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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Dalam ekstrkasi dapat digunakan berbagai macam pelarut, misalnya n-heksan dengan volume tertentu. Instrumental methods The are a wide variety of different instrumental methods available for determining the total lipid content of food materials.
The container is shaken vigorously and the organic solvent and aqueous phase are allowed to separate either by gravity or centrifugation. Lakukan refluks selama minimum 5 jam sampai pelarut Documents.
Lemao even a lipid which consists of only triacylglycerols may contain a huge number of different chemical species. Basically, the sample is placed into an NMR instrument and a radio frequency pulse is applied to it. Massa jenis densitas hasil ekstraksi dihitung dengan mennggunakan persamaan: Firstly, peroxides are primary products that are broken down in the latter stages of lipid oxidation.
The lipid is first extracted and then dissolved in an ethanol solution which contains a known excess qnalisis KOH.
The lipid content is determined by measuring the area under a peak in an NMR chemical shift spectra that corresponds to the lipid fraction. Acid value The acid value is a measure of the amount of free acids present in a given amount of fat.
It measures the concentration of relatively polar secondary reaction products, i. The concentration of different volatile fatty acid methyl esters FAMEs present in the sample aanalisis then analyzed using GC. The acid value may be overestimated if other acid components are analisiss in the system, e.
Fatty acid methyl esters by GC Intact triacylglycerols and free fatty acids are not very volatile and are therefore difficult to analyze using GC which requires that the lipids be capable of being volatized in the instrument. Separation and Analysis by Chromatography Chromatography is one of the most powerful analytical procedures for separating and analyzing the properties of lipids, especially when combined with techniques which can be used to identify the chemical structure of the peaks, e.
It is faster and simpler to carry out than the Babcock method. Saponification is the process of breaking down a neutral fat into glycerol and fatty acids by treatment with alkali: These techniques measure the heat evolved or absorbed by a lipid when it crystallizes or melts. Thus, a change in solution appearance from blue to colorless can be used as the end-point of the titration.
One of the most commonly used methods to determine peroxide value utilizes the ability of peroxides to liberate iodine from potatssium iodide. For high moisture content foods it is often better to use batch solvent or nonsolvent extraction techniques. 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. Instrumental Techniques A variety of instrumental methods can also be used to provide information about lipid composition.
Pelarut yang baik dalam ektraksi soxhlet adalah pelarut yang mempunyai titik didih rendah seperti nheksana yang mempunyai titik didih 69oC agar cepat menguap sehingga tidak menyebabkan kerusakan pada alat dan juga tidak membutuhkan watu yang lama untuk melakukan satu sirkulasi ektraksi.
Cara Kerja Adapaun langkah-langkah dalam praktikum ekstraksi soxhlet, yaitu yang pertama ditumbuk kemiri dan diambil sebanyak 50 gram. Sample Preparation It is important that the sample chosen for analysis is representative of the lipids present in the original food, and that its properties are not altered prior to the analysis.
The isoamyl alcohol is used to prevent charring of the sugars by heat and sulfuric acid which can be a problem in the Babcock method since it makes it difficult to read the fat content from the graduated flask. Secondly, the results of the procedure are highly sensitive to the soxhlwt used anakisis carry out the experiment, and so the test must always be standardized.
More recently, instrumental methods based on nuclear magnetic resonance NMR have largely replaced density measurements, because measurements are quicker and simpler to carry out although the instrumentation is considerably more expensive.
In general, sample preparation should be carried out using an environment that minimizes any changes in the properties of the lipid fraction. Kesembilan, dibiarkan cairan dingin kemudian diambil hasil ektraksi dan dimasukkan dalam rotary evaporator vaccum. These techniques are muchcruder than chromatography techniques, because they only give information about the average properties of the lipid components present, e. This information can be used to: The surfactants displace the fat globule membrane which surrounds the emulsion droplets in milk and causes them to coalesce and separate.
Below a certain stress known as the “yield stress” the product behaves like a solid with an elastic modulus because the crystal network is not disrupted, but above this stress it flows like a liquid because the crystal network is continually disrupted. They are also used as heat transfer agents during the preparation of other foods, e. Analisis lemak Documents. In practice, the efficiency of solvent extraction depends on the polarity of the lipids present compared to the polarity of the solvent.
Triacylglycerols are first saponified which breaks them down to glycerol and free fatty acids, and are then methylated. Accelerated Oxidation Tests Rather than determining the extent of lipid oxidation in a particular food, it is often more important to know its susceptibility to oxidation.
Lean meat absorbs X-rays more strongly than fat, thus the X-ray absorbance decreases as the lipid concentration increases. Babcock Method A specified amount of milk is accurately pipetted into a specially designed flask the Babcock bottle. The amount of ICl remaining is determined by adding excess potassium iodide to the solution to liberate iodine, and then titrating with a sodium thiosulfate Na2S2O3 solution in the presence of starch to determine the concentration of iodine released: A variety of methods have been developed to measure the temperature dependence of the solid fat content.
This procedure may have to be repeated a number of times to improve the efficiency of the extraction process. The Babcock method takes about 45 minutes to carry out, and is precise to within 0. Ideally, the composition of the sample analyzed should represent as closely as possible that of the food from which it was taken. After shaking the aqueous phase is separated from the non-polar solvent, placed in a test-tube, and heated for 20 minutes in boiling water, which produces a pink color.
Detergent Method This method was developed to overcome the inconvenience and safety concerns associated with the use of highly corrosive acids. Accelerated Solvent Extraction The efficiency of solvent extraction can be increased by carrying it out at a higher temperature and pressure than are normally used. These can be divided into three different categories according to their physicochemical principles: 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.
The signal from the solid fat decays much more rapidly than the signal from the liquid oil and therefore it is possible to distinguish between these two components.