Effectiveness of poly(ethylene terephthalate) and high-density polyethylene in protection of milk flavor.

The development of certain off-flavors in whole milk (3.25% milk fat) as related to packaging material [glass, high-density polyethylene (HDPE), amber poly(ethylene terephthalate) (PETE), clear PETE, and clear PETE-UV] were evaluated after exposure to fluorescent light (1100 to 1300 lx) for 18 d at 4 degrees C. Control samples packaged and stored under identical conditions were wrapped in foil to prevent light exposure. Selected flavor compounds in milk were measured analytically on d 0, 7, 14, and 18 of storage, while intensities of "oxidation," "acetaldehyde," and "lacks freshness" off-flavors were determined by sensory analysis at the same intervals. In light-exposed samples, oxidation off-flavor was significantly lower when packaged in amber PETE versus other containers. Milk packaged in HDPE containers showed a significantly higher level of oxidation off-flavor than milk packaged in PETE-UV containers but not higher than clear PETE or glass containers. No significant difference in acetaldehyde off-flavor was found between package material treatments (exposed or protected). Acetaldehyde concentration never exceeded flavor threshold levels, regardless of packaging material. Amber and PETE-UV materials proved to be a competitive packaging choice for milk in preserving fresh milk flavor.     

香辛料提取物对低温油炸肉丝软罐头的抗氧化效应研究

目的通过添加具有抗氧化活性和较高安全性的香辛料提取物,解决中式肉类菜肴的软罐头食品中变色、风味变差以及脂肪氧化酸败等问题。方法向低温油炸肉丝软罐头中添加不同添加量的迷迭香、肉桂和VE提取物以及2种人工合成抗氧化剂丁基羟基茴香醚(butyl hydroxy anisd,BHA)和没食子酸丙酯(propylgallate,PG),测定其对软罐头菜肴产品在贮藏过程中硫代巴比妥酸值(thiobarbituric acid-reacitive substances,TBARS值)、过氧化物值(peroxide value,POV值)和色差值的影响。结果添加的3种共9组天然抗氧化剂中,迷迭香提取物抑制初级氧化产物氢过氧化物和次级氧化产物丙二醛的效果最好(P0.05)。添加300 mg/kg迷迭香、90 mg/kg PG和120 mg/kg BHA的3组处理组在21 d冷藏期内,其POV值和TBARS值显著小于其他各组(P0.05),说明添加300 mg/kg迷迭香可以替代人工抗氧化剂。结论低温油炸肉丝软罐头中添加300 mg/kg迷迭香提取物,可以减缓脂肪氧化速度,进而延长产品的货架期。     

LIPID OXIDATION IN MUTTON: SPECIES-RELATED AND WARMED-OVER FLAVORS

Effects of lipid oxidation in cooked mutton on species-related flavor and warmed-over flavor (WOF) intensities were studied using various additive treatments and post-cooking storage (versus no additive/no storage) as means to produce samples of varied lipid oxidation. Ground mutton was treated with 200 ppm sodium nitrite, 0.5% sodium tripolyphosphate, 0.05% sodium ascorbate, 3% sodium lactate, 0.002% propyl gallate, or water only (control), cooked to 74C, and aerobically stored at 4C for 0, 2, or 4 days. Nitrite-treated samples showed the least lipid oxidation as determined by the 2-thiobarbituric acid reactive substances (TBARS) and had more intense species-related (muttony) flavor than all other treated samples. Some samples exhibited high TBARS after 4 days but were still rated "slight" for WOF intensity, probably due to the strong species-related flavor that could have made WOF less perceivable. Accordingly, correlations, although statistically significant, were low between TBARS and WOF intensity or between species flavor intensity and WOF intensity.     

Singlet Oxygen and Ascorbic Acid Effects on Dimethyl Disulfide and Off-Flavor in Skim Milk Exposed to Light

The light-induced off-flavor and dimethyl disulfide increased as fluorescent light exposure increased from 0,2,4,6, to 8h (p<0.05). Sensory evaluation and identified compounds suggest that dimethyl disulfide was mainly responsible for the light-induced off-flavor in skim milk. Dimethyl disulfide was formed by the singlet oxygen oxidation of methionine in milk. Gas chromatographic analysis and sensory evaluation showed that 200,500, and 1000 ppm ascorbic acid, which is a singlet oxygen quencher, lowered the formation of dimethyl disulfide and off-flavor in skim milk (p<0.05).     

Aroma analysis of light-exposed milk stored with and without natural and synthetic antioxidants

The effect of antioxidants, added in a single initial dose or in weekly additions to extended shelf life milk, was evaluated over 6 wk of lighted storage at 4 degrees C. Light-induced oxidation was measured by determining pentanal, hexanal, heptanal, and 1-octen-3-ol contents. Weekly addition of a combination of butylated hydroxyanisole and butylated hydroxytoluene (100 mg/kg of milk fat, each) maintained heptanal content of milk at levels comparable to light-protected milk, whereas an initial single addition of alpha-tocopherol significantly decreased hexanal content over the first 4 wk of storage. Odor-active compounds associated with light-induced oxidation included 2,3-butanedione, pentanal, dimethyl disulfide, hexanal, 1-hexanol, heptanal, 1-heptanol, and nonanal. The addition of butylated hydroxyanisole and butylated hydroxytoluene in a single initial addition resulted in decreases in pentanal and hexanal odor, but not in heptanal and 1-heptanol odor, whereas the addition of alpha-tocopherol and ascorbyl palmitate decreased pentanal and heptanol odor, but not hexanal and heptanal odor.     

The effect of α-tocopherol and butylated hydroxyanisole on the colour properties and lipid oxidation of kavurma, a cooked meat product

Kavurma is a cooked meat product and is consumed sliced. The amount of animal fat in kavurma (30-40%) is higher than in other meat products; therefore, lipid oxidation and colour defects are a major problem during storage and in the market place. To preserve the quality characteristics of kavurma in markets antioxidants must be added and the product must be packaged and stored at low temperature. In this study, the effects of α-tocopherol and butylated hydroxyanisole (BHA) levels on lipid oxidation and colour deterioration of sliced and vacuum-packaged kavurma were investigated. Kavurma was made from beef meat and melted beef fat in 5 groups: No-added antioxidant, 50mg/kg BHA, 100mg/kg BHA, 50mg/kg α-tocopherol and 100mg/kg α-tocopherol. The kavurma produced was sliced (3-4-cm thick) and vacuum packed and stored at 4°C for 300 days, and thiobarbituric acid reactive substance, pH, moisture, lightness, redness and yellowness values of sliced product were determined during storage. The use of antioxidants in kavurma production caused a significant (P<0.01) decrease in the thiobarbituric acid reactive substances (TBARS) values. The lipid oxidative stability effect of the antioxidants was in following order: 100mg/kg BHA>100mg/kg α-tocopherol>50mg/kg BHA=50mg/kg α-tocopherol>no-added antioxidant group. Also, TBARS values did not differ significantly (P>0.05) between 0 and 300 days in the 100mg/kg BHA and 100mg/kg α-tocopherol groups. In addition, the no-added antioxidant group had lower lightness and yellowness values than all the antioxidant groups. Sliced and vacuum-packaged kavurma with added antioxidant showed greater colour and lipid oxidative stability during storage than kavurma to which no antioxidant was added.     

复配抗氧化剂在牡丹籽油乳液中的抗氧化作用研究

为提高牡丹籽油乳液的氧化稳定性，将叔丁基对苯二酚（TBHQ）与天然抗氧化剂（生育酚、抗坏血酸）进行复配，测定不同抗氧化剂对牡丹籽油乳液的抗氧化作用，并分析了不同复配抗氧化剂的相互作用机制。结果表明：在贮藏30 d时，添加和未添加抗氧化剂牡丹籽油乳液的粒径相较于0 d 均略有增加，200 mg/kg TBHQ与800 mg/kg抗坏血酸复配时乳液的Zeta电位绝对值最大，且抗氧化作用最强；TBHQ与抗坏血酸表现出较好的协同抗氧化作用，与生育酚表现出拮抗作用；TBHQ与生育酚之间拮抗作用的原因主要是TBHQ减少了生育酚在牡丹籽油乳液中油水界面的含量，而TBHQ与抗坏血酸之间协同作用主要是由于抗坏血酸增加了TBHQ在牡丹籽油乳液中油水界面的含量。综上，TBHQ与抗坏血酸复配能提高牡丹籽油乳液的氧化稳定性。     

3种抗氧化剂处理对干制鲅鱼脂肪氧化和挥发性风味成分的影响

以新鲜鲅鱼为原料,研究叔丁基对苯二酚（tert-butylhydroquinone,TBHQ）、奎诺二甲基丙烯酸酯（trolox）和L-半胱氨酸（L-cysteine,L-Cys）对干制鲅鱼脂肪氧化与挥发性风味物质的影响。检测并分析鱼肉pH值、脂肪氧化（酸价、过氧化值、丙二醛含量）、1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除能力及挥发性风味成分的变化。结果表明：与对照组相比,经0.02%抗氧化剂浸泡处理后鱼肉的酸价、过氧化值、丙二醛含量分别至少降低1.18 mg/g、0.28 g/100 g、66.68 mg/kg,DPPH自由基清除率提高9.80%,pH值未发生明显变化,抗氧化效果表现为Trolox>L-Cys>TBHQ;此外,抗氧化剂处理降低了干制鲅鱼中挥发性风味成分的相对含量;在TBHQ组、Trolox组、L-Cys组和对照组中,含有关键风味成分的数量分别为11、3、11、13种,仅L-Cys组中的关键风味成分与对照组接近,对干制鲅鱼特有风味的影响最小。综上,氨基酸类抗氧化剂L-Cys可以取代合成类...     

Exposure to light-emitting diodes may be more damaging to the sensory properties of fat-free milk than exposure to fluorescent light

Light exposure can damage the sensory properties of milk, leading to adverse consumer responses. This is presumed to be through the action of photosensitive compounds such as riboflavin, present in milk and capable of releasing energy when irradiated, leading to damage of proteins and fats in the milk. Light-emitting diode (LED) lighting is assumed to be less damaging to milk due to lower inherent power consumption. In this study, fat-free milk was exposed to LED and fluorescent light at 2,000 lx to compare the sensory thresholds of exposure, the flavor profile of milk produced by these exposures, and resultant consumer acceptance of the samples. Additionally, the effectiveness of light-protective packaging and supplementation with antioxidants was evaluated. The sensory threshold from LED exposure was no longer than from fluorescence, whereas with antioxidants (tocopherols and ascorbic acid), the majority of the panelists failed to discriminate milk exposed to LED light even at 48 h of exposure. Trained panelists described light-exposed milk as significantly higher in cardboard, old oil, and plastic, with LED exposure resulting in a marginally more plastic aroma, and fluorescent marginally more cardboard. Consumers reported higher liking for fluorescent-exposed samples versus those exposed to LED. The antioxidant-supplemented samples, and those exposed to LED light engineered to eliminate wavelengths below 480 nm (thus most of riboflavin's absorption peaks), resulted in significantly higher old oil aroma; however, the former received higher liking scores than LED-exposed samples. Light-protective packaging offered near-complete protection from LED exposure, with a similar flavor profile as unexposed milk, and the best liking scores of any treatment. Nevertheless, consumers disliked its appearance, due to unfamiliarity, suggesting some consumer education may be needed if this were to be an efficient protective strategy.     

EFFECTS OF LIQUID SMOKE ON LIPID OXIDATION IN A BEEF MODEL SYSTEM AND RESTRUCTURED ROASTS

Commercially available liquid smokes were added to a meat model system and to a restructured beef product to assess their ability to suppress lipid oxidation. Aqueous hickory smoke was the most effective smoke in suppressing oxidation as reflected in 2-thiobarbituric acid reactive substances (TBARS) of microsomal lipids. Phenol was not antioxidative in the model system. Addition of liquid smoke had no significant effect on "stale, cardboardy, painty" flavor or aroma of restructured beef roast slices stored at 4C. The aroma and flavor of sliced beef deteriorated over the 7-day storage regardless of liquid smoke addition. Hexanal in the control roasts increased during storage from ∼0 to >3 ppm; those containing aqueous liquid smoke contained little (< 0.5 ppm) hexanal. Smokes, but not the phenol mix, kept TBARS near day zero (0.2 mg/kg) levels through 7 days.     

Effect of sodium ascorbate dose on the shelf life stability of reduced nitrite liver pâtés

The effect of sodium ascorbate (SA; 500, 750, 1000 mg/kg) and sodium nitrite (SN; 40, 80, 120 mg/kg) doses on the shelf-life stability of liver patés was investigated in a full factorial design. Clear dose-dependent responses of the added SN or SA were found for the concentrations of nitrite, ascorbic acid and dehydroascorbic acid in the raw batters and in the cooked patés before and after 48 h of chilled display. Decreasing the SN dose to 80 mg/kg had no negative impact on the colour stability (a* value) and lipid oxidation (TBARS), and no additional antioxidant effect of SA was noticed. Lowering SN to 40 mg/kg resulted in proper colour formation, but the colour stability was inferior and lipid oxidation increased. Yet, increasing the amount of SA, at this low SN dose, resulted in lower TBARS values. Decreasing the SN dose to 80 or 40 mg/kg had no distinct effect on protein oxidation, which was however only measured by carbonyl content.     

Antioxidant mechanisms of Trolox and ascorbic acid on the oxidation of riboflavin in milk under light

Antioxidant activities and the mechanism of water-soluble Trolox and ascorbic acid on the oxidation of riboflavin in milk were studied. Trolox or ascorbic acid at 0, 100, 250, 500, or 1000 ppm was added to milk with or without added 50 ppm riboflavin and stored under light at 27 °C. Headspace oxygen was analysed by GC and Trolox, ascorbic acid, and riboflavin were determined by HPLC. The headspace oxygen of milk with added 50 ppm riboflavin depleted faster than that of milk without added riboflavin (p < 0.05). Trolox and ascorbic acid decreased during storage under light and riboflavin was completely destroyed within 24 h. As the concentration of Trolox or ascorbic acid increased, the riboflavin loss decreased. Riboflavin, Trolox, and ascorbic acid competed to react with singlet oxygen which was formed in the presence of riboflavin under light. Trolox and ascorbic acid protected riboflavin in milk under light by reacting with singlet oxygen.     

Effects of Urtica dioica and Hibiscus sabdariffa on the quality and safety of sucuk (Turkish dry-fermented sausage)

In this study, the effect of Urtica dioica, Hibiscus sabdariffa butylatedhydroxytoluene (BHT) and nitrite/nitrate on the quality (pH, Hunter L-, a- and b-value and sensory attributes) and safety [2-thiobarbituric acid reactive substances (TBARS) value and biogenic amine] were investigated during the ripening periods of sucuk (Turkish dry-fermented sausage). During the first 2 days of ripening, pH values decreased (P<0.05) rapidly from 5.78 to about 4.49. pH values of batters were not significantly (P<0.05) affected by the addition of nitrite/nitrate, BHT, U. dioica, H. sabdariffa. TBARS values increased from 0.52 to about 0.95mg/kg significantly (P<0.05) during the first 4 days in control, and H. sabdariffa added batters. The highest (P<0.05) histamine concentration was determined in the control batter prepared without antioxidant. U. dioica was more effective (P<0.05) on decreasing histamine and putrescine concentration than the other antioxidants. Putrescine concentration in batters increased (P<0.05) from 1.13 to about 15.34mg/kg during the first 4 days. Tyramine concentration increased significantly (P<0.05) during the ripening period from 5.55 to 103.93mg/kg. The control batter had the highest (P<0.05) tyramine concentration about 50.21mg/kg. Hunter L-values were not affected (P>0.05) from ripening time and addition of antioxidants into batter. The Hunter a-value increased (P<0.05) during the ripening periods, however, b-values decreased (P<0.05) from 12.58 to about 10.53. Overall sensory quality evaluated from color, flavor and ease of cutting scores increased (P<0.05) from 3.25 to about 9.00.     

Influence of high-oryzanol rice bran oil on the oxidative stability of whole milk powder

The effect of high oryzanol rice bran oil (RBO) on the oxidative stability of low-heat and high-heat whole milk powder (WMP) was investigated. Milk (3.6% fat) was fortified with RBO at 0.1 and 0.2% (wt/wt) and was concentrated and dried. Control WMP was made without RBO addition. Thiobarbituric acid reactive substances (TBARS) were used to monitor oxidation during storage at 45 degrees C for 40 d. The oxidation of low-heat WMP was significantly reduced by addition of 0.1% RBO, but there was no significant effect on the oxidation of high-heat WMP. An increase of RBO to 0.2% did not significantly improve the oxidative stability when compared with 0.1% RBO. The TBARS in RBO-fortified, low-heat WMP increased with storage time up to 30 d but decreased with further storage to 40 d. The TBARS in all high-heat WMP and low-heat control WMP increased up to 20 d storage and then decreased with further storage. The most likely reason for this increase was due to the reaction of TBARS with milk proteins. Addition of RBO reduced the L (lightness) value and increased the b (yellowness) value but had no effect on the a (redness) value. When compared with the control milk powder, consumers could not detect any effect on the flavor of the reconstituted 0.1% RBO WMP but could detect a flavor difference in the 0.2% RBO WMP.     

Identification of objectionable flavors in purported spontaneous oxidized flavor bovine milk

Spontaneous oxidized flavor (SOF) has been reported over the past 5 decades as a sporadic objectionable flavor problem in bovine milk. Parameters previously reported to influence SOF development in milk have been contradictory, limiting the ability to monitor and develop mitigation strategies. The current paper investigates the causative compounds associated with milk identified as SOF milk in the Midwest dairy region of the United States. Based on GC/MS-olfactometry analysis, endo-borneol, 2-methylisoborneol, and α-terpineol were identified as the off-flavor compounds. Sensory recombination studies further confirmed the sensory contribution of these compounds to the noted off-flavor attributes in the original milk, which were described as “green,” “musty,” and “unclean.” These compounds are known microbial-derived flavor taints, indicating oxidation was not the origin of the objectionable flavor in the milk. This noted misclassification of the milk as SOF indicates the challenge of defining flavor defects without the identification of the active compounds.     

Effect of rosemary extract dose on lipid oxidation, colour stability and antioxidant concentrations, in reduced nitrite liver pâtés

The oxidative stability of liver pâté was investigated in relation to different doses of rosemary extract (RE) and sodium nitrite. Colour stability, lipid oxidation (TBARS) and concentrations of ascorbic acid, α-tocopherol, carnosic acid and nitrite were measured on the batters before cooking and on the cooked liver pâté before and after exposure to light and air for 48 h at 4 °C. Results showed that the use of RE significantly reduced lipid oxidation, whereas it had no effect on colour stability. Ascorbic acid and nitrite concentrations were significantly higher and lower respectively when RE was added. RE dose-dependently increased the concentration of carnosic acid. Lower sodium nitrite doses resulted in significantly lower nitrite concentrations and slightly lower TBARS values. It was concluded that in liver pâté sodium nitrite levels may be lowered to 80 mg/kg without negatively affecting colour and lipid stability and that the use of RE may help in maintaining lipid stability.     

响应面法优化天然抗氧化剂抑制调理鸡排褪色和脂质氧化工艺

目的：为延缓调理鸡排贮藏期间的褪色和脂质氧化,研究迷迭香提取物和抗坏血酸对其红度（a*）值和脂肪氧化的影响。方法：采用单因素试验结合中心组合试验设计,对腌制液中迷迭香提取物和抗坏血酸的添加量进行优化,以a*值和脂肪氧化值作为响应值筛选最佳配比。结果：单因素和响应面试验结果表明,迷迭香提取物和抗坏血酸添加量对鸡排a*值和脂肪氧化值具有显著影响。以a*值和脂肪氧化值为响应值,得到2 个二次多项式回归方程,决定系数R2分别为0.932 0、0.886 3,失拟项的P值均大于0.05,说明2 个模型均建立有效。迷迭香提取物的一次项（P＜0.05）、抗坏血酸的一次项和二次项（P＜0.01）对鸡排a*值影响显著;迷迭香提取物的一次项（P＜0.01）和抗坏血酸的二次项（P＜0.05）对脂肪氧化影响显著。结论：当设定a*值最高、脂肪氧化值最低时,获得最佳复配参数为迷迭香添加量0.198 g/kg、抗坏血酸添加量0.255 g/kg,经验证实验测得50 d后调理鸡排的a*值为21.88,脂肪氧化值为0.59 mg/kg,与拟合结果一致。     

Controlling Light Oxidation Flavor in Milk by Blocking Riboflavin Excitation Wavelengths by Interference

ABSTRACT:  Milk packaged in glass bottles overwrapped with iridescent films (treatments blocked either a single visible riboflavin [Rb] excitation wavelength or all visible Rb excitation wavelengths; all treatments blocked UV Rb excitation wavelengths) was exposed to fluorescent lighting at 4 °C for up to 21 d and evaluated for light-oxidized flavor. Controls consisted of bottles with no overwrap (light-exposed treatment; represents the light barrier properties of the glass packaging) and bottles overwrapped with aluminum foil (light-protected treatment). A balanced incomplete block multi-sample difference test, using a ranking system and a trained panel, was used for evaluation of light oxidation flavor intensity. Volatiles were evaluated by gas chromatography and Rb degradation was evaluated by fluorescence spectroscopy. Packaging overwraps limited production of light oxidation flavor over time but not to the same degree as the complete light block. Blocking all visible and UV Rb excitation wavelengths reduced light oxidation flavor better than blocking only a single visible excitation wavelength plus all UV excitation wavelengths. Rb degraded over time in all treatments except the light-protected control treatment and only minor differences in the amount of degradation among treatments was observed. Hexanal production was significantly higher in the light-exposed control treatment compared to the light-protected control treatment from day 7; it was only sporadically significantly higher in the 570 nm and 400 nm block treatments. Pentanal, heptanal, and an unidentified volatile compound also increased in concentration over time, but there were no significant differences in concentration among the packaging overwrap treatments for these compounds.     

Effect of dietary fat and vitamin E on alpha-tocopherol in milk from dairy cows

Diets with different fat treatments and with 25, 125, or 250 IU of supplemental vitamin E (all-rac alpha-tocopheryl acetate)/kg of dry matter (DM) were fed for 28 d to midlactation Holstein cows to determine factors affecting concentrations of alpha-tocopherol in milk. Diets contained no supplemental fat or 2.25% added fat from roasted soybeans or tallow. Vitamin E treatment had no effects on production, but fat supplementation increased milk yield (37.2 vs. 35.1 kg/d). Cows fed RSB ate more DM (24.0 vs. 21.9 kg/d) and produced more milk fat than cows fed tallow. Supplemental fat increased plasma concentrations of alpha-tocopherol and cholesterol. Increased intake of alpha-tocopherol linearly increased concentrations of alpha-tocopherol in plasma but the rate of increase was 1.9 times greater when fat was fed. Plasma alpha-tocopherol concentrations were linearly related to concentrations in milk, but a change in plasma alpha-tocopherol resulted in a smaller change in milk alpha-tocopherol when fat was fed than when it was not. Fat treatment did not affect plasma alpha-tocopherol expressed relative to plasma cholesterol (mg alpha-tocopherol/g cholesterol) or relationships between plasma alpha-tocopherol/g of cholesterol and milk alpha-tocopherol. These data suggest that concentrations of alpha-tocopherol in milk are a function of the alpha-tocopherol enrichment of the plasma lipid fraction and enrichment of that fraction is saturable.