Field of invention

The invention described herein is a biotechnological method for producing food-grade gelatine from slaughterhouse poultry waste - particularly poultry feet.

Current state of the art

Gelatine is a product derived from the cleavage of collagen, obtained by extraction from collagen feedstock - such as bones, cowhide and porcine skin. The raw base material is characterized by a high degree of cross -linking, which requires pre-treatment of the feedstock, resulting in the rupture of inter cross-links and the consequent extraction of gelatine through the use of water. The process is conducted at low or high pH values; in the case of A-type gelatine, an acidic environment is utilized (pH 1.5-3.0), while B-type gelatine pertains to an alkaline environment (pH 12.0). The acidic method is suitable for treating porcine skin, the time of processing usually totalling 18 to 30 hours. The alkaline method is primarily applicable for cowhide and the standard time of treatment is 2-3 months, but it can be up to 6 months. After a thorough rinse in cold water, the pre-treated feedstock is subjected to extraction by hot water (50 to 100 °C). After filtration, the resulting gelatine solution is subjected to other operations (deionization, concentration, sterilization and moulding into the final shape).

A generally similar technology is applied to produce fish-derived gelatine, wherein skin and bones are the raw base materials; the processing of the raw base material is usually carried out in an acidic environment.

In addition to waste stemming from cows, pigs and fish, waste from poultry slaughterhouses is indicated as a prospective source of gelatine, especially in consideration of individuals and communities that do not consume products linked with beef or pork (e.g. religious non-consumption of beef in India, and rejection of pork in accordance with Islamic and Jewish beliefs). Moreover, supplementing a dish labelled as "chicken" with beef-derived gelatine could cause issues with acceptance of such a product by customers, whereas a chicken burger containing chicken-derived gelatine would comprise 100% chicken. Hence, the potential exists for application of the technology in the manufacture of generic products in the food industry. Methods have been devised for producing gelatine from items such as the skin, heads or lower parts of the feet of chickens. These processes usually involve the separation of fats and non-collagenous proteins, enzyme -based pre-treatment and gelatine extraction, separation of the gelatine solution and processing the same into gelatine. While these have proven effective, they still fail to provide a yield of gelatine corresponding to the potential of the feedstock. In addition, such existing technologies are not sufficiently optimized in terms of the various steps necessary.

Indeed, any optimization of such a process tends to be implemented to source special types of gelatine, an example being a method for processing poultry feet under international application of PCT ref. no. WO2017050775 for sourcing pharmacologically applicable gelatine by anti-hypertensive activity.

Ground of the invention

The biotechnological method for producing food-grade gelatine from poultry waste (especially poultry feet) - described as the invention - eliminates to a large extent the above- mentioned hurdle of insufficient yield inherent in present methodologies for gelatine production.

In essence, the invention consists of a gradual process for treating slaughterhouse waste, i.e.

(a) being rinsed with water, and then super-cooled to a temperature of 0 to +5 °C or deep- frozen to a temperature of -36±2 °C for storage at -20±2 °C;

(b) subsequent pre-freezing or adjustment of temperature of the feedstock to -2 to -5 °C (this being the temperature of the core);

(c) mincing the feedstock in two stages - firstly to obtain pieces of 20-30 mm (stage 1) and then of up to 3 mm (stage 2);

(d) intense separation of non-collagenous proteins and pigments from the minced feedstock by washing out the material with NaOH solution (concentration: 0.08 to 0.15% w/w), and subsequent shaking for 30 to 50 minutes of the material at room temperature, with 3 to 5 cycles of the same;

(e) subsequent separation of fat by extraction with a mixture of solvents (ethanol + petroleum ether) mixed to obtain the volume ratio of 1:2 to 2:1, during which the material is shaken at room temperature for a period of up to 72 hours; the solvent mixture is periodically replaced at 6, 24 and 48 hours; (f) pre-treatment of the protein isolate by a proteolytic enzyme (dosage: 0.3% to 0.6%) by shaking the material for 15 to 25 hours in an aqueous medium (neutral pH 7.5±0.3) at room temperature;

(g) filtering out the protein hydrolysate and rinsing the swollen protein isolate with water;

(h) extracting the gelatine(s) - the first stage; this involves mixing the swollen protein isolate with water to obtain the ratio of 1:7 to 1: 10 w/w; extraction follows, at a temperature of 50 to 60 °C during mixing of the material for 40 to 60 minutes;

(i) inactivating the remnants of the proteolytic enzyme, by bringing the mixture to the boil and boiling it for 4 to 8 minutes;

(]) separating the gelatine solution from the remaining, undecomposed fraction of the protein isolate by filtration;

(k) extracting the gelatine(s) - the second stage; multi-level extraction of the same from the swollen protein isolate, with the temperature increasing at each level; the range of increase is from 60 to 100 °C;

(1) formation of gelatine(s) from the extracted solutions, and biotechnological processing of the remaining, undecomposed fraction to produce hydrolysed collagen.

The rinsed waste (obtained in step a) or the minced feedstock (obtained in step c) is super-cooled to a temperature of 0 to 5 °C for a period of storage of up to 36 hours, or is flash-frozen at a temperature of -36±2 °C for a period of storage of up to 24 months at -20±2 °C.

Multi-level extraction of the gelatine(s) (step k) may be carried out profitably at 3 stages: stage 1 at 60 °C; stage 2 at 80 °C or below - for provision of a solution to obtain high- quality (high Bloom value) gelatine; and stage 3 at 95 to 100 °C or below - for provision of a solution to obtain lower-quality (low Bloom value) gelatine.

The gelatinous solutions obtained at each of the levels of gelatine extraction are subjected to further technological operations to produce A/B gelatine(s), such operations comprise obtaining the correct concentration, sterilizing, bleaching, moulding the final shape (i.e. casting the solution or extruding the super-cooled gel), drying, grinding to obtain the desired mesh size and packaging.

The contribution of the method described as the invention consists of using secondary raw collagen material that is generated when slaughtering poultry; currently, such material has only been utilized to a minimal degree. Processing the feedstock to produce gelatine benefits the producer and/or processing entity through the following: permitting greater economy by harnessing the value of the raw material; the potential to broaden the assortment of products; and environmental aspects.

The method for processing chicken feet into gelatine under the invention could be described as zero-waste technology for the following reasons:

(a) any fraction of fat in the feedstock extracted by the organic solvents can be employed later - after the solvents have been eliminated by distillation - in various industrial applications (e.g. as an additive in feedstuffs and in the production of second-generation biofuel or soap);

(b) any liquid fraction eliminated following the enzyme -based pre-treatment of the raw material contains some extent of the hydrolysed protein; for example, this protein hydrolysate is applicable in the production of food or feedstuffs;

(c) any solid fraction remaining after gelatine extraction can undergo further processing via bio technological means into collagen hydrolysate - with an added proteolytic enzyme - or be used as an additive to enrich feedstuffs with proteins;

(d) waste waters may be processed in wastewater treatment plants without difficulty.

The biotechnological (enzyme-based) procedure for pre-treating the raw base material is innovative, since most feedstock currently undergoes pre-treatment in acid or alkaline environments prior to extraction, as is the case of type A/B gelatine(s). No enzyme -based method for pre-treating a raw base material is presently employed in the real world. The new method described herein for enzyme -based, technological processing of the raw base material is superior in the following aspects:

(a) economy - the process takes place under atmospheric pressure and moderate ambient temperatures and pH, is carried out in a very short time (compared with B-type gelatine) and consumes small amounts of enzyme;

(b) ecology - the enzymes used are food-grade enzymes, so do not possess the environmental impact associated with acids or alkalis; significantly less water is consumed when washing the feedstock after pre-treatment of the same; moreover, this action of washing out residues of the enzyme does not require as much water as the same action for acids or alkalis.

Clearly, a benefit of the invention is optimization of a method to produce a new type of gelatine. As previously stated, gelatine of cow and porcine origin is currently available commercially, as is fish-derived gelatine. Introducing chicken-derived gelatine could be beneficial for the following reasons: (a) it would prove suitable for individuals that do not consume products of beef or pork; e.g. due to religious beliefs - non-consumption of beef in India or the rejection of pork in Islamic and Jewish teachings;

(b) it would be possible to produce certain single-species products; indeed, adding beef gelatine into a dish labelled as "chicken" may not adhere with food inspection regulations; for instance, should a chicken burger be supplemented with chicken gelatine, it would be considered a product of 100% chicken.

Example of the invention

Preparing the base feedstock (i.e. grinding it for the desired soft structure) to enable further bio technological processing is a crucial step in the methodology. The standout feature of this invention is its requirement for conditions that prevent any denaturation of the (collagen) protein while also ensuring that the collagen transforms into gelatine with optimal efficiency (as part of the bio technological process), ultimately giving rise to the preparation of high-quality gelatine.

Adhering to fundamental conditions for health when sourcing the poultry feet constituted the primary pre-requisite for obtaining a good-quality food product free of any risk to health, i.e. poultry-derived gelatine. In this regard, washing the feedstock in water immediately after separation of the feet is important. In slaughterhouse operations, processing poultry involves transporting the feet through a system of flushing and cleaning pipes, wherein primary cleaning takes place concurrently with the required cooling of this valuable raw material.

The resultant material is only placed in containers once it has been purified and any excess water has dripped off. If the final product (gelatine) is intended for use by the food sector, the storage containers need to be placed in refrigerated premises to avoid any negative microbial propagation and decline in the value of the feedstock. The period of storage of the feet is recommended for (at the optimum temperature of 0 to 5 °C) a maximum of 36 hours after slaughter, or (for longer periods of storage) at -20±2 °C once deep-frozen at a temperature of -36±2 °C.

Homogenization (grinding) of the entire batch of poultry feet must be done as quickly as possible after extraction from the slaughter process, while ensuring the temperature in the refrigerated storage chain remains between 0 to 5 °C. Prior to such homogenization, it is recommended that the feedstock is slightly pre-frozen to a temperature between -2 and -5 °C, as measured in the core of the feedstock. Such a temperature ensures the stability of the collagen obtained subsequently.

Both the first and second stage of mincing utilized standard heavy-duty (industrial) meat choppers. The first stage of mincing (pre-mincing) involved the use of a cutting plate with a four-arm blade; the plate contained 20-30 mm, kidney-shaped holes. The second stage of mincing employed the same type of meat chopper, but this time fitted with a cutting panel of 3 mm holes and the same four-arm blades. When mincing, the temperature of the feedstock rises; note that it must not exceed 12 °C during this operation. However, if adhering to the above-mentioned procedure of mincing in two stages, an increase in the temperature of the final feedstock to approximately 0 to 3 °C is realistic. If the processed feedstock is not to be further manipulated within a maximum of 24 hours, said homogenized material has to be vacuum packed in packages wrapped with wrap of a minimum wall thickness of 80 μιη suitable for storage at low temperatures. The packed feedstock is then deep-frozen (flash- frozen) at -36±2°C. This raw material can then be stored in freezers at -20±2 °C for up to a period of 24 months.

The solids inherent to a poultry foot contain approximately 35% fat, which end up distributed throughout the feedstock. Such feet also possess soluble proteins and pigments. Before commencing the procedure for extracting gelatine, any parts associated with said contents have to be removed to prevent issues during processing and ensure there is no decrease in the quality of the resultant gelatine.

Non-collagenous proteins and pigments were removed by mixing the feedstock with a solution of 0.1% NaOH (at a ratio of 1:8), which was shaken for 45 minutes at room temperature. Upon filtration and washing the same with water, the procedure was repeated another three times.

After mechanical draining, the feedstock was mixed with a mixture of solvents - ethanol and petroleum ether (1: 1); the material to solvent ratio equalled 1:6. Afterwards, the mixture was shaken for 72 hours at room temperature. Notably, at 6, 24 and 48 hours, the mixture of solvents was filtered out and replaced with a new supply. Subsequent to this technological step was another for the isolate of the collagenous protein.

Pre-treating the feedstock prior to extracting the gelatine(s) involved mixing the isolate of the collagenous protein with water, the weight ratio for this being 1:9. The pH of the mixture was adjusted to a value corresponding to the maximum efficiency of the proteolytic enzyme used; herein, the pH was 7.5±0.3. Addition of 0.4% proteolytic enzyme then occurred (relative to the portion of the isolate of the collagenous protein), and the mixture was shaken for 20 hours at room temperature. Afterwards, the liquid fraction (hydrolysate) was filtered out, and the swollen isolate of the collagenous protein was rinsed with water.

The first stage of gelatine extraction required mixing the swollen isolate of the collagenous protein with water (at a weight ratio of 1:9). Then the mixture was stirred (using a shaft stirrer), warmed to 50 to 60 °C and extracted for 50 minutes after reaching the desired temperature. Afterwards, the mixture was warmed again, this time to 100 °C, and this temperature was maintained for 5 minutes to inactivate the enzyme.

The gelatine solution was filtered out and subjected to other standard operations employed in the industrial production of gelatine (see below).

In order to ensure maximum utilization of the input feedstock (the swollen collagenous protein isolate), the next stages of gelatine extraction were carried out (multi-level gelatine extraction): second stage of extraction at 70 to 80 °C; and third stage of extraction at 90 to 100 °C. This procedure of three-level extraction led to the preparation of high-quality (high Bloom value) gelatine(s) after first and second stages of the extractions; and lower-quality (low Bloom value) gelatine after third stage of the extraction. The quantity of the remaining solid fraction after the last (third) stage of the multi-level extraction process was minimal.

The solid fraction that remained after the last stage of extraction was applied to prepare a collagenous hydrolysate via biotechnological processing.

The gelatine solutions obtained at each level of extraction were subjected to standard technological operations employed to make type A/B gelatine(s), e.g. obtaining correct concentration, sterilizing and/or bleaching, and moulding the final shape. The latter made use of:

(a) a technique for super-cooling the gelatine solution in the form of a gel and subsequent extrusion of the same to make so-called gelatine noodles, which were then gently dried and, finally, ground to the mesh size required; or, alternatively,

(b) a technique for direct drying the gelatine solution cast in a mould, i.e. the exact same procedure for producing gelatine leaves in industry.

Industrial utilization

The methodology for production described herein as the invention is applicable in sourcing food-grade gelatine from slaughterhouse poultry waste - particularly poultry feet. The technique is optimized to increase the value of the feedstock more effectively, since the yield of gelatine corresponds better to the potential of the feedstock than is the case for existing technologies and could be described as zero-waste technology.