Soft Gelatin Kaise Banta Hai
Carolina Schmalzried
There are two general categories of animal fats: edible and inedible. Furthermore, the European Union categorised the inedible fats in three different risk categories. Another fat will be included in this chapter: Used cooking oils (UCO)/Yellow Grease (YG) and Brown Grease (BG), even though these fats consist mainly of vegetable oils. The collection and treatment of these fats are often in the portfolio of the renderers' business, rather than in that of the vegetable oil producers.
The history of rendering can be approached from different angles. Since Roman times the art of soap making from ash and rendered fat has been well known. Other applications for animal fats, such as candle making from cattle and sheep tallow, came later. In the middle of the 19th century the rendering process became industrial as well. Rendering in open pans over open fires evolved into a safer closed vessel system.
Another aspect was that as cities in Europe grew, a system of dead livestock collection and treatment or disposal outside the city walls was established for sanitary reasons. While in the Middle Ages skinning of animals for their hides and skins and maybe the production of baits for wolf hunting was the only economic benefit for the knacker, rendering animal by-products for protein and fat now became more attractive than simply disposing of the carcasses. At the end of the 19th century this proteinaceous by-product was recognised to be of value as well. First used as a fertiliser, it was soon used as a protein feed compound.
Today it is unclear whether rendering was developed from the rendering of fat and bones from slaughtered or hunted animals or due to the need to handle increasing volumes of dead livestock and slaughter by-products outside growing cities. But it must be acknowledged that rendering animal by-products was, is and will be one of the most important steps in animal disease prevention. Because animal by-products tend to deteriorate quickly since they are a nutrient-rich culture medium for all kind of pathogens, improper handling leads to severe problems with animal diseases and zoonoses. The OIE (Office International des Epizooties) acknowledged rendering as the safest, most practical way of dead livestock disposal [1,2].
It can be concluded that rendering can be seen as one of the oldest recycling systems in human history. It is fully industrialised today and animal fats and animal proteins are agricultural commodities worldwide.
Animal fats can be distinguished between edible fats and inedible fats. Not all edible fats are used in human consumption because certain qualities are needed in feed, pet food or the oleochemical industry. On the other hand inedible fats are not allowed in human consumption any more. They can only be used in feed, pet food, oleochemistry, biodiesel or to generate energy. Edible fats which have already been used in food frying processes, called 'Used Cooking Oils' or 'Yellow Grease', as well as the fatty phase from the grease trap, the so called 'Brown Grease', are also inedible fats.
Edible fats are produced from fresh slaughter by-products that were declared fit for human consumption after a veterinary inspection and are all gained from healthy slaughtered animals. Their production is normally species specific. Typical edible fats are beef tallow, pork lard, goose or duck fat.
Some beef tallow producers subdivide their production even further, e.g. into adipose material from the abdomen (like kidney fat) and subcutaneous fat. Those beef tallows have different properties because of their different fatty acid composition.
Another edible fat is produced during the gelatin process. Edible gelatin is mainly produced from pork and ruminant bones, pork skins and ruminant hide split. For the gelatin process these raw materials have to be defatted. This fat is here a co-product of the gelatin industry.
Not all animal by-products (ABP) are sent to rendering plants. Meat-rich by-products like lungs, liver and hearts are sold to wet pet food plants. Ruminant hides are used for leather production. Blood is collected to produce plasma and haemoglobin fit for human consumption. Pancreas can be used for insulin production, and bones and pork skins are important sources for gelatin manufacturing.
In developing countries this amount is naturally smaller and includes only inedible parts of the animal. Inedible by-products include all slaughter by-products which are obviously not fit for human consumption like feathers, bristles and horns or material that has been declared not fit for human consumption after a veterinary inspection at the slaughterhouse. These are, for example, infected meats, injured animals or legs, meat with haematoma or inflammation.
Inedible by-products also include all animals which happen to die on farms or were culled for animal disease eradication, or animals which are not used for human consumption, like zoo and circus animals, pets and fur animals. The sanitising process of rendering this dead livestock is a key element in animal disease prevention. The collection and proper heat treatment of all these animals is an obligation in the EU. Elsewhere in the world, it is generally voluntary, i.e. disposal by composting, land filling, burning etc. is also permitted. Other inedible material is for example eggshells, former foodstuff/outdated meat and specified risk material (SRM).
The scope of the ABPR is the safe collection, treatment and use of ABP, including full traceability at all stages. If the starting material is food grade (edible fat) and produced in a food plant, the processing conditions have to comply with food hygiene regulation 852/2004 [12] and specific rules on the hygiene of foodstuffs in regulation 853/2004 [13], even if they are finally sold for other purposes.
The ABPR also divides the material into three risk-based categories (Table 3). Category 1 is the category with the highest risk of contamination. Heavy metals, persistent organic compounds like dioxins and PCB, or non-classical diseases like TSE cannot be sufficiently destroyed by normal rendering and should thus not be recycled into the food and feed chain. Category 2 poses a known and manageable risk of diseases that can be reliably reduced by a sterilisation step. Recycling into technical products like fertiliser is allowed. Category 3 is the lowest risk category. It includes mainly ABP fit for human consumption (but not destined for human consumption), and other ABP from healthy slaughtered animals, e.g. feathers, bristles, horns. Category 3 products can be used as animal feed (but not for human food!). Catering waste including Used Cooking Oils (UCO) is considered to be category 3 as well but its use in feed is not allowed. With an increasing risk there are a decreasing number of different uses allowed. For a brief overview see Table 3.
2.2.2. Used cooking oil/Yellow grease and Brown grease. Another raw material already mentioned is used cooking oil (UCO), also known as yellow grease, and trap or brown grease. Despite the fact that both contain mainly vegetable oils and less animal fat, they should be mentioned and explained here, because in many cases renderers handle them, i.e. deal with collection, cleaning and trading.
UCO/Yellow Grease
UCO or Yellow Grease is the spent vegetable and/or animal fat and oil from deep fryers in canteens, restaurants, fish & chip shops etc. and from deep frying food industries producing products like meat balls or potato chips. After the deep frying the UCO is collected separately in bins or tanks, depending on the volumes. Outside the EU Yellow Grease can be used as feed. Currently it is mainly used for the production of biofuel.
Brown Grease/Trap Grease
Brown grease is an emulsion of vegetable and animal oil, fat, grease, solids and water. It is separated from the wastewater in a grease interceptor (grease trap) from where it can be collected for different purposes. In many countries these interceptors are obligatory for canteens, restaurants, supermarkets etc. As the brown grease is still a water/oil emulsion with an undefined amount of impurities and (usually) high free fatty acid content, its use is very limited. Some countries allow the use as feed. Other options are to use it as a substrate for biogas or wastewater treatment plants.
In general there are two different rendering systems established worldwide. Depending on whether the animal fat is gained from an already dried material or from a wet phase, the systems are named dry and wet rendering, respectively. There is no general rule when and where wet or dry rendering is preferred, but it can be observed that wet rendering is mostly used where heat-sensitive, high-value products like fish oils, edible fats or poultry fats are produced.
After size reduction in a crusher (mostly followed by a mincer), the raw material is melted in a cooker either with direct steam or indirect heat. To avoid damaging the nutritional values, this is carried out at the lowest temperature possible (70-90C). The separation of the three phases (solids, aqueous phase and melted fat) can be achieved by different techniques. The most common is drainage of the solid phase, which is subsequently pressed and dried. The liquid phase is sent to a decanter (horizontal centrifuge) or tricanter. Decanters separate two phases, tricanters three phases in one step. Solids from the decanter are dried together with the other solid phase. The liquid phase, the so-called stick water, is sent to the dryer, either directly or after a concentration step in an evaporation unit. In some cases the liquid phase is concentrated and dried separately into high-value, highly digestible proteins. The fat is cleaned.
In food plants the solids from a fat melting plant can be separated wet from the water phase and cooled. The wet cracklings (the unmelted residue after the fats have been melted) can be sold for human consumption or pet food. Figure 8 summarises the process.
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