Effects of Freeze Thawing on the Oxygenation Properties of Dark Cutting Beef

Transcription

1 Effects of Freeze Thawing on the Oxygenation Properties of Dark Cutting Beef ANDREA ENGLISH OKLAHOMA STATE UNIVERSITY INTRODUCTION Meat purchasing decisions are influenced by color more than any other quality factor (Smith et al., 2000) 68 th RECIPROCAL MEAT CONFERENCE INTRODUCTION ECONOMIC IMPACT Dark is unappealing to consumers and the high ph allows spoilage bacteria to grow readily (Tarrant, 1989) ( The NBQA in 2011 reported that 3.2% of carcasses assessed were dark cutting According to the 2000 NBQA, dark resulted in a $240 USD discount per carcass Dark costs the industry an estimated $5.81 USD per head Canada has a yearly loss of $1.4 million in dark (Wulf, 1998) Annual loss of $35 million to the Australian Beef Industry (Cooperative Research Centre CRC, 2012) FACTORS RESPONSIBLE FOR DARK CUTTING BEEF Increased stress conditions EFFECT OF ELEVATED PH ON MEAT QUALITY Elevated Meat ph Less glycogen in muscle Less lactic acid formation Elevated muscle ph 1. Water holding capacity (WHC) Light reflectance of meat 2. Increased mitochondrial activity Oxygen consumption 1

2 1. EFFECT OF PH ON REFLECTANCE PROPERTY 1. EFFECT OF PH ON REFLECTANCE PROPERTY Increased ph leads to swelling of muscle fibers Less water between muscle bundles Less reflectance of light Darker color Dark, 10x Normal ph beef, 10x Cross section of muscle bundles Dark, 20x Normal ph beef, 20x Cross section of muscle bundles 2. EFFECT OF PHON MITOCHONDRIA Mitochondria outcompete myoglobin Competition for O 2 Oxygen available to myoglobin EFFECTS OF ELEVATED PH ON MEAT QUALITY Elevated Meat ph Oxygen consumption decreases initial red color development when mitochondria outcompetes myoglobin for oxygen Myoglobin then remains in a deoxy-state resulting in a dark colored muscle (Ledward, 1992) 1.Water holding capacity (WHC) 2. Increased mitochondrial activity HYPOTHESIS Altering the mitochondrial function and muscle structure will improve the oxygenation properties of dark OBJECTIVES 1. To determine the effects of extended aging on biochemical properties of dark 2. To evaluate the effects of aging and freeze thawing on oxygenation properties of dark 2

3 Myoglobin concentration (mm) % Oxygen consumption 6/25/2015 OBJECTIVE 1 EFFECTS OF EXTENDED AGING ON BIOCHEMICAL PROPERTIES OF DARK CUTTING BEEF Normal ph, n=10 Dark cutters, n=10 Aging Periods: 0 d 16 d 38 d 58 d Upon aging sections were sliced into 2.5-cm thick steaks and used for further analysis Myoglobin was measured at absorbance 525 nm (AMSA, 2012) Mitochondria activity was measured using quantitative real-time PCR Oxygen consumption rate was measured. Greater oxygen consumption indicates greater mitochondrial activity STATISTIC ANALYSIS Data were analyzed using the mixed procedure of SAS A split plot design with repeated measure Least squares means were separated using the PDIFF option (P<0.05) in SAS Normal ph Myoglobin and mitochondrial content of dark cutting and normal ph beef 9 Mitochondrial content was 2.04 b 8 fold greater in dark 7 than normal ph. 6 a Dark cutting ab Different superscripts indicate significant differences (P<0.05). % Oxygen consumption rate during extended aging of 90 normal ph and dark b Control Dark 80 a SEM = 3.0 ; P < d 60 d c c d 38 d 58 d abcd Different superscripts indicate significant differences (P<0.05) across aging periods. 3

4 CONCLUSION Extended aging can improve the color intensity (redness) of dark cutting steaks Extended aging can decrease oxygen consumption and limit mitochondrial activity OBJECTIVE 2 EVALUATE THE EFFECTS OF FREEZE THAWING ON OXYGENATION PROPERTIES OF DARK CUTTING BEEF FREEZE THAWING Research has shown that freeze thawing can decrease mitochondrial function Freeze thawing also increases the damage to the muscle structure Limited research has determined the effects of freeze thawing on myoglobin oxygenation of dark 2.5-cm thick steak without freeze thawing 58 d aging at 2 C Normal ph, n=10 Dark cutters, n=10 5-cm thick steak for 3 freeze thawing cycles Steaks were frozen at -20 C and thawed in a controlled 15 C water bath, sliced and allowed to bloom for 120 min PVC Packaging Polyvinyl Chloride Overwrap Surface color was measured Using a HunterLab miniscan spectrophotometer Bloom was measured at 0, 15,, 60, 90 and 120 min STATISTICAL ANALYSIS Data were analyzed using the mixed procedure of SAS A split plot design with repeated measure Least squares means were separated using the PDIFF option (P<0.05) in SAS 4

5 a* value (redness) % Oxymyoglobin 6/25/ a,x d,x min a,x SEM = 1.20 c,y cb,z b,z c,y bc,y b,y Control Dark Dark Freeze LSM within a treatment with different letters (a-d) are different (P<0.05). LSM comparison at a specific bloom time across muscle type with different letters (x-z) are different (P<0.05). a,x a,x f,x e,x d,x min b,z b,z SEM = 3.20 c,z d,z d,z b,y b,y c,yc,y Control Dark Dark Freeze LSM within a treatment with different letters (a-f) are different (P<0.05). LSM comparison at a specific bloom time across muscle type with different letters (x-z) are different (P<0.05). d,y CONCLUSION Freeze thawing QUESTIONS Disrupts mitochondrial membrane Limiting mitochondrial activity Increasing blooming properties of dark ANDREA ENGLISH OKLAHOMA STATE UNIVERSITY andrea.english@okstate.edu