search
for
 About Bioline  All Journals  Testimonials  Membership  News  Donations


African Journal of Food, Agriculture, Nutrition and Development
Rural Outreach Program
ISSN: 1684-5358 EISSN: 1684-5374
Vol. 9, Num. 9, 2010, pp. 1901-1913

African Journal of Food Agriculture Nutrition and Development, Vol. 9, No. 9, Jan, 2009, pp. 1901-1913

Effect Of Ageing Under Tropical Conditions On The Eating Qualities Of Beef

Teye GA1* and I Okutu1 

1Department of Animal Science, University for Development Studies, Box TL 1882 Tamale, Ghana
*Corresponding author email:teye.gabriel@yahoo.com

Code Number: nd09111

ABSTRACT  

Beef is a major source of animal protein in Ghana but most of it comes from old and poorly conditioned animals, which produce tough meat with poor eating qualities. The eating quality of tough beef can, however, be improved by methods of tenderizing such as ageing, electrical stimulation and application of enzymes. The purpose of this work was to study the effect of ageing under tropical conditions with high ambient/room temperatures (average 35°C) on the eating qualities of beef.  Fresh beef longissmus dorsi muscle from a matured Sanga bull was used. The muscle was cut into four equal steaks measuring 10 cm long with an average weight of 373g in duplicates and subjected to ageing treatments for 5, 10 and 15 days at a temperature of 2°C ± 2°C. The control samples were frozen throughout the experiment. After each period of ageing, the samples were immediately frozen to halt further ageing process. Swabs were taken on the samples for microbiological analysis before and after each ageing period to determine the microbial quality of the steak after ageing. Fourteen untrained sensory panelists assessed the eating qualities: tenderness, beef flavour, juiciness and abnormal flavour of the samples. The ageing process resulted in highly significant improvements in tenderness and juiciness of the beef steak. Ageing for 10 to 15 days produced very tender steaks whilst the control steaks remained very tough (P< 0.001). The beef steaks became more juicy with increasing time of ageing and beef flavour intensity was significantly (P< 0.01) enhanced from day 5 to becoming strong by the day 15, whilst abnormal flavour intensity was not affected by the ageing process. On acceptability, majority of the panelists preferred the steaks aged for 10 or 15 days as the best meat. The ageing process did not have any detrimental effect on drip loss and microbial quality of the beef steaks. The problem of very tough beef from old animals in tropical countries can be minimized considerably through the practice of ageing. 

Key words: Ageing, Flavour, Beef, Juiciness, Tenderness  

INTRODUCTION

Meat  production  records  for  developing  countries,  particularly in sub – Saharan  Africa  show  that  beef  cattle  leads  the  chart  on  meat  production  and  consumption  [1]. Beef  is  a major  source  of  animal  protein  in  Ghanaian dishes [2] and  the  demand  for  it  is  constant  throughout  the year  due  to  its  relatively lower  price  [3].  Meat from cattle on the Ghanaian market mostly comes from older and poor body conditioned animals [4]. The  meat  from  these  animals  tend to be  tough  (metallic)  than  meat  from  young cattle[1]. Old animals, especially draught animals, have a high content of tough connective tissues in the muscle which make them tough and therefore require prolonged cooking at higher cost in terms of fuel wood, gas or electricity. Young animals produce more tender meat. However, the proteolytic enzyme system decreases as the animal grows older resulting in tough meat. Intense stress on an animal prior to slaughter is known to have an influence on beef tenderness. The best cut from an animal can be made tough by pre-slaughter stress whilst an older animal can produce relatively tender meat if the animal is docile, humanely handled and slaughtered and the meat is properly aged. Unfortunately, in Ghana just as in most developing countries, animals are often subjected to stressful  pre-slaughter conditions[4].

The  most  important  aspect  of  meat  quality  is the  eating  quality which  is  the  level  of  overall  eating satisfaction and a  function  of  the  combined  effects  of  tenderness,  juiciness  and  flavour [5].  Meat tenderness is an important factor in consumer perception of meat quality [3] and most consumers consider tenderness to be the single most important component of meat quality.  Meat tenderness is defined  as  the  quality  of  the  cooked  meat  which  is associated  with  easy  chewability  and minimal  loss  of  desirable texture [6]. It is also described as  the  softness  or  pressure  exerted  by  the  teeth  to  bite the  meat  and  how  easily  it  fragments [7]. Therefore, variations in tenderness at the consumer level must be controlled to improve consumer satisfaction. Meat tenderness is the most difficult trait to predict but important in determining quality and consumer acceptance. The real magnitude of the problem of tenderness is that most unsatisfied consumers rarely complained or return the products but simply avoid purchasing such tough products in the future.

Meat tenderness is influenced by pre-slaughter factors such as breed, age and feeding, and postmortem factors such as suspension of carcass during slaughter, electrical stimulation, chilling rate ageing, freezing, thawing and cooking [8, 9, 10, 11]. Quick freezing and ageing before rigor mortis sets in, pressure cooking, disruption of muscles by blades or hummer and muscle stretching are methods used to tenderize meat [12, 13]. The feeding regimes of animals can have significant effect on meat tenderness [14]. The amount of muscular exercise of the animal from which the cut is obtained also plays a role in tenderness [14,15]. Tenderness also depends on the amount of connective tissues present between the muscular fibres and to a lesser extent on the thickness of the muscle fibres themselves [5]. Meat tenderness may  be  judged  by measurement  of  soluble  collagen, sarcomere  length,  amount  of  myofibril  fragmentation  or  the  shear  force  needed  to  cleave  a  standard  sample  of   cooked  meat[16].

Postmortem  ageing  is  a natural  process  which  improves  the  palatability  attributes  of  meat,  especially  cut  from  the  loin  and  rib. The  tenderizing  effect  of  ageing  is  more  evident  in  carcasses  from  older  animals  than  in  the  usually  more  tender  lean  meat from  younger  animals [17]. Ageing  of  meat  also  called  ripening  or  conditioning  is  defined  as  the  practice  of  holding  carcasses  or  cuts  under  refrigerated  condition  at  temperatures  of  1  to  3 ºC(32 to 34ºF) [17]. Ageing, therefore, refers to holding of meat at refrigerated temperatures for an extended period to allow natural enzymatic reactions to take place to enhance tenderness and flavour,  thus, allowing proteolytic enzymes to  break  down  some  of  the  complex  proteins  contained  in  the  muscle [18,19].  Apart  from  ageing  or  conditioning  of  meat, other methods  of  meat  tenderization  are  either  too expensive or  have  a  negative  effect  on  sensory  attributes  of  meat  or  have  limitation  for  exploitation  in  restaurants  and at  household levels [20]. The  ageing  process  is  not  needed if meat is  to  be  ground,  cured  or  made  into  sausage [21]. Improving  the  tenderness  of  beef  through  ageing  or conditioning  mainly  depends  on the  optimum refrigeration temperature  of  about  2ºC which is easily applicable in the temperate countries where ambient temperatures are normally below 20ºC compared to the over 35 to 40ºC in the tropics [17].

The spoilage of meat, loss of weight and the development of off-odours and flavours during the ageing period can be attributed to one or more of the following possibilities [22]: (i) Off-odour in the chill room adsorbed by the meat. However, the most common off-odour comes from excess growth of bacteria, yeasts and moulds on the meat and chill room walls or floor. Also, storing any other product in the room that has an odour will contribute to the problem. (ii) Poor sanitation during slaughtering, chilling and packaging. Contamination with microorganisms causes off-odours, off-flavours and spoilage. (iii) Excessive ageing results in an accumulation of microorganisms which produced the off-odour. (iv) Shrinkage occurs during the ageing period; the longer the ageing period the greater the total loss in weight. Also, the longer the ageing period, the greater the need for trimming of lean and fat surfaces that have dried excessively or have detectable growth of microorganisms. Using a cost- effective method to improve the eating quality of tough tropical beef will contribute to increased meat consumption and improvement in nutritional status of most people in the developing countries.

The   objective  of  this  study  was to determine  the effect  of  ageing or conditioning at a temperature of 2°C ± 2°C  on  the  eating  quality  of  beef under tropical conditions of high ambient temperatures.

MATERIALS AND METHODS

The  experiment  was  conducted  at  the  University  for  Development  Studies  Meat and the Microbiology  Laboratories in Tamale, Ghana. Fresh post-rigor beef, longissmus dorsi loin from a matured Sanga bull (about 10 years old), butchered 24 hr after slaughtering was used. All fats and connective tissues were trimmed off the muscle.  The  muscle  was then cut  into  eight steaks  of equal length each  measuring  10 cm  long  with  an average  weight  of  373g.  The steaks were  vacuum packed  and  labeled  in  duplicates  as  Control A and B, T1A and T1B, T2A  and  T2B,  T3A  and  T3B. All samples, excluding the control were aged  at  a temperature of  2 ºC ± 2 ºC  for varying  time (days)  in a Fagor refrigerator (Talleras Raman, Spain) as follows: Samples T2 were aged for 5days, T3 were aged for 10days and T4 were aged for 15days. The control (T1) samples were frozen throughout the experimental period to prevent any enzymatic action. At the end of each period of ageing, the aged samples were also frozen to halt further ageing  All the samples were  then  thawed  for  12 hours  in a Fagor refrigerator (Talleras Raman, Spain) at  a  temperature  of  2 ± 2ºC  after  the  15th  day. The average room (ambient) temperature during the ageing period was 35 ±2 ºC.  

Microbiological analysis

Microbial  identification  and total viable count (TVC) was  determined  on  each  beef  steak  before  and  after ageing. The microbial load was obtained by swabbing the surface of the samples using sterile cotton wool. The swabbed microbes were inoculated unto separate  dishes  of  blood  agar  and  incubated  at  37ºC  for  24  hours  in  an  incubator. Cultures were made on blood agar media from various diluents and incubated separately. Gram  staining  technique  was  used  to  identify  the growth  of microorganisms  in  the  colonies. The  microbial  loads on  the  samples  were  determined and  expressed  in log10  colony  forming  units  per cm²  (cfu /cm²). 

Weight loss of samples

The beef steaks  were weighed  before  and  after  ageing  to  determine  the  differential  weight  loss  as  a  result  of shrinkage and  drip  loss  from the  steaks  during  the  ageing  periods.

Sensory analysis  

The samples were thawed and oven-grilled (Turbofan, Blue Seal oven, UK) to a core temperature of 70ºC for sensory assessment. The  grilled samples  were  trimmed  of  all  burnt  surfaces,  sliced  into  cubes  of  (2 cm3)  and  wrapped  with  coded  aluminum  foil  to  keep them  warm.  Fourteen  untrained  sensory  panelists  were  served  with  the  coded  beef  samples.  Pieces of bread were used as neutralizer between samples.  With  the  aid  of  questionnaires, the eating qualities  (tenderness, beef flavour, juiciness and abnormal flavour)  of  the  various  samples  were  determined  by  the  sensory  panelists  using a five-point category scale as follows:

  1. Tenderness: 1-Very tender, 2- Tender, 3- Intermediate, 4- Tough, 5- Very tough.
  2. Beef flavour: 1-Very strong, 2- Strong, 3- Intermediate, 4- Weak, 5- Very weak.
  3. Juiciness:      1- Very juicy, 2- Juicy,   3- Intermediate, 4- Dry,   5- Very dry.
  4. Abnormal flavour: 1- Very weak, 2-Weak, 3- Intermediate, 4-Strong, 5-Very strong.

Overall acceptance was also determined by the percentage of the panelists.

Statistical  analysis

The data generated were analysed  using a general lineal model (GLM) of analysis of variance (ANOVA) of MINITAB version 13.0 [23]. 

RESULTS

The ageing process had significant effects on most of the organoleptic qualities such as tenderness, beef flavour, juiciness and overall acceptability of the beef steaks but did not have any impact on abnormal flavour intensity in the beef steaks (Table 1). The tenderness of the beef steaks improved significantly with increasing time (days) of ageing (P < 0.001). Thus ageing for 10 to 15 days produced fairly tender steaks whilst the control steaks remained tough. There was a significant effect of ageing on juiciness of the beef steaks (P<0.001) (Table 1). The results demonstrated that the beef steaks became more juicy with increasing time of ageing.

The ageing process had significant (P< 0.01) effect on the beef flavour of the samples, such that beef flavour intensity increased gradually from day 5 and became strong by the day 15. Incidentally, the ageing process did not have any negative effect on the flavour of the samples. Hence, the intensity of abnormal beef flavor remained very weak in the samples throughout the trial. On overall acceptability, the panelists rated the control sample as the least preferred because it was considered to be tough and dry. Majority (70%) of the panelists indicated the samples aged for 10 to 15 days to be the best meat (Table 1).   

An average of 1.5 percent of the initial weights of the aged beef samples was recorded as drip and thaw loss after ageing. The control samples which were frozen throughout recorded the highest thaw/drip loss of 5 percent on thawing.

Microbiological quality

The  microbes  identified  on  all  the beef  steaks before ageing  included  Staphylococcus  spp  and  Escherichia  coli which were of identical quantities (4.7 × 10 cfu/cm2) (Table 2). The final microbial count showed marginal increases in their numbers with increasing ageing. Generally, the microbial loads recorded on the beef samples before ageing indicated that the level of contamination of the samples was very minimal.

DISCUSSION 

Eating qualities

The purpose of ageing or conditioning or "ripening" or refrigerated storage above freezing point of beef is simply to allow "natural processes" to improve its palatability attributes, mainly flavour, juiciness and tenderness. Whilst a muscle is undergoing changes associated with tenderness, chemical breakdown of certain muscle and fat constituents occurs, resulting in a more intense flavour and aroma [22]. In general, these changes in flavour and aroma are desirable to most consumers. However, undesirable flavours and aroma can develop during ageing, mainly due to the effects of microbial growth, rancidity of the fat and adsorption of off-odours if they are present in the chill room, which was not the case in this study.

The ageing process significantly improved two most important organoleptic qualities of meat namely tenderness and juiciness. This observation agrees with earlier reports that ageing improves meat tenderness [7,17, 24]. The tenderness obtained in this study due to ageing process indicates that there was some degree of degradation of some structural proteins by proteolytic enzymes (18, 19). The result indicated that there were increasing rates of tenderizing activities in the beef up to the 10th day but these activities might have decreased from the 10th and perhaps ceased at the 15th day. It has been reported that most of the advantages of ageing beef are achieved by the end of seven to 10 days of ageing [22].  The trend of the current results conforms to that of earlier reports [21,25], which indicate that tenderization is relatively rapid during the early stages (3 to 7 days) of ageing and continues to increase but at a much slower rate thereafter. During ageing, naturally  occurring  enzymes,  calpains  and  cathepsins  (proteases)  found  in muscle,  breakdown  specific  protein strands in the  muscle  fibre  in  a  process  called  proteolysis [18,19]. As meat ages, proteolysis is enhanced. The  calpain  proteolytic  enzyme  system  is  responsible  for  the  specific  peptide  bond  cleavage  which  causes  early  postmortem  tenderization [7].  The calpain system, the primary enzyme system responsible for the ageing process, is comprised of three primary components, µ-calpain, m-calpain and their inhibitor, calpastrin which are all calcium- dependent [25].The calpains undergo autolysis and as such they do not over- tenderize meat. The breaking or fragmentation of the myofibril protein strands by these natural enzymes result in improved tenderness [26]. Longer ageing periods, for instance beyond 28 days, result in little benefits to enhanced palatability and may be detrimental in terms of increased and unwanted microbial growth and abnormal flavour development[26].  

The flavour intensity obtained in this study agrees with a previous report stating that true beef flavour is fully developed at about 11 days of ageing and that cooked, un-aged beef lacks a typical beef flavour [17]. The weak abnormal flavour intensity in the samples could also be attributed to the vacuum packaging effect that prevented the meat from absorbing any flavour from the chiller and also eliminated oxidative rancidity. This finding supports an earlier report that “in the bag” ageing produces fewer off odours and off flavours in meat [17].

The  most  important  aspect  of  meat  eating  quality is  the  level  of  overall  eating satisfaction.  Eating satisfaction is a function of the  combined  effect  of  tenderness,  juiciness and flavour [5] obtained during this ageing process  thereby producing  very acceptable or palatable meat from the 10th to 15th day of ageing. Among the palatability attributes of beef, tenderness is the attribute most sought after by consumers and thus the need for ageing of beef to improve this attribute.

During the ageing process, weight loss should be expected. The weight loss is caused by dehydration of the lean and fat and can be at high proportions depending on relative humidity, air flow and the temperature in the ageing chamber. However, an additional advantage of “in the bag” ageing is reduced weight loss since moisture is retained in the bag and partly re-absorbed. The high percentage of drip lost in the control samples can be attributed to the continuous formation of ice crystal in the muscle fibres which then melt on thawing resulting in higher exudate [27]. The  plastic  packaging  does  not  allow  loss  of  moisture; instead the  meat  absorbs  this moisture    resulting in  an  increased  juiciness  and  tenderness[28].

Microbiological quality

When spoilage bacterial population reaches 10 million per gram of a food substance it will begin to produce chemical changes that are apparent to the senses [29]. The low levels of initial contamination of the samples used in this study facilitated the production of good quality meat by the end of the ageing process. The disappearance of the Staphylococcus spp was due to lack of favourable conditions (air and ideal temperature) during the ageing period. The E. coli survived because they are psychrophilic and could withstand the ageing temperatures.Meat is described as “spoiled” when bacterial count or load is more than 107/cm2 or 108/g [30] and meat will, therefore ,‘spoil’ when the TVC value goes beyond 106/cm2 because of off-odours which start to develop at approximately 107 -108 organisms cm-2 [7].The final microbial loads recorded on the samples in this study were within the marginal limits such that they will not cause spoilage of the products or harm the consumer [7, 30]. It also indicates that there was no loss of vacuum, whereby the air present in the bag,  surrounding the meat, will enhance the growth of aerobic microorganisms and cause rapid spoilage [22].

CONCLUSION  

The problem of toughness in beef from old animals in tropical countries can be reduced considerably through the practice of ageing or conditioning. Ageing will make tropical tough beef tender and juicy with enhanced beef flavour thereby improving its eating qualities. A high standard of meat hygiene is a prerequisite for ensuring that eating qualities of beef are not compromised during ageing.Packaging of the meat in polythene bags could be practiced at homes and restaurants in the tropics as this reduces or prevents contamination of the meat and weight loss during ageing. Beef can, therefore, be successfully aged in a vacuum bag under tropical conditions. At a temperature range of   2°C ± 2°C, beef should be aged for at least 10 days and not longer than 15 days for desirable eating qualities. Before ageing, all visible fat attached to the meat should be trimmed off to prevent rancidity.

REFERENCES

  1. Hill D Cattle and buffalo meat production in the tropics. ELBS edition.1990:  201 – 202.
  2. FASDEP. Food and Agriculture Sector Development Policy. Ministry of Food and Agriculture, Ghana document. 2002: 58.
  3. Salifu S and GA Teye The contribution of the various ruminant species to meat production in Tamale Metropolis. The savanna Farmer. (ACDEP) 2006; 7: (12) 34–39.
  4. Teye G A and RK Beyuo Assessment of condition of cattle slaughtered at the Tamale abattoir and the quality of their beef. Proceeding of the 25th Ghana Animal Science Association Symposium, held at the Kwame Nkrumah University of Science and Technology (KNUST), Kumasi from the 4th - 7th October 2000.
  5. Jones MSD The influence of carcass composition on meat quality. In: Quality and Grading of  Carcass  of  Meat  Animals. 1995; 6: 132 – 147.
  6. Kennedy JF Biotechnology: Enzyme  Technology. 1987; 7a. 586 -587.
  7. Warriss PW Postmortem changes in muscles and its convection into meat  In: Meat  science,An introductory   text. CABI Publishing 2001: 100– 161.
  8. Cunningham D Cooking Science and Technology. Academic Press. UDA: New York., 1998: 354-359.
  9. Carse WA Meat quality and acceleration of post-mortem glycolysis by electrical stimulation. Journal of Food Technology. 1973; 8: 163-166.
  10. Chrystall BB and CJ Hagyard Electrical stimulation and lamb tenderness. New Zealand Journal of Agricultural Research. 1976; 19: 7-11.
  11. Crouse D, Koohmaraie M and SD Seideman The relationship of muscle fibre size to tenderness of beef. Meat Science. 1991; 30: 295-302.
  12. Dransfield E Tenderness of meat, poultry and fish. In: Pearson, AM and Dutson, TR edn. Quality Attributes and their Measurement in meat, Poultry and Fish Products. Blackie Academic and Professional (Chapman and Hall), London.1994b: 289-315.
  13. Lawrie RA Lawrie Meat Science. 6thedn. England: Woodhead Publishing Ltd. UK.1998: 43-48.
  14. Wood JD, Brown SN, Nute GR, Whittington FM, Perry AM, Johnson SP and M Enser Effect of breed, feed level and conditioning time on the tenderness of pork. Meat Science. 1996;  44: 105 – 112.
  15. Taylor SA Improving tenderness by electrical stimulation or hip suspension. In: Taylor SA, Raimundo A, Severini M and Smulders FJM edn Meat Quality and Meat Packaging. ECCEAMST, Utrecht, 1996b: 89-105.
  16. Aberle DE, Forrest CJ, Gerrard ED and WE Mills Principles of Meat Science. 4th edn. USA: Kendall/Hunt. Publishing Company, 2001; 178-226.
  17. Epley RJ Ageing beef. Animal science. Found at http:// www.extension.umn.edu// distribution /nutrition /DJ5968.html, Accessed on September 30th  2007.
  18. Davey CL and RJC Winger  Muscle of meat, Biochemical aspect. In: Meat Science, Technology. Ed. Cross H.R. and Overby A.J. Elsevier Science. Amsterdam 1988: 3 -29.
  19. Lawrie RA The eating quality of meat. In: Meat Science. 5th edition Pergamon  press, 1991:  184-223.
  20. Naveena BM and SK Mendiratta. Tenderization of spent hen meat using ginger extract. British Poultry Science. 2001; 334.
  21. Field RA and CC Kaltenback. Ageing Big Game. 2007. Found at www.theoutdoor.com/ features/articles/wild_ game/ageing_ big game.html Accessed on September 30th  2007.
  22. Hedrick HB, Stringer WC and A Clarke Recommendations for Aging Beef.1993. Found at http://extension.missouri.edu/xplor/agguides/ansci/g02209.htm. Accessed on April 15th 2009.
  23. Minitab Minitab Statistical software, Release 13 for Widows95/98/2000 and Windows NT. Minitab Inc, USA 2000.
  24. Peckham GC and JH Freeland-Graves Preparation of foods and food products. In: Foundation of Food Preparation. 4th edition MacMillan. 1979: 333.
  25. Goll DE, Tompson VF, Li H, Wei W and J Cong The calpain system. Physiology. Review 2003; 83:731-801.
  26. Parrish FC Ageing beef. 2007 Found at http:/www.goodcooking.com/ steaks/ ageing/ ageing.html.  Accessed on September 30th 2007.
  27. Pearson AM and TR Dutson Growth regulation in farm animals Advances in Meat Research. 1991; 7: 521 – 530.
  28. Forrest J Meat Quality and Safety.2007 Found at http: //ag.ansc.purdue.edu/meat _quality/ ageing_ meat. Html. Accessed on 30 / 9 / 2007.
  29. Pyke M Meat, fish and poultry. In:  Food Science and Technology.  4th  edition John Murry. London. 1981: 86 -89.
  30. FAO. General hygiene rules for facilities, equipment and personnel in meat  industries. In: Guideline for slaughtering, meat cutting and further processing.  Animal Production and Health Paper. Rome, Italy.  1991; 91: 1 - 43.

© Copyright 2009 - Rural Outreach Program


The following images related to this document are available:

Photo images

[nd09111t2.jpg] [nd09111t1.jpg]
Home Faq Resources Email Bioline
© Bioline International, 1989 - 2019, Site last up-dated on 02-May-2019.
Site created and maintained by the Reference Center on Environmental Information, CRIA, Brazil
System hosted by the Internet Data Center of Rede Nacional de Ensino e Pesquisa, RNP, Brazil