GB2422766A - Feeding animals biomass derived from methanotrophic bacteria in order to improve meat quality - Google Patents

Abstract

The present invention provides a method of improving the quality (e.g. the sensory quality) of meat derived from a farmed animal, said method comprising orally administering to said animal (e.g. as part of its dietary intake) a biomass derived from a culture of bacteria including methanotrophic bacteria. Also provided is a frozen meat product obtained from a farmed animal fed a diet which comprises said biomass. A preferred culture of bacteria for use in the invention is that comprising Methylococcus Capsulatus (Bath) (strain NCIMB 11132), Ralstonia sp. DB3 (strain NCIMB 13287), Brevibacillus agri DB5 (strain NCIMB 13289), optionally in combination with Aneurinibacillus sp. DB4 (strain NCIMB 13288).

Description

Method This invention relates to a method of improving the quality and

storage stability of farmed meat and meat- containing products. More particularly, the invention relates to a method of improving the meat quality characteristics (e.g. the sensory qualities) of farmed meat in which a single-cell protein material is orally administered to an animal (e.g. as part of its dietary intake) prior to slaughter.

The production of high quality meat is important in order to provide the farmer with the maximum possible economic return. Also of particular importance are the sensory attributes of the meat since it is these which are actually experienced by the consumer and which play an important part in the consumer's decision to buy the product again. Sensory qualities of meat include flavour, odour, tenderness, juiciness, colour, etc. Such traits can be analysed by trained panels operating under strictly controlled conditions. Panel members are able to detect much smaller differences in meat quality traits than the consumer at large. Example 2 presented herein includes a description of a trained taste panel operated to assess meat quality characteristics.

Various protein-containing materials have previously been proposed as substitutes for more traditional sources of protein in animal feed, including feed for farmed animals. Protein sources which have been used in animal feed include soya protein, fish meal and fish oil-containing products. However, soya protein has a tendency to produce an allergic reaction when fed to juvenile animals, e.g. during the weaning period. Even when incorporated into the diet at low levels, fish meal and fish oil-containing products have also been found to adversely affect the quality of the final meat product in terms of its taste, colour, etc., particularly when fed to the animal late in the growing period, e.g. during the "finishing" period. For example, the feeding of fish meal to pigs during the "growing-finishing" period has been found to impart an undesirable "fishy" smell and taste to the pig meat. This is also a particular problem in poultry production.

A need therefore exists for alternative (e.g. improved) sources of protein which may be incorporated into foods for consumption by farmed animals and which do not adversely affect the quality of the final meat product. In particular, a need exists for such materials which may serve to enhance the meat quality characteristics, for example its sensory qualities.

Protein-containing microorganisms (also referred to herein as "singlecell proteins") such as fungi, yeasts and bacteria have been proposed for use in or as feeds for animals raised for human consumption. We have now surprisingly found that the biomass harvested from a culture medium comprising methanotrophic bacteria (e.g. a biomass produced as described in WO 01/60974), when used as component in the diet of a farmed animal, serves to enhance, preferably to enhance and maintain, the quality of the meat following slaughter. In particular, such a material has been found to maintain and/or improve the sensory properties (e.g. taste, odour, colour, etc.) of the meat. More particularly, the material herein described is capable of improving and subsequently maintaining the quality of farmed meat, for example following a period of storage.

One particular problem encountered when handling meat (e.g. during periods of short or long-term storage) is its susceptibility to lipid oxidation. This is the process by which meat turns rancid. Surprisingly, we have also now found that the biomass material hereinbefore described, when fed to a farmed animal as part of its diet, serves to reduce or prevent lipid oxidation of the final meat product, especially during any period in which the meat is stored, e.g. frozen. In this way, the quality of the meat is further enhanced (e.g. in terms of improved taste), particularly after short or long-term storage, for example at temperatures below ambient, e.g. on freezing.

Thus, viewed from one aspect, the invention provides a method of improving the quality (e.g. sensory qualities) of meat derived from a farmed animal, said method comprising orally administering to said animal (e.g. as part of its dietary intake) a biomass derived from a culture of bacteria including methanotrophic bacteria.

In another aspect the invention provides the use of a biomass derived from a culture of bacteria including methanotrophic bacteria in a method of improving the quality (e.g. sensory qualities) of meat derived from a farmed animal in which said biomass is orally administered to said animal (e.g. as part of its dietary intake) As used herein, the term "quality1' when used in relation to a meat product is intended to encompass all properties or attributes of the meat (whether cooked or uncooked) which may be detected by a human or non-human animal, especially those which may be detected by a human. Such properties include, for example, aroma (e.g. rancidity), taste, texture, juiciness, colour, firmness, tenderness and digestibility. "Sensory qualities" of meat are those properties which may be sensed by the animal (e.g. by a human) and include, in particular, aroma, taste, colour, etc. The term "quality" as used herein further includes the nutritional qualities of a meat product.

The term "meat" is intended to encompass both muscle (i.e. meat) and fat which may be obtained from a farmed animal following slaughter. For example, where the farmed animal is a pig, the effects herein described may be observed not only in the meat (i.e. pork) but also in the fat (e.g. the backfat) The term "farmed animal" as used herein is intended to refer to an animal which is raised for human and/or animal consumption (although, primarily, this will be raised for human consumption) . Examples of animals which may be raised according to the methods herein described include farmed mammals, e.g. pigs, sheep, goats, cattle, poultry (e.g. chicken, turkey, etc.), and veal calves. Farmed fish such as salmon and trout may also be raised in accordance with the methods of the invention. The material herein described is particularly suitable for use as a component in the diet of pigs, poultry (e.g. chickens, turkeys) and veal calves, especially during the "finishing" period.

The bacterial culture used to produce the biomass for use in the invention is preferably at least 50%, more preferably at least 60%, especially at least 70%, in particular at least 75%, e.g. 75 to 95%, more particularly 75 to 80%, by weight methanotrophic bacteria (relative to the total bacterial weight) The biomass for use in the methods of the invention is preferably biomass generated from at least one species of methanotrophic bacteria, in combination with one or more species of heterotrophic bacteria. As used herein, the term "methanotrophic" encompasses any bacterium which utilizes methane, methanol or formaldehyde for growth. The term "heterotrophic" is used for bacteria that utilize organic substrates other than methane, methanol or formaldehyde for growth.

The bacterial biomass for use in the methods herein described may be formed by growth of the bacteria on a suitable medium or substrate. The exact nature of the growth medium used to produce the biomass is not critical and a variety of suitable substrates may be used. In the case where a combination of methanotrophic and heterotrophic bacteria are used to generate the biomass, these will preferably be grown in the same culture medium, e.g. using a loop reactor provided with methane, oxygen, ammonia and mineral feeds.

Conveniently, the biomass may be produced by a fermentation process in which oxygen and a suitable substrate such as a liquid or gaseous hydrocarbon, an alcohol or carbohydrate, e.g. methane, methanol or natural gas, together with ammonia and a nutrient mineral solution are fed to a tubular reactor containing the microorganisms. A number of such processes are well known and described in the art, for example in WO 01/60974, DK-B-170824, EP-A-418187 and EP-A-306466, the contents of which are herein incorporated by reference.

The biomass material for use in the methods herein described will preferably be derived from fermentation on hydrocarbon fractions or on natural gas. Especially preferred are biomass materials derived from the fermentation of natural gas. Generally in such processes, as the concentration of microorganisms increases within the fermentor, a portion of the reactor contents or broth is withdrawn and the microorganisms may be separated by techniques well known in the art, e.g. centrifugation and/or ultrafiltration.

Conveniently, in such a fermentation process, the broth will be continuously withdrawn from the fermentor and will have a cell concentration between 1 and 5% by weight, e.g. about 3% by weight.

Suitable bacteria for use in generating the biomass are described for example in WO 01/60974, the contents of which are incorporated herein by reference. One particularly suitable combination is that comprising MeLhylococcus Capsulatus (Bath) (strain NCIMB 11132), Raistonia sp. DB3 (strain NCIMB 13287), Brevibacillus agri DB5 (strain NCIMB 13289), optionally in combination with Aneurinibacillus sp. DB4 (strain NCIMB 13288) Each of these microorganisms is available from The National Collection of Industrial Food & Marine Bacteria (NCIMB), Aberdeen, UK or from Norferm Danmark A/S, Stenhuggervej 22, DK- 5230 Odense, Denmark.

Typically, the biomass produced from fermentation of natural gas may comprise from 60 to 80% by weight crude protein; from 5 to 20% by weight crude fat; from 3 to 10%- by weight ash; from 3 to 15% by weight nucleic acids (RNA and DNA); from 10 to 30 g/kg phosphorus; up to 350 mg/kg iron; and up to 120 mg/kg copper.

Particularly preferably, the biomass will comprise from 68 to 73%, e.g. about 70% by weight crude protein; from 9 to 11%, e.g. about 10% by weight crude fat; from 5 to 10%, e.g. about 7% by weight ash; from 8 to 12%, e.g. about 10% by weight nucleic acids (RNA and DNA); from 10 to 25 g/kg phosphorus; up to 310 mg/kg iron; and up to mg/kg copper. The amino acid profile of the protein content can be expected to be nutritionally favourable with a high proportion of the more important amino acids methionine, lysine, threonine, arginine and tryptophan.

Typically these may be present in amounts of about 0.7%, 3.1%, 5.2%, 7.2%, 2.5% and 6.9%-, respectively (expressed as a per cent of the total amount of amino acids) Generally the fatty acids will comprise mainly the saturated palmitic acid (approx. 50%) and the monounsaturated palmitoleic acid (approx. 36%) . The mineral content of the product will typically comprise high amounts of phosphorus (about 1. 5% by weight), potassium (about 0.8% by weight) and magnesium (about 0.2% by weight) Typically, the resulting biomass will be produced in the form of a flowable aqueous paste or slurry.

Generally this will consist essentially of whole cell material, although a proportion of ruptured cell material may also be present.

The biomass from the bacterial culture may be used directly (i.e. without further processing) as, or as a component or precursor to a composition for use in any of the methods herein described. However, this will generally be further processed (e.g. by dewatering and/or sterilization) prior to use. For example, this may be subjected to a combination of centrifugation and/or filtration (e.g. ultrafiltration) processes whereby to reduce the water content. Following centrifugation and/or ultrafiltration the biomass material will be a relatively viscous protein slurry or paste. This may be yet further processed to remove excess water from the product. The choice of any additional drying step or steps will depend on the water content of the material and the desired moisture content of the final product. Preferably, the resulting product will have a water content of from about 2 to 10% by weight, preferably from 6 to 8% by weight, e.g. about 5% by weight. The resulting product will typically be a free-flowing granulate having a particle size of from 0.1 to 0.5mm, preferably from 0.15 to 0.2mm.

Alternatively, the biomass from the bacterial culture may be processed to break down the bacterial cells, e.g. by any combination of homogenization, hydrolysis and autolysis processes. Such treatments are described in WO 01/60974, WO 03/68002 and WO 03/68003, the contents of which are incorporated herein by reference.

In the methods of the invention the biomass material is orally administered to a farmed animal. Due to its protein content, the material will conveniently form part of the daily diet of the animal. Thus, the biomass material herein described will typically be used as, in or as an additive to an animal feed intended to be consumed by a farmed animal. For example, this may be incorporated into conventional animal feeds (e.g. meal, pellets, extruded pellets, meat-based products, cereals, soya- based products, etc.) during production or manufacture in any suitable manner. Alternatively, the biomass may be provided in the form of a feed additive to be mixed with or applied to a conventional animal feed immediately prior to consumption by the animal in an amount sufficient to provide the desired effects.

For application to an animal feed prior to consumption by the animal, the material of the invention may be conveniently provided in particulate form (e.g. as granules or in powder or pellet form) . In producing pellets containing the biomass material herein described, such material will typically be mixed with an oil selected from soya oil, rape seed oil and mixtures thereof in order to aid the pelletizing process.

The material described herein will be employed in animal feed in an amount effective for this to provide the desired quality characteristics (e.g. sensory qualities) to the final meat. Such qualities are as herein described and include, in particular, taste (i.e. flavour) and odour (i.e. rancidity) . Although it is primarily intended that the final meat product will be consumed by a human, this may also be fed to a non-human animal, e.g. a pet. The desired sensory qualities therefore also include traits which may be sensed by a non-human animal, such as a dog or a cat. The invention may therefore be used to improve the palatability (e.g. taste, smell, etc.) of meat for use in the pet food industry.

The improvements in meat quality herein described extend not only to fresh meat (i.e. at slaughter) but also meat which has been stored, e.g. frozen, for any period of time. Furthermore, quality is not limited to the sensory qualities of the meat but also includes qualities such as nutritional quality. For example, the biomass material used in accordance with the methods of the invention not only reduces the production of harmful components, such as peroxides, in the meat (since the final meat product is more stable to oxidation), but also reduces the level of loss of any nutritionally important components of the meat, such as vitamins and other unsaturated compounds.

As previously outlined herein, the "fishy" taste and smell of meat is a particular problem during meat production, especially in swine and poultry production.

Although this is a problem which is primarily associated with diets containing fish meal or fish oil-containing products, it is also encountered when feeding diets which are devoid of any fish-deriving raw materials. A particularly preferred aspect of the methods herein described is the ability to reduce the "fishy" taste and smell of the meat (including the fat) following slaughter and also during storage. The biomass material can, in particular, be used to reduce the risk of a "fishy" taste and/or smell associated with the meat product even when the animal is fed a diet which contains no (or very little) materials of marine origin.

Appropriate levels of incorporation of the material in an animal feed will depend on several factors, such as the animal species, age, gender and size of the animal for which this is intended, etc. Suitable levels may readily be determined by those skilled in the art.

Typically, when added to conventional animal feeds, levels of incorporation in the range of from 0 to 40 wt.% (e.g. for fish), preferably from 0 to 15 wt.% (e.g. for pigs and poultry), may be used.

The period during which the material might be fed to a farmed animal will similarly vary depending on factors such as the animal species, gender, time to slaughter, etc. Although this may be provided to the animal during the weaning period and/or during the growing-finishing period (i.e. that following weaning to slaughter), preferably the material will be incorporated into the diet of the animal during the growing-finishing period.

Most preferably, the beneficial effects herein described are observed when the material is fed to the animal during the period immediately prior to slaughter.

Typically, this may be fed to pigs of from 3 to 140 kg in weight, to chickens of from 50 g to 2 kg in weight, to turkeys of from 70 g to 12 kg in weight, to fish of from 1 g to 6 kg in weight, and to veal calves of from to 140 kg in weight.

Post mortem storage of animal carcases in which the carcases are maintained at temperatures below ambient, preferably below freezing, e.g. at temperatures in the range of from -1 to -30 C, e.g. from -18 to -30 C, are necessary for the purposes of transportation and storage. Post mortem storage of animal carcases at below ambient temperature, but above freezing, is also desirable since this results in tenderisation of the meat. As previously noted, the material herein described has been found to be capable of maintaining (e.g. improving) the quality of meat during handling and storage, in particular on storage at temperatures below freezing.

- 12 - Viewed from a further aspect the invention thus provides a method of maintaining the quality of meat derived from a farmed animal following slaughter, e.g. on storage at a temperature below freezing, said method comprising orally administering to said animal (e.g. as part of its dietary intake) a biomass material as herein described. The use of a biomass material as herein described in such a method forms a further aspect of the invention.

In a yet further aspect the invention provides a method of processing a meat product, said method comprising the following steps: (a) obtaining meat from a farmed animal fed a diet which comprises a biomass material as herein described; and (b) subjecting said meat to freezing.

In a still yet further aspect the invention provides a frozen meat product obtained from a farmed animal fed a diet which comprises a biomass material as herein described.

As used herein, the term "frozen meat" is intended to define a meat product which is held at a temperature below freezing, preferably at a temperature in the range -1 to -30 C, e.g. in the range -18 to -30 C.

The invention will now be illustrated further with reference to the following non-limiting Examples:

Example 1 - Biomass

Methanotrophic and heterotrophic bacteria (Methylococcus Capsulatus (Bath) (strain NCIMB 11132), Ralstonia sp.

DB3 (strain NCIMB 13287), Aneurinibacillus sp. DB4 (strain NCIMB 13288) and Brevibacillus agri DB5 (strain NCIMB 13289), each available from Norferm Danmark A/S, Stenhuggervej 22, DK-5230 Odense, Denmark) were cultivated as described in WO 01/60974 and the resulting biomass harvested and dewatered as described in WO 01/60974 to produce a spray-dried product containing about 96% dry matter, 70%- crude protein, 10% lipids and 7% ash. Hereinafter, this material is referred to as "bacterial protein meal" or "BPMT1.

Example 2 - Study

A study was carried out to evaluate the effect of BPM (as described in Example 1) on the quality of backfat and meat in pigs, including the effect of BPM on susceptibility of pork to lipid oxidation.

A total of 48 [(Norwegian Landrace x Yorkshire) x (Norwegian Landrace x Duroc) ] weanhing pigs from six litters were used (average initial weight 11.4 kg; average final weight 107.2 kg) . The experimental period lasted on average 119.4 days.

The study was conducted as a randomized complete block design. There were four dietary treatments each with 12 pigs. The study was split into a "piglet" period from weaning to week five of the experimental period, and a "growing-finishing" period from week five to slaughter.

Two separate basal diets were used, one for the "piglet" period and one for the "growing-finishing" period. The dietary treatments consisted of a barley, wheat and soybean meal (SBM) based basal diet and three test diets containing 50 g, 100 g and 150 g kg' BPM. The diet compositions were as set out in Table 1 below: Table 1 - Composition of "growing- finishing" pig diets Level of bacterial protein meal (g kg') 0 50 100 150 Crude fat 34 36 43 46 Total fat from bacterial protein meal' 0 5.5 11.0 16.4 Total soy oil2 10.8 7.1 7.5 6.5 Fatty acids, % of total fatty acids C14:0 0.232 0.783 1.118 1.290 014:1 0.00 0.00 0.042 0.057 016:0 16.98 22.49 24.96 27.11 C16:l trans n-7 0.00 0.19 0.36 0.47 016:1 cis n-7 0.13 4.50 7.15 9.93 C16:l cis n-6 0.00 2.13 3.37 4.43 016:1 cis n-5 0.00 1.25 1.98 2.49 C16:l total 0.13 8.07 12.86 17.32 018:0 2.16 1.67 1.55 1.39 C18:l cis n9 17.19 13.95 12.41 11.16 018:1 cis n7 1.11 0.92 0.87 0.81 C18:2 cis n6 55.53 45.70 40.06 35.23 018:3 cis n3 5.34 4.26 3.73 3.29 C20:0 0.28 0.23 0.21 0.19 020:1 cis n9 0.54 0.50 0.42 0.38 Saturated fatty acids (SAE) 19.65 25.17 27.84 29.98 Monourisaturated fatty acids (MUFT) 18.97 23.44 26.60 29.72 Polyunsaturated fatty acids (PUFA) 60.87 49.96 43.79 38.52 Iodine value 126.4 111.1 103.2 96.7 Based on analyzed crude fat content minus 1% soy oil inclusion in bacterial protein meal.

Based on soy oil from added soy oil, soy oil in soybean meal, and 1% soy oil in the bacterial protein meal.

The experiment started on the day of weaning. During the "piglet" period, pigs were fed according to appetite from an automatic feeder and during the "growing- finishing" period all pigs were individually fed twice - 15per day according to a restricted Norwegian feeding scale. All pigs were given free access to water.

Pigs were slaughtered at a commercial slaughterhouse.

Samples from eight pigs per treatment equally distributed across litters were taken for sensory analyses. Both left and right longissmus dorsi muscle including subcutaneous fat were removed from each carcass one day after slaughter for determination of fatty acid composition and sensory analyses. Samples were divided into two parts, vacuum packaged, and stored in a freezer at about -23 C until analyses.

Sensory analysis Sensory analyses (descriptive profiling) of fat and meat samples were conducted after one and three months of storage. Each sample was cut into 10-mm-thick slices, vacuum packaged, and heated for one hour in a 75 C water bath to a core temperature of 73 C. A trained 10-member panel evaluated each sample twice, in random order, for sensory attributes including odor (meat, acidity, rancidity, pig, fish, off-odor), flavor (meat, acidity, rancidity, pig, fish, off-flavor), colour (whiteness, hue, color intensity) and texture (hardness, tenderness, juiciness and fattiness) . Fat and meat were analysed for sensory traits separately and together.

Each assessor evaluated the samples using a continuous scale and a computerized system for direct recording of data (Compusense Five, Compusense, Guelp, Ontario, Canada) . The computer translated responses into numbers where 1 = no intensity and 9 = high intensity. The sensory evaluation was performed according to international standards (ISO 6564, 1985E Sensory Analyses-Methodology-Flavor profile method, ISO 6658, 1985E, Sensory analyses, General guidance, ISO 8586, 1993E, Sensory Analyses-General guidance for the selection training and monitoring of assessors, ISO 8589, 1988E Sensory Analyses-General guidance for the design of test rooms) Chemical analysis The fatty acid composition of fat and meat from pork chops was determined separately. Lipids were extracted with the Bligh and Dyer method (Can. J. Med. Sci. 37: 911-917, 1959) and converted to methyl esters with methanolic HC1 and 2,2- dimethoxy propane (Mason and Wailer, Analytical Chemistry, 36: 583-586, 1964) prior to analysis on a GC (HP Gl 530A) equipped with a BPX7O column (0.25 mm i.d., 60 m, 0.25 pm film, produced by SGE) . The temperature programme started at 70 C for 1 mm, increased by 30 min' to 170 C, then 1.5 min' to 200 C and 3 C min' to 220 C with a final hold time of 5 minutes. Peaks were integrated with HP GC ChemStation software (rev. A.05.02) and identified by comparison of the retention times with those of pure standards.

System performance was checked with blanks and standard samples prior to analysis. The concentration of individual fatty acids was expressed in % of total fatty acids and was determined in two replicates of all samples.

Thiobarbituric Acid Reactive Substances (TEARS) were determined in backfat and meat from vacuum-packed chops that had been stored at about - 20 C for 12 months.

TEARS were analysed with the extraction method of S rensen & J rgensen (Zeitschrift für Lebensmittel- Untersuchung und -Forschung 20(3) : 205-210, 1996) . The samples were incubated at 100 C for 35 minutes and the absorbance at 532 nm was measured with an Ultraspec 3000 spectrophotometer (Pharmacia Biotek, Cambridge, UK) against a blank containing 5 ml TBA reagent and 5 ml distilled water. TBARS were calculated from a standard curve for TEP (l,l, 3,3-tetraethoxypropane) and expressed as mg malondialdehyde per kg meat.

Results and discussion Increasing dietary levels of EPM resulted in an increase in total saturated fatty acids (SAFAs) and total monounsaturated fatty acids (MUFAs), but a decrease in total polyunsaturated fatty acids (PUFAs) and iodine (see

Table 1)

The fatty acid composition of the backfat and meat of pigs is shown in Tables 2 and 3 below: Table 2 - Effect of bacterial protein meal in diets for pigs on fatty acid profile of backfat Level of bacterial protein meal (p kg') 0 50 100 150 No. of pigs 8 8 8 8 Fatty acids, % of total fatty acids c14:0 1.34 1.43 1.45 1.44 c14:l 0.006 0.015 0.017 0.015 c16:0 24.09 24.20 23.61 23.16 c16:l trans n7 0.36 0.34 0.35 0.37 c16:l cjs n7 2.19 2.96 3. 44 4.10 cl6:1 cis n6 0 0.35 0.66 0.93 c16:l cis n5 0 0.05 0.11 0.16 c16:1 total 2.55 3.71 4.56 5.56 c18:0 13.20 14.30 15.25 15.79 c18:1 cis n9 35. 11 34.32 32.60 31.43 c18:l cis n7 2.58 3.14 3.31 3.75 c18:1 total 37.91 38.05 36.76 36.24 c18:2 cis n6 16.63 14.56 14.56 14.08 c18:3 cis n3 1.30 1.11 1.15 1.11 c20:0 0.21 0.22 0.25 0.24 c20:l cis n9 0.76 0.80 0.71 0.63 c20:2 cis n6 0.73 0.69 0.67 0.64 c20:4 cis n6 0.25 0.22 0.25 0.24 c20:3 cis n3 0.21 0.19 0.19 0.18 c24:0 0.06 0.02 0.01 0.00 c24:l cis n9 0.04 0. 02 0.06 0.07 c22:5 cis n3 0.10 0.06 0.10 0.08 Total n6 fatty acids 17.61 15.49 15.46 15.99 Total n3 fatty acids 1.61 1.37 1.44 1.38 Ratio n6/n3 10. 93 11.24 10.84 10.77 Saturated fatty acids (SAFA) 38.89 40.06 40.69 40.47 Monounsaturated fatty acids 41.23 42.65 41.95 42.55 (MUFA) Polyunsaturated fatty acids 19.22 16.84 16.92 16.34 (PUFA) Iodine value 70.70 67.65 67.30 67.03 TBARS, rrçj kg-' 0.44 0.33 0.27 0.26 Table 3 - Effect of bacterial protein meal in diets for pigs on fatty acid profile of meat Level of bacterial protein meal (g kg1) 0 50 100 150 No. of pigs 8 8 8 8 Fatty acids, % of total fatty acids 014:0 1.22 1.25 1.32 1.32 c14:l 0.01 0.00 0.00 0.01 016:0 23.75 23.84 24.01 24.21 c16:l tranìs n7 0.28 0.27 0.22 0.19 016:1 cis n7 3.11 3.30 3.94 4.44 016:1 cis n6 0.006 0.12 0.20 0.27 c16:1 cis n5 0.005 0.07 0.10 0.12 016:1 total 3.41 3.76 4.46 5.02 018:0 11.00 11.33 11.12 11.36 018:1 cis n9 35.58 34.76 37.24 37.74 018:1 cis n7 3.89 4.00 4.51 4.72 018:1 total 39.70 39.13 42.28 43.07 018:2 cis n6 13.35 12.99 10.53 9.52 018:3 cis n3 0.66 0.61 0.55 0.52 020:0 0.11 0.15 0.18 0.19 020:1 cis n9 0.64 0.63 0.67 0.67 020:2 cis n6 0.43 0.39 0.34 0.30 020:4 cis n6 2.01 2.16 1.61 1.27 020:3 cis n3 nd nd nd nd 020:5 cis n3 0.11 0.09 0.10 0.06 024:0 nd nd nd nd 024:1 cis n9 nd nd ndnd 022:5 cis n3 0.44 0.46 0.33 0.27 022:6 cis n3 0.16 0.14 0.11 0.03 Total n6 fatty acids 15.80 15.66 12.67 11.36 Total n3 fatty acids 1.38 1.30 1.09 0.87 Ratio n6/n3 11.66 12.24 11. 62 12.76 Saturated fatty acids (SAFA) 36.09 36.56 36.63 37.08 Monounsaturated fatty acids 43.76 43.52 47.41 48.77 (MtJFA) Polyunsaturated fatty acids 17.18 16.84 13.57 11.96 (PUFA) Iodine value 72.71 72.04 68.62 66.09 TRAPS, mg kg 0.26 0.20 0.15 0.03 nd = not detected Substituting BPM for SBM increased the content of the SAFA5 018:0, 020:0 in backfat, and decreased the content of 024:0, but had no effect on C16:0 or total SAFAs (Table 2) . Increasing levels of dietary BPM also led to an increase in the content of MUFAs C14:l, 016:1 trans n7, 016:1 cis n7, 016:1 cis n6, 016:1 cis n5, 018:1 cis n7, and 024:1 cis n9, but decreased the content of 018:1 cis n9. This resulted in an increase in total 016:1 fatty acids and a reduction in total C18:l fatty acids, but no changes in total MUFAs. Furthermore, there was a decrease in the content of PUFAs 018:2 cis n6, and 018:3 cis n3 in the backfat. As a consequence the level of total n6 and total n3 fatty acids as well as total PUFAs in backfat decreased. Also, there was a linear decrease in the iodine value from 70.7 in the control to 67.0 in the diet containing 150 g kg' BPM.

Increasing dietary levels of BPM resulted in a higher level of the SAFAs 014:0 and 020:0 in meat (Table 3) There was also an increase in the content of MUFAS 016:1 cis n7, 016:1 cis n6, 016:1 cis n5, 018:1 cis n9, and 018:1 cis n7 in meat. Adding BPM to diets, however, decreased the content of the n6 fatty acids 018:2 cis n6, 020:2 cis n6, 020:4 cis n6 and the n3 fatty acids 018:3 n3, 022:5 n3, and 022:6 cis n3. This led to a decrease in total n6 and n3 fatty acids, total PUFAs, and iodine value, but an increase in total MUFAs with increasing levels of dietary BPM.

The fatty acid composition in backfat and meat reflected the fatty acid composition in the diet to some extent, in that the level of PUFAs and iodine values were reduced with increasing levels of BPM, but the fatty acid composition of these tissues reflected the high level of 016:0 and total MUFA5 in the 3PM diets to a lesser extent. The decrease in the levels of total PUFAs in meat and backfat was probably a result of the fat in diets containing BPM and the reduction in soy oil. The BPM had a lower content of 018:2 cis n6 and C18:3 cis n3 fatty acids while the soy oil is rich in 018:2 cis n6. The meat has a higher level of 020:4 cis n6, 020:5 cis n3, and C22:6 cis n3 fatty acids than the backfat. The response to BPM on the concentration of total 016:1 fatty acids and total PUFAs was greater in the backfat than in the meat. The response to the increased content of 016:0 fatty acid in the BPM diets was limited in both backfat and meat.

The results show clear changes in fatty acid composition of the back fat and meat even at the lowest BPM inclusion level (Table 1) . The results suggest that the improvement in backfat quality is a result of reduced content of PUFAs and n3 fatty acids (especially 020 and 022 fatty acids) as well as iodine value with increasing levels of BPM in diets.

After one year of storage, there was a quadratic effect of BPM on TBARS in backfat (Table 2) and meat (Table 3) Pigs fed diets containing all levels of BPM had lower TEARS than the control. The meat and backfat from pigs fed the 100 and 150 g kg' BPM diets had the lowest TBARS.

The addition of 50 g kg1 BPM gave an intermediate reduction in TEARS. The reduction in TEARS is probably a result of the reduction of PUFAs and iodine value in backfat and meat. These results suggest that the addition of EPM to diets for pigs improve the oxidative stability of backfat and meat. -22 -

Sensory traits Effect on sensory traits after one month (i.e. short- term) storage is shown in Table 4 below: Table 4 - Effect of bacterial protein meal in diets for pigs on sensory quality of pork after short- term storage Level of bacterial protein meal (g kg') 0 50 100 150 No. of pigs 8 8 8 8 Live weight, slaughter, kg 108.81 107.47 106.65 104.5 Carcass weight, kg 73.57 72.96 71.69 70.28 P2 backfat thickness, rrm 12.1 12.4 15.2 15.2 After one month of storage Odor intensity 6.84 6.31 6.45 6.62 Rancid odor 1.95 1.10 1.20 1.48 Diverging odor 2.10 1.68 1.66 1.83 Meaty odor 4.31 4.61 4.20 4.05 Acidic odor 3.28 3.77 3.32 3.09 Pig odor 2.72 2.74 2.67 3.10 Taste intensity 6.52 6.41 6. 37 6.61 Rancid taste 1.54 1.20 1.18 1.19 Diverging taste 2.25 2.06 2.27 2. 38 Meaty taste 4.94 5.01 5.11 5.01 Acidic taste 3.88 4.08 4.07 3.85 Pig taste 3.19 2.94 3.06 3.60 Sweet taste 2.82 2.98 2.74 2.93 Bitterness 4.07 3.86 3.97 4.01 Metal taste 3.86 3.87 3.89 3.95 Hardness 5.52 5.41 5.30 5. 13 Tenderness 4.36 4.52 4.52 4.75 Juiciness 3.83 3.76 3.96 4.3 The addition of BPM to diets affected odour intensity of pork. Pigs receiving the 50 and 100 g kg' BPM diets had lower odour intensity than the pigs fed the control and the 150 g kg1 BPM diets. There was also a significant difference in rancid odour and rancid taste intensity -23 - among the treatments. Of special interest is the reduction in rancid odour and taste of pigs with BPM diets dependent upon the level of BPM added.

Furthermore, increasing levels of BPM gave an increase in juiciness of pork after one month of storage.

Effect on sensory traits after three months (i.e. intermediate) storage is shown in Table 5 below: Table 5 - Effect of bacterial protein meal in diets for pigs on sensory qualities of pork after intermediate- term storage Level of bacterial protein meal (g kg1) 0 50 100 150 No. of pigs 8 8 8 8 After three months of storage Odor intensity 7.03 6.83 6.75 6.87 Rancid odor 2.12 1.71 1.58 1.98 Diverging odor 2.24 2.66 2.51 1.91 Meaty odor 3.85 3.84 4.16 3.90 Acidic odor 3.33 3.23 3.61 3.41 Fig odor 3.88 3.70 3.40 3.94 Taste intensity 6.63 6.52 6. 41 6.59 Rancid taste 1.84 1.46 1.53 1.58 Diverging taste 2.53 2.59 2.62 1. 92 Meaty taste 4.51 4.52 4.59 4.74 Acidic taste 3.83 3.93 4.04 4.17 Fig taste 3.28 3.23 2.76 3.37 Sweet taste 3.26 3.35 3.37 3.39 Bitterness 4.01 4.11 4.08 3.94 Metal taste 4.48 4.41 4.47 4.46 Hardness 4.87 4.99 4.90 4. 58 Tenderness 5.18 5.13 5.17 5.42 Juiciness 4.07 4.16 4.32 4.87 Increasing dietary levels of BPM tended to reduce odour intensity and rancid odor following intermediate -24 - storage. There was a reduction in odour intensity and rancid odour in pork with all levels of BPM compared to the control, but the lowest values were achieved by the addition of the intermediate levels of 3PM of 50 and 100 g kg diet. Pork from pigs fed diets containing 3PM also had lower rancid taste intensity.

These results confirm that substituting SBM and soy oil with BPM improves the sensory quality of pork both after short term and intermediate time storage with respect to odor and taste intensity, rancid odor and taste intensity, and diverging odor and taste. The improvement in sensory quality of pork was found for all levels of 3PM, most likely due to the increase in C16:1 fatty acid and reduction of PUFAs as well as iodine value in meat and backfat of pigs fed diets containing 3PM. As a consequence, the meat and backfat is more stable towards oxidation as suggested by the reduction in secondary oxidation products measured with TBARS in these tissues. Furthermore, there were significant differences among treatments for hardness and juiciness scores. The highest level of 150 g kg BPM diet gave lower hardness scores, but the highest juiciness score.

The latter was also seen after short-term storage.

Conclusions

In backfat, substituting SBM and soy oil with 3PM at levels up to 150 g kg1 BPM in pig diets from weaning until slaughter increased the level of total C16:1 fatty acids, but decreased the level of total C18:l fatty acids, total n6 and n3 fatty acids, and the level of PUFAs and iodine value in backfat.

In meat, substituting SBM and soy oil with BPM at levels up to 150 g kg' BPM in pig diets from weaning until slaughter increased the level of total C16:1 fatty acids and total C18:1 fatty acids, and thus the total content of MUFAs, but reduced the level of total n6 and n3 fatty acids, total PUFAs and iodine values.

Increasing dietary levels of BPM reduced the susceptibility of pork to lipid oxidation as measured by TEARS in backfat and meat after 12 months storage.

The inclusion of EPM to diets improved sensory quality of pork both after short term and intermediate term storage with respect to odour and taste intensity, rancid odour and taste intensity, and diverging odor and taste.

The changes in the fatty acid composition in backfat and meat and the improvement in sensory quality were found for all levels of dietary BPM tested.

Claims (10)

1. Claims: 1. A method of improving the quality (e.g. the sensory quality) of

   meat derived from a farmed animal, said method comprising orally administering to said animal (e.g. as part of its dietary intake) a biomass derived from a culture of bacteria including methanotrophic bacteria.
2. 2. The use of a biomass as defined in claim 1 in a method of improving the quality (e.g. the sensory quality) of meat derived from a farmed animal in which said biomass is orally administered to said animal (e.g. as part of its dietary intake)
3. 3. A method of maintaining the quality of meat derived from a farmed animal following slaughter, e.g. on storage at a temperature below freezing, said method comprising orally administering to said animal prior to slaughter (e.g. as part of its dietary intake) a biomass material as defined in claim 1.
4. 4. The use of a biomass as defined in claim 1 in a method of maintaining the quality of meat derived from a farmed animal following slaughter, e.g. on storage at a temperature below freezing, in which said biomass is orally administered to said animal prior to slaughter (e.g. as part of its dietary intake)
5. 5. A method of processing a meat product, said method comprising the following steps: -27 - (a) obtaining meat from a farmed animal fed a diet which comprises a biomass material as defined in claim 1; and (b) subjecting said meat to freezing.
6. 6. A frozen meat product obtained from a farmed animal fed a diet which comprises a biomass material as defined in claim 1.
7. 7. A product as claimed in claim 6 which is maintained at a temperature in the range -1 to -30 C, preferably in the range -18 to -30 C.
8. 8. A method, use or product as claimed in any one of claims 1 to 7, wherein said biomass or biomass material is derived from a culture of bacteria comprising methanotrophic and heterotrophic bacteria.
9. 9. A method, use or product as claimed in claim 8, wherein said culture comprises Methylococcus Capsulatus (Bath) (strain NCIMB 11132), Ralstonia sp. DB3 (strain NCIMB 13287), Brevibacillus agri DB5 (strain NCIMB 13289), optionally in combination with Aneurinibacillus sp. DB4 (strain NCIMB 13288)
10. 10. A method, use or product as claimed in any preceding claim, wherein said biomass or biomass material is produced by fermentation on hydrocarbon fractions or on natural gas.