WO1987003454A1

WO1987003454A1 - Vacuum deodorization of meat

Info

Publication number: WO1987003454A1
Application number: PCT/AU1986/000368
Authority: WO
Inventors: Denis William Roberts; Simon Gregory Skevington; Robert John Bruns
Original assignee: Australian Meat And Livestock Corporation
Priority date: 1985-12-03
Filing date: 1986-11-28
Publication date: 1987-06-18

Abstract

Meat, particularly mutton, is deodorized to remove undesirable taste and smell by passing steam at subatmospheric pressure and a temperature of 45-60oC through the comminuted meat for 0.5 to 3.0 hours. Additives may increase the volatility of the odoriferous substances. Food acids, fruit extracts, reducing sugars etc may be added to enhance the flavour and colour of the deodorized meat.

Description

VACUUM DEODORIZATION OF MEAT Field of the Invention

This invention relates to a method and apparatus for removing odours and flavours from meat, such as mutton or fish, with minimum denaturation of proteins, melting of fats, change of colour or comminution. It is industrially applicable in the field of food processing. Prior Art

Steam has been used previously to deodorize milk products such as butter, cream and oils for use in substances such as margarine and cooking oil. Steam under a vacum and therefore at lower temperatures has not been used for the deodorization of meat.

The object of the invention is to reduce the odour and flavour of strong smelling and tasting meat, such as mutton, so as to enhance its acceptability to the consumer. Summary of the Invention

The invention provides a method of deodorizing meat (including fish) to remove odours and flavours, which comprises comminuting the meat, and passing steam at subatmospheric pressure and a temperature less than 75° (but above the temperature at which food poisoning and pathogenic bacteria grow) through the comminuted meat for a period of time sufficient to remove undesirable odours and flavours. The invention also provides an apparatus for carrying out the method. In one form the apparatus comprises a means to produce steam under a vacuum using a heat recovery system or a low grade heat source, means to pass the steam over and/or through the meat to be deodorized to remove the required volatiles and a means to recondenεe the steam using a heat recovery system or low grade heat sink.

Brief Description of the Drawings The invention will be better understood by reference to the following description of one specific embodiment thereof shown in the.accompanying drawings wherein: Fig. 1 shows a schematic representation of the deodorizing apparatus;

Fig. 2 is a sectional front elevation of the meat vessel showing the steam inlet and outlet and meat trays; and Fig. 3 shows a perforated tray. Description of Preferred Embodiments

The meat to be deodorized is placed on the perforated/mesh trays 1 which are installed in the meat vessel 2 where steam produced in the boiling vessel 3 is passed over and/or through the meat with the aid of the blower 4 before being recondensed in the condensing vessel 5. The heat to produce the steam is recovered from the condensing vessel 5 by using a heat pump 6 and then transferred to the boiling vessel 3. A vacuum pump 7 is used to lower the system pressure to the required vacuum, 0.10 - 0.14 bar absolute. A water make up valve 8 is installed in the boiling vessel 3 to replace the water evaporated. A drain valve 9 is installed in the bottom of the condensing vessel 5 to remove the condensate.

An alternative embodiment of the invention is the use of Mechanical Vapour Recompreεsion (MVR) to replace the heat pump. The principle of MVR is to use a blower to raise the boiling temperature/pressure of the steam at the blower exit and pass this steam through a heat exchanger in the boiling vessel. The high pressure steam will give off its heat to the low pressure water in the vessel hence producing low pressure steam and condensing the high pressure steam.

A further alternative is the use of a low grade, heat source, or high grade heat source such as boiler steam, to produce steam and a low grade heat sink, or any heat sink below the required steam temperature to condense the steam. Generally, about 0.3 to 4.0 kg of steam is required for each kilogram of meat.

Chemicals such as erythorbic or ascorbic acids or their salts, anti-oxidants. extracts of fruits such as apricots or peaches, extracts of plants or grains or vegetables such as pentose sugars can be added to the meat to enhance or modify the flavour and/or colour. The addition of citric acid or its salts, chelating agents. lactose or other reducing sugars is particularly preferred.

Chemicals such as those that would increase the volatility or steam volatility of odoriferous substances, or their precursors or their rate of diffusion through the meat to the seat surfaces where volatilisation can take place may also be added. Glycerol. steam volatile fatty acids or their salts or alcohols are examples of such chemicals that can be added to increase the rate or degree of deodorization. Chemicals such as proteolytic or other enzymes, or phosphates or modifying agents including gums and/or starches, or flavour substances can be added to alter the tenderness, water holding capacity, emulsifying capacity or texture or flavours or shelf-life of the meat. The steam can be used as saturated or superheated steam to modify the moisture content of the meat.

The meat to be deodorized can be in the form of mince, flakes, sliced or otherwise comminuted to particle sizes permitting suitable time periods for diffusion of odoriferous substances or their precursors to the meat surfaces for volatilisation so that deodorization is achieved in suitable time periods. The temperatures of the steam can be raised to a maximum of 60°C, from the 45-52^βC normally used, to increase the throughput of the invention even to positive saturated steam pressures. Temperatures up to 75^βC during all or part of the deodorization process may be used as part of a meat curing and/or cooking process. The invention also includes the • use of a combination of temperatures during the deodorization process. Temperatures in the range of 45 to 52°C result in minimum loss of colour, functionality of meat protein and rendering out of fat. or free fat development. The treatment time is generally 0.5 to 3.0 hours, preferably 0.5 to 1.0 hours.

The process can be modified to incorporate a continuous flow of meat through the invention or the use of perforated trays in a batch system as described previously. It should also be noted that the temperature used is outside the range in which normal food poisoning and pathogenic bacteria will grow and is one in which many spoilage organisms are killed. Thus it can lead to an increase in microbiological shelf-life from a pasteurisation effect.

The various aspects of the invention will be better understood by reference to the following experiments conducted on mutton, a meat often considered to have an unacceptable odour.

EXAMPLE 1 - ELIMINATION OF MUTTON AROMA 1 - EXPERIMENTAL

Before a small scale vacuum steam distallation plant was designed, a series of laboratory experiments were performed. a) The first of these were laboratory experiments to determine the time at which mutton started to lose moisture at various temperatures. The mutton was blended to a paste and mixed thoroughly. Using a press the meat was divided into equal slabs 2mm thick. These slabs were sealed in aluminium foil to prevent moisture exchange. A water bath with a thermamix was used to maintain the meat samples at the desired temperature. Seven samples were used at each temperature. These were a control, which was not placed in the water bath, and six samples which were left in the bath for times ranging from half a minut to 60 minutes. After removal from the water bath, the samples were placed in the refrigerator at 5°C for 24 hours. This allowed the meat to stabilize at an equilibrium moisture level. The samples were then opened, the free moisture drained off and the meat was patted dry.

All meat samples were analysed using the AOAC method (AOAC. 1975). b) The remainder of the laboratory experiments were performed using a small-scale laboratory plant. The experiments included use of meat with different particle size time/temperature trials and determining whether it was better to pass steam over or through the meat. The results were assessed by smell (daodorization compared with a control sample of the same meat) and appearance (visual) . The small scale plant could be regulated to produce a large volume of steam at a precise temperature and pressure over a specific time. This plant could be operated at temperatures between 40°C and 100^βC. At 50°C, 289 cubic metres of steam per hour was passed through the distillation chamber. The system could hold up to 6kg of minced meat on 12 stacked trays. The trays were perforated to allow steam to pass through them. Once in operation the small scale plant was used to obtain data on optimum conditions for the deodorization. Using the optimum conditions established by experimentation a batch of mutton was deodorized and tested. The appearance and extent of deodorization was assessed by a specially trained panel of testers and also by head space analysis on a gas chromatograph. Test Panel

The panel was composed of seven persons who had participated in meat testing panels previously. The meat samples were boiled with a little water in sealable containers in a microwave oven. The containers were sealed on removal from the oven. The panel were then asked to swirl the container, open it and smell the aroma. The trials consisted of four samples - raw lamb, raw mutton, raw beef and deodorized mutton. The panel were asked to identify the type of meat from smell alone and rate the intensity of the aroma (strong, moderate, weak) . The panel were not informed what types of meat were presented, and were asked to rate relative aroma intensities and to identify the type of meat. Gas chromatoqraphy analysis The samples for gas chromatograph (GC) analysis were prepared by placing 5g of meat in a 10ml screw cap septum vial. This was then placed in an oven at 140 C. After 15 minutes the sample was taken from the oven and using a pre-warmed (100^βC) 5 ml syringe. 1 ml of heat space gas was injected into the splitting injector. The GC was fitted with a HP Ultra 1 25 m x 0.2 mm crosslinked methyl silicone column which was temperature programmed to hold at 30 C for 1 minute then to rise at the rate of 15^βC/minute to 150°C. 2 - RESULTS AND DISCUSSION

The mutton used in the deodorization study contained 62.4% moisture and 16.25% fat on wet weight.

The times at which the meat started to loose moisture at the various temperatures were determined. The results show any deodorization (without curing/cooking) would have to be carried out at temperatures of less than 65°C. At dedorizing temperatures below 65°C there is only a small moisture loss for up to 60 minutes. Below 55°C there is little likelihood of decolorization due to moisture loss but the deodorization effect may not be as efficient.

The second series of experiments which were carried out on the small scale laboratory plant confirmed the results from the first experiment on moisture loss. The results are summarised in Table 1.

TABLE 1

Resuits of trial iuεinq laboratory plant

Trial Temp Time Steam Particle Finish Deodori¬

(°C) (hr) Passage Size Colour zation

1 50-60 1 Through Minced Grey Yes

2 40-50 1 Through Paste Red Slight

3 40-50 1 Through Paste Red Slight

4 40-50 2 Through Paste Red Yes

5 40-50 1/2 Through Paste Red No

6 50-60 1/2 Through Paste Grey Slight

7 50-60 1 Over Paste Grey No The laboratory plant was difficult to maintain at a uniform temperature and steam flow. After one hour of running, the steam condensate collected was 300 mis. As expected the degree of deodorization is proportional to the temperature and volume of deodorization is proportional to the temperature and volume of steam interacting with the meat. At the low temperatures, which are necessary to avoid decolorization. a large volume of steam was needed to achieve deodorization. The interaction of steam with the meat was better when the steam was passed through the meat and resulted in a higher degree of deodorization. The greater the surface area of meat in contact with the steam, the more efficient is the deodorization. At temperatures greater than 50°C the rate of colour change increases with time and temperature. At and below 50°C no permanent change in colour was apparent.

The pH of the raw meat was 6.05 and the deodorized meat was 5.95 indicating a slight increase in acidity. This may be due to oxidation effects.

A small scale deodorization plant was designed and built using the information collected from the trials of the laboratory plant. This plant was operated at different temperatures for varying times to determine the most effective conditions for deodorizing the mutton. A reasonable degree of deodorization was achieved using 50°C for one hour. At this temperature and time the meat remained visually acceptable.

Using these conditions a large batch of meat was deodorized for evaluation by the taste panel and gas chromatographic comparison to the raw meat.

The results of the taste panel trial determining the degree of deodorization are summarized in Table 2. TABLE 2

Summary of Taste Parcel Results for Identification of Deodorization Mutton

Panel Test Deo. Mutton Mutton Member

Identification Similar to lamb PMutton Intensity WK ST

Identification WK Mutton Intensity ST

Identification Lamb Mutton

Intensity WK MD

Identification Lamb Mutton Intensity MD ST

Identification Lamb Mutton Intensity MD MD

Identification Similar to lamb Mutton Intensity WK MD

Identification Mutton Mutton Intensity WK ST

ST = STRONG; MD = MEDIUM; WK = WEAK The taste panel results show a definite decrease in the intensity of the odour. The deodorized mutton was only once identified correctly but was mostly incorrectly determined to be lamb. Two of the panel members commented that the lamb and deodorized mutton had a very similar aroma with the deodorized mutton having a slightly weaker intensity.

These results indicated a marked decrease in odour intensity and the possibility of a loss of the mutton "characteristic" odour.

The gas chromatographε from deodorized mutton showed a decrease in overall peak areas compared to raw mutton. The reduction in total peak area is 71.85% (217.688 for raw mutton to 61.273 for deodorized mutton). Some individual peaks were decreased more than others. The only peaks which remained roughly the same were those at retention times 1.28 and 1.7. The peak at retention time 1.36 increased slightly in the deodorized sample.

The chro atographs produced by similar samples tended to vary slightly in individual peak areas. This was observed in both the raw mutton and the deodorized mutton. It was probably due to differences in fat to lean meat concentrations, variations in cooking times and temperatures or syringe temperature (which may lead to condensation of less volatile components).

Claims

THE CLAIMS

1. A method of deodorizing meat (including fish) to remove odours and flavourε, which compriεeε comminuting the meat, and pasεing steam at subatmospheric preεεure and a temperature leεε than 75°C (but above the temperature at which food poisoning and pathogenic bacteria grow) through the comminuted meat for a period of time sufficient to remove undesirable odours and flavours.

2. A method according to claim 1 wherein the comminuted meat is in the form of minced meat, flaked meat or paste.

3. A method according to either preceding claim wherein the steam pressure is 0.10 to 0.14 bar abεolute.

4. A method according to claim 1 wherein the temperature is lesε than 60°C.

5. A method according to claim 4 wherein the temperature is from 45 to 52°C.

6. A method according to claim 1 wherein a temperature of 60-70°C is used to simultaneously cure and/or cook the meat.

7. A method according to claim 1 wherein the time is 0.5 to 1.0 hours.

8. A method according to claim 1 which further comprises the addition to the meat of a εubεtance which increaεes the volatility of the odoriferous substances or their precurεorε.

9. A method according to claim 1 which further compriεeε the addition of erythorbic acid, aεcorbic acid, citric acid or εaltε thereof; an antioxidant; a fruit extract; a chelating agent, lactose or other reducing sugar; such as to enhance the flavour and/or colour of the deodorized meat, or to improve the extent of deodorization.

10. A method according to claim 1 wherein the meat is mutton.