Beyond the state-of-the-art
A variety of by-products have made a contribution to the value of the animal, by finding a better wayfor further processing. Traditional exploitation of the protein rich solids includes use in foods, petfoods, livestock feeds, and fertilizers.
Fats have been transformed into soaps and oleochemicals, inaddition to being used in food, pet foods and feed applications. However, many of these traditionalapplications have been lost or severely curtailed as a result of BSE and more stringent rules onlivestock feed. Therefore new outlets have been searched for.
The project PROSPARE aims to exploit these unmarketable animal residues based on efficientbioconversion technological methods and biocatalysts with subsidiary production of renewable energyand biologically valuable substances.These novel innovative technologies will be based on new enzyme compositions and technologicalequipment and will address physical and chemical properties of different types of by-products derivedfrom poultry slaughtering, in particular meat&bone and feathers residues that constitute the lion shareof the proteins of the by-products. With these technologies, a large quantity of refined fat will begenerated whose potential for traditional markets as well biofuel will be assessed.
For the conversionto biofuel in additional a new, robust technology will be developed.Poultry industry is currently most important source of inexpensive meat-derived proteins for humannutrition. Further growth and development of this sector of food industry is largely limited by thedeficit of balanced feed rich in proteins (of plant and/or animal origin). Moreover growth of poultryindustry generates large amount of waste. An average plant producing 10 mln. broilers a yeargenerates about 1,000 tons of feathers and 5,000 tons of meat & bone residues which are currentlylargely discarded and lead to environmental problems. Thus technologies developed in the frameworkof PROSPARE will target initially the poultry by-products. If the generic approach is successful itcould be easily extended to other animal derived by-products.
Meat&bone enzymatic treatment
Bones and meat trimmings contain up to 10% of a valuable and easily accessible protein fit even for human consumption. Although its mechanical separation is inefficient, solubilization by enzymatic hydrolysis may provide almost quantitative extraction of proteins/peptides to the liquid phase.
The enzymatic hydrolysis at neutral pH and relatively low temperature allows conservation of all the biologically valuable compounds such as amino acids, fats and VOC’s providing aroma. The known to date enzymatic protocols result in peptide mixtures poorly characterised and with unpleasant bitter taste that make them unsuitable for human consumption. In the frame of the project, the applicants will optimize the hydrolysis conditions in order to develop a range of Functional Animal Proteins (FAP) modifications adapted to a number of different food endproducts.
FAP enriched by short-chain peptide fractions could be applied to additives for diet food, whereas FAP with a higher content of long-chain peptides with a high water-retention and emulsifying ability may be demanded by meat-processing industries for the production of dry-bouillions. New enzymes and enzymatic blends produced by the applicants will be tested in parallel with commercially available preparations with regard to increase the protein yield from the raw material conserving optimal organoleptic and functional properties of the product.
The procedure of fat extraction from the bone and meat trimmings under mild conditions will be combined with the enzymatic hydrolysis. This will allow inexpensive production of high-quality fat as a side-product of FAP. This fat will be separated and channelled for food and animal feeding application as well as for biofuel production. Furthermore complete extraction of fat from the peptide hydrolyzates (FAP) will improve conservancy of the protein stuffs up on drying and storage, their solubility and dietary properties.
Mild conditions of short-term hydrothermic and enzymatic hydrolysis steps, finely tuned to the concrete types of the poultry slaughtering raw materials, will ensure high conservancy of the biologically valuable compounds and functional properties of the food and animal feeding stuffs - taste, aroma, rheology, balanced amino acid composition, digestibility, antioxidant ability, controlled contents of bioactive peptides, absence of non-natural or poorly metabolized compounds.
FAP produced by new technologies is planned to be used as a food protein substance in instant foods and processed meat products. Therefore it should be compared with protein additives present on the market. These are soy bean protein and its hydrolysates, chicken egg white protein, whey milk protein, cow milk caseins. In contrast to the soy bean derived protein or milk casein or egg white, the meat protein does not contain allergens or protease inhibitors which suppress intestinal digestion. The animal protein is low glycosylated and not phosphorylated.
Its amino acid composition is relevant to the human or mammalian physiological demands. Taking into account the safety impact, FAP may occupy the same market niche as the dry plasma protein which is the most valuable but deficient source of the food protein currently on the market.
Feathers contain 85% keratin (calculated on the basis of the dry weight), a poor soluble and heatresistant protein with high content of cysteine and multiple intramolecular cross-links. Peptide bonds within the keratin fibers are stabilized by a regular net of hydrogen bonds and poorly accessible for enzymatic hydrolysis due to physical masking from water. Specialized keratine-hydrolyzing enzymes (keratinases) are not yet commercially available although certain subtilisin-like proteases of bacillar and fungal origin exhibit slightly elevated activity toward this substrate.
A series of preliminary studies using simple laboratory equipments, were performed by the applicants of this project, aimed to test the feasibility of the new approach and to implement the technology of short-term heating process, taking also into account variations in temperature, humidity and duration of treatment.
The preliminary results obtained, showed a deeper state of hydrolysis of the feather keratin when compared to the conventional protocols. In particular, if the material to be treated was additionally humidified, optimal digestibility was observed.
Apparently short-term heating of the humidified feathers above 100°C activates water molecules that can attack peptide bonds in the fibers. Simultaneously applied mechanical pressure prevents secondary agglomeration of the meal granules that conserve a porous surface susceptible to the enzymatic proteolysis. Precise adjustment of the temperature and the treatment duration to the input material, humidity and size of the granules, to be extensively studied in the project, is pivotal for the results of the new technological treatment, since it seems that an insufficient heating does not provide the necessary water activation energy, whereas an excessive heating causes its prompt evaporation from the granules, decreasing the water activity.
In the frame of the project we plan to understand physico-chemical mechanisms underpinning the feather pre-treatment step that will enable proper tuning and control of the process. Moreover, the feasibility of the proposed treatment on the pilot scale is to be confirmed and optimized. We also plan to carry out an optimisation procedure based on a multifactor experiment which should provide 80- 85% digestibility of the obtained feather meal (compared to <55 % in the best available commercial preparations).
Further enhancement to the properties of the resultant feather meal could be achieved through application of the proper enzymatic treatment. Preliminary experiments show that, close to 100 % solubility of the net protein could be achieved through careful adjustment of the enzymatic hydrolysis step in terms of process conditions and enzyme compositions. During the project implementation we’ll optimize the combined extrusion-enzymatic technology and test it on laboratory scale.
To summarize, this project aims to provide technological innovations on two levels.
First of all, it is aimed to recover the fat to a very large extent by using the new technology for bioconversion of the meat&bone trimmings. By using this biocatalytic approach under mild conditions, the fat is less prone to degradation (hydrolysis of the lipids) and a fat-stream with a higher quality is anticipated.
Secondly, it is a goal of this project to provide a new robust technology for producing biodiesel from animal fats which is economically favourable.