Top loin steaks were used to determine the influence of packaging procedure on the microbial growth and succession on the top and bottom surfaces of steaks during a 12 day storage period. The following packaging treatments were used: (1) Gas permeable Resinite film overwrap as a control; (2) gas flush with 1% CO, 40% O₂, 59% N₂ for 2 minutes followed by film overwrap; (3) loose packaging in gas impermeable barrier bags with 100 to 150 cc ambient air; (4) 15% CO₂, 40% O₂, 45% N₂ gas atmosphere; (5) 60% CO₂, 40% O₂ gas atmosphere; and (6) 10% CO₂, 5% O₂, 85% N₂ gas atmosphere. Total psychrotrophic counts obtained from the top and bottom surfaces did not differ significantly for most sampling periods. Similar growth patterns were observed on both steak surfaces, increasing (P <.05) primarily between Day 3 and Day 9 of post-treatment storage. The steaks packaged within the gas atmospheres had lower (P<.05) total growth than the control steaks. Comparing atmospheres, the steaks packaged in relatively low CO₂ and O₂ levels (10% and 5%, respectively) had lower (P<.05) microbial growth than steaks packaged in 15 to 60% CO₂ and 40% O₂ when initial contamination was low. Pseudomonas dominated the microflora on the steak surfaces in all packaging treatments during early storage. Other aerobic organisms which survived gas atmosphere treatments include Coryneforms, Micrococcus, and Microbacterium, although they did not show large increases in growth. Coryneforms were also competitive on the bottom surface of the control steaks despite domination by the pseudomonad organisms. Loose packaging in impermeable barrier bags allowed the growth of Serratia liquifaciens after 6 days of storage. This bacterium also tended to dominate the flora within the gas atmosphere packages, although other facultative organisms (Enterobacter aerogenes and Yersenia enterocolitica) were also identified. When initial contamination was low, the gas atmospheres provided an effective means of prolonging the shelf-life of fresh beef steaks.

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Call number: LD2668 .T4 1978 G94 / Master of Science

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1986 P57 / Master of Science / Animal Sciences and Industry

Typescript. / Digitized by Kansas Correctional Industries

The objectives of this study were to develop MAP conditions, using mixtures of oxygen (O₂) and carbon dioxide (CO₂), to prolong the shelf-life of ground turkey thigh meat. The effect of fat level and effectiveness of natural antioxidants were evaluated. Product quality was determined semi-weekly by sensory, microbial, chemical, and instrumental analysis to evaluate rancidity, and sensory flavor changes. Thiobarbituric acid (TBA) tests were conducted to objectively measure changes in oxidative rancidity. Microbial analysis included psychrotrophic, lactic acid, and anaerobic bacteria enumerations, pH determinations were conducted to evaluate the effects of each treatment on the meat. Instrumentation color analysis CIE L* a* b* values were determined to measure color changes. Test results indicate the pH changed significantly only in the air packaged samples. Psychrotrophic, lactic acid and anaerobic bacteria counts were significantly lower (P<0.05) in the 100% CO₂ packaged samples, than all other treatments and the control. Low TBA values, less than 4, were found with the 100% CO₂ samples. Sensory evaluation found the 80% O₂/20% CO₂ and 60% O₂/40% CO₂ packages were no longer acceptable at day 14, and air samples were unacceptable at day 18. The 100% CO₂ sample maintained acceptable over-all taste throughout the test period. Colorimeter values did show the 100% CO₂ atmosphere caused discoloration of the product during the first week. Fat level did not affect microorganism growth or shelf-life extension. Rosemary oleoresin was effective as an antioxidant. TBA values of rosemary treated samples remained under 1.0 for the entire 28-day storage period. / Master of Science

Master of Science / Food Science Institute-- Animal Science & Industry / J. Scott Smith / Ammonia leaks in meat chilling/frozen storage or processing facilities are not uncommon. Often the meat products are packaged in polymer films that theoretically protect the product from contamination. Unfortunately, there is almost no data on whether ammonia can permeate packaging films. The objectives of this study were to evaluated meat contaminated by low levels of ammonia under frozen storage conditions (-17 ± 3[degree]C), and further evaluated the permeability of common meat packaging films including: low density polyethylene (LDPE), 3 mil Cryovac (E-2300), and 3 mil vacuum (V-PA/PE) at freezing (-17 ± 3 [degree]C) and room temperatures (21 ± 3 [degree]C). Fresh beef Semitendinosus muscles were fabricated to form 10 x 5 x 2.3 cm steaks. The packaging films were fabricated into 10 x 5 cm pouches and filled with 50 mL deionized water. The meat and the pouches were exposed in a plexiglass enclosure, contained in a freezer, to 50, 100, 250, and 500 ppm ammonia gas (85 mL/min) for exposure times of 6, 12, 24, and 48 hr. The ammonia levels in the meat samples were 34.2 (50 ppm exposure), 51.5 (100 ppm exp.), 81.1 (250 ppm exp.), and 116 ppm (500 ppm exp.), and the pH values ranged from 5.56 to 5.75 (control ranged from 5.31 to 5.43) at 48 hr. At freezing temperatures, ammonia residues remained undetected, and no differences in pH were found in the pouches. At room temperature, all pouches were slightly permeable to ammonia; the levels observed in the pouches were, 7.77 ppm (pH, 8.64) for E-2300, 5.94 ppm (pH, 8.38) for LDPE, and 0.89 ppm (pH, 7.23) for V-PA/PE at 500 ppm exposure for 48 hr (unexposed samples pH ranged from 5.49 to 6.44). The results showed that meat packaging materials have low ammonia permeability and thus protect meat products exposed to ammonia exposure during frozen storage. Moreover, meat content is low even with ammonia exposures as high as 500 ppm for up to 48 hr.

Thesis (PhD (Food Sc))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Ostrich meat has become increasingly popular in South Africa and abroad, driven by the health conscious trend and ostrich meat’s natural low intramuscular fat, high polyunsaturated fatty acid and low cholesterol content. This increased demand led to the investigation of novel packaging regimes to improve its attractiveness and shelf-life. Different modified atmospheric packaging regimes were studied for fresh and frozenthawed ostrich M.iIliofibularis steaks stored at ±4°C for 10 days. Oxygen MAP (30 CO2:70 O2) was applied with great success to fresh steaks, and resulted in significantly improved colour stability, decreased drip loss and a 10-day shelf-life. Oxygen MAP of frozen-thawed ostrich steaks was not successful as the colour deteriorated within 3 days, coupled with high lipid and protein oxidation. The microbial shelf-life was not influenced by freezing and thawing. The use of nitrogen MAP (30 CO2:70 N2) as an alternative to vacuum packaging for fresh and frozen-thawed ostrich meat was inconclusive due to trace amounts of residual oxygen in the headspace accelerating myoglobin oxidation by depleting the metmyoglobin reducing activity. The differences in oxidative stability of the fresh and frozen-thawed ostrich meat led to the investigation of the source of these differences and a system that would allow control over the freezing and thawing practice. This was supported by the industry that is under increasing pressure to reduce the excessive (15-20%) thaw weight loss that is continually reported. Subsequently, a mathematical prediction model based on the control volume approach was developed that predicted the rate of freezing and thawing of intact whole vacuum-packed ostrich muscle. The model predicted with greater accuracy than existing models, and can be used successfully by the industry to optimally design, control and operate their systems. Furthermore research was conducted to investigate the effect of different freezing and thawing rates on the ice crystal formation and the quality of ostrich M. femorotibialis stored at ±4°C post freeze/thaw. Five characteristic freezing rates (FR (time from 0°C to -7°C): 1, 2, 4, 8, 24h) were paired with five characteristic thawing rates (TR (time form -7°C to 0°C): 1.5, 3, 6.5, 14, 21h) in a completely randomised block design. Results showed that thawing had no impact on any of the tested quality parameters, including thaw loss. Freezing rate however did influence the ice crystal formation and at a characteristic freezing rate of one hour (FR_1h) only intracellular ice crystals were observed throughout the M. femorotibialis leading to the lowest thaw loss (2.57%) and highest shear force. Freezing rate of 2h, 4h and 8h (FR_2h, FR_4h and FR_8h) were dominated by extracellular ice crystals. FR_2h and FR_8h showed major dehydration of the muscle fibres and excessive distortion of the muscle fibre matrix that led to significantly lower oxidative stability. FR_24h (approximately commercial rates) formed columns of ice from the surface to the centre of the meat resulting in the highest thaw loss (6.24%). FR_4h was judged to deliver the best quality product with moderate thaw (3.93%) and drip loss, low cooking loss, good colour stability and extremely low TBARS. FR_4h is an achievable rate of freezing for the industry and if implemented should decrease the thaw loss problem as well as increase revenue and throughput in the processing facility. / AFRIKAANSE OPSOMMING: ‘n Hedendaagse strewe na ‘n gesonde lewenstyl tesame met die natuurlike lae vetinhoud (d.i. hoë poli-onversadigde vetsure en lae cholesterolvlak) van volstruisvleis het gelei tot ‘n toename in die nasionale en internasionale aanvraag. Hierdie het ook die behoefte laat ontstaan om nuwe verpakkingstegnieke te ondersoek om sodoende die aanvaarbaarheid en rakleeftyd van die produk te verleng. Die invloed van verskeie gewysigde atmosferiese verpakkingsmetodes (GAV) op die kleurstabiliteit, drupverlies en rakleeftyd van vars en bevrore/ontdooide volstruisvleis (spesifiek M. Iliofibularis), gestoor by ±4°C vir 10 dae, is ondersoek. Die suurstof GAV (30 CO2:70 O2) van vars volstruisvleis het ‘n verbetering in kleurstabiliteit, verlaagde drupverlies en 'n verlengde mikrobiese rakleeftyd (10 dae) tot gevolg gehad. Die suurstof GAV van bevrore-ontdooide volstruisvleis het geen voordelige effek op kleurstabiliteit en rakleeftyd getoon nie. Die bevrore/ontdooide monsters het totaal verkleur na 3 dae en ‘n hoë vlak van lipied- en proteïenoksidasie is waargeneem. Die bevriesing en ontdooiing het geen invloed op rakleeftyd gehad nie. Die moontlikheid om stikstof GAV (30 CO2:70 N2) as 'n alternatief tot vakuumverpakking vir vars en bevrore/ontdooide volstruisvleis te gebruik, is beïnvloed deur die teenwoordigheid van oorblywende suurstof in die lugruimte van die GAV, met ‘n gevolglike toename in die tempo van mioglobien oksidasie as gevolg van ‘n afname in die metmioglobien reduksie aktiwiteit. Die verskil in die oksidatiewe stabiliteit van vars en bevrore/ontdooide volstruisvleis het gelei tot ‘n verdere ondersoek na die oorsaak van die verskille en die ontwikkeling van ‘n moontlike protokol om die oksidatiewe stabiliteit en dus rakleeftyd van volstruisvleis, te verbeter en bestuur. Die behoefte aan so ‘n protokol is beklemtoon deur die bedryf wat onder toenemende druk verkeer om buitensporige ontdooiingsverliese (15-20%) te verminder. ‘n Wiskundige voorspellingsmodel, gebaseer op die beheer-volume benadering, is ontwikkel om die tempo van bevriesing en ontdooiing van vakuumverpakte heel volstruisspiere te voorspel. Die model het tempo van bevriesing en ontdooiing met groter akkuraatheid as die bestaande modelle voorspel en kan suksesvol gebruik word in die bestuur van slagpale. Verder navorsing is onderneem om ondersoek in te stel na die effek van die tempo van bevriesing en ontdooiing op die kwaliteit van die bevrore-ontdooide volstruisvleis tydens berging by ±4°C. Die invloed van die kombinasie van vyf bevriesingstempo’s (FR (tydsverloop 0°C tot -7°C): 1, 2, 4, 8, 24 h) met vyf ontdooiingstempo’s (OT (tydsverloop -7°C to 0°C): 1.5, 3, 6.5, 14, 21 h) is ondersoek. Die resultate het getoon dat ontdooiingstempo geen beduidende invloed op enige van die kwaliteit kriteria, insluitend ontdooiingsverlies, gehad het nie. Bevriesingtempo het egter ‘n groot rol ten opsigte van yskristalvorming gespeel. Teen ‘n kenmerkende bevriesingstempo van een uur (FR_1h) was slegs intrasellulêre yskristalle waargeneem dwarsdeur die M. femorotibialis wat gelei het tot die laagste ontdooiingsverlies (2.57 %). Die ander bevriesingstempo’s, d.i. FR_2h, FR_4h en FR_8h, het gelei tot die vorming van meestal ekstrasellulêre yskristalle. Bevriesingstempo’s van FR_2h en FR_8h het beduidende dehidrasie van die spiervesels en vervorming van die spiervesel matriks tot gevolg gehad, wat tot verhoogde oksidasie gelei het. ‘n Bevriesingstempo van FR_24h (d.i. kommersieële tempo), het gelei tot die vorming van yskolomme van die oppervlak na die middelpunt van die spier, wat gevolglik die grootste ontdooiingsverlies (6.24%) tot gevolg gehad het. ‘n Bevriesingstempo van vier ure (FR_4h) is bestempel as die mees geskikte bevriesings tempo as gevolg van ‘n matige ontdooiingsverlies (3.93%), drupverlies, lae kookverlies, goeie kleur stabiliteit en uiters lae lipiedoksidasie te verseker. Die FR_4h bevriesingstempo is haalbare in die bedryf. Indien dit geïmplementeer word, sal dit waarskynlik die deurset van die slagpalesiklus asook die kostedoeltreffendheid van die volstruisbedryf vebeter, deur die vermindering van ontdooiingsverlies en verbetering van die algehele kwalitiet van die vleis.