LAB 18 REFLECTIVE EXERCISES Lan Section Weve you abie to verity the claim that m
ID: 1033601 • Letter: L
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LAB 18 REFLECTIVE EXERCISES Lan Section Weve you abie to verity the claim that milk is nearly a "complete food"? Explain your answer 2 Desoribe how your experimental values for the amounts of fat, protein, and water in the milk sample compare to the average values for cows" milk glven in Table 181 (pg. 253). 3 identity potential sources of error from your experiment that could explain any differences between your experimental values for the nutrient and water content of milk and the average values reported in Table 18.1. 4 Explain the chemical cause of the change you observed when you added acetic acid to the milk sample. Lab 18 The Components of Milk 269Explanation / Answer
1. Milk is considered as complete food because it contains all essential nutrients like carbohydrates, proteins, fats, fibers and vitamins except iron.
2.Table 18.1 is not supplied. Need to know the table.
3. Table 18.1 is not supplied. Need to know the table.
4. Casein, as a curd protein. It has isoelectric point of 4.6. It does not dissolve in any solvent whose pH is less than 4.6. Casein consists of micelles. A protein subunit stabilizes each of the micelles to keep them dispersed into separate micelles throughout the milk. Upon acidification, the anoinic part of protein gets neutralised and precipitates out, which then makes the milk curdle/coagulate. Chemically, the casein micelle is destabilised and therefore, aggregated due to the decrease of its isoelectric charge to that of the isoelectric point.
5. Excess addition of acetic acid to the milk solution is avoided because this will cause the lactose in the milk to hydrolyze to glucose and galactose.
6. Lemon juice is also acidic in nature, so in presence of lemon juice milk milk gets coagulated.
7.
8. Milk contains calcium and phosphate. Calcium helps protect teeth against any gum disease and keeps our jaw bone strong and healthy.
9. Lactose is the major carbohydrate in the milk of most species which is a disaccharide composed of the monosaccharides D-glucose and D-galactose, joined through a ß-1,4-glycosidic linkage.
10. Whole proteins can be isolated from milk components by two techniques based either on simultaneous precipitation of casein and proteins under the triple action of a high heat treatment , by pH lowering and calcium chloride addition , or on selective retention of protein components by an ultrafiltration membrane.
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