Effects of Sodium Nitrite and Tocopherol Incorporated Poly(Lactic Acid) Biodegradable Films on Dark-Cutting Beef Color

This study aimed to develop poly(lactic acid) (PLA) biodegradable film containing sodium nitrite and α-tocopherol, and to examine its effect on dark-cutting beef color attributes. Using a twin-screw extruder, PLA pellets were manufactured as a low-concentration (LC) PLA pellet containing 0.12% sodium nitrite and 0.5% α-tocopherol or a high-concentration (HC) PLA pellet containing 0.6% sodium nitrite and 2.5% α-tocopherol. Extruded PLA pellets were oven-dried before being compressed and molded into film sheets using a hot press. In this study, 7 normal-pH and 7 dark-cutting strip loins were selected from a commercial processor. Loins were sliced into 2.54-cm thick steaks and randomly assigned to the respective loin-type treatments. The packaging treatments include normal-pH polyvinyl chloride (PVC), dark-cutting PVC, dark-cutting vacuum, LC-PLA dark-cutting in vacuum, and HC-PLA dark-cutting in vacuum. Normal-pH steaks were packaged with PVC overwrap, while dark-cutting control steaks were packaged in PVC overwrap and vacuum-sealed. The respective PLA films (LC or HC) were placed directly on the surface of the dark-cutting steak surface before vacuum packaging, resulting in LC-PLA and HC-PLA treatments. All steaks were placed in a simulated retail dis-play maintained at 2±1°C for 6 d, during which their surface color was evaluated every 24 h using a HunterLab spectrophotometer and a trained panel (n=6). Half of the steaks were removed from display on d 5 and cooked to 71°C on a George Foreman grill to evaluate the cooked color. The remaining steaks were evaluated on d 6 for microbial growth and lipid oxidation. A significant increase (P<0.05) in surface redness value was observed for steaks packaged with LC-PLA and HC-PLA within the first 24 h of display. Moreover, HC-PLA steaks exhibited higher redness values (P<0.05) than LC-PLA, dark-cutting PVC, and dark-cutting vacuum-packaged steak treatments over the entire display period. Steaks packaged with HC-PLA demonstrated greater external cooked color redness (P<0.05) and greater internal cooked color redness (P<0.05) than normal-pH steaks in PVC overwrap and dark-cutting steaks in PVC overwrap and vacuum packaging. Notably, LC-PLA steaks presented similar external and internal cooked color redness (P>0.05) compared to dark-cutting steaks in control vacuum packages (without nitrite). There were no differences (P>0.05) in aerobic plate count and lipid oxidation between nitrite-embedded and control vacuum dark-cutting treatments. Results indicate that using lower concentrations of sodium nitrite (0.12%) andα-tocopherol (0.5%) in PLA films can help improve the surface color of raw dark-cutting steaks while minimizing unpleasant cooked color associated with nitrite-embedded film

Preparación y caracterización de almidón de mandioca termoplástico combinado con poli (ácido láctico). Estudio del comportamiento producido por el agregado de grafeno como material de carga

El poli (ácido láctico) (PLA) y el almidón de mandioca son biopolímeros derivados de fuentes renovables y biodegradables con adecuadas propiedades para ser utilizados en el área de envases para alimentos, insumos médicos y agricultura. El creciente interés por mezclas de PLA y almidón de mandioca termoplastificado (TPCS) requiere que sus propiedades sean caracterizadas y analizadas para poder adaptarlas a las diversas aplicaciones. Además, la incorporación de nanopartículas como material reforzante es un área de investigación de importantes avances en la actualidad, buscando mejorar las propiedades de las mezclas poliméricas. El objetivo de esta tesis fue el desarrollo y la caracterización de mezclas de PLA, TPCS y nanoplacas de grafeno (GRH) utilizando el método de funcionalización reactiva; y el análisis de la biodegradabilidad en condiciones simuladas de compostaje. Las mezclas, física (PLA-TPCS), funcionalizada (PLA-g-TPCS) y nanoreforzada (PLA-g-TPCS-GRH), fueron desarrolladas por sistema lote con un mezclador y por extrusión de tornillo doble. Los films fueron desarrollados por prensado a alta temperatura y extrusión de tornillo simple. El procesamiento por extrusión de tornillo doble fue el más eficiente desde el punto de vista de la calidad del grado de mezclado de las mezclas obtenidas; como así también, la extrusión de tornillo simple en cuanto a la producción de los films. La funcionalización reactiva disminuyó la tensión interfacial entre el PLA y el TPCS, observándose la presencia de pequeños dominios de TPCS en la mezcla funcionalizada, a diferencia de la escasa compatibilización obtenida en la mezcla física. Además, la mezcla funcionalizada exhibió un mejor comportamiento desde el punto de vista de las propiedades mecánicas que la mezcla física. La incorporación de GRH a la mezcla funcionalizada de PLA y TPCS resultó en un material con mejores propiedades mecánicas y una disminución de la permeabilidad al oxígeno respecto de films de PLA y PLA-g-TPCS. Las GRH no mostraron una gran dispersión en la matriz de PLA-g-TPCS-GRH, observándose la presencia de aglomeraciones con escasa exfoliación. El mecanismo de “Crack-bridging” fue identificado como el responsable del comportamiento mecánico de los films en presencia de las GRH. La biodegradación de los films desarrollados se evaluó en condiciones simuladas de compostaje utilizando un respirómetro de medición directa. El estudio se realizó utilizando dos medios como sustrato: compost y vermiculita inoculada. El PLA alcanzó valores de mineralización de alrededor de 60% a día 120 en vermiculita inoculada y a día 60 en compost. Con una degradación de tipo hidrolítica durante el primer mes de la prueba, evidenciado por una reducción significativa del peso molecular. Para la muestra física se pudo observar, en compost, el desarrollo del efecto priming debido a las condiciones ofrecidas por dicho sustrato. En general, la fase de TPCS presentó una alta tasa de biodegradación y un alto % de mineralización en ambos sustratos. Las muestras de PLA-GRH tuvieron comportamientos disímiles según la carga de GRH utilizada, afectando la duración de la etapa de degradación hidrolítica, principalmente en compost. Las mezclas de PLA-g-TPCS-GRH mostraron una evidente fase de retardo en comparación con la mezcla sin GRH. La funcionalización reactiva del PLA con TPCS ha sido una metodología efectiva para el desarrollo de mezclas de base biológica; como así también las mezclas nanocompuestas obtenidas por agregado de GRH. Los films desarrollados han mostrado un comportamiento adecuado desde el punto de vista de sus propiedades y de su grado de biodegradabilidad demostrando que pueden ser una opción a los materiales derivados del petróleo actualmente en el mercado.Poly(lactic acid) (PLA) and cassava starch are biodegradable polymers made from renewable sources with suitable features for packaging, agricultural, and medical devices. The growing interest of using renewable polymer blends such as the once made from PLA and thermoplastic cassava starch (TPCS) requires a full study and characterization of their properties so that they can meet the performance requirements and their field of applications can be extended. Additionally, the incorporation of nanoparticles to PLA and TPCS blends with the aim to tailor and to improve their properties is an area of increasing interest. The overall goal of this dissertation was to develop PLA and TPCS blends reinforced with graphene nanoplatelets (GRH) by using the reactive compatibilization technique and characterizing their properties as well as their biodegradability in simulated composting conditions. Physical (PLA-TPCS), reactive (PLA-g-TPCS), and nanoreinforced (PLA-g-TPCSGRH) polymeric blends were produced by using a mixer and a twin-screw extruder. Films were made by compression molding and cast film extrusion. Blends and films manufactured by twinscrew and cast film extrusion, respectively, showed better overall properties. A lower interfacial tension between PLA and TPCS was achieved by using the reactive functionalization technique; showing smaller domains of TPCS for the reactive blends and poor compatibilization for the physical blend with bigger domains of TPCS. Hence, the reactive blends showed enhanced mechanical properties than the physical blend. A significant improvement in mechanical properties and oxygen barrier was achieved by the addition of GRH to the reactive blends in comparison to neat PLA and PLA-g-TPCS blends. GRH was unevenly dispersed in the PLA-g-TPCS-GRH matrix, showing poor exfoliation. A mechanism of crack-bridging was identified as the main responsible for the rupture of films reinforced with GRH. The biodegradation of films was evaluated in simulated composting conditions by using a direct measurement respirometer system. Inoculate vermiculite and compost were used as media. PLA films reached a value of mineralization of around 60% at day 120 in inoculated vermiculite and day 60 in compost. Hydrolytic degradation was the primary mechanism of degradation of PLA during the first 30 days of testing, showing a significant reduction of the weight number average molecular weight. A priming effect was developed in compost for the physical blend of PLA and TPCS due to the conditions of the compost media. Furthermore, blends with a TPCS phase presented a high rate of biodegradation and mineralization in both media. PLA added with different loads of GRH showed a different duration of the initial hydrolytic phase in compost. Reactive blends of PLA and TPCS with GRH showed a more significant lag phase than the reactive blend without GRH. The production of PLA and TPCS blends reinforced with GRH using reactive functionalization is an efficient methodology for the development of biobased polymer blends. Developed films showed good mechanical and barrier properties, and acceptable degree of biodegradability. The produced blends are an excellent alternative to replace fossil-derived films currently available in the market.Fil: Bher, Anibal Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; Argentin

Carta manuscrita de Alejandro Bher a Arturo Reyes

Junta de Andalucía, Grupo de Investigación PAI-HUM-0159; Archivo Arturo Reye

Compression molded LLDPE films loaded with bimetallic (Ag-Cu) nanoparticles and cinnamon essential oil for chicken meat packaging applications

This study describes the development of bioactive linear low-density polyethylene (LLDPE) films, blended with cinnamon essential oil (CEO), and selected concentrations of silver-copper (Ag-Cu) nanoparticles (NPs), and processed by compression molding. Influence of Ag-Cu NPs and CEO on thermo-rheological, structural, barrier, morphological and antimicrobial properties of LLDPE composite films were investigated. Ag-Cu NPs reinforcement effectively improved the mechanical and barrier properties of the films, whereas, CEO improved the flexibility of the composite films by lowering the complex viscosity and the melting temperature. The composite films exhibited excellent anti-UV properties, and appearance of new peaks corresponding to the aromatic domain with N-H bending vibration was confirmed by FTIR spectroscopy. Films loaded with Ag-Cu NPs and 50% CEO showed maximum antimicrobial activity against Listeria monocytogenes, Salmonella Typhimurium and Campylobacter jejuni. Chicken samples contaminated with S. Typhimurium and C. jejuni; packed in the composite films containing 4% (w/w) Ag-Cu and 50% CEO (w/w), and stored at refrigerated temperature for 21 days showed a complete inhibition.Fil: Ahmed, Jasim. Kuwait Institute For Scientific Research; KuwaitFil: Mulla, Mehrajfatemah. Kuwait Institute For Scientific Research; KuwaitFil: Arfat, Yasir Ali. Kuwait Institute For Scientific Research; KuwaitFil: Bher, Anibal Ricardo. Universidad Nacional de San Martín; Argentina. Michigan State University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Jacob, Harsha. Kuwait Institute For Scientific Research; KuwaitFil: Auras, Rafael. Michigan State University; Estados Unido