Fresh produce is often touted for its many health benefits; however, various items have been linked to foodborne disease outbreaks. This is especially a concern for immune suppressed individuals who are classified as severely neutropenic (white blood cell count under 500 neutrophils/μL of blood). At this degree of suppression, many are urged to follow a restrictive diet that reduces the potential of exposure to microbial populations. Currently no processing technique is used to sanitize microorganisms from fresh produce. Electron beam (e-beam) irradiation is a non-thermal process that has been approved by the FDA to treat fresh foods and is able to eliminate bacteria. Another technology used to extend shelf life is modified atmosphere packaging (MAP). The objective of this study was to evaluate the use of e-beam irradiation at current FDA-approved doses (< 1 kGy) to determine whether bioburden on fresh fruits can be reduced while maintaining sensory quality. Aerobic plate count methods were employed to determine the bioburden of treatments over a 21 day storage period under both ambient and MAP conditions. A previously identified bacterial plate count benchmark of < 500 CFU/ gram will be used to determine the applicability of the e-beam treatment. A consumer study using a 9 point hedonic scale as well as instrumentation measuring color, texture, moisture content, total soluble solids and titratable acidity were used to compare the treated fruit to the control. E-beam consistently reduced the bioburden on strawberries, fresh-cut watermelon and significantly (p<0.05) for avocado samples. Avocado, grapes and watermelon showed potential to be labeled as clean foods (below 500 CFU/gram). Fruit firmness (as measured by deformation) was not negatively affected by e-beam treatment and was preserved over storage with MAP treatment. Color was not adversely affected by e-beam or MAP, except for avocados that were significantly more grey in the presence of O_(2). Most importantly, consumers rated e-beam and MAP treated samples as acceptable (score above 5) in qualities of color, odor, flavor and firmness. E-beam proved to be an effective tool in reducing bioburden at low doses while maintaining fruit quality.

This dissertation discusses, in brief, the production and transport property characterization of films made from the extrusion and biaxial stretching of [beta] nucleated isotactic polypropylene and the extrusion of PEBAX block copolymers. Multilayered films for modified atmosphere packaging applications were also produced by coextrusion and biaxial stretching of these two materials and similarly characterized. Current membranes for packaging applications are generally produced by coating a porous support with a polymeric solution to deposit an active layer for separation. The goal of this project is to displace membranes produced by solvent-based processes, which are environmentally hazardous and thus costly, with equivalent or superior materials produced using melt extrusion. / text

No description available.

The antimicrobial efficacy of carvacrol, trans-cinnamaldehyde, eugenol and thyme oil (0.5, 1, 2 and 5% v/v) was evaluated against Salmonella on turkey breast cutlets as 2 min dip treatments at 4°C. Carvacrol revealed maximum efficacy against Salmonella on turkey cutlets and was selected for 30s and 60s dip treatments at 4°C. Only 5% carvacrol was effective and exhibited 1.0 and 1.8 log CFU/g reduction of Salmonella with 30s and 60s dip treatments, respectively. However, carvacrol showed synergistic activity with carbon dioxide in modified atmosphere packaging (95% CO2/5% O2) against Salmonella and Campylobacter and caused 1.0-2.0 log CFU/g reductions with lower concentrations (0.25, 0.5 and 1.0%). This combination reduced the growth of lactic acid bacteria. In the third experiment, efficacy of lauric arginate (200 and 400ppm) against C. jejuni was tested on chicken breast fillets. Both these concentrations significantly reduced C. jejuni on chicken fillets (1.0-1.5 log CFU/g) at 4°C.

Three types of dried milk (whole, nonfat, and buttermilk) were packaged in a modified atmosphere with a novel palladium-based oxygen removing catalyst and stored for eight weeks at 50°C. Powders stored in air with no catalyst and powders stored with the catalyst in an atmosphere modified to contain 5.7% hydrogen in nitrogen were evaluated by instrumental, chemical, and sensory methods. Hexanal concentrations were measured weekly using solid phase microextraction (SPME) and gas chromatography (GC) to compare the degrees of oxidation in the powders stored with the catalyst to those stored without it. Color changes were also monitored weekly using Hunter's L-, a-, and b-values. At the end of the eight-week period, a paired comparison sensory test was used to ascertain if the catalyst had an effect on odor. Anisidine values were also measured at this point to determine levels of oxidation in the powders. No significant difference was found in levels of oxidation between samples packaged with and without the catalyst in the modified atmosphere. At the end of eight weeks, the average hexanal concentration in the whole milk powder stored with the oxygen scavenger was 1.19 ± 0.20 ppm, while the average hexanal concentration in the air-packed whole milk powder was 1.06 ± 0.08 ppm. The average hexanal concentrations for the buttermilk stored with the catalyst and without were 0.84 ± 0.18 and 0.79 ± 0.15 ppm, respectively. In the nonfat milk powder, the sample stored with the catalyst had an average hexanal concentration of 0.91 ± 0.14 ppm and the sample stored in air without the catalyst had an average hexanal concentration of 0.83 ±0.20 ppm. Difference testing by volunteer sensory panelists also revealed no significant differences. It was expected that the milk powders stored with the catalyst in the modified atmosphere would have lower levels of oxidation and off-odors at the end of the eight weeks. However, the treatment ultimately resulted in no chemical or sensory differences. Thus, the catalyst proved ineffective in the given conditions. This could be due to a loss of the hydrogen required for the catalyst to function as time progressed or a lack of significant oxidation under the conditions employed. / Master of Science in Life Sciences

Numerous food-borne outbreaks of Escherichia coli O157:H7 have been linked to leafy greens in recent years. An overwhelming amount of lettuce and spinach on the market is sold in modified atmosphere packaging as ready to eat salad mixes. The objectives of this study were to determine the effects of modified atmosphere, storage temperature, and inoculum size on survival of E. coli O157:H7 on cut and whole leaf lettuce and spinach. E. coli O157:H7 H1730 was inoculated onto cut and whole leaves of leaf lettuce and spinach. Samples were held under normal atmospheric conditions or in a modified atmosphere package at either 4ºC or 10ºC to simulate display and abuse temperatures. Leaves were sampled at Days 0, 1 and every other day until visual spoilage occurred (7 days for lettuce, 9 days for spinach). E. coli O157:H7 was able to survive at 4° and 10°C regardless of atmosphere and inoculum size for 7 days on cut and whole lettuce and 9 days on cut and whole spinach. Overall, numbers of E. coli O157:H7 increased (1 log) throughout the storage period on spinach, and decreased on lettuce (1-1.5 log). Significantly higher (P < 0.05) numbers of E. coli O157:H7 were found on lettuce and spinach stored at 10ºC than when stored at 4ºC. There were no significant differences (P > 0.05) in Numbers of E. coli O157:H7 with respect to atmosphere, leaf type or inoculum size. If contamination of lettuce or spinach with E. coli O157:H7 occurred, the pathogen may survive well under typical packaging and storage conditions. / Master of Science in Life Sciences

Master of Science / Department of Animal Sciences and Industry / Melvin C. Hunt / The objective of this study was to determine the effects of Zilmax® feeding duration (7.56 g/ton Zilmax for 0, 20, 30, or 40 d) on color development and stability of crossbred beef (B) and Holstein (H) semimembranosus (SM) steaks packaged in polyvinyl chloride overwrap (PVC), high-oxygen (80% O2, 20% CO2, HiOx) modified atmosphere packaging (MAP), and low-oxygen (0.4% CO, 30% CO2, 69.6% N2, LoOx) MAP. A 7.62-cm thick portion from beef and Holstein SM muscles (n = 120 total, 30 from each feeding duration) was removed, vacuum packaged, and stored until d 21 when two, 2.54-cm thick steaks were cut, overwrapped with PVC, and placed into retail display for 0 or 3 d. On d 10, the remaining muscle of the SM was enhanced, and five, 2.54-cm thick steaks were cut and assigned to 0, 3, or 5 d (HiOx) and 0 or 9 d (LoOx) of display. Measurements taken on the deep (DSM) and superficial (SSM) portions were: pH, L*, a*, b*, hue angle, and saturation indices, initial color, display color, and discoloration. No Diet × Display Day (P > 0.05) interaction occurred for display color or discoloration scores of B steaks in PVC. On d 1, PVC 30 d H steaks were brighter (P < 0.05) than 40 d H steaks in PVC; no differences (P > 0.05) in H PVC display color due to diet occurred on d 0, 2, and 3. For steaks in HiOx, the DSM of 20 and 30 d B steaks on d 4 and the DSM of 20 d B steaks on d 5 was brighter (P < 0.05) red than 40 d Zilmax B DSM. HiOx 20 d H steaks were darker red (P < 0.05) on d 5 of display and more discolored (P < 0.05) on d 3 to 5 than HiOx H steaks from all other diet regimens. For LoOx, 30 d B steaks were brighter (P < 0.05) red than 0 or 40 d steaks on d 0 and 9 of display. The DSM and SSM of LoOx H steaks from cattle fed Zilmax tended (P > 0.05) to be brighter red than control H steaks through 9 d of display. In conclusion, both HiOx and LoOx minimized color differences due to SM muscle areas. Feeding B cattle Zilmax for 20 or 30 d yields steaks equal to or better in color traits than cattle fed 0 or 40 d when packaged in PVC, HiOx, or LoOx. H steaks in LoOx had slight benefits in color stability when cattle were fed Zilmax for any duration, whereas H steaks in PVC had color advantages with only the 20 and 30 d durations. Packaging 20 d H steaks in HiOx resulted in less desirable color characteristics than all other feeding treatments. Keywords: zilpaterol, beef, Holstein, display color, modified atmosphere packaging, semimembranosus

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Modified atmosphere packaging (MAP) is a dynamic process of altering gaseous composition inside a package. It relies on the interaction between the respiration rate (RR) of the produce, and the transfer of gases through the packaging material. These two processes are dependent on numerous factors such as storage temperature, film thickness and surface area, produce weight as well as free headspace within the pack. Therefore, in order to achieve the desired modified atmosphere in a given package, it is important to understand the three basic disciplines of MAP, namely produce physiology, polymer engineering, and converting technology. In this study the effects of storage conditions and duration on physiological responses i.e. respiration (RR) and transpiration rate (TR) of two pomegranate cultivars ‘Acco’ and ‘Herskawitz’, were investigated and mathematical models were developed to predict these physiological responses at given time and storage conditions. The result of this study showed that RR of whole pomegranate fruit was significantly higher than that of fresh arils, and that temperature had a significant impact on the RR of both whole fruit and fresh arils. The influence of time, and the interaction between temperature and time also had significant influences on RR of fresh pomegranate arils. These findings highlight the significance of maintaining optimal cold-storage condition for packaged arils or whole fruit along the supply chain. In addition, mathematical models based on the Arrhenius-type equation and the power function equation coupled with Arrhenius-type equation accurately predicted the effect of temperature and the influence of time and temperature on the RR of fresh pomegranate arils for both cultivars. Furthermore, the results of experimental and model prediction studies showed that both relative humidity (RH) and storage temperature had significant effects on TR. RH was the variable with the greatest influence on TR, and it was observed that arils were best kept at 5°C and 96% RH to maintain quality for 8 days. The applicability of the transpiration model developed was validated based on prediction of TR of pomegranate arils under different combinations of storage conditions. The model adequately predicted TR and provides a useful tool towards understanding the rate of water loss in fresh pomegranate arils as affected by storage conditions and duration. The effect of passive-MAP engineering design parameters as a function of produce weight contained, storage temperature and duration on fresh pomegranate arils was investigated. The result showed that produce weight of aril content, temperature and the interaction between temperature and time had slight but insignificant effects on measured physicochemical quality attributes. However, headspace gas concentration was significantly influenced by produce weight and storage temperature. Oxygen (O2) composition decline below 2% after day 3 and 5 at 15 and 10 ºC, respectively, while samples at 5 °C did not reach below 2% throughout the study. On the other hand, CO2 levels increased significantly during storage for all packaging conditions. This study showed the importance of a systematic approach to the design of optimal MAP systems. At lowest storage temperature the inability to achieve desired modified atmosphere (MA) required for optimal storage of arils despite the increase in produce weight, suggests that the use of active gas modification (gas flushing with recommended atmosphere) would be necessary. However, the present results show that at higher temperature macro/micro perforations would be required on the polymeric films used in the present study in order to avoid critical levels of O2 and CO2. The influence of passive MAP, storage temperature and duration on volatile composition and evolution of packaged pomegranate arils was investigated. The results showed that changes in aroma compounds were dependent on cultivar differences, storage condition and duration. Using GC-MS analysis of pomegranate juice HS-SPME extracts, a total of 18 and 17 volatiles were detected for ‘Herskerwitz’ and ‘Acco’, respectively. Furthermore, flavour life (7 days) was shorter than the postharvest life (10 days) for both cultivars. There was a decrease in volatile composition during the storage period (aldehydes < alcohols < esters) while the concentration (%) and composition of ethyl esters increased with storage time. These results highlight the need for a more precise definition of flavour shelf life for MApackaged pomegranate arils and other packaged fresh produce. The importance of maintaining optimal cold storage condition, selection of appropriate packaging materials and a systematic approach to the design and application of MAP systems has also been shown. / AFRIKAANSE OPSOMMING: Gemodifiseerde atmosfeer-verpakking (GAV) is ’n dinamiese proses waartydens die gassamestelling binne-in ’n verpakking gewysig word. Dit berus op die wisselwerking tussen die respirasietempo (RT) van die produkte en die oordrag van gasse deur die verpakkingsmateriaal. Hierdie twee prosesse is van verskeie faktore soos bergingstemperatuur, dikte van die film en oppervlakte, gewig van die produkte asook vry boruimte binne-in die pakkie afhanklik. Om dus die gewenste gemodifiseerde atmosfeer in ’n gegewe verpakking te verkry, is dit belangrik om die drie fundamentele dissiplines van GAV te begryp, naamlik produkfisiologie, polimeerontwerp, en omsettingstegnologie. In hierdie studie is die gevolge van bergingstoestande en -duur op fisiologiese reaksie, met ander woorde, respirasie- (RT) en transpirasietempo (TT) van twee geselekteerde granaatkultivars ‘Acco’ en ‘Herskawitz’, ondersoek en wiskundige modelle is ontwikkel om ons in staat te stel om hierdie fisiologiese reaksies by gegewe tyd- en bergingstoestande te voorspel. Die resultaat van hierdie studie het aangetoon dat die respirasietempo (RT) van heel granaatvrugte aansienlik hoër was as die RT van vars arils, en temperatuur het beduidende uitwerking op RT van beide heel vrugte en vars arils gehad. Die invloed van tyd, en die wisselwerking tussen temperatuur en tyd het ook ’n beduidende invloed op die RT van vars granaatarils gehad. Hierdie bevinding beklemtoon die belang van die handhawing van optimale koelbewaringstoestande vir verpakte arils of heel vrugte met die aanvoerketting langs. Daarbenewens wiskundige modelle wat gebaseer op die Arrhenius-tipe vergelyking en die magsfunksie-vergelyking gepaard met Arrhenius-tipe vergelyking, die uitwerking van temperatuur en die invloed van tyd en temperatuur op die RT van vars granaatarils vir beide kultivars onderskeidelik voldoende en akkuraat voorspel. Afgesien die resultate van eksperimentele en modelvoorspellings die studies aangetoon dat beide relatiewe humiditeit (RH) en bergingstemperatuur ’n beduidende uitwerking op TT het. RH was die veranderlike met die grootste invloed op TT, en it was waargeneem dat dit die beste was om arils teen 5°C en 96% RH te bewaar (8 dae). Die toepaslikheid van die transpirasiemodel wat ontwikkel is, is bevestig op grond van voorspelling van TT van granaatarils onder verskillende kombinasies van bergingstoestande. Die model het TT voldoende voorspel en sou ’n bruikbare instrument wees ten einde die waterverliestempo in vars granaatarils en ander vars produkte, soos deur bergingstoestande en duur beïnvloed, te begryp. Die uitwerking van passiewe-GAV ontwerpparameters as ’n funksie van gewig van die produkte, bergingstemperatuur en duur op vars granaatarils is ondersoek. Dit het aan die lig gebring dat gewig van die produkte, temperatuur en die wisselwerking tussen temperatuur en tyd ’n geringe maar onbeduidende uitwerking op gemete fisikochemiese gehalteeienskappe gehad het. Die gaskonsentrasie in die boruimte is betekenisvol beïnvloed deur gewig van die produkte en bergingstemperatuur. Die O2-samestelling het tot benede 2% gedaal na 3 en 5 dae by 15 en 10 ºC, onderskeidelik, terwyl monsters by 5 °C deur die studie heen nooit laer as 2% was nie. Aan die ander kant, CO2-vlakke het gedurende berging betekenisvol verhoog wat betref alle verpakkingstoestande. Hierdie studie het die belangrikheid van ’n sistematiese benadering by die ontwerp van ’n optimale GAV-stelsel aangetoon. By die laagste bergingstemperatuur dui die onvermoë om die gewenste gemodifiseerde atmosfeer (GA) wat vir optimale berging van arils benodig word, te verkry – ondanks die toename in die gewig van die produkte – daarop dat die gebruik van aktiewe gasmodifisering (gasspoeling met aanbevole atmosfeer) nodig sou wees. Egter die huidige uitslae aangetoon dat by hoër temperatuur, sou makro/mikroperforasies op die polimeerfilms wat gebruik word in die onderhawige studie egter nodig wees ten einde kritiese vlakke van O2 en CO2 te verhoed. Die invloed van passiewe GAV, bergingstemperatuur en duur op onstabiele samestelling en evolusie van verpakte granaatarils is ondersoek. Die resultate aangetoon dat veranderinge in aromaverbindings afhanklik was van kultivarverskille, bergingstoestande en duur. Met behulp van GC-MS-analise van granaatsap HS-SPME-ekstrakte, het ons ’n totaal van 18 en 17 vlugtige stowwe vir ‘Herskawitz’ en ‘Acco’, onderskeidelik bespeur. Verder het ons waargeneem dat die smaakleeftyd (7 dae) korter was as die na-oesleeftyd (10 dae) vir beide kultivar. Daar was ’n afname in vlugtige samestelling (aldehiede < alkohole < esters) terwyl die konsentrasie (%) en samestelling van etielesters het met bergingstyd verhoog. Hierdie resultate het die aandag gevestig op die behoefte aan ’n meer presiese definisie van geur-raklewe vir GA-verpakte granaatarils en ander verpakte vars produkte. Die belang van die handhawing van die optimale koelbewaringstoestand, seleksie van geskikte verpakkingsmateriaal en ’n sistematiese benadering tot die ontwerp van ’n optimale GAVstelsel, is ook beskryf.

Fresh produce is increasingly implicated in outbreaks of foodborne illness. Internalization of bacterial pathogens into produce is of particular concern as internalized pathogens are unlikely to be removed by surface sanitizers. It is therefore necessary to develop treatments that will reduce their prevalence and numbers on fresh produce. Irradiation is a penetrating nonthermal treatment that effectively eliminates bacteria. Irradiated baby spinach leaves up to 1.0 kGy showed negligible (P>0.05) changes in color, texture, vitamin C, total carotenoids, and chlorophyll content compared to non-irradiated controls throughout storage (15 days at 4oC). This research also shows that irradiation effectively reduces viable Escherichia coli cells internalized in lettuce, and that decontamination is not influenced (P>0.05) by lettuce variety. Irradiation effectively reduced the population of internalized pathogens in a dose-dependent manner (3-4 log reduction at 1.0 kGy). Microscopy images suggest that the contamination sites of pathogens in leafy vegetables are mainly localized on crevices and in the stomata. A careful design of the treatment (understanding dose distribution) will effectively eliminate pathogens while maintaining produce quality. The use of modified atmosphere packaging increased (P<0.05) the sensitivity of pathogens (Salmonella spp. and Listeria spp.) to irradiation in baby spinach leaves (up to 25%). Increasing concentration of oxygen increased (P<0.05) sensitivity of both microorganisms. Radiosensitization could be affected (P<0.05) by production of ozone, which increases with increasing dose-rate and oxygen concentration, and reducing temperatures. Antimicrobial effectiveness of various active compounds was determined against Salmonella spp. and Listeria spp. Inclusion complexes were prepared with antimicrobial compounds and -cyclodextrin. The effectiveness of the microencapsulated compounds was tested by spraying them on the surface of baby spinach leaves inoculated with Salmonella spp. The increase in radiosensitivity (up to 40%) varied with the antimicrobial compound. Spherical poly (DL-lactide-co-glycolide) (PLGA) nanoparticles with entrapped eugenol and trans-cinnamaldehyde were synthesized for future antimicrobial delivery applications. All loaded nanoparticles proved to be efficient in inhibiting growth of Salmonella spp. and Listeria spp. The entrapment efficiency for eugenol and trans-cinnamaldehyde was 98% and 92%, respectively. Controlled release experiments (in vitro at 37oC for 72 hrs) showed an initial burst followed by a slower release rate of the antimicrobial entrapped inside the PLGA matrix.

Meat is one of the most important food products. European Union countries, including Lithuania, are the main meat producers in the world - their production comprises more than 16 % of processed meat. In the world commerce meat products conclude 12,8 % of market place, of which 39 % - pork. The purpose of the work - to analyse the preservative gas impact on freshness sustention of pork products. The main tasks are to review the freshness rates of pork products, their evaluation methods; to discuss the ways of long-lasting freshness sustention, which are usable in the processed food industry; to analyse the preservative gas method on the freshness sustention of meat products; to research and to compare the microbiological pollution of the sausages, packed in the preservative gas and not packed in it. The methods of research are: analysis of the primary documents; analysis of the secondary documents; analysis of the scientific literature; analysis of the statistics, microbiological research of pork sausages. The most effect of the preservative gas usable for the packing meat products is obtained by packing smoked sausages, which microbiological pollution after 20 days, increases 1,2 – 2 times.