Call number: LD2668 .T4 1984 J375 / Master of Science

A study was conducted to determine the feasibility of utilizing potassium sorbate as a fungistatlc agent in country ham processing. The study was divided into three phases: the first utilized 60 and 90 day old cured country (long cut) ham; the second used country ham slices; and the third phase utilized 70 day old country cured (packer style cut) hams. Samples were incubated at various temperatures and relative humidities to determine the extent of protection offered by sorbate against fungal growth. Intensity of fungal growth was determined subjectively through periodic visible evaluations and were quantitated by culture plating methods. A UV spectrophotometric technique was utilized to determine the concentrations of sorbic acid deposited on ham surfaces or slices by various methods of application. Of the different methods of application that were tested, the 5% (W/V) 1 minute spray offered the lowest effective level for inhibition of fungal growth. The 5% l minute spray significantly lowered initial mold and yeast colony counts and protected the hams for 30 to 60 days under conditions conducive to fungal outgrowth (21.1±5°C and 70±5% relative humidity). An analogous 10% spray provided a slightly greater measure of mold inhibition than the 5% treatment under identical conditions. / Master of Science

A previously developed technique was adapted to study the influence of certain microbiological populations and their effects on processed meat. The technique consisted of an initial reduction of surface bacteria on conventionally handled muscle tissue via a hot water dip, followed by processing at 28ºC in a sterile plastic isolator where Pediococcus cerevisiae was introduced into the curing solution. This treatment was compared to Reduced Initial Count and Conventional samples. Identification of the bacteria in the curing solution of each treatment indicated that a Lactobacillus spp. was predominant in the Reduced Initial Count treatment. The inoculated Pediococcus cerevisiae was predominant in the Gnotobiotic treatment, while Staphylococcus epidermidis and Flavobacterium diffusum were predominant in the Conventional treatment depending upon the trial. Tenderness, pH, and bacterial load were significantly affected by treatment. Oxidation and muscle composition were not affected by treatment. Samples from all treatments were acceptable organoleptically. / Master of Science

Sodium hypophosphite was evaluated for inhibition of growth and toxin production of Clostridium botulinum in a model meat system. Fresh comminuted pork was formulated to contain 0, 1000, or 3000 ppm sodium hypophosphite, with or without 50 ppm sodium nitrite, and 156 ppm sodium nitrite. The test formulations were inoculated with an equal mixture of 9 different strains of C. botulinum spores, vacuum packaged, pasteurized, and incubated for 60 days at 27°C. Packages were removed from incubation as swells developed and were analyzed for botulinal toxin by the mouse bioassay. In the first experiment, first toxic samples occurred at 5, 12, and 60 days of incubation for 0, 1000, and 3000 ppm sodium hypophosphite, respectively. Combinations of 1000 or 3000 ppm hypophosphite with nitrite delayed toxic swells by 17 and 14 days respectively, as compared to 6 days for 50 ppm nitrite alone. An experiment on the effects of sodium chloride on sodium hypophosphite inhibition showed that as the sodium chloride level was increased from O to 1.25 to 2.5%, hypophosphite inhibition was enhanced. For any sodium chloride level tested, increasing the hypophosphite concentration, caused a reduction in the rate of toxic swell formation. A combination of 2.5% salt, 50 ppm nitrite, and 3000 ppm sodium hypophosphite was the most effective combination tested. First toxic swell was delayed to day 24, and subsequent swells to day 33. The effects of various divalent cations on hypophosphite inhibition were studied. Cations produced no effect on sodium hypophosphite inhibition of C. botulinum. All experiments showed sodium hypophosphite to delay swell and toxin formation caused by Clostridium botulinum. / M.S.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Thesis (MScVoedselwet)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Red meat has a limited shelf-life at refrigerated temperatures, where spoilage is mainly due to the proliferation of bacteria, yeast and moulds, acquired during the dressing process. In addition, almost a fifth of food-borne disease outbreaks, caused by microorganisms such as Escherichia coli 0157:H7, Listeria monocytogenes and Staphylococcus aureus are associated with red meat. To improve the microbiological quality of red meat, systems such as HACCP, GHP and GMP are currently practiced; however, these practices are not able to extend the shelf-life of these products. At present suitable food-grade preservatives are recommended, but the use of some of these preservatives is increasingly being questioned with regard to their impact on human health. Additionally, food service customers demand high quality products that have a relatively long shelf-life, but still prefer the appearance of minimally processed food. All these factors challenge the food manufacturing industry to consider more natural means of preservation. Antimicrobial metabolites of food grade bacteria, especially lactic acid bacteria, are attracting increasing attention as food preservatives. Bacteriocins are antimicrobial peptides (3 to 10 kDa) with variable activity spectra, mode of action, molecular weight, genetic origin and biochemical properties that are bacteriostatic or bactericidal to bacteria closely related and bacteria confined within the same ecological niche. Micro-organisms were isolated from beef, lamb and pork, obtained from four commercial retailers. The number of viable cells three days after the sell-by date at 4ºC ranged from 80 cfu.g-1 to 1.4 × 108 cfu.g-1. Fifty-three percent were Gram-negative bacteria, 35% Gram-positive and 12% yeast. The microbial population of the meat was greatly influenced by the origin, i.e. the retailer. Bacteriocins produced by Enterococcus faecalis BFE 1071, Lactobacillus curvatus DF 38, Lb. plantarum 423, Lb. casei LHS, Lb. salivarius 241 and Pediococcus pentosaceus ATCC 43201 were screened for activity against bacteria isolated from the different meat samples. Sixteen to 21% of the isolates, identified as members of Klebsiella, Shigella, Staphylococcus, Lactobacillus, Lactococcus, Leuconostoc, Enterococcus, Pediococcus, Streptococcus and Bacillus were sensitive to the bacteriocins. Curvacin DF 38, plantaricin 423 and caseicin LHS (2.35 to 3.4 kDa) had the broadest activity range and inhibited species of Lactobacillus, Pediococcus, Enterococcus, Listeria, Bacillus, Clostridium and Propionibacterium. The bacteriocins remained stable at 121ºC for 20 min, in buffers with a pH ranging from 2 to 10 and in NaCl concentrations of between 0.1 and 10% (m/v). Like most peptides, they were sensitive to proteolytic enzymes. Curvacin DF 38 is sensitive to amylase, suggesting that the bacteriocin might be glycosylated. To assess the efficiency of curvacin DF 38, plantaricin 423 and caseicin LHS as meat preservatives, they were partially purified by ammonium sulphate precipitation and separation in a Sep Pak C18 cartridge. The shelf-life of pork may be extended by up to two days. Meat samples treated with bacteriocins were darker than the control (untreated) sample. Descriptive sensory evaluation by a seven-member panel indicated that there were significant differences (P ≤ 0.05) regarding the aroma, sustained juiciness, first bite and metallic taste attributes of the control and the 4 day-treated samples. The control and 2 day-treated samples and the 2 day- and 4 day treated samples did not differ significantly regarding these attributes. There were no significant differences regarding the initial juiciness, residue and pork flavour attributes. Concluded from the results obtained in this study, bacteriocins produced by Lb. curvatus DF 38, Lb. plantarum 423 and Lb. casei LHS effectively extended the shelf-life of pork loins by up to 2 d at refrigerated temperatures with no drastic changes on sensory characteristics. In edition, the stability of these bacteriocins broadens their application as preservatives in many foods. / AFRIKAANSE OPSOMMING: Die rakleeftyd van rooivleis by yskastemperature is beperk, waar bederf hoofsaaklik deur die vermenigvuldiging van bakterieë, giste en swamme veroorsaak word. Die meeste van hierdie kontaminante is afkomstig van die slagtingsproses. Byna ’n vyfde van alle uitbrake van voedselvergiftigings wat deur organismes soos Escherichia coli 0157:H7, Listeria monocytogenes en Staphylococcus aureus veroorsaak word, word met rooivleis geassosieër. Die praktyke HACCP, GMP en GHP word tans toegepas om die mikrobiologies kwaliteit van vleis te handhaaf, maar is egter nie voldoende om die rakleeftyd van rooivleis the verleng nie. Die preserveermiddels wat huidiglik aanbeveel word vir dié doel, word toenemend bevraagteken aangaande die invloed daarvan op die menslike gesondheid. Hierby is daar ’n aanvraag na hoë kwaliteit, ongeprosesseerde produkte met ’n verlengde rakleeftyd. Gevolglik word die voedsel vervaardigings industries aangemoedig om meer natuurlike vorms van preservering the oorweeg. Die aandag word tans op die anti-mikrobiese metaboliete van voedselgraad microbes, veral melksuurbakterieë, gevestig. Bakteriosiene is anti-mikrobiese peptiede (3 tot 10 kDa) met verskeie aktiwiteitsspektra, werkswyse, molekulêre massa, genetiese oorsprong en biochemiese eienskappe. Bakteriosiene is meestal bakterie-dodend of - staties teen taksonomies naby geleë organismes en organismes vanuit dieselfde ekologiese nis. Mikroörganismes is geïsoleer vanuit bees-, skaap- en varkvleis, verkry vanaf vier supermarkte. Die aantal lewensvatbare selle per gram (cfu.g-1) het drie dae na die “verkoop”-datum by 4ºC vanaf 80 cfu.g-1 tot 1.4 × 108 cfu.g-1 gevarieër. Drie en vyftig persent van die isolate is as Gram-negatief, 35% as Gram-positief en 12% as giste geïdentifiseer. Die sensitiwiteit van hierdie isolate teen bakteriosiene wat deur Enterococcus faecalis BFE 1071, Lactobacillus curvatus DF 38, Lb. plantarum 423, Lb. casei LHS, Lb. salivarius 241 en Pediococcus pentosaceus ATCC 43201 geproduseer is, is vervolgens getoets. Tussen 16% en 21% van die isolate was sensitief teen die bacteriosiene en is onder andere as Klebsiella, Shigella, Staphylococcus, Lactobacillus, Lactococcus, Leuconostoc, Enterococcus, Pediococcus, Streptococcus en Bacillus geïdentifiseer. Die bakteriosiene met die wydste aktiwiteitsspektrum, naamlik, curvacin DF 38, plantaricin 423 en caseicin LHS is verder ondersoek. Hierdie antimikrobiese peptiede (2.35 tot 3.4 kDa) toon aktiwiteit teen spesies van Lactobacillus, Pediococcus, Enterococcus, Listeria, Bacillus, Clostridium and Propionibacterium. Die bakteriosiene is stabiel by 121ºC vir 20 min, in buffers met ‘n pH-reeks van tussen 2 en 10 en soutkonsentrasies vanaf 0.1% tot 10%. Soos die geval by meeste peptiede is hierdie bakteriosiene sensitief vir proteolitiese ensieme. Curvacin DF 38 is ook sensitief vir amylase, wat daarop dui dat hierdie bakteriosien moontlik geglikosileer is. Die effektiwiteit van curvacin DF 38, plantaricin 423 en caseicin LHS as preserveermiddel in voedselsisteme is getoets deur dit te suiwer (ammonium sulfaat presipitasie en Sep Pak C18 kolom) en op vark lendestukke aan te wend. Mikrobiese analise het bewys dat die rakleeftyd van vark met sowat 2 dae verleng kan word. Volgens die vleiskleurevaluering was die bakteriosien behandelde vark donkerder as die kontrole. Die aroma-, sappigheid-, tekstuur- en metaalgeur-eienskappe van die kontrole en die 4-dag behandelde monster het volgens ‘n opgeleide sensoriese paneel betekenisvol verskil (P ≤ 0.05). Die kontrole en die 2-dag behandelde en die 2-dag behandelde en die 4-dag behandelde monsters het nie betekenisvol verskil nie. Daar was geen betekenisvolle verskil aangaande die aanvanklike sappigheid-, residu- en varkgeur-eienskappe nie. Hierdie sensoriese eienskappe is belangrik ten opsigte van die verbruiker se aanvaarding van die produk. Vervolgens kan uit hierdie resultate afgelei word dat die bakteriosiene wat deur Lb. curvatus DF 38, Lb. plantarum 423 en Lb. casei LHS geproduseer word voldoende is om die rakleeftyd van vark lendestuk by 4ºC met 2 dae te verleng met min of geen effek op die sensoriese persepsie van die vleis. Hierdie bakteriosiene is ook stabiel onder verskeie kondisies wat die toepassing as preserveermiddel aansienlik verbreed.

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.

Orientador: Nilo Sérgio Sabbião Rodrigues / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-22T11:11:16Z (GMT). No. of bitstreams: 1 Moraes_Fabianede_M.pdf: 11400492 bytes, checksum: ccae3b13c04ead483ac2377969757130 (MD5) Previous issue date: 2013 / Resumo: A carne assada, um item bem aceito pelos clientes de restaurantes coletivos, é comumente preparado com lagarto bovino (músculo Semitendinosus). O mercado da alimentação fora de casa está em franca expansão. Para atender à maior demanda dos restaurantes de coletividade, é necessário o aumento da produção e a busca e aprimoramento de tecnologias. O preparo de alimentos pelo sistema cook chill preserva as características sensoriais, reduz as perdas de processo, e resulta em alimento mais padronizado e microbiologicamente mais estável, quando comparado com sistemas convencionais, permitindo melhor programação e centralização da produção. Visando à comparação destes dois sistemas para a produção de lagarto bovino, na Etapa I desse estudo foi executado um planejamento experimental para a maximização do rendimento e da força de cisalhamento no produto processado pelo sistema cook chill. Foi aplicado um delineamento composto central rotacional para as variáveis independentes: tempo de cozimento, escala de injeção de vapor e temperatura do forno. Para a definição dos níveis das variáveis independentes foram realizados estudos preliminares. Foram obtidos maiores rendimentos no cozimento com menores tempos de cocção, maiores escalas de injeção de vapor e temperaturas intermediárias. A carne cozida a 177,7 °C apresentou menor força de cisalhamento, que é maior com o aumento do tempo de cozimento. Para a Etapa II, foram selecionados dois tratamentos dentre os dezessete do sistema cook chill da Etapa I: um de mínima força de cisalhamento (cook chill 1) e outro de máximo rendimento no cozimento (cook chill 2), os quais foram comparados com o sistema convencional por análises físico químicas, microbiológicas e sensoriais, no processamento e durante a estocagem. Os dois sistemas propiciaram carne assada de boa qualidade, em relação aos parâmetros analisados. As carnes processadas pelo sistema cook chill obtiveram melhor avaliação para os atributos sensoriais: aparência e gosto salgado. Embora a carne processada pelo sistema convencional tenha sido mais bem avaliada no atributo textura no corte com a faca e sua força de cisalhamento tenha sido a maior, não houve diferença significativa para o atributo textura na mastigação. A maior oxidação lipídica encontrada no lagarto processado pelo sistema cook chill 2 não impactou nos resultados da análise sensorial. Obteve-se carne com boa qualidade microbiológica até o quinto dia de estocagem nos três processamentos, destacando-se a carne processada pelo sistema cook chill 1 pelas baixas contagens microbianas mesmo no décimo dia de estocagem. Assim, o processamento de carne assada pelo sistema cook chill é vantajoso, principalmente, por permitir a produção de alimento com características mais estáveis, propiciar melhor programação e favorecer o aumento e a centralização da produção em restaurantes de coletividade / Abstract: Roast beef is a well accepted item by food service customers and it is commonly prepared with Semitendinosus beef. The food service market is currently booming. To meet the higher demands, it is necessary to increase production, develop new technologies as well as improve existing ones. Food preparation by the cook chill system preserves sensory characteristics, reduces water loss and delivers more standardized and microbiologically stable food, when compared to conventional systems, allowing better planning and centralization of production. In order to compare these two systems in terms of production of Semitendinosus muscle, Phase I of this study involved an experimental design to maximize cooking yield and shear force on the product processed by cook chill system. It was applied a central composite design for the independent variables: cooking time, steam scale injection and oven temperature. To define the levels of these independent variables preliminary studies were performed. Cooking yield is maximized when time is reduced, and higher scales of steam injection and intermediate temperatures are applied. The meat cooked at 177.7 ° C had lower shear force which increases when cooking time increases. For Phase II, two treatments were selected from the seventeen treatments in Phase I: one of minimal shear force (cook chill 1) and another of maximum cooking yield (cook chill 2), which were compared with the conventional system using physical chemical, microbiological and sensorial analysis during processing and storage. The two processing systems, cook chill and conventional, resulted in roast beef of good quality, in relation to the analyzed parameters. Meats processed using the cook chill system had better sensory evaluation in terms of the following attributes: appearance and salty taste. Although meat processed by the conventional system were more thoroughly evaluated in terms of cutting texture and had the biggest shear force, there was no significant difference in the mouth texture attribute between the samples. The higher lipid oxidation found on the meat processed by cook chill 2 system did not impact the sensorial analysis results. Meat with good microbiological quality were obtained up to the fifth day of storage for the three cases, especially for meat processed by cook chill 1 system, that showed low results until the tenth day of storage. Roast beef processing by cook chill system is advantageous, especially because of its ability to produce food that is higher in terms of stability, provide better programming and promote the increase and centralization of production in food service / Mestrado / Consumo e Qualidade de Alimentos / Mestra em Alimentos e Nutrição

Tesis por compendio / [ES] Se han desarrollado mediante termoprocesado películas multicapa biodegradables activas para el envasado de alimentos, combinando películas de almidón mejoradas y de una mezcla de poliésteres (PLA-PHBV), con diferentes ácidos fenólicos (ferúlico, p-cumárico y protocatecuico). En las películas almidón de yuca o de maíz se incorporaron gomas de origen microbiano (xantana y gelano) (10%) para mejorar sus propiedades funcionales. Las gomas mejoraron las propiedades mecánicas y de barrera al vapor de agua y al oxígeno de los films de almidón. Estos films se combinaron con films mezcla de PLA:PHBV en bicapas almidón-poliésteres por termocompresión. Las bicapas presentaron una alta capacidad barrera al oxígeno y al vapor de agua comparado con sus respectivas monocapas. La capa de poliéster contribuyó al refuerzo mecánico de la bicapa, aportando alta capacidad de barrera al vapor de agua, mientras que la capa de almidón aportó alta capacidad de barrera al oxígeno a la bicapa. La bicapa con almidón de yuca y goma gelano presentó la mejor adhesión entre capas, con propiedades funcionales adecuadas para el envasado de alimentos. Los ácidos ferúlico, p-cumárico y protocatecuico, con propiedades antimicrobianas y antioxidantes, se incorporaron (2%) en los films mezcla de PLA:PHBV para obtener films activos. Los ácidos fenólicos modificaron positivamente las propiedades de la mezcla de poliésteres, incrementando su módulo de elasticidad y resistencia a la fractura y su capacidad de barrera al vapor de agua y al oxígeno, al tiempo que aumentaron levemente la Tg del material. El ácido protocatecuico provocó los mayores efectos, afectando a la cristalización del PHBV. La liberación de estos compuestos en diferentes simulantes alimentarios (con polaridad alta e intermedia) fue muy limitada en cuanto a velocidad y cantidad liberada, lo que disminuyó la capacidad de las películas para inhibir de forma significativa el crecimiento de Listeria innocua inoculada en medio de cultivo. Estos films, con y sin compuestos activos, se desintegraron en condiciones de compostaje, sin efecto significativo de los ácidos fenólicos. Los films sin activos y con ácido ferúlico se biodegradaron completamente después de 20 días de compostaje, mientras que los films que contenían ácido p-cumárico y protocatecuico lo hicieron en 21 y 26 días, respectivamente. Por lo tanto, ninguno de los ácidos fenólicos incorporados inhibió el proceso de biodegradación, pero se retardó el proceso, dependiendo del grado de retención del compuesto en la matriz polimérica. Los films bicapa biodegradables constituidos por una capa de almidón-gelano y otra de PLA:PHBV, con y sin ácidos fenólicos, se caracterizaron en sus propiedades mecánicas y de barrera al vapor de agua y al oxígeno y se utilizaron para el envasado de carne de cerdo, evaluando su calidad durante el almacenamiento a 5 °C. La presencia de ácidos fenólicos disminuyó el módulo elástico y la tensión de fractura de las bicapas y mejoró su capacidad de barrera al vapor de agua y al oxígeno. Esto último, junto al efecto activo de los ácidos, contribuyó a mejorar la conservación de la carne durante el almacenamiento, reduciendo los niveles de oxidación lipídica, cambios de pH y pérdidas de peso de las muestras envasadas, así como el crecimiento microbiano, especialmente coliformes totales y bacterias ácido-lácticas. Los films bicapa biodegradables con ácidos fenólicos, a base de almidón y poliésteres, se muestran como una estrategia adecuada para obtener materiales de envasado activo, con propiedades funcionales próximas a las de algunos plásticos sintéticos comúnmente utilizados en el envasado de alimentos. Estos materiales pueden alargar la vida útil de los alimentos, mitigando el impacto ambiental de los envases plásticos ya que pueden ser compostados. / [CA] S'han desenvolupat, mitjançant termoprocesat, pel·lícules multicapa biodegradables actives per a l'envasament d'aliments, combinant pel·lícules de midó millorades i d'una mescla de polièsters (PLA-PHBV), amb diferents àcids fenòlics (ferúlic, p-cumàric i protocatecuic). En les pel·lícules midó de iuca o de dacsa es van incorporar gomes d'origen microbià (xantana i gellan) (10%) per a millorar les seues propietats funcionals. Les gomes van millorar les propietats mecàniques i de barrera al vapor d'aigua i a l'oxigen dels films de midó. Aquests films es van combinar amb films mescla de PLA:PHBV en bicapes midó-polièsters per termocompresió. Les bicapes van presentar una alta capacitat barrera a l'oxigen i al vapor d'aigua comparat amb les respectives monocapes. La capa de polièster va contribuir al reforç mecànic de la bicapa, aportant alta capacitat de barrera al vapor d'aigua, mentre que la capa de midó va aportar alta capacitat de barrera a l'oxigen a la bicapa. La bicapa amb midó de iuca i goma gellan va presentar la millor adhesió entre capes, amb propietats funcionals adequades per a l'envasament d'aliments. Els àcids ferúlic, p-cumàric i protocatecuic, amb propietats antimicrobianes i antioxidants, es van incorporar (2%) en els films mescla de PLA:PHBV per a obtindre films actius. Els àcids fenòlics van modificar positivament les propietats de la mescla de polièsters, incrementant el seu mòdul d'elasticitat i resistència a la fractura i la seua capacitat de barrera al vapor d'aigua i a l'oxigen, al mateix temps que van augmentar lleument la Tg del material. L'àcid protocatecuic va provocar els majors efectes, afectant la cristal·lització del PHBV. L'alliberament d'aquests compostos en diferents simulants alimentaris (amb polaritat alta i intermèdia) va ser molt limitada en quant a velocitat i quantitat alliberada, la qual cosa va disminuir la capacitat de les pel·lícules per a inhibir de manera significativa el creixement de Listeria innocua inoculada en medi de cultiu. Aquests films, amb i sense compostos actius, es van desintegrar en condicions de compostatge, sense efecte significatiu dels àcids fenòlics. Els films sense actius i amb àcid ferúlic es biodegradaren completament després de 20 dies de compostatge, mentre que els films que contenien àcid p-cumàric i protocatecuic ho van fer en 21 i 26 dies, respectivament. Per tant, cap dels àcids fenòlics incorporats va inhibir el procés de biodegradació, però es va retardar el procés, depenent del grau de retenció del compost en la matriu polimèrica. Els films bicapa biodegradables constituïts per una capa de midó-gellan i una altra de PLA:PHBV, amb i sense àcids fenòlics es van caracteritzar en les seues propietats mecàniques i de barrera al vapor d'aigua i a l'oxigen i es van utilitzar per a l'envasament de carn de porc, avaluant la qualitat a llarg del emmagatzematge a 5 °C. La presència d'àcids fenòlics va disminuir el mòdul elàstic i la tensió de fractura de les bicapes i va millorar la seua capacitat de barrera al vapor d'aigua i a l'oxigen. Això últim, junt a l'efecte actiu dels àcids, va contribuir a millorar la conservació de la carn durant l'emmagatzematge, reduint els nivells d'oxidació lipídica, canvis de pH i pèrdues de pes de les mostres envasades, així com el creixement microbià, especialment coliformes totals i bacteris àcid-làctics. Els films bicapa biodegradables amb àcids fenòlics, a base de midó i polièsters, es mostren com una estratègia adequada per a obtindre materials d'envasament actiu, amb propietats funcionals pròximes a les d'alguns plàstics sintètics comunament utilitzats en l'envasament d'aliments. Aquests materials poden allargar la vida útil dels aliments, mitigant l'impacte ambiental dels envasos plàstics ja que poden ser compostats. / [EN] Active biodegradable multilayer films have been developed by thermoprocessing for food packaging purposes, combining improved starch films and a blend of polyesters (PLA-PHBV), with different phenolic acids (ferulic, p-coumaric and protocatechuic). Into the cassava or maize starch films, gums of microbial origin (xanthan and gellan) were incorporated (10%) to improve their functional properties. The gums improved the mechanical and barrier properties to water vapor and oxygen of the starch films. These films were combined with PLA:PHBV blend films in starch-polyester bilayers by thermocompression. The bilayers exhibited high barrier capacity to oxygen and water vapor compared to their respective monolayers. The polyester layer contributes to the mechanical reinforcement of the bilayer, providing high water vapor barrier capacity, while the starch layer provided high oxygen barrier capacity to the bilayer. The bilayer with cassava starch and gellan gum showed the best interlayer adhesion, with adequate functional properties for food packaging applications. Ferulic, p-coumaric and protocatechuic acids, with antimicrobial and antioxidant properties, were incorporated (2%) in the PLA: PHBV blend films to obtain active films. Phenolic acids positively modified the properties of the polyester blend, increasing its elastic modulus and resistance to break and its barrier capacity to water vapor and oxygen, while slightly increasing the Tg of the material. Protocatechuic acid caused the greatest effects, affecting the crystallization of PHBV. The release of these compounds in different food simulants (with high and intermediate polarity) was very limited in terms of release rate and released amount, which reduced the ability of the films to significantly inhibit the growth of Listeria innocua inoculated in culture medium. These films, with and without active compounds, disintegrated under composting conditions, without significant effect of phenolic acids. Films without active compounds and with ferulic acid biodegraded completely after 20 days of composting, whereas films containing p-coumaric and protocatechuic acids did so in 21 and 26 days, respectively. Therefore, none of the incorporated phenolic acids inhibited the biodegradation process, but the process was delayed, depending on the degree of retention of the compound in the polymeric matrix. The biodegradable bilayer films with a layer of starch-gellan and another of PLA: PHBV, with and without phenolic acids, were characterized as to their mechanical properties and barrier capacity to water vapor and oxygen and were used for packaging of pork meat whose quality development was analysed throughout storage time at 5 °C. The presence of phenolic acids decreased the elastic modulus and resistance to break of the bilayers and improved their barrier capacity to water vapor and oxygen. The latter, together with the active effect of the acids, contributed to improving the preservation of the meat during storage, reducing the levels of lipid oxidation, changes in pH and weight losses of the packed samples, as well as microbial growth, especially total coliforms and lactic acid bacteria. Biodegradable bilayer films with phenolic acids, based on starch and polyesters, appeared as a suitable strategy to obtain active packaging materials, with functional properties close to those of some synthetic plastics commonly used in food packaging. These materials can extend the shelf-life of foods, mitigating the environmental impact of plastic packaging since they can be composted. / The authors would like to thank the Ministerio de Ciencia e Innovación of Spain, for funding this study through the Project AGL2016-76699-R and PID2019-105207RB-I00, and the predoctoral research grant # BES-2017-082040 / Hernández García, E. (2022). Biodegradable Multilayer Films for Active Food Packaging, Based on Starch and Polyesters with Phenolic Acids [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181473 / TESIS / Compendio