Evaluation of the effects of selected phytochemicals on quality indices and sensorial properties of raw and cooked pork stored in different packaging systems

The effects of lutein (100, 200 μg/g muscle), sesamol (250, 500 μg/g muscle), ellagic acid (300, 600 μg/g muscle) and olive leaf extract (100, 200 μg/g muscle) on lipid oxidation (thiobarbituric acid-reactive substances TBARs), colour (CIE L∗, a∗, b∗), pH, texture profile analysis (TPA), water holding capacity (WHC), cooking losses and sensorial properties of fresh and cooked pork patties were investigated. Raw and cooked minced pork (M. longissimus thoracis et lumborum) containing added lutein, sesamol, ellagic acid or olive leaf extract were stored aerobically or in modified atmosphere packs (MAP) for up to 8 and 12 days, respectively. Lutein, sesamol, ellagic acid and olive leaf extract had no significant effect on microbial status, cook loss, pH or WHC. Lipid oxidation was reduced (P < 0.001) in raw and cooked pork patties stored in aerobic packs and in MAP following addition of sesamol, ellagic acid and olive leaf extract. Antioxidant effectiveness in raw and cooked patties was in the order: sesamol = ellagic acid > olive leaf extract > lutein. Lutein increased (P < 0.001) b∗ yellowness values in raw pork patties. Addition of lutein, sesamol, ellagic acid and olive leaf extract to pork had no detrimental effects on the organoleptic properties of cooked patties but altered (P < 0.05) instrumental textural attributes. Results highlight the potential of using natural functional ingredients in the development of functional pork products with enhanced quality and shelf-life.     

Effect of lutein,sesamol, ellagic acid and olive leaf extract on the quality and shelf-life stability of packaged raw minced beef patties

The effects of lutein (100 and 200 μg/g muscle), sesamol (250 and 500 μg/g muscle), ellagic acid (300 and 600 μg/g muscle) and olive leaf extract (100 and 200 μg/g muscle) on total viable counts (TVCs), lipid oxidation (thiobarbituric acid-reactive substances, TBARS), colour, oxymyoglobin oxidation, pH, water-holding capacity (WHC), sensorial properties of raw beef patties (M. longissimus thoracis et lumborum) stored in modified atmosphere packs (80% O₂:20% CO₂) (MAP) aerobically at 4 °C for up to 8 and 12 days, respectively, were examined. All the nutraceuticals reduced (P < 0.001) TVCs. The addition of sesamol, ellagic acid and olive leaf extract reduced (P < 0.001) TBARS in raw beef patties in both packaging systems. Sesamol addition to beef resulted in lower (P < 0.01) a* redness values and increased oxymyoglobin oxidation. Conversely, lutein and olive leaf extract reduced (P < 0.001) oxymyoglobin oxidation relative to the control. The graded addition of ellagic acid and olive leaf extract improved (P < 0.001) WHC.     

The effect of lutein, sesamol, ellagic acid and olive leaf extract on lipid oxidation and oxymyoglobin oxidation in bovine and porcine muscle model systems

The effect of lutein (100, 200, 300 μg/ml), sesamol (500, 1000, 2000 μg/ml), ellagic acid (300, 600, 900 μg/ml) and olive leaf extract (100, 200, 300 μg/ml) on oxymyoglobin oxidation and lipid oxidation in bovine and porcine muscle model systems (25% M. longissimus thoracis et lumborum homogenates) was examined. Radical scavenging activity, using the DPPH assay, and iron-chelating activities of lutein, sesamol, ellagic acid and olive leaf extract were assessed at concentrations ranging from 200 to 1000 ppm. The radical scavenging activity was of the order: ellagic acid > sesamol > olive leaf extract > lutein. None of the natural antioxidants examined exhibited iron chelating activity. Following induced lipid oxidation (FeCl₃/sodium ascorbate addition), lipid oxidation and oxymyoglobin oxidation were measured after 24 h at 4 °C. In bovine and porcine muscle model systems, lipid oxidation decreased (P < 0.001) following addition of each of the natural antioxidants relative to the control and antioxidant potency followed the order: sesamol > ellagic acid > olive leaf extract > lutein. Ellagic acid and olive leaf extract decreased oxymyoglobin oxidation (P < 0.001) while sesamol increased oxymyoglobin oxidation in both systems. The natural antioxidants examined may have applications in the development of nutritional enhanced meat products with enhanced shelf-life characteristics.     

Addition of grape seed extract and bearberry to porcine diets: Influence on quality attributes of raw and cooked pork

The effect of supplementation of pig diets with grape seed extract (GSE) (100, 300, 700 mg/kg feed) and bearberry (BB) (100, 300, 700 mg/kg feed) for 56 days pre-slaughter, on the oxidative stability and quality of raw and cooked M. longissimus dorsi (LD) was examined. Susceptibility of porcine liver, kidney and heart tissue homogenates to iron-induced (1 mM FeSO₄) lipid oxidation was also investigated. In raw LD steaks, stored in modified atmosphere packs (75% O₂:25% CO₂) (MAP) for up to 16 days at 4 °C, surface lightness (CIE ‘L’ value), redness (CIE ‘a’ value), lipid stability (TBARS, mg MDA (malondialdehyde)/kg muscle) and pH were not significantly affected by supplemental GSE or BB. Similarly, the oxidative stability and sensory properties of cooked LD steaks, stored in MAP (70% N₂:30% CO₂), for up to 28 days at 4 °C, were not enhanced by dietary GSE or BB. Iron-induced lipid oxidation increased in liver, kidney and heart tissue homogenates over the 24 h storage period and susceptibility to oxidation followed the order: liver > heart > kidney. Dietary GSE or BB did not significantly reduce lipid oxidation in tissue homogenates. Potential reasons for the lack of efficacy of supplemental GSE and BB on pork quality were explored.     

Evaluation of the antioxidant potential of grape seed and bearberry extracts in raw and cooked pork

The effect of grape seed extract (GSE) and bearberry (BB), on lipid oxidation (TBARS, mg malondialdehyde (MDA)/kg muscle), colour (CIE ‘a’ redness value), pH, microbial status (log₁₀CFU colony forming units/g pork) and sensorial properties of cooked pork patties was investigated. GSE (0–1000 μg/g muscle) and BB (0–1000 μg/g muscle) were added to raw pork (M. longissimus dorsi) patties which were stored in modified atmosphere packs (MAP) (75% O₂:25% CO₂) for up to 12 days at 4 °C. Cooked pork patties were stored in MAP (70% N₂:30% CO₂) for up to 4 days at 4 °C. Mesophilic plate counts and pork pH were unaffected by GSE and BB. GSE and BB addition decreased (P < 0.05) lipid oxidation (TBARS) in raw pork patties on days 9 and 12 of storage, relative to controls. Antioxidant activity of GSE and BB was observed in cooked pork patties demonstrating the thermal stability of GSE and BB. The ‘a’ redness values of raw and cooked pork patties marginally increased with increasing GSE concentration. The sensory properties of cooked pork patties were unaffected by GSE and BB addition. Results obtained demonstrate the potential for using health promoting nutraceuticals in meat and meat products.     

Extracts of olive polyphenols improve lipid stability in cooked beef and pork: Contribution of individual phenolics to the antioxidant activity of the extract

Crude polyphenol extracts (50 or 100 mg gallic acid equivalents (GAE)/kg meat) from the waste waters of olive oil pomace reduced the formation of 2-thiobarbituric reactive substances (TBARS) in pre-cooked beef (63–83%) and pork (47–66%). When compared with other antioxidants, the ranking of activities were: tea ? olive > wine. The olive extract contained hydroxy-tyrosol (70.6%), tyrosol (17.5%), caffeic acid (9.5%), p-coumaric acid (1.9%) and vanillic acid (0.3%). Relationship between polyphenol composition and antioxidant activity of a blend containing oleuropein, tyrosol, hydroxy-tyrosol, quercetin, rutin and caffeic, vanillic and coumaric acids was described by a first order polynomial model. Quercetin, hydroxy-tyrosol, caffeic acid and oleuropein had the highest contributions to the linear term followed by rutin and tyrosol. We detected the strongest positive synergism between tyrosol and quercetin, hydroxy-tyrosol, oleuropein and to a lesser degree with caffeic acid whilst the effect of vanillic and coumaric acids were not significant.     

Utilization of adzuki bean extract as a natural antioxidant in cured and uncured cooked pork sausages

A commercial adzuki bean extract (AE) was evaluated for antioxidant effectiveness in cured and uncured cooked pork sausages. TBARS values, instrumental color evaluation and sensory panel scores were assessed. For uncured sausages, AE at 0.2% was equally effective as 0.1% butylated hydroxytoluene (BHT) in reducing TBARS values. Similarly, AE at 0.2% significantly (P<0.01) reduced the TBARS in cured sausages. Incorporation of 0.2% AE into sausages produced higher (P<0.05) CIE lab color a* value and lower (P<0.05) L* and b* values. Sensory panels did not detect any difference in color, odor, taste, flavor, and overall acceptance in uncured pork sausages with addition of 0.2% AE. However, there were adverse changes in the color and odor of cured sausages, even though the taste, flavor, and overall acceptance were similar. Therefore, the results suggest that AE is a potential antioxidant.     

Effect of dietary antioxidant and fatty acid supply on the oxidative stability of fresh and cooked pork

The effect of dietary oil (linseed or soybean oil) and antioxidant treatment (α-tocopheryl acetate (AT; 40ppm) versus a cocktail (AOC; 200ppm): α-tocopheryl acetate+rosemary+citric acid+gallic acid) on colour, lipid and protein oxidation of fresh and processed pork was investigated. No effect of oil source on different parameters of oxidation was seen. No effect of antioxidant treatment on colour stability of fresh longissimus thoracis (LT) or cooked cured ham (CCH) was observed. For both antioxidant treatments, lipid oxidation in fresh LT and CCH was well controlled during display. However, lipid oxidation increased significantly in pre-frozen uncured cooked meat under aerobic conditions. No unambiguous effect of antioxidant treatment on protein oxidation was observed. There seemed to be no clear link between colour, protein and lipid oxidation. At the dose used in this study, no additional or synergistic effects of the extra components of the AOC on the different oxidation parameters was found.     

Characterisation of oregano water extracts and their effect on the quality characteristics of cooked pork

The present study characterises oregano water extracts and reports their effects on the shelf life and quality characteristics of cooked pork. Some changes in oregano extract taking place during its thermal treatment were observed. The main volatile compound in the unheated and heated extracts was carvacrol; however, the second major constituent in the unheated extract β-caryophyllene was absent in the heated one. Colour changes during heating were characterised by an International Commission on Illumination (CIE L a b) method. The heated extract better scavenged 1,1-diphenyl-2-picryl hydrazyl radicals, most likely owing to the formation of stronger radical-scavenging derivatives during thermal treatment. The effect of oregano extracts on the shelf life and colour characteristics of stored meat samples in most cases was not significant; however, sensory assessment clearly showed that the addition of extracts had some negative influence on meat flavour and colour.     

Textural attributes and oxidative stability of pork longissimus muscle injected with marbling-like emulsified lipids

The objective of the study was to create marbling-like fat in lean pork with acceptable oxidative stability through the injection of canola/olive oil-substituted emulsions. Pork loins were injected with 5% water as control (CW) or 5% emulsion containing no tocopherols (E) or 0.07% tocopherols (ET) and stored at 2 °C in an oxygen-enriched package for up to 3 weeks. Lipid oxidation was totally inhibited in ET pork but increased 3-fold to 0.20mg malonaldehyde/kg in CW and E pork after 3 weeks. ET treatment also had a positive effect on meat red color. Emulsion-containing pork, showing less protein oxidation (carbonyl and disulfide formation), had reduced drip loss and shear force than CW samples (P<0.05). The results indicated that incorporation of antioxidant-containing emulsions could create marbling-like texture in lean pork without compromising oxidative stability.     

Antioxidant potential of curry (Murraya koenigii L.) and mint (Mentha spicata) leaf extracts and their effect on colour and oxidative stability of raw ground pork meat during refrigeration storage

The aim of this study was to investigate the antioxidant activity of different solvent extracts of curry and mint leaf and their effect on colour and oxidative stability of raw ground pork meat stored at 4 ± 1 °C. The results indicated that among the two individual leaf categories, the ethanol extract of curry leaf (EHEC) and the water extract of mint leaf (WEM) showed higher DPPH and ABTS⁺ activity. EHEC also exhibited the highest total phenolic contents while these were the lowest for WEM. WEM showed the highest superoxide anionic scavenging activity (%). The pork meat samples treated with EHEC and WEM showed a decrease in the Hunter L- and a-values and a increase in b-value during storage at 4 °C. However, the pH and TBARS values were higher in control samples irrespective of storage periods. In conclusion, EHEC and WEM have the potential to be used as natural antioxidants to minimise lipid oxidation of pork products.     

Effect of antioxidant on the fatty acid composition and lipid oxidation of intramuscular lipid in pressurized pork

To investigate the effect of antioxidants on lipid oxidation and fatty acid composition in pressurized pork, minced pork with or without 1% Na(2)EDTA was pressurized at 500MPa before 7days storage at 4°C. TBARS value, lipid content and fatty acid composition in untreated and high-pressure (HP) treated samples were analyzed. HP treatment induced marked increases in TBARS values and lipolysis of partial phospholipids causing an increase of free fatty acid content. Preferential hydrolysis for polyunsaturated fatty acids (PUFA) in phospholipids resulted in the percentage of PUFA in phospholipids decreasing markedly and thereby that in free fatty acids increasing significantly. Addition of 1% Na(2)EDTA to minced pork before HP significantly decreased the TBARS values in pressurized samples, but did not inhibit the lipolysis of phospholipids, causing the fatty acid composition of phospholipids and free fatty acids to change similarly to those samples without Na(2)EDTA.     

Individual effects of l-arginine or l-lysine on stability of pork or chicken emulsion sausages with partial replacement of porcine backfat by soybean oil

The individual effects of l -arginine or l -lysine on the physical (cooking loss (CL), total expressible fluid (TEF) and expressible fat (EFAT)) and chemical (thiobarbituric acid-reactive substances (TBARS), and carbonyl and total sulphhydryl (T-SH) content) stability of pork or chicken emulsion sausage with partial replacement of porcine backfat by soybean oil were determined. l -arginine or l -lysine increased pH but decreased CL, TEF and EFAT. Confocal laser scanning microscopy revealed that supplementation with l -arginine or l -lysine caused more regular and uniform oil droplets, for enhanced physical stability of pork or chicken sausage. Subjected to the same treatments, chicken sausage displayed higher physical stability than pork sausage. Overall, chicken sausages treated with l -arginine or l -lysine had lower TBARS and carbonyl content but higher T-SH content than the corresponding control during storage; for pork sausages, l -arginine or l -lysine treatment generally resulted in higher TBARS throughout storage, lower carbonyl content during the initial 14 days and higher T-SH content on days 7 and 14 but lower T-SH content on days 1 and 21. Generally, l -arginine/l -lysine effectively increased the chemical stability of chicken sausage but decreased the chemical stability of pork sausage.     

Effect of high-pressure treatment on the fatty acid composition of intramuscular lipid in pork

To investigate the effect of high-pressure (HP) treatment on lipid oxidation and fatty acid composition of intramuscular lipid in pork, the longissimus muscles from Rongchang (RC) pig were pressurized at 200, 350 and 500 MPa for 20 min at 20 °C prior to 7 days storage at 4 °C. The changes in TBARS number, lipid content and fatty acid composition of total intramuscular lipids, phospholipids, triglycerides and free fatty acids in untreated and HP treated samples were analyzed. HP treatment had no significant effect on the content and fatty acid composition of total lipids and triglycerides in the samples, but treatment at 350 MPa and above led to marked increases in TBARS values and lipolysis of partial phospholipids causing a correlative increase of free fatty acid content. A preferential hydrolysis for polyunsaturated fatty acids (PUFA) in phospholipids was observed, which resulted in the percentage of PUFA in phospholipids decreasing markedly and thereby that in free fatty acids increasing significantly.     

Antioxidant activity of black currant (Ribes nigrum L.) extract and its inhibitory effect on lipid and protein oxidation of pork patties during chilled storage

This experiment was conducted to assess the antioxidant efficacy of black currant (Ribes nigrum L.) extract (BCE) in raw pork patties during chilled storage. The extracting conditions of frozen BCE including ethanol concentrations (0-100%) and extracting times (0.25-12h) were studied. BCE extracted with 40% ethanol for 2h had the highest anthocyanin content, the strongest radical scavenging activities as well as the second strongest reducing power. BCE was condensed and added to pork patties at 5, 10 or 20 g/kg. Compared with the control, BCE treatments significantly decreased the thiobarbituric acid-reactive substance values and carbonyls formation and reduced the sulfhydryl loss of pork patties in a dose-dependent manner (P<0.05), which showed that the BCE significantly inhibited lipid and protein oxidation. The BCE-treated patties showed significantly higher redness (P<0.05) than the control. The findings demonstrated strong potential for BCE as a natural antioxidant in meat and meat products.     

Effect of varying oxygen concentrations on the shelf-life of fresh pork sausages packaged in modified atmosphere

A total of 105 fresh pork sausages were packaged in atmospheres varying in oxygen concentration, using the following mixtures (%O₂/%CO₂/%N₂): 0/20/80, 0/20/80 + O₂ scavenger, 20/20/60, 40/20/40, 60/20/20, and 80/20/0. In addition, two batches were subjected to vacuum packaging or over-wrap with O₂-permeable film. They were stored for 20 days at 2 ± 1 °C in the dark. Values of pH, CIE L*, a* and b* color parameters, surface metmyoglobin percentage, TBA-reactive substances, psychrotroph aerobe bacterial numbers and sensory discoloration and off-odor were assessed throughout storage. Packaging in the absence of O₂, either under vacuum or in atmosphere with O₂ scavenger, led to extension of shelf-life in terms of both color and odor stability due to low oxidation rates. Increase of O₂ caused a significant enhancement of oxidation, decrease of shelf-life due to discoloration and off-odor development. The highest O₂ concentration gave rise to a significant color improvement, though only for a limited period of 8 days.     

Effects of muscle cortisol concentration on muscle fiber characteristics, pork quality, and sensory quality of cooked pork

The effect of muscle cortisol concentration on muscle fiber characteristics and technological and sensory quality of pork was investigated. With the exception of the percentage of type IIA fibers, muscle fiber characteristics were not associated to cortisol levels. However, muscle cortisol concentration was positively associated with muscle pH(24h) (r = 0.23, P<0.05) and negatively associated with drip loss (r = -0.49, P<0.001), lightness (r = -0.24, P<0.05), shear force (r = -0.25, P<0.05), and texture profile analysis-hardness (r = -0.35, P<0.01). Additionally, the water-holding capacity of meat samples was affected by cortisol levels, with lower cortisol concentrations associated with less tender samples. These results indicate that the concentration of cortisol in the muscle is related with meat quality as well as the sensory quality of cooked pork.     

Effect of different dietary levels of natural-source vitamin E in grow-finish pigs on pork quality and shelf life

Improving pork quality and shelf life is important in today’s swine industry because higher levels of DDGS are incorporated into pig diets. Relatively high level of poly-unsaturated fatty acids (PUFA) in DDGS may increase pork susceptibility to lipid oxidation and thus reduce pork shelf life. Antioxidants such as vitamin E may delay the onset of pork lipid oxidation when used as an ingredient in the diet. This experiment examined carcass characteristics, meat quality, shelf life, and color stability in pork from pigs (n = 150) fed five levels of a natural vitamin E (Nova-E) and one level of synthetic vitamin E. Natural vitamin E and synthetic vitamin E had no effect on carcass characteristics or meat quality. Increasing dietary natural vitamin E from 10 to 200 mg/kg decreased lipid oxidation. Lipid oxidation of pork chops and ground pork was similar between pigs fed 40 mg/kg and higher levels of natural vitamin E, indicating no additional benefits from supplementing beyond 40 mg/kg natural vitamin E. Supplementing 200 mg/kg synthetic vitamin E decreased pork lipid oxidation when compared to supplementing 10 mg/kg natural vitamin E. High levels of natural vitamin E or synthetic vitamin E, however, did not prevent discoloration of loin chops. These data indicate that natural vitamin E was effective to help reduce lipid oxidation and the effective minimal level of dietary supplementation appeared to be 40 mg/kg.