J. Sci. Food Agric. 1980, 31, 950-958

Oils and Fats Group and Meat Panel Symposium Animal Fats: Their Utilisation in Meat, Food and Manufacture The,following are suinmrrries of papers presented a1 a joint meeting o f t h e Oils and Fats Group and the Meat Panel of the Food Croup of the Socizty of Chemical Industry, and partly supported by the Nritiotial Rendzrers Associrction Inc (Brussels). It was held on 9-10 October 1980 at the Society of Chemical Industry, 14 Belgruve Squrire, Lotidoti S W l X 8PS. The summaries so published are entirely the responsibility of the authors and in no way reflect the views of'the Editorial Bourd of the Journal of the Science of Food and Agriculture.

Fat in Meat-Its Influence on Quality and Cost

Douglas N. Rhodes

Meat Research Instiiute, Lungford, Bristol BS18 7 0 Y

Modern living demands fewer expendable calories in the human diet and the modern consumer prefers less fat on the meat purchased. Meat animals have been traditionally bred and raised to produce fat and modern farming and meat retailing are both changing to meet the new requirements. Such changes have been rapid and extensive in pig meat but the process can only be much slower in cattle although selection and the introduction of leaner breeds new to this country are both progressing. The level of fatness of beef appearing at retail is higher than the demand curve and retailers are forced to trim (and waste) considerable quantities of fat.

Experimental work will be described which shows that the eating quality of the lean of the beef is not meaningfully related to the level of fatness of the carcass as is often claimed, whether that level of fatness is the expression of a breed characteristic, the sex of the animal or the system of raising.

It is concluded that the avoidance of the production of waste fat by continuing toward the pro- duction of leaner carcasses will not be accompanied by any diminution in quality, except in so far as the individual consumer likes to eat fat.

Controlling Fat Production in Meat Animals

Jeffrey D. Wood

Meat Reseorch Institute, Langfbrd, Brisiol BS18 7 0 Y

The need to reduce the fat content of carcasses stems from consumer dislike of eating fat and possible health risks associated with excessive consumption of animal fat. Incentives for farmers t o produce leaner carcasses arise from the lower feed costs of producing lean rather than fat tissue, since the energy cost of depositing lean is approximately one quarter of that of fat; and from premiums paid on lean carcasses. However, these are often small and less of an inducement than they could be. Often, the return on lean carcasses is similar to that on carcasses of average composition.

Lean content can be increased by genetic selection between and within breeds. Usually the leanest types at a particular body weight will have the largest mature size and are less mature and, therefore, leaner than the fatter types. This generalisation is modified by appetite; for instance Pietrain pigs have lower appetites than large Whites and this prevents them from being fatter a t commercial

0022-5142/80/090C-O950 $02.00 0 1980 Society of Chemical Industry

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Animal fats 951

slaughter weights as would be expected from their smaller mature size. Texel sheep and Limousin cattle also possibly owe their high lean content to a low appetite. Genetic factors are also important in determining the sites of fat deposition within the body. This has less effect on the ratio of subcutaneous: intermuscular fat (the carcass fats) than on the ratio of carcass fat: inter-abdominal fat (perirenal, retroperitoneal, omental and mesenteric). ‘Dairy’ cattle breeds and ‘ewe’ sheep breeds have higher proportions of these internal depots than the ‘beef’ and ‘ram’ breeds, respectively.

The use of intact male animals results in higher feed conversion efficiency and leaner carcasses compared with castrates. Although low appetite and larger mature size may contribute to this, other factors such as the stimulation of protein synthesis by steroid sex hormones are important. The extent ofthis effect can be clearly demonstrated: it was necessary in one experiment, for example, to reduce the daily feed of castrated male pigs to 61 7; of that of littermate boars to limit their rate of fat deposition to that of the boars. In the commercial production of beef the natural steroid production, reduced by castration, is then restored artificially by the implantation of androgens or oestrogens, either synthetic or natural. Whether changes in temperament justify such a circuitous route is not clear, but oestrogens are frequently more effective than androgens in restoring the body composition toward that of the intact male. Combinations of oestrogen, such as hexoestrol and androgen, such as trenbolone acetate, are especially effective, possibly because of oestrogen- induced increases in appetite and hormone release and androgen-stimulated increases in protein synthetic rate.

Growth hormone stimulates lean tissue growth and the concentration of plasma growth hormone is inversely related to percentage body fat in cattle and pigs. Daily injections of growth hormone into pigs also achieves significant increases in content of lean. Exploitation of this technique is hindered by the scarcity and cost of the hormone.

Other hormones show less potential for decreasing fat deposition. Insulin, although it has an anabolic effect on protein synthesis, causes an increase in appetite and increased fat deposition. Fat-mobilising hormones would appear to have limited potential. Even if the mobilised fat could be trapped efficiently for protein growth, much energy has already been wasted in the synthesis of fat. Recent studies to combine fat-mobilising hormones with anabolic hormones indicate that some success may be achieved in this direction.

There is clearly a limit to the improvement in the proportion of carcass lean which can be ob- tained through genetic and dietary changes. Further improvement will depend upon the develop- ment of the current methods of hormone manipulation and a better knowledge of the mechanisms controlling tissue growth.

Fats and Fatty Tissues in Meats

Michael B. Enser

Agriciiftiirul Reserircli Cuiiticil Meur Research Inslitiite, Lmlgford, Bristol BS18 7DY

Animal fats can be divided into the structural lipids and the storage lipids. Structural lipids consist of various phospholipids and cholesterol together with small quantities of cholesterol esters and triglyceride. They are the basis of the plasma membrane and intracellular structures of vital impor- tance in the working of the body. In muscle, phospholipids constitute 0.5-1.5% of the wet weight. In meat animals the only storage lipid of significance is triglyceride and, although small quantities may occur as droplets within muscle cells, triglycerides are normally sorted in specialised cells, the adipocytes. The triglyceride content of adipose tissue may vary from about 2 %, at which the tissue is barely recognisable as ‘fat’, to 85 % in tissue from fat animals.

The growth of adipose tissue occurs through an increase in the size and number of fat cells and

952 Oils and Fats Group and Meat Panel

as the tissue accumulates fat the proportions of water and dry matter decrease. The degree of adipose tissue development depends on the availability of food, surplus to that required for growth and maintenance. A number of other factors will be discussed. Age: as animals grow the proportion of food required for growth of ther tissues decreases and more of the diet is diverted to fat deposi- tion. Sex: male animals are leaner than females which are leaner than castrates. Species: the body site a t which fat is deposited is species or breed dependent e.g. pigs have major subcutaneous fat depots whereas in dairy cattle and birds the internal depots are more important. Production of meat from young animals of large breeds or the use of bulls, may result in low levels of fat in the subcutaneous adipose tissue.

The fatty acid composition and triglyceride structure of the adipose tissue lipids are important determinants of the characteristics of the tissue. Triglycerides of pig adipose tissue differ from those of the other meat animals in that the P-hydroxyl of the glycerol is esterified mainly to saturated fatty acids. Changes in this structure account for most of the fat softening effects of dietary copper. Many other factors affect the fatty acid composition: (a) Dietary fat: in non-ruminants fatty acids of the diet with a chain length greater than capric acid are incorporated. (b) Digestive system: in monogastric animals this has little effect, but in the ruminant the bulk of the polyunsaturated fatty acids are hydrogenated to give saturated and cis- and trans-monounsaturated fatty acids. This system can be by-passed by feeding lipids microencapsulated in proteins which have been treated to resist runien degradation. (c) Site of adipose tissue in the animal: the melting point of fat increases from the outer subcutaneous layer toward the deep internal depots. In most species this involves an increase in saturated fatty acids a t the expense of monounsaturated fatty acids. Linoleic acid IS incorporated preferentially into the internal depots of ruminants, but into the sub- cutaneous fat of pigs, particularly the outer layer. (d) Rate of fat deposition: the diet of most meat animals is low in fat, so high rates of fat deposition depend on in vivo fat synthesis. The products are saturated and monounsaturated fatty acids which dilute out dietary unsaturated fatty acids. (e) Fatty acid metabolism: essentisl dietary fatty acids like linoleic acid and linolenic acid, which cannot be synthesised by the animal, are used preferentially for phospholipid biosynthesis or synthesis of other essential fatty acids. Residual linoleic acid may be stored, but linolenic acid rarely is stored in quantity.

Modern production trends toward larger, leaner animals results in small but positive increases in the proportion of dietary fatty acids in the depot fat but in non-ruminants the fatty acid com- position can be controlled by varying the dietary fat.

Measurement of Fat in Frozen Meat

Donald H. Palmer

Bntchelors Foods Lid, Ashford, Kent

An apparatus based on a television scanning technique has been developed by Unilever Research to measure the fat content of frozen blocks of deboned beef. The apparatus was designed to simulate trade practice which involves cutting a block into slices, viewing the cut surface and calculating the block mean.

The talk was concerned with the application of the apparatus to 90% VL (visual lean) beef and calibration against a panel of trade experts and chemical fat values. Correlation values of 0.94 (a) and 0.96 (b) were achieved for the relation between the apparatus and trade experts (a) and chemical fat (b), respectively. This allows the apparatus to be used for both quality control (acceptance/ rejections of meat on VL) and process control (advice to production on utilisation by chemical fat).

Animal fats 953

Fat Emulsions in Meat Products

Michael D. Ranken

Leatherhead Food Research Association, Randalls Road, Leatherliead, Surrey

One of the purposes for which meat products may be made is to present in an acceptable manner those fatty portions of the carcass which would be unacceptable if they were served to consumers as ordinary ‘meat’. As a result of studies in the early 1960s it has usually been assumed that to incor- porate such fat into, say, a sausage it is necessary to form a heat-stable emulsion of the lipid in an aqueous solution or suspension of lean meat protein. On this assumption, tests have been devised which measure the ‘emulsifying capacity’ of protein suspensions, meat homogenates etc, but the results of such test have been found to be poorly correlated with the actual performance of meat products. However, animal fatty tissue does not consist only of lipids, but of a cellular structure which contains the lipid and i f the cells remain undamaged, as for instance when a joint of meat is roasted, the lipid remains in place even when it is melted during a cooking process. The extent to which the fatty tissue becomes damaged during manufacture is therefore the primary factor which determines the amount of fat which will appear as cooking loss. The factors which control this include cell wall thickness, which is found to be closely correlated with the degree of unsaturation of the lipid, and whether the fatty tissue is frozen at the time of comminution. Freezing of the water in the connective tissue cell walls produces a rigid structure whose cells are more easily damaged on mincing or chopping than when they are unfrozen and relatively pliable.

By attention to factors such as these it is possible to manufacture even a finely-chopped sausage in such a way that a high proportion of individual fat cells remains intact, little lipid is released from the fatty tissue and there is therefore little possibility or need for a true emulsion to be formed. Only in cases of extreme comminution is emulsification proper likely to be involved.

The Efficient Removal of Fat from Animal By-products Using a Continuous Dry Rendering Plant

A. Haydn John

Granox Limited, Widnes, Cheshire

The Rendering Industry is the link between the Meat Producing Industry and the Oils and Fat Industry and it is a highly efficient illustration of waste recovery and recycling.

Continuous rendering plants utilise wastes from the Meat Industry in the form of fat, bones, offal, heads etc, and convert these materials into tallow of various grades and meat and bone meal which is recycled back to animal feed compounders. A typical plant would have a capacity to render 10 t h-’ of raw material, the nature of the raw material governing the yield and grade of tallow produced. Fresh fat and bones, correctly processed, give high quality tallow in respect to colour, free fatty acids etc, suitable for the Edible Oil Industry, while lower grades of materials generally produce tallow related to technical grades.

There are various types of continuous rendering plants available on the market and the selection is governed by individual renderers requirements relating to the availability, tonnage and grading of his raw materials. Suffice to say that all the various types have common objectives i.e. to render the raw materials as efficiently as possible in producing tallow and meat and bone meal. The pro- cesses are common on the grounds that the raw material is first broken in uniform particle size to give even cooking, the rendering in the cooking stage separates the moisture from the fat and solids and following discharge of the combined fat and solids from the cooker, free fat is drained away from the solids by screening, and finally, the solids are pressed in a screw-presser to remove fat down to 10% in the final solids. The solids are then ground and screened to produce finished meat and bone meal while the tallow is centrifuged to remove fine particles and further water washed and centrifuged according to requirements.

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954 Oils and Fats Group and Meat Panel

The cooking process is related to time, temperature and pressure. Cooking temperatures vary from 140°C down to 95°C depending on the type of plant selected, but in all cases it is essential that close control of conditions is practised to produce a satisfactory end product, even to close control of tallow storage, which fallows the production stage. Good clean tallow, free from impurities and moisture will have a good storage life, but will quickly degrade if not given the right conditions.

Problems arising in the Rendering Industry are from man made impurities in the raw material in the form of metal objects and plastics. The first is of nuisance value, but can be readily removed by magnets installed in the process lines. The second is more difficult in that plastic objects either have to be removed by hand prior to processing, a difficult job given the nature of some of the raw materials, and the tonnage involved, or has to be removed after processing where it melts into the tallow. At the present time the first alternative is generally practised, but filtering at control temperatures and conditions is also being developed as an alternative. In addition, the rendering process gives rise to odour problems, which are generally treated by incineration of the offensive vapours, or chemical scrubbed before release to the atmosphere.

In general, the modern continuous rendering plant requires a substantial capital investment, allied to a high level of commercial and technical expertise; giving a resultant efficient link between the Meat and Oil and Fat Trade.

The Physical Properties of Premier Jus

Geoffrey A. Le Grys and Roger E. Angold

RHM Research Ltd. Lincoln Road, High Wycombe, Bucks

Premier Jus is received from the renderers in solid form. In many applications it is used as received. In such situations the physical properties such as hardness and stickiness markedly affect its be- haviour on the plant. l t is noted that these physical properties correlated strongly with fat supplier and that variations in chemical composition and solid fat index are unable to explain the observed differences.

A microscopic examination of the fats from the various suppliers showed radically different crystallite morphology. Although the basic microcrystalline structure was similar it is observed that a hard non-sticky fat is composed of a random network of crystalline needles while a soft sticky fat has a crystal structure based on individual crystals of similar size to the hard fat but arranged in a three-dimensional spherulite structure about 0.5 mm in diameter.

It is observed that these different crystalline forms can be achieved by small changes in cooling temperature (5-10°C) during crystallisation in a scraped surface heat exchanger and that the physical properties reflect changes in cooling temperature. It is concluded that cooling at relatively high temperatures only few crystal nucleation sites are produced and these form the basis of the spherulite crystal domains, cooling to lower temperatures increases the number of nucleation sites which form the hard continuous network of interlocking crystals.

The US Rendering Industry and Product Utilisation

Peter J. Ferry

National Renderers Association Inc, Briissels, Belgiiini

The US Rendering Industry in 1978 produced and/or processed almost 3.8 x lo6 t of tallow and grease, 2.27 x 106 metric t of cracks or greaves, 318 x lo3 metric t of feather meal and over 8 x 108 cattle hides. Based on current values, the US Rendering Industry in 1978 was worth $2.4 billion.

Animal fats 955

World production of animal fats in 1978 stood at 10 675 000 metric t of which tallow and grease was 6 475 000 metric t and lard was 4 200 000 metric t. This year production is projected to remain near the 1978 level.

As the Livestock and Poultry Industries are both a source of raw materials and a major market for the renderers product in animal and poultry feeds, a brief look at the present and near future of these industries will provide some insight into the Rendering Industry.

The second sector in which animal fats and their by-products are rapidly growing in importance is the industrial area. About 3000 industrial products nowadays contain tallow or its derivates. Some of the major fields include the chemical industry, paints and plastics materials, pharmaceuticals cosmetics, textile industry, rubber etc.

The third field of application is the Soap Industry where tallow represents the base material, where despite the constant challenge from other basic products, animal fats and proteins are keeping up their important role in world economy.

The National Renderers Association takes pride in contributing to the general economic develop- ment and to the betterment of our environment by recycling waste in useful products. Some of the National Renderers Association’s objectives are: to promote a large consumption of this substance in all sectors of the trade; sponsor research in order to discover new and better applications and; disseminate information resulting from this research and thus; develop new markets for animal fats and proteins.

Use of Animal Fats in Soap Manufacture

Peter M . Garnham

Lecvr Brothers Ltd, Port Siinlight, Wirral, Merseyside L26 4XN

All popular brands of soap sold in the UK are sodium salts of fatty acids, produced from sodium hydroxide and a mixture of triglycerides. Tallow is the main triglyceride used, and this is blended with varying amounts of coconut oil or palm kernel oil, the relative amounts depending upon the type of soap required. Higher levels of tallow give harder soaps with a slower rate of wear; higher levels of CNO or PKO give greater solubility and better lathering characteristics.

Some manufacturers split the glycerides first, remove the glycerine, distil the resultant fatty acids, and then neutralise with sodium hydroxide to produce soap; at Port Sunlight the more traditional method of directly saponifying a bleached tallow/oil blend, and then removing glycerine, is used. Potassium hydroxide can be used as a complete or partial replacement for sodium hydroxide in certain specialist soaps (e.g. liquid soaps, shaving soap) ; a number of alternative fatty materials are also used, for blending purposes and in specialist soaps.

The relevant quality aspects concerning the use of tallow in soap manufacture are covered by British Standardslvz and these standards are widely used in UK industry. Colour is of major impor- tance because it has a major effect on the colour of the finished soap; UK tallow is graded by colour,l and only the top grades can be used in high quality toilet soaps. Titre or iodine value tests are used to indicate the relative amounts of stearic and oleic fatty matter in tallow; these affect, among other things, the hardness and ‘processability’ of the soap. Free fatty acid (FFA) content is a good general indication of tallow quality (particularly of its handling prior to delivery), and although high FFA levels do not directly affect the soap quality, they do give reduced glycerol yields.

Polythene contamination of tallow has been a major problem over the past 10 years, and arises from the inclusion of polythene bags with the meat when it is rendered. This causes processing problems in soap manufacture, and can affect the quality of the finished soap; ideally the polythene content should be controlled to well below 100 mg kg-l to satisfy the soap manufacturer.

The other quality aspects of importance are rancidity, because of its effect on both odour and general degradation, and general contamination (e.g. by water, solvent, dirt, ash, unsaponifiable

956 Oils and Fats Group and Meat Panel

matter). These contaminants all decrease the yield of fatty matter, and some can also have serious effects on processing.

References 1 . 2.

BS 3919:1976 Specification for technical tallow and grease. BS 684:1976-79 Methods of analysis for fats and fatty oils.

Processed Food Ingredients from Animal Fats

J. Derek Horn

Croda Food Ingredients Ltd, Widnes, Cheshire

The source, production and utilisation of food emulsifiers is discussed, together with the way in which such emulsifiers can assist the usage of refined deodorised animal fats in the production of a wide range of prepared foods. The advantages of certain animal fats in spray-dried emulsion or microencapsulated form are also examined.

Emulsifiers Most emulsifiers are combinations of a water miscible component-glycerol, sorbitol, propylene glycol or sugar being typical examples-with a fatty acid. Refined deodorised and hydrogenated (RDH) tallow is rich in stearic acid (66%) and as such is a major ingredient in the production of over twenty permissible food emulsifiers. The starting basis may be RDH tallow, which is reacted with additional glycerol to produce glycerol monostearate (GMS), or the fatty acids of RDH tallow reacted with an equivalently higher glycerol quantity.

RDH tallow however, is not exclusively stearin. It will also contain 28 % palmitic acid and traces of other fatty acids. The GMS will thus take its title from the 66% stearic content but will not be exclusively this.

As the component ingredients of an emulsifier are both water compatible and fat compatible it is easy to envisage them as a key to two normally non-miscible liquids. It is not a difficult step from this point to appreciate that there will be a greater affinity between the fatty acids if they are com- patible i.e. the stearic acid of glycerol monostearate will be compatible with the 66% stearic content of RDH tallow. However as RDH tallow contains 28 % palmitic and so does a GMS from RDH tallow then the affinity is strengthened. Carrying this to the logical conclusion the fatty acid profile of an emulsifier system for any processed food product should attempt to match as closely as possible the fatty acid profile of lipids involved. This is not always feasible, but the emulsifier manufacturer will generally have a range of products with various sources of fatty acids to aid maximum versatility.

The functions and advantages of animal fat derived emulsifiers was outlined to give some indica- tion of the many areas of involvement throughout the Food Industry.

Spray-dried and microeticapsulated atiimal fats Probably the main advantages of these products are their cost effectiveness as ‘creamers’ in powdered convenience soup, sauce and dessert mixes and their ‘low lauric’ nature. Lipids containing high lauric content fats are highly susceptible to splitting and off-flavour development by the enzyme lipase, even in ‘dry’ mixes. Selected animal fats are low in lauric and offer excellent stability to the convenience mix manufacturer in either the spray-dried emulsion or the even more stable micro- encapsulated form. The production and advantages of both forms of powdered fats are discussed including a more recently developed acid-stable creamer for low pH fruit-based desserts.

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Application of Animal Fats in Shortening and Margarine

Laurence Eyres and Mervyn E. Pattinson

Ahels Litnited, PO 9573, Newmarket, New Zealand

Tallow is produced in New Zealand as a major by-product of the Meat Industry. That material is produced by rendering mainly beef tissue but bulk tallow, as received by the industry, may contain up to 202; mutton fat. Tallow consists predominantly of triacylglycerols with small amounts of partial glycerides, free fatty acids (FFA) and unsaponifiable matter. The fatty acid and triacylglycerol composition of tallow were presented as analysed by gas-liquid chromatography (g.1.c.) of the methyl esters on SILAR 5CP and as intact triacylglycerols on short OV 1 columns. The trans- isomers in tallow were analysed on a 5.5 m 15 % OV-275 column. Solvent fractionation and wide- line nuclear magnetic resonance (n.m.r.) have been used to classify the triacylglycerol classes in tallow with respect to solid content and function in a fat blend which forms the basis for formulating margarines and shortenings. Tallow is detergent fractionated into oleo oil and oleo stearine melting at 38-39‘C and 54-56’C, respectively. These three raw materials form the basis of the majority of the bakery formulations presented. Using the triacylglycerol classification scheme the raw materials are divided into three fractions namely : (i) the high melting triacylglycerols melting at 60-63 “C (mainly trisaturated); (ii) intermediate fraction melting at 35-40°C; (iii) beef oil fraction melting at less than 20°C.

I t can be shown that the melting point of blends is purely a function of the fraction (1) con- centration. Using the Clausius-Clapeyron equation a straight line relationship is shown between the logarithm of the trisaturated (1) fraction and the melting point of the fat composition. The handling, quality assessment and processing of tallow is conducted along fairly conventional lines. Tallow as received has FFA maximum of 1 % and bleaches to less than 0.5R in a 5+ inch cell using 1 % activated earth.

Tallow is both simultaneously refined and fractionated using a continuous centrifugal process and use is also made of physical refining using a semi-continuous deodoriser. Hydrogenation and interesterification are employed to modify the physical properties of tallow and its fractions and the g.1.c. is employed to monitor ’trans-isomer formation and triacylglycerol composition. Anisidine value is employed to monitor the effect of processing on the quality of the fat. Hydrogena- tion is the major technique for reducing Anisidine value to low values.

Employment of g.l.c., n.m.r. and melting point techniques permits the formulation of tallow and its fractions on a rational basis into various products. Examples of these are bakery margarines of quite different properties, cake shortenings, cream fillings and filled milk infant formulae.

Fatty Acids from Tallow

Colin C. Brown

Uttichetna Chetiiicals Ltd., Bebington, Wirral, Merseyside L62 4 0 F

There are more than 30 fatty acid producers in Europe and Scandinavia today and they made an estimated 750 000 t of fatty acids in 1978. Perhaps 40% of this tonnage is tallow based, and annual tallow requirements would therefore be about 330 000 t year-1.

The total availability of domestic low grade tallow to the industry does not match this demand, thus a fair proportion of useage must be imported and this is generally of US origin. Unichema International produce oleochemicals from many different types of oils and fats but tallow is by far the most important raw material. Although we can utilise tallow qualities unacceptable to the majority of other consumers, we cannot accept deliveries of higher than 0.25”/, ash content, or materiai containing over 200 mg kg-l of polythene. Tallow contaminated with mineral oil or other

958 Oils and Fats Group and Meat Panel

unsaponifiable matter is equally of little use to us. Our rigorous control of incoming raw material quality pays handsome dividends, particularly during the splitting operation. Tallow raw material is here fed into the base of a stainless steel column and homogenised with water at high temperatures and pressures, the glycerine ‘sweetwater’ runs from the bottom, and the split fatty acid is taken from the top. High soap contents in the charge material can cause undesirable emulsification in the column and polythene contaminant can be deposited inside the equipment causing a very real safety hazard. Vacuum distillation of this split fatty acid often follows. The distillate is of similar composition to the parent triglyceride, containing 50 % of oleic acid and approximately 50 % of equal proportions of the saturated palmitic and stearic acids. Segregation of this product into the unsaturated fatty acids (oleines) and saturated fatty acids (commercial stearines) can be achieved: (i) by hydraulic pressing of blocked tallow fatty acids. (ii) by solvent segregation, the Emersol Process. (iii) by wet separation.

The quality of oleine produced by these processes depends on the mode of operation of the plant, but the linoleic/linolenic acid content, which for many purposes should not exceed 12%, is governed by the quality of tallow utilised initially. Our tolerance, therefore, for incorporation of soft tallows, hot fat and skin grease etc. is limited. Stearines may also be produced by hydrogenation of tallow fatty acids, the resultant product will contain a much higher proportion of stearic acid than a segregated product.

Unichema can also produce high purity fatty acids by fractional distillation of a variety of fatty acid feedstocks. Up to 98 % purity of a specific chain length fatty acid can be produced in this way. Stearines find application in rubber compounding, metal stearate manufacture, production of nitrogen derivatives, as raw material for stearate esters, in candle making, soapmaking and as the oil phase of many cosmetic and toiletry creams and lotions.

The point of unsaturation in oleic acid can be chemically modified, as in the production of epoxi- dised oleate plasticiser esters, or the molecule can be cleaved by ozonolysis to yield pelargonic acid and the dibasic azelaic acid. Esters of oleic acid can be designed to match specific lubricant require- ments, and by ‘going full circle’ triglyceride oleate esters of specific composition can be derived. The fluid nature of the oleate soap can be used to advantage in many industries, e.g. in textile scouring, latex stabilisation, emulsion polymerisation etc. The distilled fatty acids from tallow are also used in the manufacture of fatty alcohols by reduction, and as a raw material for specialised soap production.

Fatty acids may have been around for many years, but we continue to grow in technical sophisti- cation, and will continue also to optimise the efficient use of tallow as one of the main renewable resources available to us.

Nutritional Value of Fats in Feed

R. Eric Atkinson

Consultant 10 National Renderers Associurion, Brussels

The paper discussed the basis of the Feed Industry which was the production not of cheap feed but of cheap final products, meat, eggs or milk. As raw material cost is some 85 % of the selling price of feed the evaluation of raw materials is a critical process, and formulation a matter for computer logic.

Fat is included in the ration for its energy value, having some 23-times the energy of cereal pro- ducts but considerable uncertainty exists about the relative values of different fats. Animal fat has often been shown in tables with a much lower value than vegetable fat based on feeding experiments when abnormal quantities of fat were fed in order to get repeatable answers. It was suggested that these answers wereincorrect in normal feeding situations, that not only did they undervalue fats as a group but especially animal fats.

Recent American work was cited in support of the contention that in normal feeding situations any fat of equal purity is likely to give equal results and the level of admixture and unsaponifiable material are the critical areas to watch, not the split of fatty acids.