PREPARASI SAMPEL Pengeringan sampel. Analisis Kadar Lemak dalam Bahan Pangan. PERALATAN SOXHLET Analisis Sifat Fisiko-Kimia Lemak atau. Berat lemak diperoleh dengan cara memisahkan lemak dengan pelarutnya. dll. dietil ksi Soxhlet Prinsip Analisis • Ekstraksi lemak dengan pelarut. Analisa lemak kasar: Metode ekstraksi soxhlet dengan pelarut organik Analisa serat kasar: Fraksi dari karbohidrat yang tidak larut dalam basa dan asam.
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In a food that contains many different components whose concentration may vary, it is difficult to disentangle the contribution that the fat makes to the overall measurement from that of the other components.
For this reason, a number of accelerated oxidation tests have been developed to speed up this process. The fire point is the temperature at which evolution of volatiles due to the thermal decomposition of the lipids proceeds so quickly that continuous combustion occurs a fire.
A simple test to determine the ability of lipids to withstand cold temperatures without forming crystals, is to ascertain whether or not a sample goes cloudy when stored for 5 hours at 0oC. If the solid fat content or crystal structure is important it may be necessary to carefully control the temperature and handling of the sample.
Basically, the sample is placed into an NMR instrument and a radio frequency pulse is applied to it. Thus different molecules can be separated on the basis of the strength of their interaction with the matrix. The sample is then centrifuged while it is hot oC which causes the liquid fat to rise into the neck of the Babcock bottle.
Lipid oxidation is one of the major forms of spoilage in foods, because it leads to the formation of off-flavors and potentially toxic compounds. The container is shaken vigorously and the organic solvent and aqueous phase are allowed to separate either by gravity or centrifugation.
Dalam ekstrkasi dapat digunakan berbagai macam pelarut, misalnya n-heksan dengan volume tertentu.
The percentage of lipid in the initial sample Msample can then be calculated: In many foods the lipid component plays a elmak role in determining the overall physical characteristics, such as flavor, texture, mouthfeel and appearance. The solid fat content is defined as the percentage of the total lipid that is solid at a particular temperature, i.
A number of these instrumental methods have major advantages over the extraction techniques mentioned above because they are nondestructive, require little or no sample preparation, and measurements are usually rapid, precise and simple.
If lipid oxidation is a problem it is important to preserve the sample by using a nitrogen atmosphere, cold temperature, low light or adding antioxidants. Food manufacturers often measure the variation of SFC with temperature when characterizing lipids that soxhllet used in certain foods, e. In fact, solvent extraction techniques are one of the most commonly used methods of isolating lipids from foods and of determining the total lipid content of foods.
This solution is then titrated with alkali KOH until a pinkish color appears. Some of the most important reasons for determining the type of lipids present in foods are listed below: TBARS is an example of a measurement of the increase in concentration of secondary reaction products.
To determine the concentration of lejak components it is necessary to break the bonds which hold the lipid and non-lipid components together prior to solvent extraction. Introduction In addition to their nutritional importance lipids are also used in foods because of their characteristic physicochemical properties, such as mouthfeel, flavor, texture and appearance. The lipid content is determined by measuring the area under a peak in an NMR chemical shift spectra that corresponds to the lipid fraction.
The density of liquid oil is less than that of most other food components, and so there is a decrease in density of a food as its fat content increases. The temperature at which the fat just starts to move downwards due to its weight is called the “slip point”. A typical accelerated oxidation test is the active oxygen method AOM. Published on Nov View Download 4. Sample Selection and PreservationAs with any analytical procedure, the validity of the results depends on proper sampling and preservation of the sample prior to analysis.
In addition, they are often dried to remove any residual moisture which might interfere with the analysis. Nevertheless, foods lipids contain a wide variety of different triacylglycerols, each with their own unique melting point, and so they melt over a wide range of temperatures.
Ekstraksi dilakukan dengan memanaskan pelarut organic sampai semua analit terekstrak Khamnidal. Melting point In many situations, it is not necessary to know the SFC over the whole temperature range, instead, only information about the temperature at which melting starts or ends is required.
The signal from the solid fat decays much more rapidly than the signal from the liquid oil and therefore ldmak is possible to distinguish between these two components. Oxidation of unsaturated lipids can be minimized by adding antioxidants, or by flushing containers with nitrogen gas and avoiding exposure to heat and light.
Since each food is different it is necessary to use different procedures for each one.
The stronger the affinity between a specific molecule and the matrix, the more its movement is retarded, and the slower it passes through the column.
Hasil ekstraksi dipindahkan ke rotary evaporator vacuum untuk diekstrak kembali berdasarkan titik didihnya. The lekak is poured into a metal container and heated at a controlled rate, with a flame being passed over the surface ana,isis the sample at regular intervals.
Analisis lemak Documents. Some foods contain lipids that are complexed with proteins lipoproteins or polysaccharides glycolipids. A number of liquid extraction methods do not rely on organic solvents, but use other chemicals to separate the lipids from the rest of the food.