BY-PRODUCTS OF THE NEAT-FREEZING INDUSTRY

New Zealand Journal of Agriculture, Volume 81, Issue 4, 16 October 1950, Page 337

BY-PRODUCTS OF THE NEAT-FREEZING INDUSTRY

. This is the second of two articles an the meat-freezing industry by I. B. Chisholm. The first appeared in the . September issue ol the "Journal." EDIBLE MEAT BY-PRODUCTS Edible meats include any part of the animal other than the . carcass meat which, when properly processed, is directly or indirectly a nourishing food. All these meats usually come under control of the one department, which Is equipped with stainless steel tables that are easily kept clean and have an abundant supply of hot and cold water, all of which are necessary for the preparation of edible products under sanitary conditions. The department should be close to a freezing chamber especially set up for the chilling and freezing of such products quickly and efficiently. In New Zealand some of the smaller edible meats are not saved because the production of such meats is so small that collection is not warranted Brains The heads are opened by a powered blade so designed as to split the head lengthwise and leave the brain untouched. The brains are placed on trays to drain, after which they are packed in boxes to be sold fresh, frozen, or preserved in cans. Few works save beef and hog brains. Tongues Ox tongues are carefully removed from the head on the killing floor and sent to the department where they are washed free of blood and slime and hung up to drain. The tongues may be divided into two classes: Long-cut are tongues trimmed smooth on the sides and butt without the windpipe attached; short-cut are tongues which are cut through the thyroid cartilage, leaving the epiglottis attached. Tongues may be sold fresh, cured, or canned, or frozen in moulds for export. Sheep, lamb, calf, and hog tongues are washed and drained. These may be sold fresh, cured, or frozen on local markets, or canned for local or overseas consumption. Sweetbreads The by-product known as sweetbreads is actually the thymus gland, which consists of two portions, one situated on both sides of the windpipe and the other covering the upper part of the heart. Each of these portions is . removed separately from the pluck and they are sometimes packed separately as heart or throat sweetbreads.

The thymus gland inhibits the activity of the sex glands, so is prominent only in young animals. In calves at maximum development the gland may weigh up to l|lb., after which it slowly diminishes until in 3-year-olds just a vestige of the original gland remains. After the lambs reach approximately 6 months of age the gland quickly disappears.

When the sweetbreads are picked from the windpipe and from the fat surrounding the heart they are placed in ice-chilled water to harden the adhering fat. Later the fat is picked off and the sweetbreads are placed again in iced water, where they are best left overnight to remove any blood clots, The sweetbreads are then drained on wire-mesh trays and packed in greaseproof paper -lined moulds or in cartons, These may be sold fresh or frozen according to requirements. The sweetbreads of calves are often frozen separately on galvanised iron or wooden trays and disposed of in bulk to hospitals or similar institutions, i_i . means The hearts of beef, calves, sheep, lambs, and hogs are all handled in much the same manner. The hearts are cut from the plucks, washed in cold running water, and drained on wiremesh trays. When these are graded into sound and cut hearts they are placed inverted on trays or in bulk in moulds, which are packed on shelf coils in the freezer at 8 to 10 degrees F. Apart from small local requirements the bulk of hearts are packed in hessian bags lined with stockinette and pvnorfpd ana expo e . Livers Livers of beef, calves, sheep, lambs, and hogs require careful handling and close inspection before they are passed for human consumption. The livers are trimmed of all surplus fat and connective tissue, leaving the lymph portal gland intact when export livers are

being handled. The gall sacs are pulled off and sent to the gall room for further processing. Common diseases of the livers are hydatid cysts and fluke; tuberculosis occurs in beef and hogs only. Livers with fluke and hydatid cysts and malformed livers are rejected and sent to the tallow and manure department, The vers passed should be hung on hooks to cool and drain before packing. sheep, lamb, calf, and hog livers are packed in cardboard cartons lined with wax-covered inserts or in pails and placed on shelf coils for freezing hard, after which they are packed in more substantial outer cartons ready for export. Beef livers are usually frozen hard in wooden or iron moulds and packed in hessian bags lined with stockinette, Kidneys , ’ . . . u Kidneys are removed from sheep, beef, calves, and hogs only. The fadneys are usually removed from the carcass on the killing floor and sent to the fancy meats department, where the connecting vein and casing are cut off. After-inspection the sound kidneys are wl ? ed over with warm damp cloths to remove any fat still adhering. They may be f rozen separately on trays to be disposed of locally or packed in cartons or boxes for export ‘ ei- r |<. rTS Skirts, which are muscular portions of the diaphragm, are usually divided into two classes— and thin pieces for sheep and lambs. Skirts are used

for manufacturing purposes. The thick skirts from beef carcasses are frozen flat separately on trays and exported, the thin skirts being sometimes left on the dressed carcasses. Spleen or Melt The spleen or melt is a ductless gland and is situated across the stomach between that organ and the belly wall. Its action in the animal is primarily to store blood and iron and generate white blood corpuscles, thus giving the gland high protein content. Spleens are saved from beef, sheep, and hogs in a few of the bigger freezing works where meats are manufactured on a large scale. Lungs Lungs may be used for meat-manu-facturing purposes, but are usually processed into meals or manures. Ox and Hog Tails Tails are washed and trimmed and drained before packing and may be sold fresh or frozen locally or overseas. Hog tails are sometimes cured and/or frozen for local or export trade. Ox Cheeks Cheeks are cut from the head on the killing floor and sent to the fancy meats department at regular intervals. Here they are washed and scrubbed in warm water and drained before packing in wooden or iron moulds. They are usually exported, but may be used for local manufacture.

Caul Suet Caul suet (omentum) extends from the stomach to the colon and surrounding the viscera. From beef, the fat is usually processed into first-grade edible beef tallow, but may be handled as a fancy product to be sold in its raw state or as dripping. The caul fat from spring lambs is often used in the fancy dressing of the carcass, but the bulk of the raw fat is rendered into firstgrade edible mutton tallow. From hogs, the fat is processed into a second-grade lard. Kidney Fat Kidney fat is found in the lumbar region of the carcass covering the kidneys. Known as kidney knobs on the hindquarters of chilled beef, this fat may be made into dripping or firstgrade beef tallow. The kidney fat is removed from sheep only on the killing floor (lamb fat is left in the dressed carcass) and rendered into first-grade mutton tallow. Flare fat (as it is known) from hogs is processed into a fine-grade leaf lard. Ox Tripes Ox tripes are selected for good colour ana condition from ox stomachs, the rumen and reticulum (honeycomb) portion of each stomach being used. In the tripe room they are scalded and cleaned in a perforated cylinder which rotates inside a drum. The tripes are placed in the cylinder and water at

approximately 145 degrees F. is run into the drum followed by a mixture of hydraulic lime and soda crystals, the quantity varying with the number of tripes in the cylinder. The cylinder is revolved quickly and the temperature is maintained at 140 degrees F. until the tripes are clean. While the cylinder is still revolving, the washings are run out and the tripes are rinsed out in cold water for a few minutes, after which they are removed. A close examination of each tripe is made and any pieces of its original contents that still remain are scraped off. The tripes are then drained for at least 30 minutes if they are to be taken to the freezer for storage or for export. Cooking The cleaned tripes are placed in an open cooking vat. containing fresh water and cooked at 200 to 210 degrees F. until they are just tender. It is not uncommon for the tripes to be bleached in a weak solution of hydrogen peroxide. Tripes may be sold fresh or frozen for local or export trade, according to demand. Other Edible Meats There are other minor edible meat by-products, namely: Cattle: Giblet meat, fries, heads, head meat, lips, snouts, rennets, udders, bones (gelatine), fats (oleo-stearine), feet (jelly), meat trimmings, and blood. Sheep: Cheek and head meat, cutlets, ears, faces, giblet meat, heads, lips, snouts, stomachs, fries, and meat trimmings.

Hogs. Cheek and head meat, cutlets, ears, faces, giblet meat, lips, snouts, chitterlings, stomachs, skins, trotters, meat trimmings, and blood. These, although mostly used for manufacturing purposes, are important to the industry.

FATS AND OILS

The technology of fats and oils, like that of many other by-products, is very specialised and possibly more so because of the many variations in the processing of each product.

Correct handling of the raw materials from the moment they leave the carcass on the killing floor to the rendering department is as important as the processing itself. Chemical and bacterial action commences almost immediately on the killing floor and delay in delivering the materials to be processed, or contamination at any stage, accelerates the process of decomposition.

Two principal causes of decomposition are: Rancidity, which is an oxidisation process which produces free fatty acids; and hydrolysis, which is the action, under certain conditions, of the fat taking up the elements of water, yielding glycerol and fatty acids.

All raw fats should be rendered immediately or chilled if they must be held over; if they are held over without being chilled, the bacteria will split the glycerine and fatty acids, which are basic constituents of fat, and the proteins will decompose to produce free nitrogen and ammonia, thus reducing the content of these elements in the resulting tankage.

The selection of raw materials to be rendered down to yield the best possible tallows and oils is the first important step. Materials for edible fats generally comprise all fats and fresh bones (from the boning room) which have not been contaminated by offal during slaughter or succeeding processes. Inedible fats include condemned carcasses, condemned or rejected offals of all types, trimmings, scrapings, and generally all other materials which have no further economic value as individual products. The rendering of crude fats or raw materials may be done by three principal methods: Open pan and wet and dry rendering. Open Pan Method Among other methods the steamjacketed open pan is generally used by bacon companies or freezing works for rendering lard, because the daily production of these fats is usually hot large enough to warrant the use of larger and heavier rendering plants. This method is rather primitive for rendering inedible materials, as the odours given off are objectionable. To render edible pig fats into lard, all fats are hashed up through a mincer into a steam-jacketed kettle. Cooking is continued with agitation until there is no further steam coming from the contents of the kettle and the light brown dry cracklings (fibre of fatty cells) float on the fat. The hot fat is then run off through sieves to the refining tanks. The cracklings may be pressed to remove the excess lard, which is sent to the refiners. Wet Rendering For the process of wet rendering a vertical tank or cylinder known as a

digester is used. The top of the digester is dish shaped and is provided with a manhole through which the raw materials are loaded. At the bottom of the side is another manhole through which the offal or hash remaining after cooking is withdrawn. At the level of this opening perforated steel plates cover the cone-shaped bottom of the tank, which prevents the materials blocking the outlet valves. Water is run into a level just above the plates to prevent the materials from packing too tightly and to assist the cooking process. When the digester is almost full it is closed up and the steam turned on. A pet-cock may be left slightly open to allow circulation of the steam, but too much circulation would cause the contents to agitate, resulting in emulsification of the fat, and would prevent proper separation. Cooking time depends on the size of the digester and the materials being rendered. There are two methods generally used in New Zealand of removing the crude tallow from the digester when the materials are cooked. Blowing When the steam is turned off the digester is sealed up tightly and its contents are left for half an hour to settle and separate. Then a valve at the bottom of the digester is carefully opened and the pressure still inside forces out the water or gravy, which has separated from the tallow, into the save-all tanks. A small tell-tale tap shows when all the gravy is blown out and at that point the pipeline is diverted into the refining tanks to deliver the crude tallow. Floating After cooking, the pressure is slowly released from the digester and the contents left to separate for half an hour. Water is slowly introduced from the bottom, floating up the tallow to the top of the tank and running it direct to the refiners. Steam-jacketed Rendering In a steam-jacketed digester the materials are cooked in the same manner as in wet rendering, with the exception that a gravy from previous cookings is used in place of water. In digester cooking it is necessary to have a circulation method; therefore in a jacketed system gravy is used .with the purpose of concentrating the liquids to a heavier density. This has no advantagein fact it has a slight disadvantageto fats in that the gravy has a high free fatty acid content. The use and value of this gravy system are described in the fertiliser section.

Dry Rendering

The raw materials are placed in a horizontal steam-jacketed cooking tank or cylinder equipped with a number of rotating arms to agitate the materials during cooking and to keep the surface of the shell clean to aid transmission of heat to the materials. In the rendering of raw fats it is common practice to expel the moisture through vents during cooking. In the processing of other heavier or uncrushed materials the cylinder is tightly sealed after

allowing the first gases to escape for a few minutes at the beginning of cooking. The steam that is developed from the moisture in the product is allowed to build up inside the melter with the purpose of disintegrating the meat, bones, and fat cells, thus giving the highest possible yield of fat from.successive operations. After internal pressure cooking the gases are released into deodorising tanks and cooking is continued to remove the remaining moisture through open vents. During the latter part of the cooking the free fat in the melter is run out into holding tanks. The cooked materials are then ejected from the melter into an open tank with a perforated false bottom, where the excess free fat drains away to the holding tanks or refiners.

Refining

The common principles involved in the refining of all fats are to remove moisture and impurities. In a few works in New Zealand fuller’s earth is used as a bleaching and refining agent; it has the value of improving the colour and subsequently the grade of the fat. A comparatively simple method of refining is to spray water over the fat while it is still very hot in the refiner to wash down the impurities. A little salt may be sprinkled over the fat if desired to help this action. The fat is left to settle and after a period the water which has separated to the bottom is slowly run off to the saveall tanks. There are many methods of cooling fats, either mechanically or manually, but in all cases, to avoid separation of the oils, it is necessary to agitate the product continually until it is sufficiently cool to run into drums or casks. Neatsfoot Oil The trotters or shins and feet of sheep, lambs, and cattle are cooked in a digester in much the same manner as other materials. After cooking, the contents are kept hot and left to settle for a few hours, when water is introduced into the digester to float off the separated oil to storage tanks. Any impurities that may be still in the neatsfoot stock are left to settle and are later drawn off. In the storage tanks the oil is left to “seed” or “grain” in a low-tempera-ture room. At the correct temperature the heavier fats crystallise and solidify while the oil remains liquid. This is known as seeding or graining, as the stearine takes on a seedy or granular appearance. When the fat is seeded it is stirred up and run into filter bags. Pressure is exerted on the bags to force out the pure neatsfoot oil and leave the solid stearine in the bags. Maintaining the correct temperature is important to separate only the pure oil from the stearine, which runs into holding tanks from which the drums are filled. The stearine remaining in the bags may be pressed again to yield a second flow of pure oil or may be shaken out of the bags and melted down to be sold as stearine or as tallow.

The pure neatsfoot oil is valuable for frying fish, in working up fine leather, • in steel cutting, and in oiling delicate machinery. Oleo Stock „,,.■ , , . , . 9i e 0 stock is not commonly packed in New Zealand. It is rendered fro* ll caul and crown fat and some of the internal organs of cattle and calves. While a sufficient quantity of fat is being collected to render, it is quickly chilled in water, as delay will destroy the best flavour of and product. Later the fat is drained and put through -a Jacketed kettle drops it into a waterjacketed kettle pan fitted with a mechanical agitator. A water-jacketed pan is necessary strictly to control the temperature during rendering. During rendering fine salt is !he in fib?e °The fit is until it reaches 155 degrees l/and temnerature is maintafned until rendering is f com Dieted After Settling for aonroximatelv an hour the clear ifauid fP+ P is drawn off into anoffier Jacketed tank! again salted, and left to settle lor tank, again salted, and left to settle tor several hours to separate moisture and impurities, which are later removed. This product is pure oleo stock, which is later seeded, pressed, and separated to yield oleo oil and oleo-stearine. The oleo, oil is used in the production of oleomargarine, as it has a high vitamin A content, and the oleo-stear-ine is used in confectionery as a filler or as a hardening constituent of certain lard substitutes.

Quality of Fats and Oils 1 All fats and oils are periodically tested by laboratory analysis as a guarantee to the buyer and a guide to the packer. The four important terms in the manufacture and sale of fats an j oils are titre, free fatty acid content, moisture, and impurities or foreign matter m . 8 ’ . . . . separated 1 crystalnSe or sffiidff? and is an ffidicSon of hardness 1 Har/ffits have hi eh titres and liquid oil low titras ’ Titre in ‘ dicates to a soapmaker whether the resultin g soa P soap maker easily. er the mutton tallow is the hardest fat, having a titre tallow is the hardest fat having parison with that of edible beef tallow of about 45 degrees c and of inef iible tallows of under 44 degrees C. Briefly free fatty acids determine the quality of the fat or oil In the live animal the fat is neutral; that is, it hs n 0 free fatty acids but immediately after killi ng chemical action which takes P lace frees the fatty acids - This action is further accelerated by contaminntinn of the raw materials tammation of the raw materials n Moisture content between 0.28 and 0-36 per cent, for fats and under 0.10 P 6l cent, for oils is considered ideal and is a good indication of carefully Prepared products. Foreign matter should be nil or a very slight trace. The products of animal fats and materials are further processed or used as such for many purposes, namely,

confectionery, cosmetics, oils and greases, candles, gelatine, tar, cooking, metal polish, textile finishing, and leather working and dressing. FERTILISERS AND MEALS When the various offals are rendered down and the tallow or oil is drawn off, there remains a cooked hash or, in the case of fat, cracklings. These become by-products of fats and oils, the outlet for which is provided in the form of fertilisers and meals. This is very desirable, because to some extent it is returning to the farm in various forms some of what has been taken out. Whether these cooked materials are further processed into fertilisers and/or meals largely depends on the type of plant available at the particular works. The packer will, if possible, produce from the materials available meals in preference to fertilisers, because animal feeds command higher prices and are of greater value to the farmer in that the high food value of the meals is used directly by the animal, thus giving the farmer greater control of diet and subsequently growth of the animal. This in particular is a desirable feature in cattle, pig, and poultry farming, and today, with a ready market for these products, it is the aim of each works to pack the best possible products of the available materials. Dried Blood The blood is conveyed from the killing floor by gravity or force by various means to the rendering department, where it runs into an open tank. Here it is cooked by live steam until it coagulates, which takes about' 20 minutes, depending on the type of tank and steam feed. After cooking, the water is drawn off and the solid blood removed. This usually is pressed to reduce the moisture content before it is passed into steam-jacketed mechanical driers. The product then becomes a dark-red powder which is ground up and bagged. Blood as a fertiliser is valuable for its nitrogen content of approximately 13 per cent, and as a meal the high protein content of about 80 per cent, makes it an excellent ingredient in mixed feeds. Liver Meal Liver meal is a product which depends to a large extent on correct handling and selection of the raw materials. It is made up from lungs and rejected or condemned livers of. cattle, sheep, lambs, and pigs. These offals may be steam rendered and dried in a dry-rendering machine or cooked and dried in 8 to 10 hours by the dryrendering process. The powdered product, which is brownish red, is finely ground up and bagged. Liver meals usually carry a guarantee of having not less than a 65 per cent, protein content. Meat Meal All soft tankage remaining in the digesters after cooking and removal of the tallow may be processed into meat meal. The composition of these soft materials depends on what other meals and fertiliser may be packed at the

plant, as these must absorb some of the materials which might well be put into meat meals. As a result of this, each packer will have his own way of processing this product, but m the final analysis the meals may be very similar in that they have not less than 60 per Snt nrS content P cent, prorem content. The digester tankage is pulled out of the digesters and the surplus moisture and fat removed by a hydraulic press, The tankage passes on to a dry-rend-ering machine, which is considered the ideal equipment for processing meals. In the fat and oil section under the heading of steam-jacketed rendering the gravy system was mentioned, Normally the water or soup which separates from the fats and oils is sent to the save-all tanks, where, further fat is recovered. This soup has a wnctStoafeduS addedVmea?meall to bring up any deficiency of protein. ?Sed S fn place of watt?*lnd ffiVook? Ing 1 will place 01 water ana m cook mg will increase m volume by the moisture in the materials after rookinff the soun is Mown into evaporating tanks instead of save-alls and the tallow is sent to the refiners in the ordinary wav. * ’ - ■ From the evaporating tanks the soup remainine is concentrated to me soup remaining is concentrated to about a third of its original volume. The concentrated stick? as it is now called, is added as required to the dry-rendering machine with the pressed tankage and

dried out. The meal after cooling is ground up and bagged. The surplus stick may be further processed to solid matter and sold as high-protein material. Where bones are part of the tankage of a digester the product becomes e lower grade meal or fertiliser, comes a lower grade meal or fertiliser, namely, meat and bone meal or part of blood and bone manure, whatever the packer desires. Dx no J llt | ooneausT Pnnednct eronoraiiv nnmnriwc all ,f° P ?® h2 n clean beef bones which have been cooked m a digester ana dried in a mechanical steam-jacketed drier. The bone, which is valuable for its lime content, is milled to the degree of fineness required by the buyer. Blood and Bone Manure Like other products, blood and bone 'TTI may be made ? P of many tyl ? es of o flf a i s but as a rule may comprise _ n ad 01 P art 01 tde cooked materials irrespective of their source. This tanka § e j s pressed to remove the surplus moisture and fat and then dried. The blood, in a cooked or dried form, may be mixed with the tankage either before or after drying in a sufficient quantity to give the finished product quantity to give of nitrogen content, the guarantee of nitrogen content, which is usually about 7 per cent. After mixing, it is ground up to be used as a fertiliser.

Various Other By-products .... . , , , „ , S in l jg cover ed ?th P b fnnetion of New I Laland Creeling works These 01 iNe mcinallv elue gelatine and reated products and ’only a few of al] late d products, and only a few of all these materials which may be saved are collected. These include body hide trimmings, leg, face, and hide pieces, horn piths, sinews, and certain bones, all of which come from cattle to be processed into glue and gelatine. The raw materials are cleaned and salted down in heaps and later forwarded to g rms whose business it is to process su ' c h products. Collected to a less extent are bones, horns, and hoofs for specialised processing into buttons, bone handles, hairpins, and combs, Summary The method of handling and pro- ? e;s „ s ”«rnedihrougffit 1 by thTlizl°and cogSSion of th? plant and its type o f .equipment, labour available ruling 01 equipment, laooui avaiiaoie, 1 uiing prices, and ready markets for finished products. Each packer has his own ideas' of how to make the best of the animal by-products, but today he is relying more and more on the work of the analysing chemist for guidance. The chemist can minimise waste, mamtain the highest possible standard of nroductZ and work with the aim JJf helnffig to produce better products of ? e l P “ g 22 P ? P r „t banner Products ; »-•