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MATERIALS AND METHODS
The baby foods tested were from the Chill Baby Fresh Organic Food range namely Smashing Sweet Potato (SSP), Cheeky Chickpea (CC), and Crazy Chicken Hotpot (CCH). The foods were tested in their raw form and following microwave-cooking and boiling, as per manufacturer’s instructions. All work was conducted in an amber laboratory to minimise photodecomposition of the carotenoids. Raw, microwave- and hob-cooked samples were accurately weighed (2 g) and homogenized in 5 ml HBSS. A simulated human in vitro digestion model was performed by the method of Garrett et al.8 with minor modifications9. Five millilitres of the resultant digesta were frozen at -80°C until analysis. The remainder of the digesta was ultracentrifuged at 223,680 g (NVT90 rotor, Beckmann instruments) for 95 min to isolate the micelle (aqueous) fraction. Samples were extracted and carotenoid content was determined by HPLC as previously described9. Efficiency of micellarisation is expressed as a percentage of carotenoid transfer from digesta to the micelles.
SSP had the greatest total carotenoid content (2.8 mg/100g) compared with CC (1.2 mg/100g) and CCH (0.8 mg/100g). Both the CC and CCH meals did not contain any detectable amounts of lycopene. Micellarisation of the carotenes (-carotene and lycopene) was greatest (P<0.01) from the SSP meal (79% and 56%, respectively) compared with the CC and CCH foods (0 – 33%). On the other hand, the transfer of xanthophyll carotenoids (zeaxanthin and lutein) was highest (P<0.01) from CCH with levels of 95% and 40%, respectively. Although cooking enhanced the -carotene and lutein content of micelles from the SSP meal, the effects were not significant. Therefore, cooking the baby foods by hob or microwave did not significantly affect carotenoid micellarisation.
Carotenoid micellarisation ranged from 0 - 99% depending on the meal, carotenoid, and the cooking method tested. The presence of meat in CCH may have affected carotenoid micellarisation from this food. Likewise, the fact that CC and SSP are purely vegetable-based may have influenced the micellarisation of carotenoids from these baby foods. Therefore, carotenoid content and micellarisation from baby foods was more than likely influenced by the different types and amounts of ingredients used to prepare each product.
This research was funded by Science Foundation Ireland as a Science Teachers Research Assistance (STAR) 2008 programme under the PI Award 04/IN3/B509.
PHYSIOCHEMICAL AND MICROBIOLOICAL CHANGES IN HIGH-PRESSURE PROCESSED CHICKEN BREAST MUSCLE DURING CHILLED STORAGE
E.E. Forde, M. Cruz-Romero and J.P. Kerry
Department of Food & Nutritional Sciences, University College Cork, Cork
Microbiological and physicochemical changes in vacuum packaged (VP) chicken breast high-pressure (HP) treated at 300, 400 or 600 MPa for 5, 15 or 30 min and stored at 4°C for up to 21 days, were investigated and compared to changes in untreated chicken breast. After HP treatment, chicken breast had significantly (P < 0.05) higher pH, cooking loss, lipid oxidation (TBARS), Warner-Bratzler (WB) shear force and CIE L*, a* and b* values compared to untreated samples; the values were dependant on the pressure and length of the treatment applied. During storage, the TBARS and WB shear force increased significantly (P < 0.05) in samples HP-treated at 400 or 600 MPa and the increase of these parameters were dependant on the length of treatment. HP treatment reduced the microbiological load to below the detection limit and delayed subsequent microbial growth compared to untreated samples. From a microbiological point of view HP treatment at 600 MPa can increase the shelf-life of chicken breast meat further than 21 days, but this pressure adversely affected the physicochemical (TBARS and texture) and sensory quality parameters. HP treatment, in combination with adequate chilled storage, can extend the shelf-life and increase the safety of chicken muscle.
HP technology is gaining importance in the food industry because of its ability to inactivate microorganisms and enzymes at ambient or low temperatures, without affecting flavour, colour, and nutritional constituents of food. The objectives of this study were to investigate the microbiological and physicochemical changes in chicken breast HP-treated and stored vacuum-packed under chilled conditions (4°C) and compared to untreated samples.
MATERIALS AND METHODS
Chicken breasts were packed individually into vacuum pouches and vacuum-sealed. Samples were placed in a second vacuum pouch, to which 100 ml of water was added, and this pouch was again vacuum-sealed. Packaged samples were then HP-treated at 300, 400 or 600 MPa at 20°C for 5, 15 or 30 min in an Iso-Lab 900 Power High Pressure Food Processor (Stansted Fluid Power Ltd., Stansted, UK) and one lot was left untreated. Microbiological and physicochemical analyses were carried out every 7 days. The following analyses were performed during storage of untreated and HP-treated chicken breast: cook loss1, WB shear force1 (TA-XT2i, Stable Micro Systems, Golaming, UK) and lipid oxidation2 using the 2-thiobarbituric acid (TBA) test and expressed as mg malonaldehyde/kg of chicken breast. Composition and pH measurements of the chicken breast were carried out according to AOAC methods3. CIE L*, a* and b* values (lightness, redness and yellowness respectively) of the chicken were measured using a Minolta CR-300. Total viable counts in HP-treated and untreated chicken breasts were determined using a spread plate technique on plate count agar (Merck, Germany). Microbial counts were expressed as colony-forming units (CFU)/g of chicken meat.
Results and Discussion
HP-treatment showed significantly decreased moisture content (P < 0.05) compared to untreated chicken. During storage, WB shear force values and the TBARS increased significantly (P < 0.05) in samples HP-treated at 400 or 600 MPa and the increase of these parameters were dependant on the length of treatment. After HP treatment, chicken breast had significantly (P < 0.05) higher pH and cooking loss. Significant increases (P < 0.05) were seen in CIE L*, a* and b* values compared to untreated samples with the values being dependant on the pressure and length of the treatment applied. Fresh chicken breasts are generally considered of good quality when TVC < 5 x 105 CFU/g, hence, the limit of acceptability was set at this value. HP treatment reduced the microbiological load to below the detection limit and delayed subsequent microbial growth compared to untreated samples. HP treatment at 600 MPa increased the shelf-life of chicken breast further than 21 days, but this pressure adversely affected the physicochemical (TBARS and texture) and sensory quality parameters.
HP-treatment increased the WB shear-force and the cook loss of the chicken breasts compared to untreated chicken. HP-treatment resulted in increased L*, a* and b* values in the chicken breasts. The lipid oxidation and pH values of the chicken increased, with increasing treatment time and pressure. Immediately after HP-treatment, the bacterial load was reduced to below the detection limit and the subsequent microbial growth was delayed. HP can extend the shelf life of chicken breast meat further than 21 days but the quality attributes such as lipid oxidation and texture (WB shear force) of the chicken were affected significantly.
This project is funded by the Irish Government under the National Development Plan 2000-2006.
1Honikel, K.O. (1998). Reference Methods for the Assessment of Physical Characteristics of Meat. Meat Science 49, 447-457.
2Siu, G.M. and Draper, H.H. (1978). A survey of the malonaldehyde content of retail meats and fish. Journal of Food Science 43, 1147-1149.
3AOAC. (1999). Official methods of analysis of AOAC international. P, Cunniff, 16th edition, 5th revision. Maryland: AOAC International
THE EFFECT OF MECHANICAL DAMAGE ON THE KINETICS OF PPO ACTIVITY AND CORRELATION WITH HYPERSPECTRAL IMAGING
E. Gaston1, J.M.Frias1, P.J. Cullen1, A. A. Gowen2, M. Taghizadeh2 and C.P. O’Donnell 2
1 School of Food Science and Environmental Health, Dublin Institute of Technology, Dublin
2 Biosystems Engineering, University College Dublin, Dublin
Rough handling of crops may accelerate mushroom browning, largely mediated by polyphenol oxidases (PPO). Hyperspectral imaging (HSI) has been proven a useful tool to study mushroom quality deterioration. Agaricus bisporus mushrooms were damaged by using a shaking table and stored at 5°C and 10°C. Hyperspectral images of mushroom caps were obtained in the wavelength range of 400-1000 nm. Mushroom pericarps were used to obtain enzyme extracts. PPO activity was measured by following the oxidation rate of catechol at 410 nm. Results suggested that damage induces an increase in PPO activity, not immediately after damage but at a later stage during storage. Enzyme activity and HSI data were correlated using partial least squares regression (PLSR) and random forest (RF) models. It was found that the log of PPO activity could be reasonably predicted using a 10-component PLSR model (r2 = 0.89). Random forest models analysis identified a band between 410-430 nm as the most relevant to describe PPO activity. This work demonstrates that the activity of browning enzymes is affected by mechanical damage and may be correlated to HSI results.
Horticultural products such as mushrooms are subjected to external mechanical forces during crop picking and transport practices. Rough handling and distribution may initiate browning by protease mediated activation of extracellular PPO1, a common and economically detrimental phenomenon in the mushroom industry. Enzymatic browning is a consequence of the oxidation of phenolic compounds into quinones, which is largely mediated by polyphenol oxidases2. Hyperspectral imaging is an emerging technology that integrates conventional imaging and spectroscopy to attain both spatial and spectral information from an object. HSI has recently been proven to be a useful tool to study mushroom quality deterioration3. The objectives of this work were to evaluate the effect of mechanical damage on mushroom tyrosinase kinetics and to investigate the potential use of HSI to predict PPO activity on the mushroom pericarp.
MATERIALS AND METHODS
Agaricus bisporus mushrooms were grown under controlled conditions at Teagasc Research Station, Kinsealy, Ireland. Mechanical damage of the mushrooms was induced by a shaking table at controlled amplitude and time: different shaking times led to different damage levels. Mushrooms were stored at 5°C and 10°C. Hyperspectral images of mushroom caps were obtained using a pushbroom line-scanning HSI instrument, operating in the wavelength range of 400-1000nm with a resolution of 5 nm. Average reflectance spectrum (R) was obtained from an area of 100×100 pixels on each mushroom cap. PPO activity was measured spectrophotometrically by a modified method based on that of Galeazzi et al4. Mushroom pericarps were used to obtain enzyme extracts. PPO activity was measured by following the oxidation rate of catechol at 410 nm. The slope of the straight-line section of the activity curve was used to express the enzyme activity. Data was collected for undamaged (U) and two groups of damaged (D10min, D20min) mushrooms on days 0,1,2,3 and 6 after damage. Multivariate data analysis was performed using R 2.8.0 (www.r-project.org). All test of significance were performed at p<0.05 unless otherwise stated.
RESULTS AND DISCUSSION
ANOVA of the factors (Day, Damage) and their interactions (Day*Damage, Day*Temperature, Day*Damage*Temperature) showed that damage and storage temperature influenced PPO kinetics. Moreover, damage influenced PPO kinetics differently depending on the storage temperature. TUKEY test and pairwise comparisons among factor levels showed that PPO activity of undamaged mushrooms did not vary over the storage time (p>0.05). PPO kinetics of U and D samples were significantly different, but D10min and D20min kinetics did not differ significantly (p>0.05). Partial Least Squares models were built using leave-one-out cross validation to investigate the correlation between HSI data and PPO activity. A 10-component PLSR model correlated log (PPO Activity) and log (1/R) resulting in R2 of 0.89 and RMSEP of 0.27 logs. Random forest models were built with the same purpose and explained 82% variance. RF identified a band between 410-430 nm as the most influential wavelengths for the prediction of PPO activity in the mushroom pericarp.
Mechanical damage resulting from inappropriate handling of crops generated an increase of polyphenol oxidase activity on mushroom caps, not immediately after the injury but at a later stage during storage. Storage temperature was an important variable to control in order to prevent browning development on mushroom caps. PPO activity and HSI data showed a strong correlation. Further research could contribute to assess the potential of HSI systems to predict PPO activity of horticultural products.
This project was funded by the Government Department of Agriculture and Food under the Food Institutional Research measure (FIRM, project code 6RDDIT487). The authors would like to thank Helen Grogan and Ted Cormican from the Teagasc Research Station at Kinsealy, Ireland, for production of mushrooms and advice.
1 Burton, K.S. (2004) Cultural factors affecting mushroom quality – cause and control of bruising. Science and Cultivation of Edible and Medicinal Fungi, 397-402.
2 Jolivet, S., Arpin, N., Wichers, H. J. and Pellon, G. (1998). Agaricus bisporus browning: a review. Mycological Research 102 (12), 1459-1483.
3 Gowen, A. A., O’Donnell, C.P., Taghizadeh, M., Gaston, E., O’Gorman, A., Cullen, P.J., Frias, J.M., Esquerre, C. and Downey, G. (2008). Hyperspectral imaging for the investigation of the quality deterioration in sliced mushroom (Agaricus bisporus) during storage. Sensing and Instrumentation for Food Quality and Safety 2 (3), 131-143.
4 Galeazzi, M. A. M., Sgarbieri, V. and Costantinides, S. M. 1981. Isolation, purification and physiochemical characterization of polyphenol oxidase from a dwarf variety of banana (Musa cavendishii L.). Journal of Food Science, 46(1), 150-155.
EXAMINATION OF COMMERCIAL PROTEOLYTIC ENZYMES FOR THE PRODUCTION OF BOVINE PROTEIN HYDROLYSATES.
P. Harnedy1, R. Di Bernardini1, D. Bolton1, J. Kerry2 and A.M. Mullen1
1 Ashtown Food Research Centre, Teagasc, Ashtown Dublin 15.
2 Department of Food & Nutritional Sciences, University College Cork, Cork
During the normal post-mortem aging process, proteolytic degradation of meat proteins by endogenous muscle proteases result in the formation of smaller proteins and polypeptides. Proteolytic degradation of meat proteins using exogenous enzymes can also yield protein fragments of varying size and diverse functional properties. Many studies have demonstrated that enzymatic hydrolysis of proteins can have an affect on their bioactive, sensory and functional properties. The objective of this study was to validate protein hydrolysis methods for the generation of bovine liver, lung and brisket sarcoplasmic/cytoplasmic protein hydrolysates utilising two selected commercial enzymes. One-dimensional gel electrophoresis profiles of each of the hydrolysed protein fractions showed the proteolytic breakdown and formation of protein fragments/polypeptides at different time points, with good reproducibility observed between gels. MALDI ToF mass spectrometry results in addition to identifying the size of the low molecular weight peptides (<5kDa) produced showed that the peptides in this region were reproducibly generated.
Enzymatic hydrolysis of food proteins have been shown to improve the physicochemical, functional, sensory and bioactive properties of the native protein without affecting its nutritive value1, 2. Bioactive peptides are peptides that in addition to their nutritional value exert a physiological effect in the body. A wide range of activities have been described, including antihypertensive, antioxidant, antimicrobial, antithrombotic, immuno or cytomodulatory and mineral binding. Moreover, some of these peptides exhibit multifunctional properties3. Post-mortem proteolytic degradation of muscle proteins by endogenous proteolytic enzymes results in the creation of smaller protein and polypeptide fragments, which in turn are degraded to smaller peptides4. Meat protein hydrolysates can also be produced by microbial fermentation or utilizing commercial proteolytic enzymes from plant, animal or microbial sources or combinations thereof. Proteolysis simulation programs, such as Biopep and ExPASy, are available for the prediction of potential cleavage sites cleaved by protease in a given protein sequence5, 6. Using this information it is possible to select enzymes that potentially would deliver bioactive peptides of interest. The objective of this study was to validate protein hydrolysis methods for the generation of bovine protein hydrolysates, using one-dimensional gel electrophoresis in conjunction with MALDI ToF mass spectrometry.
MATERIALS AND METHODS
All bovine muscle and organ tissue, brisket (two aged time periods), lung and liver were obtained from the abattoir (Meat Industrial Development Unit) at Ashtown Food Research Centre, Teagasc. Extraction of sarcoplasmic/cytoplasmic protein fractions from all tissue samples was carried out in accordance with the method of Jang and Lee7. The protein content and profiles of each fraction was determined by the Bradford protein assay kit (Bio-Rad) and one dimensional gel electrophoresis respectively. Two commercial enzymes were selected and each protein fraction was incubated with each enzyme separately for seven different time periods. One-dimensional gel electrophoresis was used to monitor the progress and repeatability of each enzymatic hydrolysis. Selected hydrolysates were further analysed by MALDI ToF mass spectrometry.
RESULTS AND DISCUSSION
One-dimensional gel electrophoresis profiles of resultant protein hydrolysates illustrated the enzymatic degradation and formation of protein fragments/polypeptides at different time points for each of the tissue protein types, with good reproducibility observed between gels. Comparison of the two enzyme proteolytic profiles for each of the tissue type protein fractions demonstrated that in some cases the same parent protein was the target of enzymatic hydrolysis while in more cases different proteins were hydrolysed. MALDI ToF mass spectrometry provided information on the occurrence of peptides in the region <5kDa, the region below the detectable level of one–dimensional gel electrophoresis. In addition to supplying data on the size of the peptides formed and degraded, MALDI ToF mass spectrometry illustrated the repeatability of the hydrolysis method.
These findings in addition to providing validated protein hydrolysis methods for the generation of beef protein hydrolysates also supplied important information regarding the size of protein fragments and peptides created as a result of enzymatic bovine protein hydrolysis, information that is essential for the production of protein hydrolysates with desired sensory, functional or bioactive properties.
Funding for this research was provided under the National Development Plan, through the Food Institutional Research Measure, administered by the Department of Agriculture, Fisheries & Food, Ireland.
1 Arihara, K. (2006) Meat Science 74: 219-229.
2 FitzGerald, R.J. and O'Cuinn, G. (2006) Biotechnology Advances 24: 234-237.
3 Meisel, H. (2004) Biofactor 21: 55-61
4 Bauchart, C., Rédmond, D., Chambon, C., Patureau Mirand, P., Savary-Auzeloux, I.
Reynes, C. and Morzel, M. (2006) Meat Science 74: 658-666
5 Dziuba, J., Iwaniak, A. and Niklewicz, M. (2003) Database of protein and bioactive
peptide sequences - BIOPEP http://www.uwm.edu.pl/biochemia.
6 ExPASy peptide cutter program: http://www.expasy.org/tools/peptidecutter/
7 Jang, A. and Lee, M. (2005) Meat Science 69: 653-661
Antioxidant activity studies of lutein, sesamol, ellagic acid and olive leaf extract
J. Hayes1, P. Allen1, V. Stepanyan1, J. Kerry2
1Ashtown Food Research Centre, Teagasc, Ashtown, Dublin 15, Ireland.
2Department of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
This study was conducted to investigate lutein, sesamol, ellagic acid and olive leaf extract for their scavenging activities against DPPH• (using diphenyl-p-picrylhydrazyl radical), ABTS•+ (2, 2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid diammonium salt radical), oxygen radicals (ORAC), chelating activity of Fe2+, antioxidant activity evaluated by β-carotene bleaching and ferric reducing antioxidant power (FRAP) and their correlations for used standards with these methods (gallic acid, Trolox, ascorbic acid, EDTA and ferrous sulphate). Inhibition of autooxidation of linoleic acid (β-carotene bleaching) in the presence of the plant extracts was in the order of ellagic acid>sesamol>lutein>olive leaf extract. Ellagic acid and sesamol had the highest ferric reducing antioxidant power and oxygen radical absorbance capacity. Sesamol, ellagic acid and olive leaf extract were the most active antiradical scavengers against DPPH· and ABTS•+ with scavenging activity in the order of ellagic acid>sesamol>olive leaf extract>lutein. None of the nutraceuticals possessed any chelating activity against Fe2+. All of the tests proved that all of the chosen nutraceuticals exhibited different levels of antioxidant potency and showed variation in different tests.
Lutein is a carotenoid found in green leafy vegetables such as spinach and is known to protect the eye’s retina from light-initiated oxidative damage. Ellagic acid a phenolic antioxidant found in numerous fruits such as raspberries and strawberries and has a variety of biologic activities, including potent antioxidant, anticancer and anti-inflammatory activities. Sesamol is a phenol which exhibits anticarcinogenic activity and helps inhibit atherosclerosis. Olive leaf extract is a phenolic compound derived from olive leaves known to have anti-oxidative and anti-inflammatory properties and protect low density lipoprotein from oxidation. Testing the activity by more than one assay is desirable because different methods measure different characteristics of the antioxidant. Therefore, this study was conducted to investigate lutein, sesamol ellagic acid and olive leaf extract for their scavenging activities against HO•, DPPH•, ABTS•+, and oxygen radicals, chelating activity of Fe2+, total phenolic contents and antioxidant activity, evaluated by β-carotene bleaching and ferric reducing antioxidant power.
MATERIALS AND METHODS
Fe2+ chelating activity: measured by the ferrous iron-ferrozine complex method1.
Free radical scavenging activity: measured with DPPH free radical using the method of Yen & Wu,2. IC50 value denotes the concentration of samples required to scavenge 50% of DPPH radicals. Degradation rate of β-carotene/linoleic acid emulsion: measured using method of Emmons, et al., 3. Total antioxidant status (TAS): measured by degree of suppression of ABTS•+ radical cation produced by reaction of ABTS·+ (2,2’-Azino-di-[3-ethylbenzthiazoline sulphonate]) with peroxidise(metmyoglobin) and hydrogen peroxide as described by Miller et al, 4. Oxygen radical absorbance capacity (ORAC): measured by inhibition of the peroxyl-radical-induced oxidation initiated by thermal decomposition of [2,2’-azobis(2-amidino-propane) dihydrochloride (AAPH)], a biological relevant radical source5. Ferric reducing antioxidant power (FRAP): Adjusted from Stratil, et al.,6. The results were corrected for dilution and expressed in μM trolox per 100 g dry weight (dw). Statistical analysis: All tests were carried out in triplicate and the results were presented as means ± SD. Analysis of variance (ANOVA) was carried out using GenStat Release (10.1) Copyright 2007, Lawes Agricultural Trust (Rothamsted Experimental Station). Analysis of variance was performed by ANOVA procedures (SAS 9.0 for Windows).
Results and Discussion
Lutein, sesamol, ellagic acid and olive leaf extract showed no chelating ability against Fe2+. The percentage autooxidation of linoleic acid was significantly reduced in presence of ellagic acid and sesamol. Sesamol, ellagic acid and olive leaf extract showed strong scavenging effect of up to 90% against DPPH free radical. The strongest radical scavengers based on IC50 were in the order of: ellagic acid > sesamol > olive leaf extract > lutein. Antioxidant potency for FRAP & ORAC followed the order of: ellagic acid > sesamol > olive leaf extract > lutein. Antioxidant efficacy for TAS was in the order of: ellagic acid > sesamol > olive leaf extract > lutein.
This research indicates that lutein, sesamol, ellagic acid and olive leaf extract may serve as potential dietary sources of natural antioxidants for improving human nutrition and health.
This project is funded by the Food Institutional Research Measure (FIRM) as part of the Irish National Development Plan.
1Yen, G. C. and J. Y. Wu (1999). Antioxidant and radical scavenging properties of extracts from Ganoderma tsugae. Food Chemistry, 65, 375-379.
2Decker, E. A. and B. Welch (1990). Role of ferritin as a lipid oxidation catalyst in muscle food. Journal of Agriculture and Food Chemistry, 38, 674-677.
3Emmons, C.L., Peterson, D.M., and Paul, G.L. (1999). Antioxidant capacity of oat (Avena Sativa L.) extracts. Journal of Agricultural and Food Chemistry, 47, 4894-4898.
4Miller, N.J., Rice-Evans, C., Davies, M.J., Gopinathan, V. and Milner, A. (1993). A novel method for measuring antioxidant capacity and its application to monitoring the antioxidant status in neonates. Clinical Science, 84, 407-412.
5Prior, R. L., Hoang, H., Gu, L., Wu, X., Bacchiocca, M., Howard, L., Hampsch – Woodill, M., Huang, D., Ou, B. & Jacob, R. (2003). Assays for hydrophilic and lipophilic antioxidant capacity (oxygen radical absorbance capacity (ORACFL) of plasma and other biological food samples. J. Agric. Food Chem, 51, 3273-3279.
6Stratil, P., B. Klejdus & Kubán, V. (2006). Determination of total content of phenolic compounds and their antioxidant activity in vegetables - Evaluation of spectrophotometric methods. J. Agric. Food Chem, 54, 607-616.
The effect of plant extracts on colour and lipid stability in model porcine muscle systems
J. Hayes1, P. Allen1, V. Stepanyan1, E. Ryan2, M. O’Grady2, J. Kerry2, N. O’Brien2
1Ashtown Food Research Centre, Teagasc, Ashtown, Dublin 15, Ireland.
2Department of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
This study was carried out to investigate the influence of selected plant extracts, lutein (L), sesamol (S), ellagic acid (EA) and olive leaf extract (OL), on oxymyoglobin oxidation, metmyoglobin formation and lipid oxidation (TBARS) in porcine muscle model systems. Following induced lipid oxidation (FeCl3/sodium ascorbate addition), lipid oxidation, oxymyoglobin oxidation and metmyoglobin formation were measured immediately and after 24 hours storage at 4oC. Lipid oxidation decreased significantly relative to the control (P<0.001) following the addition of S, EA and OL and TBARS formation in the control samples after 24 h storage at 4oC were 20-fold higher than samples with S and EA. Antioxidant potency followed in the order of S = EA > OL > L. EA and OL decreased oxymyoglobin oxidation (P<0.001) and also inhibited metmyoglobin formation (P<0.001). L had no effect on oxymyoglobin oxidation or metmyoglobin formation (P>0.05). The addition of sesamol at all concentrations significantly increased oxymyoglobin oxidation (P<0.001) resulting in increased levels of metmyoglobin at a concentration of 1000μg/ml.
Oxidative processes such as lipid oxidation and oxymyoglobin oxidation in meat products represents a challenging problem to the meat industry. Antioxidants delay auto oxidation, protect lipids from oxidation and stabilise oxymyoglobin. Current recommendations restrict the use of synthetic antioxidants which has prompted a huge interest in the use of natural occurring ingredients. L is an oxygenated carotenoid, which significantly reduces the risk of age-related macular degeneration1. EA and S are polyphenol antioxidants found in numerous fruits and vegetables and have been found to exhibit anticarcinogenic activity and inhibit atherosclerosis2. OL is a phenolic compound derived from olive leaves, known to have anti-oxidative properties. Incorporation of phytochemicals/nutraceuticals into ‘functional’ meat products offers considerable health benefit potential to consumers and would be highly beneficial to the meat industry.
MATERIALS AND METHODS
M. longissimus thoracis et lumborum muscle homogenates (25%) were prepared in 0.12M KCL 5mM histidine (240ml), pH 5.5, using an Ultra-turrax tissue homogeniser. Lipid oxidation of muscle homogenate samples (46g) held at 4oC, was initiated by the addition of pro-oxidants, 45M FeCl3/sodium ascorbate (1:1). L, S, OL and EA (plus 2ml NaOH) were solubilised in distilled water and added to LD homogenates at the following concentrations: L, 100g/ml, 200g/ml, 300g/ml; S, 500g/ml, 1000g/ml, 2000g/ml; OL, 100g/ml, 200g/ml, 300g/ml; EA, 100g/ml, 200g/ml, 300g/ml. Lipid oxidation and oxymyoglobin measurements were measured initially and in samples held at 4oC for 24 hours. Measurement of lipid oxidation: Lipid oxidation was measured following a modification of the 2-thiobarbituric acid-reactive substances (TBARS) method3. The malondialdehyde content of the sample was calculated using an extinction coefficient of 1.56 x 105 M-1 cm-1. Results were expressed as TBARS in mg malondialdehyde (MDA)/mg protein. The protein concentration of the homogenates was determined using bovine serum albumin (BSA) as a standard4. Measurement of oxymyoglobin oxidation: The relative proportions of oxymyoglobin (OxyMb) and metmyoglobin (MetMb) were calculated5. Statistical analysis: Data was analysed using one-way analysis of variance (ANOVA) and the F-protected LSD test in GenStat Release (10.1).
Results and Discussion
Following induced lipid oxidation (FeCl3/sodium ascorbate addition), lipid oxidation, OxyMb oxidation and MetMb formation was measured immediately and after 24 hours storage at 4oC. In model porcine muscle systems lipid oxidation decreased (P < 0.001) relative to the control following the addition S, EA and OL. Lipid oxidation decreased with increasing concentration of OL. Increasing concentrations of EA had no effect on reducing lipid oxidation further as lipid oxidation was significantly reduced to a similar level (P > 0.05) at all concentrations. The antioxidant potency followed the order of S = EA > OL > L. The antioxidant efficacy of L, S and OL correlated well with their corresponding IC50 values. OxyMb oxidation was significantly (P < 0.001) reduced following the addition of EA and OL at all concentrations. OL was the most effective plant extract in reducing OxyMb oxidation. The level of OxyMb increased (P < 0.05) following addition of S at a concentration at all concentrations. This is a negative effect as an increase in MetMb (i.e. browning) would have a detrimental effect on overall meat colour. Increasing concentrations of EA resulted in increased OxyMb oxidation. Antioxidant efficacy was in the order of OL > EA > L > S.
These health-promoting nutraceuticals demonstrated antioxidant activity in a model meat system by reducing lipid and OxyMb oxidation in the bovine model muscle systems. The results indicate that these nutraceuticals have potential in the development of healthier pork products.
This project is funded by the Food Institutional Research Measure (FIRM) as part of the Irish National Development Plan
1O'Connell, E.D., Nolan, J.M., Stack, J., Greenberg, D., Kyle, J., Maddock, L., Beatty, S. (2008). Diet and risk factors for age-related maculopathy. Am. J. Clin. Nutr. 87, 3, 712-722.
2Decker EA. (1995). The role of phenolics, conjugated linoleic acid, carnosine, and pyrroloquinoline quinone as nonessential dietary antioxidants. Nutr. Rev. 53, 49-58.
3Siu, G.M. and Draper, H.H. (1978). A survey of malonadehyde content of retail meats and fish. J. Food Sci, 43, (4), 1147-1149.
4Markwell, M.A.K., Haas, S.M., Bieber, L.L. and Tolbert, N.E. (1978). A modification of the lowry procedure to simplify protein determination in membrane and lipoprotein samples. Anal. Biochem. 87, 206-210.
5Krzywicki, K. (1982). The determination of haem pigments in meat. Meat Sci. 7, 29-36.
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