Examining Properties Of Lipids Biology Essay

Lipids are one of the major constituents in nutrient. Some belongingss of lipoids are soluble in organic dissolvers, non polar ( e.g. triacylglycerol and cholesterin ) or polar ( e.

g. phospholipids ) , and may be present as solid ( fats ) or liquid ( oil ) at ambient temperatures. The monomer of lipoids is fatty acid that contains an aliphatic concatenation with a carboxylic acid group. In nature, most fatty acids consist of even figure of Cs in a consecutive concatenation and vary from 14 to 24 Cs. Short-chain fatty acids have less than 14 Cs and can be found in tropical oils and dairy fats ( McClements & A ; Decker, 2008 ) . Fatty acids are besides classified as concentrated or unsaturated ( incorporating dual bonds ) .The spirit of nutrient is mostly determined by the presence of volatile compounds in the comestible fats or oils as the merchandise of lipid oxidization or natural drosss. The sensed olfactory property and gustatory sensation of nutrient are frequently influenced by the type and concentration of lipoids present ( McClements & A ; Decker, 2008 ) .

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Free fatty acids are normally related to the development of unwanted belongingss in nutrient because they can do off-flavor, cut down oxidative stableness, cause foaming, and cut down fume point. However, the presence of short-chain free fatso acids is sometimes desirable in cheese merchandises where they contribute to season profiles.The two types of lipid chemical impairment are hydrolytic and oxidative reactions. The production of volatile short-chain free fatso acids that form off-flavor from triacylglycerols is known as hydrolytic rancidity. We use lipase enzyme to analyze how the enzyme causes hydrolysis rancidity in milk and how the olfactory property develop in the terminal merchandise.

Interaction of lipoids with O or other free extremist beginnings causes a series of chemical reactions that are known as oxidative reaction. During lipid oxidization, the fatty acids esterified to lipoids will interrupt down to organize little, volatile molecules that produce the off-aromas ( McClements & A ; Decker, 2008 ) .The volatile compounds produced from lipid debasement are by and large damaging to nutrient quality, although these aroma-contributing compounds are preferred in some nutrients. By understanding the mechanism of lipid oxidization and hydrolytic reactions, we can develop techniques to forestall unwanted lipid debasement. Antioxidants have been used in nutrient industries to forestall lipid oxidization in the nutrient merchandises.

These antioxidants have different mechanism in forestalling lipid oxidization.The aims of the experiment were to separate the olfactory properties of short concatenation fatty acids ( C2 to C6 ) , place the enzyme catalyzed rancidity in milk, and analyze the mechanism of some prooxidants and antioxidants in lipid oxidization.


The stuffs and methods used for each lab exercising were listed as follow.Experiment 1.

Olfactory properties of free fatty acids.Some short concatenation fatty acids ( C2 to C6 ) involved in this experiment were acetic ( C2 ) , butyric ( C4 ) , valeric ( C5 ) , caproic ( C6 ) , caprylic ( C8 ) , and linoleic ( C18:2 ) . The short concatenation fatty acids were diluted to 500 ppm in H2O and the olfactory properties were carefully smelled and noted.Experiment 2. Enzyme catalyzed hydrolytic rancidity in milk.Whole milk and lipase were used in this experiment. Lipase ( 0.

5 g ) was added to 100 milliliter of whole milk and allow sit at room temperature for 1-2 hours. Any olfactory properties which had developed were noted.Experiment 3. Lipid oxidization.For lipid oxidization experiment, the stuffs needed were phosphotidylcholine liposomes as a beginning of lipid, buffer pH 7.0, ferrous chloride as a beginning of metal, ascorbic acid, EDTA, propyl gallate, AAPH, thiobarbituric acid ( TBA ) , and H2O. In 7 separate trial tubings, 1 milliliter of phophotidylcholine liposomes was assorted to 4 milliliter of buffer pH 7.

To each sample, the undermentioned accelerators were added:0.25 milliliter Ferric chloride ( 750 AAµM )0.25 milliliter Ferric chloride and 0.

25 milliliter ascorbic acid ( 2.5 millimeter )0.25 milliliter Ferric chloride, 0.25 milliliter ascorbic acid, and 0.25 milliliter EDTA ( 2.5 millimeter ) *0.25 milliliter Ferric chloride, 0.25 milliliter ascorbic acid, and 0.

25 milliliter propyl gallate ( 5 millimeter ) *0.25 milliliter AAPH ( 50 millimeter )0.25 milliliter AAPH and 0.25 milliliters EDTA*0.25 milliliter AAPH and 0.25 milliliter propyl gallate*( * antioxidants were added before prooxidants )All volumes were brought up to 6 milliliter with buffer. The solution was incubated at 37 AA°C for 30 proceedingss and agitate on occasion to blend O in the samples.

After 30 proceedingss, 1 milliliter of sample was assorted with 2 milliliters of TBA and was placed in a boiling H2O bath for 15 proceedingss. The samples were centrifuged and the optical density was read at 534 nanometers.


Table 1. Olfactory properties of short concatenation fatty acids.Free fatso acidsOlfactory propertiesAcetic ( C2 )Strong/sharp, white acetum aromaButyric ( C4 )Pungent, puke aromaValeric ( C5 )Strong, scent like aged cheeseCaproic ( C6 )Strong, scent like acetumCaprylic ( C8 )Strong, scent like bluish cheese, sweet olfactory propertyLinoleic ( C18:2 )Very strong aroma ( resembles organic structure olfactory property )Figure 1. Thiobarbituric Acid Reactive Substances ( TBARS ) measuring informations on lipid oxidization by several accelerators ( ascorbic acid / AA, ethylene diamine tetraacetic acid / EDTA, propyl gallayte / PG, amidinopropane dihydrochloride / AAPH ) .


Experiment 21. How does lipase do rancidity?Experiment 31. Describe how make both the prooxidants and antioxidants inhibit lipid oxidization.2.

Make these antioxidants inhibit both prooxidants? Why or why non?



The replies of the undermentioned inquiries have been described in the Discussion.Experiment 2How does lipase do rancidity?Experiment 3Describe how make both the prooxidants and antioxidants inhibit lipid oxidization.Make these antioxidants inhibit both prooxidants? Why or why non?


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