Storage stabilities of pork scratchings,peanuts, oatmeal and muesli: Comparison of ESR spectroscopy,headspace-GC and sensory evaluation for detection of oxidation in dry foods

Peanuts, pork scratchings, oatmeal and two types of muesli were stored in two experiments, where external factors (light, oxygen concentrations, product-headspace ratios) were varied, and where packaging materials with different properties (light transmission and oxygen permeability) were used. The oxidative changes in the products were followed by the formation of hexanal as detected by headspace gas chromatography (headspace-GC), free radicals as detected by electron spin resonance (ESR) spectroscopy and sensory evaluations. Generally, increased oxygen availability and exposure to light resulted in increased lipid oxidation. Statistical analysis of the results revealed that light accounted for the greatest systematic variation of the relative levels of free radicals in peanuts, oatmeal and muesli, whereas the oxygen availability had the largest influence on the formation of hexanal. The opposite was observed for pork scratchings, where oxygen had the most significant effect on the formation of radicals. It is concluded that ESR and headspace-GC complement each other in detecting the oxidative changes.     

Oxidative changes in pork scratchings,peanuts, oatmeal and muesli viewed by fluorescence,near-infrared and infrared spectroscopy

The possibility of using rapid spectroscopic methods to detect lipid oxidation of four standard food products—peanuts, pork scratchings, oatmeal and muesli—were investigated in a large screening experiment. Fluorescence, near-infrared [including visual (Vis/NIR)] and infrared (IR) spectra have been recorded during and beyond the normal shelf lives of the products and related by means of multivariate data analysis to reference oxidation measures of free radicals and hexanal, as well as to sensory evaluation. For pork scratchings, the three spectroscopic techniques were able to monitor the progressing level of oxidation: IR with good correlation to hexanal (r²=0.86), Vis/NIR with good correlations to free radicals (r²=0.82) and fluorescence with good correlations to both free radicals (r²=0.76) and hexanal (r²=0.83). In the case of IR, the best result was obtained using the region including the out-of-plane C–H of trans-fatty acids. For the other three products, the results were generally inferior except for good correlations between fluorescence spectra and free radicals in peanuts (r²=0.73) and between Vis/NIR spectra and hexanal for muesli products (r²=0.8).     

Antioxidant ability of BHT‐ and α‐tocopherol‐impregnated LDPE film in packaging of oatmeal

Cereals in general, and particularly oatmeals, are considered rather sensitive to oxidation owing to their relatively high fat content. The addition of antioxidants can sometimes prolong the shelf‐life of products. The aim of the present study was to investigate how the rate of lipid oxidation of a packaged oatmeal product was affected by the nature and level of antioxidants incorporated in an LDPE film structure. The stability of the product, which was determined by hexanal analysis using GC–MS and by electronic nose analysis, showed very small variations over the chosen storage period. No oxidation, as determined by hexanal levels in the oatmeal, was initiated during storage, but small variations in volatile profile were seen among the samples analysed by the electronic nose. The product stored in the BHT‐impregnated LDPE film had undergone the least change during 10 weeks of storage at 20 °C. α‐Tocopherol‐impregnated LDPE film did not appear to prolong the shelf‐life of the oatmeal at all. © 2000 Society of Chemical Industry     

Monitoring oxidative quality of pork scratchings,peanuts, oatmeal and muesli by sensor array

A sensor array (electronic nose) was successfully applied for predicting the content of hexanal and other volatiles in different dry fat‐containing products, showing the potential of replacing time‐consuming traditional laboratory analysis by faster in‐process monitoring methods. Unfortunately, prediction of free radical content was not successful, making early prediction of oxidation by sensor array infeasible. Owing to the non‐specificity of the sensors, a generic model could not be generated even though a series of standards was shown to have a high correlation between hexanal concentration and individual or multiple sensor responses. PCA models of sensor array responses of eg pork scratchings revealed a clear separation of samples stored in the experimental factor light versus darkness. Copyright © 2004 Society of Chemical Industry     

Oxidative stability of frozen pork patties: Effect of fluctuating temperature on lipid oxidation

The mobility of solutes in fat from pork belly, in lean pork belly and in lean pork longissimus dorsi, containing 1% NaCl was characterized by the ESR spin probe technique using the nitroxyl spin probes TEMPO and TEMPOL. The mobility of TEMPO in fat increased for temperature above -60 °C and the mobility of TEMPOL in lean meat increased for temperature above -40 °C. Temperatures for studying the effect of fluctuating temperatures during frozen storage of meat were selected based on the ESR characterization of the mobility of solutes. The oxidative stability of pork patties during frozen storage was measured as thiobarbituric acid reactive substances (TBARS), during storage at -10, -23 and -40 °C and with fluctuations between these temperatures, of pork patties made from pork loin (low fat 1.8%) or pork belly (high fat 22.7%). Lower storage temperatures resulted in less lipid oxidation, and temperature fluctuations between -40 and -23 °C and fluctuations between -23 and -10 °C resulted in oxidation intermediate to oxidation in samples stored at constant low or high temperatures of the fluctuation interval. The level of α-tocopherol was unaffected by the extent of oxidation in the frozen samples, an observation which is discussed in relation to differences in molecular mobility between oxygen and α-tocopherol.     

Effects of Dietary Antioxidants and Oxidized Oil on Membranal Lipid Stability and Pork Product Quality

The effects of dietary tocopherol and oxidized oil on the oxidative stability of membranal lipids in pig muscles and on the oxidative stability of pork products during refrigerated and frozen storage were evaluated. Membrane-bound α-tocopherol stabilized the membranal lipids and reduced the extent of lipid oxidation occurring in pork patties and pork chops during storage. Oxidized dietary oil had an adverse effect on the stability of both the membranal lipids and pork products. The addition of salt to the pork patties accelerated the oxidative process when the patties were stored under fluorescent light and in the dark.     

石榴皮提取物与焦磷酸钠复配对猪肉饼品质的影响

为探究焦磷酸钠(sodium pyrophosphate,TSPP)、异抗坏血酸钠(sodium D-isoascorbate,D-VCNa)与石榴皮提取物(pomegranate peel extract,PPE)复配使用在肉制品中是否具有协同增效作用,以丁基羟基茴香醚(butyl hydroyanisole,BHA...     

Oxidative stability of pork meat lipids as related to high-oleic sunflower oil and vitamin E diet supplementation and storage conditions

The aim of this research work was to evaluate the oxidative stability of pork meat lipids as related to dietary supplementation with high-oleic sunflower oil (HOSO) and/or α-tocopheryl acetate (VE), as well as the influence of storage conditions. Four different diets (control; HOSO; VE; HOSO+VE), were fed to swines until slaughtering. Meat slices were packed in vessels with transparent shrink film and exposed to white fluorescent light for 3 days at 8 °C. HOSO supplementation increased oleic acid content of pork meat. The highest levels of peroxide value (PV) and cholesterol oxidation products (COPs) were detected in the control group, whereas HOSO-enriched diets displayed the highest thiobarbituric reactive substance (TBARs) content. After storage under light exposure, pork meat slices exhibited a decrease of PV, which resulted in an increasing trend of TBARs and COPs. Feeding enrichment with both HOSO and vitamin E can be, therefore, used as an appropriate supplementation strategy to produce pork meat with a suitable oxidative stability.     

Oxidative stability of processed pork. Assay based on ESR-detection of radicals

The tendency to radical formation as an early event in lipid oxidation was used to characterise the oxidative stability of processed pork in an assay based on the spin trapping technique and electron spin resonance (ESR) spectroscopy. Pork cooked at different temperatures was evaluated, and it was found that heating at 95 °C resulted in higher radical formation than heating at 70 °C or at 120 °C. The tendency to formation of radicals (identified as carbon-centered radicals from the hyperfine coupling constants) was found to correlate with the rate of oxygen depletion as measured electrochemically, and the ESR assay should be further explored as a tool for the prediction of oxidative stability of meat products.     

Effects of dietary soybean oil on lipid and protein oxidation in pork patties during chill storage

The effect of dietary soybean oil on lipid and protein oxidation in low and high fat pork patties made from quadriceps femoris during chill storage in a high oxygen atmosphere packaging (80% O(2)/20% CO(2)) in the dark for 7 days was investigated. Pigs were fed either a standard diet or a diet added 2% soybean oil. After slaughter high fat pork patties were prepared for both feeding regimes by addition of back fat from pigs fed the same diet whereas low fat pork patties were prepared without addition of back fat. The 2% soybean diet increased the amount of unsaturated fat in the pork. Secondary lipid oxidation products determined as thiobarbituric acid reactive substances (TBARS) were found to increase in the pork patties with increased unsaturated fat. Increased unsaturated fat in the pork patties had no effect on protein oxidation determined as free protein thiol content and protein carbonyl content. A small, but significant increase in protein oxidation was found in the high fat pork patties independent on dietary fat. In conclusion, protein oxidation is unaffected by dietary fat in pork patties during chill storage for periods normally used in retail trade, and lipid and protein oxidation are not coupled under these conditions.     

Effect of tocopherol concentration on rancidity development during frozen storage of a cured and an uncured processed pork product

This research evaluated the effect of addition during processing of various concentrations of tocopherol (0-1000 mg/kg) on the subsequent lipid oxidation and rancidity development during frozen storage of two pork products-a coarsely ground cured sausage and an uncured restructured pork roast. The results indicated that tocopherol had little effect on lipid oxidation, as measured by TBARS values and sensory evaluation during frozen storage at -18?°C for 37 weeks for either product. However, lipid oxidation only occurred to a limited extent even in products without tocopherol and was insufficient to cause rancid flavour development. It was, therefore, not possible to determine if tocopherol added during processing was effective as an antioxidant in preventing lipid oxidation in processed pork products during frozen storage.     

Lipid oxidation of irradiated pork products

The effect of irradiation (2, 5 and 8 kGy) and vacuum storage for 60 days on fatty acid and cholesterol oxidation was determined in three Italian cured pork products (salame Milano, coppa and pancetta).A significant increase in the degree of fatty acid oxidation was observed starting from 8 kGy irradiation dose. Unlike the unirradiated samples, the vacuum storage was not sufficient to curb fatty acid oxidation in the irradiated pork products.The cholesterol oxidation of all of the pork products investigated was affected by the highest dose of irradiation and sometimes by storage. The effect induced by the ionising radiation was different depending on the type of pork product. The cholesterol oxide molecules were qualitatively similar in both irradiated and unirradiated pork products and the levels detected were about 100 times lower than the toxic level for in vitro and in vivo experiments.     

Measurement of lipid oxidation and porphyrins in high oxygen modified atmosphere and vacuum-packed minced turkey and pork meat by fluorescence spectra and images

This paper illustrates that fluorescence spectroscopy and imaging can be used to measure the extent and distribution of lipid oxidation in meat. Minced turkey thighs and pork semimembranosus muscles were stored for 7 and 12 days at 4°C in high oxygen (O(2)) modified atmosphere packages and vacuum. Turkey meat packed in high O(2) atmosphere was oxidised already after 7 days of storage. The sensory rancid odour score was 4.7 (on a scale from 1 to 9) and the TBARS value was 1.86mg MDA/kg. There was also an increase in fluorescence emission intensity in the 410-550nm region, which arises from lipid oxidation products. The combination of unsaturated fatty acids and access to O(2) resulted in lipid oxidation gradients in the turkey meat samples, and these gradients were clearly visualised by fluorescence images. In comparison, pork meat was more stable against lipid oxidation, with TBARS values <0.2mg MDA/kg and no development of fluorescent lipid oxidation products was detected. The fluorescence spectra measured in the present experiment suggest that turkey thighs and pork semimembranosus muscle in addition to protoporphyrin also have a natural content of Zn protoporphyrin. The porphyrin content was higher in pork meat than in turkey meat. It increased during storage time when the meat was packed in vacuum, and it decreased with O(2) availability. The distribution of porphyrins in the meat was visualised by fluorescence imaging.     

LIPID OXIDATION AND SENSORY CHARACTERISTICS OF FRESH AND CURED SAUSAGES FROM α-LINOLENIC ACID ENRICHED PORK

Forty-eight female piglets were raised with four levels of α-linolenic acid (0, 1.5, 2.5, 3.5%) to determine the effect of dietary fat on the fatty acid composition, sensory and storage stability of pork products. The degree of polyunsaturation in neutral lipids and phospholipids were increased significantly by the dietary LNA. The thiobarbituric acid reactive substances (TBARS) vaues of freshly prepared breakfast sausages with vacuum packaging remained low, but those of the loosely packaged, i. e., nonvacuumized, sausages increased more than 3 times during the 48 h storage period. The TBARS values of breakfast sausages frozen-stored for 3 months showed extensive lipid oxidation. The dietary LNA treatments and packaging had significant effects on the susceptibility of breakfast sausages to lipid oxidation. However, the oxidative stability of cured products was not affected by the dietary treatments. The results indicated that the pork enriched with polyunsaturated fatty acids could be used in cured products or uncured meat products protected by ‘hot vacuum packaging’without any sensory or quality deterioration due to lipid oxidation.     

高湿度结合不同温度解冻对猪肉理化及蛋白特性的影响

探究相对湿度（relative humidity,RH）90%下,不同温度（0、4、8?℃和12?℃）解冻对猪肉品质特性的影响,以鲜肉和传统低温（4?℃,RH?65%～73%）解冻肉为对照,分析处理组和对照组的解冻效率、保水性、嫩度、色泽、脂质过氧化、pH值、新鲜度的变化,并利用差示扫描量热仪和流变仪测定蛋白热变性及动态流变特性。结果表明：相较于传统低温解冻,高湿（RH?90%）、低温（0～12?℃）解冻可提高解冻效率,且解冻后猪肉的保水性、色泽、嫩度显著提高（P＜0.05）,明显抑制脂肪氧化程度,降低蛋白变性程度,可最大限度维持“鲜肉”的品质;其中,高湿环境下4?℃和8?℃解冻效果明显优于0、12?℃处理组,解冻后猪肉的保水性、色泽、嫩度得到改善,脂肪氧化程度降低,同时4?℃和8?℃解冻后猪肉蛋白变性程度较低,G′较高。因此RH?90%、4～8?℃解冻是较合适的解冻条件,该条件可提高解冻效率、维持猪肉品质。     

COMPUTER SIMULATION OF VITAMIN DEGRADATION IN A DRY MODEL FOOD SYSTEM DURING STORAGE1

During storage of dry foods, oxidative mechanisms can result in nutrient degradation. Accurate prediction of the vitamin content for dry foods during storage is essential to provide the processor with the assurance of meeting label claims. Since appropriate shelf-life tests for measurement of vitamin degradation represents an alternative worth considering. A mathematical model of the relationship between the rate constant of ascorbic acid oxidation and water activity was established. Computer simulation to predict product moisture content and ascorbic acid degradation in a dry model food product was developed by considering the simultaneous influence of water activity and temperature on rate constants which change with storage time due to varying storage environments. The computer simulation predicts product moisture content and vitamin degradation in good agreement with the experimental data. The simulation will account for the influence of storage temperature and relative humidity as well as characteristics of the food product and package material.     

Effects of supranutritional dietary vitamin E levels on subcellular deposition of α-tocopherol in the muscle and on pork quality

The influence of three levels of vitamin E in the diet of pigs on the subcellular deposition of α-tocopherol in the muscle and on selected quality characteristics of pork meat (oxidative stability of lipids, colour, drip loss, microbial growth) was studied. The content of α-tocopherol in adipose tissue and L. dorsi muscle as well as in mitochondrial and microsomal fractions of the muscle significantly increased (P < 0.05) with increasing levels of dietary vitamin E. The differences in the concentrations of α-tocopherol in the subcellular fractions were evident in the enhanced stability of the membranes when exposed to metmyoglobin/hydrogen peroxide. The beneficial effect of dietary vitamin E on the oxidative stability of pork lipids during the storage of pork chops and ground pork was also demonstrated. Even though lipid oxidation increased in all cases during storage, the pork products from the pigs receiving the highest level of vitamin E (200 IU kg^?1 feed) exhibited the smallest increase in thiobarbituric acid reactive substances. In addition, increased colour stability and decreased drip loss were observed on keeping pork chops, which had been previously frozen for three months, at 4°C under fluoresent light for 10 days. The possible effect of α-tocopherol on membrane fluidity in this context is discussed.     

Functional properties of raw and cooked pork patties with added irradiated, freeze-dried green tea leaf extract powder during storage at 4 °C

Functional and sensory properties of raw and cooked pork patties with added irradiated freeze-dried green tea leaf extract powder were studied. Components of green tea were extracted by 70% ethanol, and the extract was irradiated to obtain a bright color. The irradiated green tea extract was freeze-dried and the powdered sample (0.1%) was added to the pork patties (Trt C). Pork patties without any ingredient (Trt A) and with nonirradiated, freeze-dried green tea extract powder (Trt B) were also prepared for comparison. Lipid oxidation, radical scavenging effect, color, and sensory properties of pork patties with treatments were analyzed at 5-day intervals for 15 days with storage at 4?°C. The lipid oxidation had a lower (P<0.05) and radical scavenging effect was greater (P<0.05) in the raw and cooked pork patties with added Trt B and Trt C, than those of Trt A (control). The pork patties with Trt B and Trt C had a higher Hunter color a*-value and less cooking loss than that of Trt A. Sensory panelists preferred the odor of the raw pork patties and color of the cooked pork patties of Trt C (P<0.05). Generally, no significant difference between Trt B and Trt C was found. Therefore, irradiated, freeze-dried green tea extract powder can be used for producing functionally-improved meat products.     

The Effect of Buckwheat Hull Extract on Lipid Oxidation in Frozen‐Stored Meat Products

This study investigated the effect of antioxidants on lipid stability of frozen‐stored meat products. Buckwheat hull extract was used to enrich fried meatballs made from ground pork. During 180‐d storage of meat products, lipid oxidation (peroxide and 2‐thiobarbituric acid reactive substances [TBARS] value) was periodically monitored. The results were compared with butylated hydroxytoluene (BHT). The addition of antioxidants decreased lipid oxidation in stored meatballs. The highest ability to control peroxide and TBARS values was demonstrated for buckwheat hull extract. Moreover, buckwheat hull extract showed a higher 2,2‐diphenyl‐1‐picrylhydrazyl free radical scavenging activity as well as higher Fe(II) ion chelating ability, as compared with BHT. The total content of phenolic compounds are highly correlated to the individual polyphenols in extract of buckwheat hull, among which the following were assayed: 3,4‐dihydroxybenzoic acid, 4‐hydroxybenzoic acid, gallic acid, isovanillic acid and p‐coumaric acid, and flavonoids: isoorientin, quercetin, quercetin 3‐d ‐glucoside, rutin, and vitexin. These results indicate that plant extracts can be used to prolong shelf life of products by protecting them against lipid oxidation and deterioration of their nutritional quality.     

Effect of irradiation and packaging conditions after cooking on the formation of cholesterol and lipid oxidation products in meats during storage

The effect of irradiation and packaging conditions on the content of cholesterol oxidation products (COPs) and lipid oxidation in cooked turkey, beef, and pork during storage was studied. Ground turkey leg, beef, and pork were cooked, packaged either in oxygen-permeable or oxygen-impermeable bags, and irradiated at 0 or 4.5 kGy. Lipid oxidation and COPs were determined after 0 and 7 days of storage at 4°C. Packaging of cooked meat was more important than irradiation in developing COPs and lipid oxidation in cooked meats during storage. 7-Hydroxycholesterol, 7β-hydroxycholesterol, β-epoxide, and 7-ketocholesterol were among the major COPs formed in cooked turkey, beef, and pork after storage, and their amounts increased dramatically during the 7-day storage in aerobic conditions. Irradiation had no significant effect on the amounts of any of the COPs found in cooked turkey and beef, but increased (P<0.05) the amounts of - plus 7β-hydroxycholesterol, β-epoxide, 7-ketocholesterol, and total COPs in aerobically packaged cooked pork. The amounts of COPs and lipid oxidation products (TBARS) closely related to the proportion of polyunsaturated fatty acids in meat. The results indicated that the composition of fats in meat is important on the oxidation rates of lipids and cholesterol, and packaging is far more important than irradiation in the formation of COPs and lipid oxidation in cooked meat.