Depth-dependent magnetism in epitaxial MnSb thin films: effects of surface passivation and cleaning.

Depth-dependent magnetism in MnSb(0001) epitaxial films has been studied by combining experimental methods with different surface specificities: polarized neutron reflectivity, x-ray magnetic circular dichroism (XMCD), x-ray resonant magnetic scattering and spin-polarized low energy electron microscopy (SPLEEM). A native oxide ∼4.5 nm thick covers air-exposed samples which increases the film's coercivity. HCl etching efficiently removes this oxide and in situ surface treatment of etched samples enables surface magnetic contrast to be observed in SPLEEM. A thin Sb capping layer prevents oxidation and preserves ferromagnetism throughout the MnSb film. The interpretation of Mn L(3,2) edge XMCD data is discussed.

Effect of grape seed extract on oxidative, color and sensory stability of a pre-cooked, frozen, re-heated beef sausage model system.

To compare grape seed extract (GSE) to common antioxidants in a pre-cooked, frozen, stored meat model system sausage was manufactured from lean beef (70%), pork fat (28%), and salt (2%). Antioxidants added for comparison with control included grapeseed extract (100, 300, and 500 ppm), ascorbic acid (AA, 100 ppm of fat) and propyl gallate (PG, 100 ppm of fat). Product was formed into rolls, frozen, sliced into patties, cooked on a flat griddle to 70 °C, overwrapped in PVC, then frozen at - 18 °C for 4 months. GSE- and PG-containing samples retained their fresh cooked beef odor and flavor longer (p < 0.05) than controls during storage. Rancid odor and flavor scores of GSE-containing samples were lower (p < 0.05) than those of controls after 4months of storage. The L* value of all samples increased (p<0.05) during storage. Thiobarbituric acid reactive substances (TBARS) of the control and AA-containing samples increased (p < 0.05); those of GSE-containing samples did not change significantly (p > 0.05) over the storage period.

Effect of salmon type and presence/absence of bone on color, sensory characteristics, and consumer acceptability of pureed and chunked infant food products.

Salmon-based infant food (puree) and toddler food (puree plus chunks) were manufactured from pink salmon, with and without bone, and from Sockeye salmon, with and without bone, to contain 45% salmon, 55% water, and 5% starch. Products were retort processed at 118 to 121 degrees C for 55 min in a steam-jacketed still retort. A trained descriptive panel (n = 7) evaluated infant and toddler foods separately. Instrumental color, pH, and water activity were also determined. Infant and toddler foods were also evaluated by a consumer panel (n = 104) of parents for product acceptability. During the manufacturing process (cooking, homogenization, retort processing), salmon infant food from pink salmon lost much of its characteristic pink color while that from sockeye salmon retained a greater amount. Bitterness was more evident in samples with bones. In the toddler food formulation containing chunks, the odor and flavor characteristics were influenced primarily by the type of salmon. The presence of bone affected visual pink color and lightness, and salmon odor only. Consumers scored products made with sockeye salmon as more acceptable despite the fact that they had more off-flavor than products from pink salmon. The appearance and thickness of the pureed infant food was more acceptable than the toddler food with chunks despite the chunky toddler product having more acceptable salmon flavor. This indicates that the color and appearance of the prototypes were the main drivers for liking. Of the total number of parents surveyed, 73% would feed this salmon product to their children.

Effect of inclusion of salmon roe on characteristics of salmon baby food products.

Baby food was formulated from sockeye salmon (puree alone, puree + chunks, puree + pink row, puree + pink row + chunks, puree + red row, puree + red roe + chunks). In the 1st study, physical (pH, instrumental color, water activity) and descriptive sensory (odor, flavor, texture, visual color) characteristics were determined. Samples containing roe were lighter and less red (by approximately 3 to 4 a* units) than formulations without roe regardless of the type of roe added. Visual pink color followed the same trend. Formulations with roe, both pink and sockeye, were almost twice as fibrous as formulations without roe. Salmon flavor was stronger in samples containing roe from sockeye salmon. In the 2nd study, retort processed samples were stored at room temperature for 6 mo. Sweaty odor decreased over storage time. Visual cream-brown color correlated with L*, a*, b*, and chroma values (r =-0.80, 0.75, 0.80, and 0.84, respectively). TBARS values of all samples were < 0.35 mg MDA/kg and declined after month 0 indicating that these products were oxidatively stable. Overall, adding roe to these products lightened them and increased fibrous texture. Samples containing sockeye salmon roe had stronger salmon flavor. Once retort processed, these products were quite stable in terms of color, odor, and TBARS. Potential nutrient contributions of this type of product to the infant diet warrant additional research.

Effect of natural and synthetic antioxidants on the oxidative stability of cooked, frozen pork patties.

The effect of grape seed extract (GS; 0.02%), oleoresin rosemary (OR; 0.02%), water-soluble oregano extract (WS; 0.02%), propyl gallate (PG; 0.02% of fat), butylated hydroxyanisole (BHA; 0.02% of fat), and butylated hydroxytoluene (BHT; 0.02% of fat) on the oxidative and color stability of precooked pork patties stored at -18 degrees C for up to 6 mo were determined. Pork lean and trim were ground and mixed (30% fat). Antioxidants mixed with salt (2%) were added. Patties were formed, cooked to 71 degrees C, over wrapped in PVC, and stored at -18 degrees C. Lipid oxidation was determined using thiobarbituric acid-reactive substances (TBARS) and descriptive sensory evaluation. Color was determined instrumentally and visually. Samples were evaluated after 0, 1, 2, 3, 4, 5, and 6 mo of frozen storage. Based upon TBARS values, PG (0.21 mg MDA/kg) and GS extract (0.23) had more antioxidant activity over the storage period than did WS, OR, BHA, and BHT. GS had no effect on a* or b* values. Grape seed extract (0.02%) has the potential to inhibit oxidative rancidity as well as current synthetic antioxidants.

Irradiation effects on meat flavor: A review.

Irradiating fresh meat, even at low doses, can result in off-odors and flavors which have been described as rotten egg, bloody, fishy, barbecued corn, burnt, sulfur, metallic, alcohol or acetic acid. The odors vary with the type of meat, temperature during irradiation, oxygen exposure during and/or after the irradiation process, packaging and presence of antioxidative substances. Irradiation can induce formation of isooctane-soluble carbonyl compounds in the lipid fraction and low molecular weight, acid-soluble carbonyls in the protein fraction of meat. Increasing irradiation dose increases these compounds however, cooking reduces them. Among the volatile components, 1-heptene and 1-nonene are influenced most by irradiation dose, and aldehydes (propanal, pentanal, hexanal) are influenced most by packaging type (aerobic vs vacuum). Sulfur-containing volatiles formed from sulfur-containing compounds (primarily amino acids) also contribute to irradiation odor. Dimethyltrisulfide is one of the most potent off-odor compounds, contributing fishy, putrid odors, followed by bismethylthiomethane (sulfurous). Reducing the temperature during the irradiation process reduces the effects on odor/flavor because free radical generation and dispersion are reduced. Ultimately, radiolysis of water into free radical species (OH,H, H(3)0(+), e(aq)(-)) may be the initiators of both lipid oxidation breakdown products and sulfur-containing volatiles responsible for irradiation odor. Methods to decrease the detrimental effects of irradiation include oxygen exclusion (vacuum packaging), replacement with inert gases (nitrogen), addition of protective agents (antioxidants), and post-irradiation storage to allow flavor to return to near-normal levels (re-packaging or double packaging in oxygen permeable film).

Characterization of striping in fresh, enhanced pork loins.

To investigate the striping phenomenon in fresh, enhanced pork, a series of experiments were undertaken to identify possible causes of the problem. No one factor (individual brine components, brine pH, ingredient concentration, enhancement pressure, meat and brine pH, or enhancement level) was specifically identified, which could be used to reduce the severity of the striping problem. Furthermore, tumbling the product for 2h, did not reduce the amount of striping, indicating once striping has occurred, it is permanent. Evaluation of the striping pattern indicates that the stripes are formed not only at the needle injection site, but also follow the muscle fiber orientation. The use of darker pork provided more of a contrast when evaluating striping, thus exacerbating the perceived level of striping.

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 200mg/kg decreased lipid oxidation. Lipid oxidation of pork chops and ground pork was similar between pigs fed 40mg/kg and higher levels of natural vitamin E, indicating no additional benefits from supplementing beyond 40mg/kg natural vitamin E. Supplementing 200mg/kg synthetic vitamin E decreased pork lipid oxidation when compared to supplementing 10mg/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 40mg/kg.

Effects of carbon monoxide-modified atmosphere packaging and irradiation on E. coli K12 survival and raw beef quality.

The objective of this study was to evaluate the combined effects of irradiation and carbon monoxide in modified atmosphere packaging (CO-MAP) on total plate counts, Escherichia coli K12, color, and odor of fresh beef during refrigerated storage. Beef was packaged aerobically or in CO-MAP, and irradiated at 0, 0.5, 1.0, 1.5 or 2.0kGy then held at 4°C for 28days. Raw beef odor decreased and acid/sour, rancid and grassy odors increased starting on day 14. Initially, no difference existed for visual green color scores due to gas atmosphere. After 14days of storage, aerobically packaged beef was greener and less red than CO-MAP packaged beef. The a∗ value of CO-MAP packaged beef was higher than that of aerobically packaged beef. Red color of CO-MAP packaged samples decreased slightly in some irradiated samples after 14days of storage. On day 0 and thereafter, no coliforms were detect after irradiation at 1.5 or 2.0kGy regardless of packaging format. These findings suggest that CO-MAP could be used to preserve beef color irradiated at doses sufficient to reduce microbial loads to safe levels during 28days of storage.

Quality changes in beef complexus, serratus ventralis, vastus lateralis, vastus medialis, and longissimus dorsi muscles enhanced prior to aging.

Beef complexus (chuck), serratus ventralis (chuck), vastus lateralis (round), vastus medialis (round), and longissimus dorsi (loin) muscles were enhanced (0.3% salt, 0.4% phosphate), vacuum packaged, and aged for 7 or 14 d. Enhancement increased positive sensory attributes (tenderness, juiciness, beef flavor, saltiness) and decreased negative attributes (off-flavors) of all muscles but had greater effects on some than on others. It increased the oily mouthfeel (10%) and saltiness (40%) and decreased the L* value and chroma of the complexus (chuck). It increased tenderness, juiciness, and beef flavor and decreased off-flavors, visual red and brown colors, shear value, and cook loss of the serratus ventralis (chuck), vastus lateralis (round), vastus medialis (round), and longissimus dorsi (loin). Aging slightly decreased rancid and liver off-flavor scores, visual brown color, and shear value and increased the hue angle and L* and b* values.

Effect of enhancement and ageing on flavor and volatile compounds in various beef muscles.

To identify and quantify selected flavor-active volatile compounds and relate them to sensory characteristics, the gluteus medius (round), rectus femoris (round), vastus lateralis (round), vatsus medialis (round), teres major (chuck), infraspinatus (chuck), complexus (chuck), serratus ventralis (chuck), psoas major (loin) and longissimus dorsi (loin) were removed from heifer carcasses, enhanced, vacuum packaged, aged for 7 or 14days, steaks were cut, vacuum packaged and frozen (48h). Flavor-active volatiles affected by enhancement and ageing in the various muscles included nonanal, 2,3-octanedione, pentanal, 3-hydroxy-2-butanone, 2-pentyl furan, 1-octen-3-ol, butanoic acid, pentanal and hexanoic acid, compounds often associated with lipid oxidation. Enhancement decreased hexanal and hexanoic acid. Ageing decreased butanoic acid. Pentanal content varied among muscles depending on enhancement and ageing. Livery off-flavor was positively correlated with pentanal, hexanal, 3-hydroxy-2-butanone and hexanoic acid. Rancid off-flavor was correlated with pentanal and with 2-pentyl furan but not with hexanal.

Intramuscular fat content has little influence on the eating quality of fresh pork loin chops.

Fresh pork loins (n = 290) were selected from a commercial packing facility based on subjective marbling of the intact loin and 24-h pH to determine the influence of marbling on sensory attributes. The study was designed using pigs from a similar genetic background, raised in similar production facilities, and slaughtered on a single kill day to minimize the effects of genetics, management, environment, and slaughter day. Loins were vacuum-packaged, transported to the University of Illinois Meat Science Laboratory, and aged for 7 d, after which a chop was removed from the area of the tenth rib for proximate analysis. Quality measurements, including National Pork Producers Council color, marbling, and firmness, ultimate pH, Minolta L*, a*, and b*, and drip loss, were determined after aging. After the proximate composition was completed, 150 loins were selected to provide a continuous and uniform distribution of extractable lipid, ranging from 1 to 8%, and a pH range from 5.5 to 5.8. Trained sensory panel analyses (end point cooking temperatures of 62, 71, or 80 degrees C) as well as measurement of Warner-Bratzler shear force (cooked to 71 degrees C) were performed on chops from the 150 loins. Consumer evaluation was also conducted on a subset (n = 40) of these loins, which were broken down into 5 discrete levels of intramuscular lipid, with averages of 1.6, 2.5, 3.6, 4.5, and 5.7% extractable lipid. Consumers were also asked to select the chops they would most prefer from a retail display case based on the amount of marbling present. Results from the consumer portion of the study indicated that intramuscular fat content had limited effects on perceived tenderness, juiciness, pork flavor, and oiliness; some significant differences (P < 0.05) were detectable, but they were numerically small. Most consumers also selected lean chops from the retail case, with nearly 50% selecting chops with less than 1.7% extractable lipid. Warner-Bratzler shear force was negatively related (P < 0.0001) to extractable lipid, with an R(2) value of 0.10. Results from the trained panel sensory analysis indicate that the percentage of extractable lipid did not correlate strongly with perceived tenderness, juiciness, or pork flavor for this group of pork loins that was controlled for genetics, pH, management, and day of slaughter.

Sweet taste in man: a review.

A greater understanding of the molecular mechanisms of sweet taste has profound significance for the food industry as well as for consumers. Understanding the mechanism by which sweet taste is elicited by saccharides, peptides, and proteins will assist science and industry in their search for sweet substances with fewer negative health effects. The original AH-B theories have been supplanted by detailed structural models. Recent identification of the human sweet receptor as a dimeric G-protein coupled receptor comprising T1R2 and T1R3 subunits has greatly increased the understanding of the mechanisms involved in sweet molecule binding and sweet taste transduction. This review discusses early theories of the sweet receptor, recent research of sweetener chemoreception of nonprotein and protein ligands, homology modeling, the transduction pathway, the possibility of the sweet receptor functioning allosterically, as well as the implications of allelic variation.

Quality changes in beef gluteus medius, infraspinatus, psoas major, rectus femoris, and teres major enhanced prior to aging.

The objective of this study was to evaluate the effects of enhancement and aging on quality characteristics of the gluteus medius (round), rectus femoris (round), teres major (chuck), infraspinatus (chuck), and psoas major (loin). Muscles were enhanced, vacuum packaged, and aged for 7 or 14 d. Aging affected enhanced compared with nonenhanced beef differently. After 7 d of aging, enhanced beef experienced more cook loss and was less red (higher hue angle, lower a* values, and chroma) than did nonenhanced beef; after 14 d of aging, these differences were lost. Enhancement increased tenderness and brown color of the gluteus medius (round); however, it decreased visual green and red colors. Enhanced gluteus medius experienced 3.1% lower purge losses, lower L* values, and chroma than their nonenhanced counterparts. Enhancement increased infraspinatus (chuck) tenderness and visual brown color, and decreased visual red and green colors, purge loss, L* value, a* value, and chroma. The enhanced infraspinatus was substantially more tender than the other muscles evaluated, other than the gluteus medius; however, it was also substantially more visually brown. Enhancement decreased purge loss of the psoas major. Enhancement increased L* and a* values, hue angles, and chroma than other enhanced muscles. After enhancement the tenderness of the rectus femoris increased by 10%, decreased purge losses from 4.5% to 1.7%, and decreased green color by 18%. It reduced L* and a* values and chroma. Aging increased tenderness. Overall, muscles from the chuck (infraspinatus and teres major) appeared to benefit the most from enhancement.

Effect of natural antioxidants on oxidative stability of cooked, refrigerated beef and pork.

The effect of grape seed extract (GS; 0.01% and 0.02%), oleoresin rosemary (OR; 0.02%) and water-soluble oregano extract (WS; 0.02%) on oxidative and color stability of cooked beef and pork patties stored at 4 degrees C for 8 d was determined. Fresh beef or pork lean and trim were ground, mixed (30% fat), and divided into 5 portions. Antioxidants mixed with salt (2%) were added. Patties were formed, cooked to an internal temperature of 71 degrees C, overwrapped in PVC, and stored at 4 degrees C. Lipid oxidation, assessed using thiobarbituric acid reactive substances (TBARS) and sensory evaluation, instrumental and visual color, and pH were determined after 0, 2, 4, 6, and 8 d. Based on TBARS values and off-odors associated with lipid oxidation such as rancidity, wet cardboard (for beef patties), and grassy (for beef and pork patties), grape seed extract resulted in the best antioxidant activity in both meat species. It did not change instrumental color measures of redness, yellowness, or color intensity, and appeared to reduce visual green discoloration in beef patties. The higher GS concentration (0.02%) exhibited more antioxidant activity than the lower concentration (0.01%). Therefore, grape seed extract at 0.02% has the potential to reduce oxidative rancidity and improve shelf life of refrigerated cooked beef and pork patties.

Effect of carbon monoxide in modified atmosphere packaging, storage time and endpoint cooking temperature on the internal color of enhanced pork.

The objective of this research was to evaluate the effects of gas atmosphere, refrigerated storage time, and endpoint temperature on internal cooked color of injection-enhanced pork chops. Enhanced chops were packaged in 0.36% CO/20.34% CO(2) (CO-MAP), 80% O(2)/20% CO(2) (HO-MAP), or PVC-overwrapped (PVC-OW; controls), stored at 4°C for 0, 12, 19 or 26 days, displayed for 2 days then cooked to six endpoint temperatures (54, 60, 63, 71, 77, and 82°C). L(∗), a(∗), and b(∗) values, hue angle and chroma were determined on the internal cut surface of cooked chops. Chops packaged in CO-MAP had the highest a(∗) values; a(∗) value began increasing on day 14. The lowest hue angles occurred in chops cooked to lower endpoint temperatures. Chops in CO-MAP had lower hue angles and higher chroma than those in HO-MAP and PVC-OW. Above 71°C, hue angle and chroma increased. Overall, CO-MAP packaged chops stored for longer time periods then cooked to lower endpoint temperatures appeared reddest. HO-MAP packaged chops were less red, did not change over time, and appeared more well done at lower endpoint temperatures than those in other gas atmospheres. CO-MAP packaged chops retained redness even after cooking at 82°C.

The effects of shelf-life enhancers on E. coli K12 survival in needle-injected, surface contaminated beef strip steaks enhanced using recycled solutions.

The objective of this study was to evaluate the efficacy of shelf-life enhancers (sodium lactate [SL] or sodium lactate+sodium diacetate [SLDA]) on limiting the growth of Escherichia coli K12 in needle-injecting surface-contaminated beef strip steaks with recycled enhancement solutions. Strip loins were injected to 10% over initial weight. SLDA was most effective in controlling bacterial growth followed by SL alone. The salt/phosphate combination in the enhancement solution was ineffective. SL decreased a(∗) (less red) and b(∗) values (less yellow) of the steaks compared to the salt/phosphate control. SLDA decreased L(∗) values compared to SL alone. SL and SLDA were equally effective in reducing purge loss from the steaks. Steaks enhanced with a "fresh" enhancement solution had higher a(∗) values (more red) and higher E. coli contamination levels than steaks enhanced with recycled solutions. Recycling did not affect L(∗) value, b(∗) value, or purge loss.

The effects of shelf-life enhancers on E. coli K12 survival in needle-injected, surface contaminated beef strip steaks enhanced using recycled solutions.

The objective of this study was to evaluate the efficacy of shelf-life enhancers (sodium lactate [SL] or sodium lactate + sodium diacetate [SLDA]) on limiting the growth of Escherichia coli K12 in needle-injecting surface-contaminated beef strip steaks with recycled enhancement solutions. Strip loins were injected to 10% over initial weight. SLDA was most effective in controlling bacterial growth followed by SL alone. The salt/phosphate combination in the enhancement solution was ineffective. SL decreased a(∗) (less red) and b(∗) values (less yellow) of the steaks compared to the salt/phosphate control. SLDA decreased L(∗) values compared to SL alone. SL and SLDA were equally effective in reducing purge loss from the steaks. Steaks enhanced with a "fresh" enhancement solution had higher a(∗) values (more red) and higher E. coli contamination levels than steaks enhanced with recycled solutions. Recycling did not affect L(∗) value, b(∗) value, or purge loss.

Instrumental evaluation of pH effects on ability of pork chops to bloom.

Color plays an important role in consumer purchase decisions of pork. For this reason, the objective of this study was to determine the usefulness of instrumental measures of bloom and bloom as a function of pH. Color was measured with two instruments on pork chops of varied ultimate pH (5.1-6.1) in a vacuum package and again after blooming. During bloom, Hunter a* increased while Minolta a values changed little. Bloom had no effect on either measure of lightness (L* or L). With bloom, Hunter Hue Angle decreased indicating an increase in red color, while Minolta Hue Angle measurement increased with bloom, implying a decrease in true red color. Although lightness was unaffected by bloom, pH had a significant effect on Hunter L* and Minolta L values. Increasing pH resulted in an increase of Hunter a*, but not Minolta a, in both unbloomed and bloomed chops. Hunter Hue Angle was consistently higher than Minolta Hue Angle regardless of bloom status or pH.

Antioxidant and modified atmosphere packaging prevention of discoloration in pork bones during retail display.

The objective of this study was to evaluate the ability of antioxidants to prevent discoloration in pork rib bones. Pork rib bones were removed from carcasses, frozen (-20°C, 24h), split lengthwise, exposed to antioxidant solutions (ascorbic acid, citric acid, propyl gallate or ascorbic/EDTA mix), packaged (modified atmosphere [80% O(2) and 20% CO(2)] or air), then displayed in a retail case at 4°C for 8days. Dark pigment formation was visually evaluated during the display period. Instrumental color was determined at the end of the 8-day display period. Visual bone discoloration increased over time for all treatments. After 2days of display, samples treated with propyl gallate were visually redder, less discolored and less green/black than samples treated with other antioxidants. After 8days of display, propyl gallate-treated samples had higher a* and b* values, as well as chroma (intensity). However, this difference was no longer large enough to be visually detected.