Fatty Acids of Neutral and Phospholipids, Rancidity Scores and TBA Values as Influenced by Packaging and Storage

The fatty acid (FA) of neutral lipids (NL) and phospholipids (PL) and this composition's relationship to rancidity score and TBA values of cooked beef patties, during frozen storage at times up to 4½ months under vacuum and nonpackaged conditions were studied. The predominant FA in the NL was C_18:1 (46.0%), followed by C_16:0 at 29.2%. However, the PL fraction gave a more balanced distribution of FA. In the neutral lipid fractions, reduction in the C_16:1 and C_18:2 fatty acids made significant contributions to increased rancidity scores and TBA values but in the phospholipid fraction, changes in the C_18:3 and C_20:4 were of greatest importance. After 3 months of frozen storage a regression model containing the neutral lipid fatty acids C_18:1 and C_18:2 and the phospholipid fatty acids C_18:3 and C_20:4 accounted for 88% and 85% of the variation in rancidity score and TBA value.     

Packaging and Storage Effects on Microbiological Quality of Dried Herbs

Two hundred herb samples were investigated for microbiological quality. Effects of drying method, type package, and storage conditions were determined for dill, basil, marjoram, and wild marjoram. Total aerobic count ranged from 10⁴ to 10⁷/g dried material. Molds and aerobic sporeformers, especially Bacillus cereus, were detected in most samples; fecal indicator organisms were found infrequently. The number of most vegetative microbes was affected by the drying method. Microbes survived air-drying better than freeze-drying. Packaging affected microbial content. The lethal effect of storage time was most clearly shown when the herbs were packed in oxygen-containing packages.     

Effects of Packaging Method, Display Light and Storage Time On The Microbial Growth and Rancidity of Fresh Pork

Effects of display light, packaging methods and storage time on total aerobic, lipolytic and proteolytic counts and oxidative rancidity of fresh pork stored at 2 ± 1° C were studied at the initial, 7th, 14th and 21st day of storage. Display light significantly increased the total aerobic psychrotroph count. Effects on lipolytic and proteolytic psychiotroph counts were not significant. No anaerobic psychrotrophs were encountered. Total and proteolytic counts of PVC film overwrapped chops and proteolytic and lipolytic psychrotroph counts of chops vacuum packaged accelerated linearly with time. Increases in lipolytic psychrotroph count of PVC packaged and total aerobic psychrotroph count of vacuum packaged chops were quadratic. TBA number and rancid odor scores were not significantly affected by treatments.     

Rumen Ammonia Concentration as Influenced by Storage Time,Freezing and Thawing,Acid Preservative,and Method of Ammonia Determination

Twenty-five milliliters of rumen fluid from five cows on a variety of diets were added to either 25 ml .1 N HCl, 5 ml 25% metaphosphoric acid, 5 ml 20% trichloroacetic acid, 5 ml 3 N H₂SO₄, or no preservative. Replicate samples were stored at −20°C until analyzed. One replicate set was analyzed at 7 d, refrozen and analyzed at 35 d, refrozen, thawed, and reanalyzed at 65 d. Another set was thawed and analyzed at 35 d and yet another set kept frozen until analyzed at 65 d. Fresh and frozen samples were quantitated for ammonia by Conway microdiffusion and phenol-hypochlorite reaction.Ammonia recoveries were 93.8 and 94.1% for the Conway and phenolhypochlorite methods. Storage time and refreezing and thawing had a variable effect on ammonia concentration. Samples with no preservative yielded higher ammonia than those with preservative; ammonia was accentuated by refreezing and thawing up to 65 d. Hydrochloric acid samples had lower ammonia than other acids, especially for the phenolhypochlorite method. Overall, the Conway method resulted in higher ammonia for frozen samples than the phenolhypochlorite method (10.4 vs. 9.0 mg/dl); however, this varied depending on acid.When rumen fluid samples are to be stored with an acid preservative, .1 N HCl is not recommended. Repeated freezing and thawing of rumen samples used for ammonia analysis should be avoided because of variable results.     

Cooking Quality of Brown Rice as Influenced by Gamma Irradiation, Variety and Storage

Two long grain and one medium grain brown rice varieties were gamma-irradiated at 1.0 and 2.0 kGy to ascertain if cooking time could be decreased and to determine effects of storage on chemical and physical characteristics. A tendency toward decreased cooking time was observed as dose level increased. Cooking time was not significantly (P> 0.05) affected by storage. A trend was noted in water uptake ratios, soluble starch of residual cooking water and volume expansion due to irradiation. Storage of irradiated rice produced similar changes to those of nonirradiated rice. Variety also contributed to differences in irradiated samples, such as cooking times, water uptake, starch retention and grain volume expansion.     

Cholesterol Content and Sensory Analysis of Ground Pork as Influenced by Fat Level and Heating

Eight treatment combinations for the formulation and heating of fresh ground pork were investigated: four raw fat levels (4, 9, 18, 23%) and two internal end point temperatures (71°C and 77°C). In the raw state, ground pork containing 4 or 9% fat contained less cholesterol, more moisture and was judged to be more red than samples containing 18 or 23% fat. Tenderness, juiciness and amount of mouthcoating increased as fat level in the cooked patties increased. Internal end point temperature (71°C or 77°C) did not affect sensory scores of cooked pork patties. Cooked patty cholesterol content (wet weight) did not differ among the four fat levels. High-fat ground pork retained less cholesterol than low-fat ground pork.     

Effect of Salt, Sugar and Storage Time on Microbiological, Chemical and Sensory Properties of Chinese Style Dried Pork

A Chinese dried pork product was manufactured with combinations of 15, 22.5, and 30% sugar and 0.5, 1.5, and 2.5% salt and evaluated for microbiological, chemical and sensory properties at 0, 7, 14, and 21 days of storage. Aerobic and anaerobic plate counts and TBA values increased during storage with the high sugar and salt combination resulting in the least microbial growth. No major rancidity problems developed. A 30% sugar and 2.5% salted product resulted in the highest panel flavor scores when evaluated by a group of panelists from the Orient.     

Lipid Oxidation in Cooked Pork as Affected by Vitamin E, Cooking and Storage Conditions

The individual and combined effects of muscle vitamin E level, cooking conditions (duration, temperature and rate) and packaging on lipid oxidation in refrigerated cooked pork were examined. Oxidative stability following cooking was higher in pork with a higher vitamin E level (p<0.01), cooked at a lower cooking temperature (p<0.01), cooked for a shorter time (p<0.01), cooked at a faster cooking rate (p<0.05) or stored in vacuum packs (p<0.01). Significant two-way and three-way interactions were observed between the effects of muscle vitamin E level, cooking conditions and packaging on lipid oxidation. Adopting more than one of these approaches to minimize lipid oxidation was more effective than adopting a single approach.     

Changes in Quality of All-Beef and Soy-Extended Patties as Influenced by Freezing Rate, Frozen Storage Temperature, and Storage Time

All-beef and soy-extended patties were frozen to - 18°C in either 24, 48, 72 or 96 hr and stored at -23, -18 or -7°C for 0, 6, 9, 12, 18 or 24 months prior to evaluating various quality factors. In evaluations made immediately post-freezing, freezing to - 18°C in 96 hr reduced beef flavor intensity and juiciness for both types of patties. Except for juiciness, storage at -7°C for just 6 months produced sizeable reductions in quality. Longer storage produced gradual, but continual deteriorations in quality, especially color, odor, flavor and TBA values. Inclusion of soy reduced many of the negative effects of storage on quality.     

Sensory and Chemical Characteristics of Pork Chops as Affected by Precooking, Curing and Frozen Storage

Four processing procedures were compared as methods of reducing warmed-over flavor (WOF) of pork chops during frozen storage for 84 days, These procedures were (1) oven-broiled chops, (2) chops from loins precooked with no additives, (3) chops from loins cured with 0.5% salt and 40 ppm NaNO2 and precooked, and (4) chops from loins cured with 2% salt and 120 ppm NaNO2 and precooked. Samples were evaluated by the TBA test, Warner-Bratzler shear, hydroxyproline assay and by sensory analysis after frozen storage at -18°C. Chops from the three precooked treatments were more tender than oven-broiled chops. Nitrite inhibited WOF development of precooked chops during frozen storage and 40 ppm nitrite was nearly as effective as 120 ppm.     

Protein Stability of Frozen Milk as Influenced by Storage Temperature and Ultrafiltration

Milk and milk concentrates containing 12–35% total solids were stored at 0, –2, –4, –6, –8, –12, and –20°C and protein stability of the thawed products was evaluated periodically. Samples stored at –4 to – 12°C exhibited poorer protein stability than samples stored at higher or lower temperatures. Ultrafiltered (UF) skimmilk with permeate: retentate ratios of 10:90, 20:80, and 30:70 were stored at –8°C and they remained stable at least three times longer than frozen control samples of UF skimmilk stored at the same temperature. When the extent of UF was increased to 40:60, protein stability in the frozen retentate declined somewhat as compared to that of less concentrated retentates.     

TBA Values, Sensory Characteristics, and Volatiles in Ground Pork During Long-term Frozen Storage: Effects of Packaging

Ground pork (30% fat) was packaged in vacuum bags (V), polyvinyl chloride film (P), Saran Wrap?(S), aluminum foil (A), or Saran?-aluminum foil combination (SA) and frozen at - 17°C for 13, 26, and 39 wk. Samples were analyzed for TBA value and pH. Volatiles were steam distilled, volatilized at 60°C, and 1 mL samples of headspace gas was analyzed using gas chromatography and mass spectrometry. Spectra for individual peaks on the total ion chromatograms were identified with spectra from known standards. Ground pork (cooked to 75°C) was evaluated by a trained sensory panel for flavor and texture. Rancid and acid odor and flavor scores and TBA values increased over time regardless of packaging treatment; however, V-packaged pork had lower scores and P-packaged had higher scores at all time periods than did that in other materials. Eighteen volatiles were identified and quantified using GC/MS; 3-hydroxy-2-butanone had the highest correlation coefficients with TBA value, odor, and flavor scores.     

四种不同气调包装的冷却猪肉在冷藏过程中的理化及感官变化

冷却猪肉分别采取真空包装、CO-MAP(CO+CO2+N2)包装、高氧-MAP(高浓度O2+CO2+N2)和低氧-MAP(低浓度O2+CO2+N2)包装后,在(4±1℃)贮存三周,每周测定各项理化指标(TVB-N和TBARS),并进行感官评定。结果表明:1)采用CO-MAP包装的冷却猪肉在贮存过程中不仅TVB-N和TBARS较低,而且红色稳定无任何异味。2)真空包装组的冷却猪肉在贮存期间TVB-N和TBARS也较低,在贮存末期呈淡紫色有轻微异味。3)含氧气调包装中,冷却猪肉的TVB-N值和TBARS值相对较高,特别是脂肪氧化加速,鲜红色泽1周后很快变为褐色,并有不良气味产生,所以含氧包装仅适合保质期在1周以内的冷却猪肉。     

Cholesterol Content and Sensory Analysis of Ground Beef as Influenced by Fat Level, Heating, and Storage

Twelve treatment combinations including three fat levels, two internal endpoint temperatures, and two storage periods for ground beef patties were studied. Quality and sensory attributes as well as cholesterol content were evaluated. As fat level increased in raw patties, cholesterol content, drip and total cook loss, fat and cholesterol content of cook drip increased whereas red color intensity and evaporative losses decreased. Cholesterol content, evaporative and total losses, and beef-flavor intensity increased with higher internal endpoint temperature. Red color intensity of raw patties and cholesterol content of raw and cooked patties decreased with storage. No differences in cholesterol content could be attributed to fat content of raw product; therefore, choosing low fat ground beef to lower cholesterol may not be justified.     

Effect of Packaging on Physical and Sensory Characteristics of Ground Pork in Long-term Frozen Storage

Effects of packaging materials on water-holding capacity (WHC), thaw and cook losses, TBA value, moisture and fat content, and sensory characteristics of ground pork held in frozen storage for 13, 26, or 39 wk were examined. Moisture and juiciness decreased and total losses (thaw + cook) increased over time regardless of packaging. WHC decreased most in PVC-packaged pork (fresh = 0.53, 39 wk = 0.17) and least for vacuum-packaged pork (39 wk = 0.25). After 39 wk TBA values were highest for PVC-packaged (2.98) and lowest for vacuum-packaged pork (1.16). Rancid and sour odors and flavors followed similar trends.     

Effect of Packaging on Color and Physical Characteristics of Ground Pork in Long-term Frozen Storage

Ground pork, 30% fat, was packaged in 454g units in Cryovac bags heat scaled under vacuum (V), Saran Wrap? (S), aluminum foil (A), Saran? overwrapped with aluminum foil (SA), and polyvinyl chloride (PVC) and frozen 13, 26, or 39 wk at ? 17°C. TBA values increased over time regardless of packaging. Those materials that excluded oxygen delayed lipid oxidation longest. Red color (CIE a* value and % reflectance difference at 630 and 580 nm) decreased over time; this was greater on exterior than interior of the meat block. Materials that excluded oxygen prevented loss of red color during the first 26 wk storage. Changes in redness and TBA appeared unrelated to pH. Changes in L* and b* values did not appear related to packaging treatment or storage time.     

Survival and Growth of Listeria monocytogenes on Lettuce as Influenced by Shredding, Chlorine Treatment, Modified Atmosphere Packaging and Temperature

The effects of shredding, chlorine treatment and modified atmosphere packaging on survival and growth of Listeria monocytogenes, mesophilic aerobes, psychrotrophs and yeasts and molds on lettuce stored at 5°C and 10°C were determined. With the exception of shredded lettuce which had not been chlorine treated, no significant changes in populations of L. monocytogenes were detected during the first 8 days of incubation at 5°C; significant increases occurred between 8 and 15 days. Significant increases occurred within 3 days when lettuce was stored at 10°C; after 10 days, populations reached 10⁸-10⁹ CFU/g. Chlorine treatment, modified atmosphere (3% O₂, 97% N₂) and shredding did not influence growth of L. monocytogenes. It was concluded that L. monocytogenes is capable of growing on lettuce subjected to commonly used packaging and distribution procedures used in the food industry.     

Poststorage Behavior of Apple Fruit After Low Oxygen Storage as Influenced by Temperatures During Storage and in Transit

‘Delicious’, ‘Newtown’ and ‘Granny Smith’ apples (Malus domestica Borkh.) maintained acceptable flesh firmness and high levels of titratable acids and soluble solids after 9 months of storage in 1% 0₂ at either 0°C or 3.3°C. Low-0₂-stored ‘Delicious’ were kept at 0°C for 6 wk without developing physiological disorders before or after 8 days of ripening at 20°C. Storage at 3.3°C caused ‘Delicious’ to soften faster during 6 wk of post-storage holding plus 8 days of ripening. ‘Newtown’ apples developed flesh browning and alcohol flavor after 9 months of low 0₂ storage at 0°C. ‘Newtown’ fruit stored at 3.3°C developed only minimal incidence of flesh browning and alcohol flavor. ‘Granny Smith’ fruit were free from scald, core flush, flesh browning and alcohol flavor after low 0₂ storage, regardless of storage temperature. However, core flush and flesh browning appeared when ‘Granny Smith’ were kept for 6 wk at 0°C plus 8 days at 20°C.