BS 4401-4-1970 Methods of test for meat and meat products - Determination of total fat content《肉及肉制品试验方法 第4部分 脂肪总含量测定》.pdf

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1、BRITISH STANDARD CONFIRMED MAY1986 BS4401-4: 1970 Incorporating Amendment No.1 Methods of test for Meat and meat products Part4: Determination of total fat contentBS4401-4:1970 This British Standard, having beenapproved by the Committee on Meat and Meat Products, waspublished under the authorityof t

2、he Executive Boardon 25 November 1970 BSI 04-1999 The following BSI references relate to the work on this standard: Committee references FFFA/6 andFFFA/6/2 ISBN 580 06444 1 Co-operating organizations The following Government departments and scientific and industrial organizations were represented on

3、 the BSI committee responsible for this British Standard: Agricultural Research Council British Bacon Curers Federation British Food Manufacturing Industries Research Association Fatstock Marketing Corporation Ltd. Food Manufacturers Federation Incorporated Institute of Meat Lard Association Meat an

4、d Livestock Commission Ministry of Agriculture, Fisheries and Food Ministry of Technology Laboratory of the Government Chemist National Association of Poultry Packers Ltd. National Council of Associations of Fresh Meat Wholesalers National Farmers Union National Federation of Meat Traders Associatio

5、ns Incorporated Sausage and Meat Pie Manufacturers Association Society for Analytical Chemistry Society of Chemical Industry Ulster Farmers Union Amendments issued since publication Amd. No. Date Comments 6557 December 1990 Indicated by a sideline in the marginBS4401-4:1970 BSI 04-1999 i Contents Pa

6、ge Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Definition 1 3 Sample 1 4 Method A 1 5 Method B 2 6 Test report 4 Figure 1 Fat-extraction apparatus 5BS4401-4:1970 ii BSI 04-1999 Foreword In order to keep abreast of progress in the industries concerned, British Standards are

7、subject to periodical review. Suggestions for improvements will be recorded and in due course brought to the notice of the committees charged with the revision of the standards to which they refer. A complete list of British Standards, numbering over5000, fully indexed and with a note of the content

8、s of each, will be found in the British Standards Yearbook. The BS Yearbook may be consulted in many public libraries and similar institutions. This standard makes reference to the following British Standards: BS2071, Soxhlet extractors. BS2648, Performance requirements for electrically heated labor

9、atory drying ovens. BS3978, Water for laboratory use. BS4523, Method for the determination of bromine index. BS5348, Methods for sampling meat and meat products. BS5348-1, Taking primary samples. The separate parts of this British Standard describe methods prepared by Sub-committee6 Meat and Meat Pr

10、oducts, of ISO/TC34Agricultural Food Products. Apart from editorial modifications, Method A of Part4 is identical with ISO1443:1973. In the United Kingdom this method has gained little acceptance, preference having been given to a method based on that of Werner Schmid for the determination of fat in

11、 cheese, as described in BS770-3 1) . Both methods are based on the freeing of bound and occluded fat by boiling with acid, followed by extraction of fat with an organic solvent, but the ISO method involves a filtration step before extraction and the solvents are different in the two methods. It has

12、 therefore been considered necessary to include both methods in Part4 of BS4401. The choice of method is left to the parties concerned, but since the two methods do not necessarily give identical results on the same sample it is essential to specify, in the contract or other agreement, the method to

13、 be used, and to state this also in the test report. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal o

14、bligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to5 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover

15、. 1) BS770, Methods for chemical analysis of cheese Part3: Determination of fat content (reference method).BS4401-4:1970 BSI 04-1999 1 1 Scope This Part of BS4401 describes two reference methods for the determination of the total fat content of meat and meat products. NOTEThe fat extracted by these

16、methods cannot be used for the determination of the characteristics of the fat. 2 Definition For the purposes of this British Standard the following definition applies. total fat content the fat extracted under the operating conditions described the total fat content is expressed as a percentage by

17、mass 3 Sample 3.1 Take a representative sample in accordance with BS5348-1 2) . 3.2 Store the sample in such a way that deterioration and change in composition are prevented. 3.3 Render the sample uniform by passing it at least twice through a mechanical meat mincer, laboratory size, fitted with a p

18、late with holes of diameter not exceeding4mm, and mixing. Keep it in a completely filled airtight container and store it in such a way that deterioration and change in composition are prevented. Analyse the sample as soon as possible, but in any case within24 hours. 4 Method A 3) 4.1 Principle. Meth

19、od A consists of the boiling of the test portion with dilute hydrochloric acid to free the occluded and bound lipid fractions, filtration of the resulting mass, drying and extraction, with hexane or light petroleum, of the fat retained on the filter. 4.2 Reagents. All reagents shall be of a recogniz

20、ed analytical reagent quality. Water complying with BS3978 4)shall be used. 4.2.1 Extraction solvent. Hexane or, alternatively, light petroleum distilling between40 C and60 C, and having a bromine index less than1 5) . For either solvent, the residue on complete evaporation shall not exceed0.002g/10

21、0ml. 4.2.2 Hydrochloric acid, approximately4N solution. Dilute100ml of concentrated hydrochloric acid d 20 =1.19g/ml with200ml of water and mix. 4.2.3 Blue litmus paper. 4.2.4 Anti-bumping granules. 4.3 Apparatus. The following apparatus, in addition to usual laboratory equipment not otherwise speci

22、fied, is required. 4.3.1 Conical flask,250ml. 4.3.2 Clock glass or Petri dish, diameter not less than80mm. 4.3.3 Extraction thimble, made of filter paper and defatted. 4.3.4 Cotton wool, defatted. 4.3.5 Continuous or semi-continuous extraction apparatus, e.g.the Soxhlet type 6) , with an extraction

23、flask of about150ml. 4.3.6 Electrically heated sand bath or water bath, or similar suitable apparatus. 4.3.7 Electrically heated drying oven, adjusted to operate at103 2 C, complying with the requirements of BS2648 7) . 4.3.8 Desiccator containing an efficient desiccant. 4.3.9 Analytical balance. 4.

24、3.10 Fluted filter paper, qualitative, of medium speed 8) . 4.4 Procedure 4.4.1 Test portion. According to the expected fat content, weigh3g to5g of the minced sample(3.3), to the nearest0.001g, into the250ml conical flask(4.3.1). 4.4.2 Determination. Dry the flask of the extraction apparatus(4.3.5)

25、, provided with some anti-bumping granules(4.2.4), for1h at103 2 C in the drying oven(4.3.7). Allow the flask to cool to room temperature in the desiccator(4.3.8) and weigh to the nearest0.001g. Add to the test portion50ml of the hydrochloric acid solution(4.2.2) and cover the conical flask(4.3.1) w

26、ith a small watch glass. Heat the conical flask on a non-asbestos wire gauze by means of a gas burner until the contents begin to boil. Continue boiling over a small flame for1h and shake occasionally. Add150ml of hot water. 2) BS5348, Methods for sampling meat and meat products Part1: Taking primar

27、y samples. 3) Corresponding to ISO Recommendation R1443. 4) BS3978, “Water for laboratory use”. 5) See BS4523, “Method for the determination of bromine index”. 6) BS2071, “Soxhlet extractors”. 7) BS2648, “Performance requirements for electrically heated laboratory drying ovens”. 8) Whatman No.2V is

28、suitable.BS4401-4:1970 2 BSI 04-1999 Moisten the fluted filter paper(4.3.10) held in a glass funnel with water and pour the hot contents from the flask on to the filter. Wash the flask and the small watch glass thoroughly three times with hot water and dry in the oven. Wash the filter with hot water

29、 until the washings do not affect the colour of the blue litmus paper(4.2.3). Put the filter paper on the clock glass or Petri dish(4.3.2) and dry for1h in the oven at103 2 C. Allow to cool. Roll up the filter paper and insert it into the extraction thimble(4.3.3). Remove any traces of fat from the

30、clock glass or Petri dish, using cotton wool(4.3.4) moistened with the extraction solvent(4.2.1), and transfer the cotton wool to the thimble. Place the thimble in the extraction apparatus. Handle the filter paper either with tongs that can be rinsed or with paper cover slips on the fingers. Pour th

31、e extraction solvent into the dried flask of the extraction apparatus. Wash the inside of the conical flask used for the disintegration with hydrochloric acid, and the covering small watch glass, with a portion of the extraction solvent and add it to the extraction flask. The total solvent quantity

32、shall be one and a half to two times the capacity of the body of the extractor. Fit the flask to the extraction apparatus. Heat the extraction flask for4h on the heated sand bath, water bath or other apparatus(4.3.6). After extraction, take the flask containing the liquid from the extraction apparat

33、us and distil off the solvent, using, for example, the heated sand bath, water bath or other apparatus. Evaporate the last traces of the solvent on the water bath, using air blowing if desired. Dry the extraction flask for1h in the drying oven at103 2 C and, after allowing to cool to room temperatur

34、e in the desiccator, weigh to the nearest0.001g. Repeat these steps until the results of two successive weighings do not differ by more than0.1% of the mass of the test portion. Verify the completion of the extraction by taking a second extraction flask and extracting for a further period of1h with

35、a fresh portion of the solvent. The increase in mass shall not exceed0.1% of the mass of the test portion. Carry out two determinations on the same prepared sample. 4.5 Expression of results 4.5.1 Method of calculation and formula. The total fat content of the sample, as a percentage by mass, is equ

36、al to: Take as the result the arithmetic mean of the two determinations, if the requirement of4.5.2 is satisfied. Report the result rounded to one decimal place. 4.5.2 Repeatability. The difference between the results of two determinations carried out simultaneously or in rapid succession by the sam

37、e analyst should not be greater than0.5g of total fat per100g of sample. 5 Method B 5.1 Principle. Method B consists of the heating of the test portion with hydrochloric acid to disintegrate the meat fibre and to liberate the fat, followed by extraction of the fat with diethyl ether. 5.2 Reagents. A

38、ll reagents shall be of a recognized analytical reagent quality. Water complying with BS3978 9)shall be used. 5.2.1 Hydrochloric acid, d 20=1.19g/ml. 5.2.2 Diethyl ether, fat-free. 5.2.3 Light petroleum, distilling between40 C and60 C. For both solvents, the residue on complete evaporation shall not

39、 exceed0.002g/100ml. 5.3 Apparatus. The following apparatus, in addition to usual laboratory equipment not otherwise specified, is required. where m 0is the mass, in grammes, of the test portion, m 1 is the mass, in grammes, of the extraction flask with anti-bumping granules, m 2is the mass, in gram

40、mes, of the flask and anti-bumping granules with the fat after drying. 9) BS3978, “Water for laboratory use”. m 2 m 1 () 100 m 0 -BS4401-4:1970 BSI 04-1999 3 5.3.1 Fat extraction tube, conforming to the details given in Figure 1, fitted as shown with a two-holed bark cork and a wash-bottle fitting a

41、nd provided also with a solid bark cork or ground-glass stopper. The cork used to close the tube shall be sound and free from pores or channels which would allow leakage of solvent, and shall previously have been extracted with diethyl ether(5.2.2). The narrow tube with the hook-shaped lower end (se

42、eFigure 1) is a sliding fit in the cork and is long enough for the opening at its lower end to be placed, if necessary, at a distance of25mm from the bottom of the tube. Rubber stoppers shall not be used. 5.3.2 Boiling brine bath (optional). 5.3.3 Hand centrifuge, capable of spinning at up to1000rev

43、/min. 5.3.4 Flat-bottomed flask,150ml, wide-mouthed, of as low a mass as possible. 5.3.5 Electrically heated drying oven, adjusted to operate at100 1 C, complying with the requirements of BS2648 10) . 5.3.6 Desiccator, containing an efficient desiccant. 5.3.7 Analytical balance. 5.4 Procedure 5.4.1

44、Test portion. According to the expected fat content, weigh2g to3g of the minced sample(3.3) to the nearest0.001g, into the fat extraction tube(5.3.1). 5.4.2 Determination. Add8ml of water and10ml of the hydrochloric acid(5.2.1) to the test portion in the fat extraction tube and boil gently, either i

45、n the boiling brine bath(5.3.2) or over a flame for atleast30 minutes to disintegrate the meat fibre and liberate the fat. Cool the tube slightly, but insufficiently to cause solidification of the fat. Add about50ml of diethyl ether(5.2.2), close the tube with the solid cork, which is wetted with wa

46、ter before insertion, or with the ground-glass stopper, and cool to room temperature. Mix the contents of the tube by several sharp inversions, holding in the stopper against any internal pressure. Again cool the tube and spin in the centrifuge(5.3.3) to precipitate any matter suspended in the ether

47、 layer. NOTEAny emulsion formed which does not separate during centrifuging may be cleared by the addition of a few millilitres of ethanol. Carefully remove the stopper, avoiding any loss of liquid by spurting, and wash it and the neck of the tube with diethyl ether, allowing the washings to run int

48、o the tube. Insert the wash bottle fitting which is so adjusted for length that the inlet is2mm to3mm above the interface between the two layers, and transfer the supernatant layer to the flask(5.3.4), which has been previously washed with diethyl ether. Wash down the inside of the tube and the wash

49、 bottle fitting with10ml of diethyl ether and transfer this wash to the flask. Repeat the washing. Wash the jet of the fitting with diethyl ether at appropriate times to prevent any loss of fat. At this stage it is necessary to commence evaporation of the solvent from the flask. Repeat the extraction of fat by the addition of a further50ml of diethyl ether, shaking the tube vigorously for30s, cooling as before, centrifuging, etc. and finally washing down with one10ml portion of diethyl ether. Repeat the extraction a third time. It