made from glutinous and non-glutinous rice flour is as follows: Figure 1: Steamed desserts made from glutinous (left) and non-glutinous rice flour (right). The textural comparison of the two samples is as follows: Sample Texture Stickiness Hardness
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Glutinous Moist and quite sticky but did not stick to hands when touched and water could hardly be squeezed out Soft and elastic Non-glutinous Dry and not sticky Hard and rubber-like Experiment 2: Amylose content of rice by iodine colorimetry The standard curve of amylose absorbance at 620nm is as follows: The amount of glutinous and non-glutinous rice flour used were 101.4mg and 100.5 mg
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