Multidisciplinary Quality Characterization for the Development of Active and Intelligent Packaging Technologies for Muscle Foods

Abstract

Fresh food products such as meat and fish are highly susceptible to spoilage. Despite high efforts and advances in food processing and packaging technologies, inevitable microbial activity is the primary reason for their deterioration. Spoilage of muscle foods packaged under modified atmospheres typically manifests itself as changes in the properties of the food product and the surrounding headspace, leading to consumer rejection.Food spoilage is thus a major ecological and economic concern that calls for the development of innovative packaging solutions. These solutions could extend the product’s shelf life by targeting the spoilage microbiota (active packaging) or by providing with realtime information about the product’s quality status (intelligent packaging). Consequently, significant improvement in food quality and decrease of food waste could be foreseen, ultimately benefitting the whole food supply chain.<br/><br/>This doctoral dissertation contributes to the development of active and intelligent packaging technologies for muscle foods by means of interdisciplinary quality characterization, involving aspects of packaging material development, food spoilage analysis and multivariate statistical analysis. The main purpose of the dissertation was to define the key aspects of the food quality characterization process within the aforementioned context, to develop novel methods to enhance this process and to address specific research questions about muscle food quality. The theoretical framework and current scientific knowledge is thus reviewed with a focus on the properties and spoilage of muscle foods, the use of silver and oxygen absorbers as well as intelligent packaging concepts. The experimental part of the dissertation describes the materials and methods used for assessing the quality status of meat and seafood packaged under modified atmospheres. The doctoral dissertation is based on four original manuscripts P1-P4 where an antimicrobial releasing system (P1), antimicrobial absorbing system (P2) or quality monitoring principles for an intelligent packaging system (P3-P4) were studied.<br/><br/>In the first manuscript (P1), preparation and antimicrobial characterization of silver-containing packaging materials is described. Silver-containing films were produced by coextrusion and liquid flame spraying. Antimicrobial efficiency of the films was examined with bioluminescence imaging as well as with traditional antimicrobial assay. Selected films were used in meat packaging and their impact on the meat microbiota was assessed with chemical, sensory analyses and microbiological analyses, including 16S rRNA sequencing.<br/><br/>In the second manuscript (P2), statistical analysis was used for characterizing the impact of high-O2 (80/20/0), common anoxic (0/20/80) and enhanced anoxic (0/20/80 + O2 absorber) atmospheres (O2/CO2/N2 %) on physicochemical properties of pork sirloin. Changes in headspace gas composition (O2/CO2 %), surface pH and color (CIELAB) was monitored as a function of time. Mixed ANOVA was used for determining the effects of storage time, atmosphere and blooming time on the studied variables.<br/><br/>In the third manuscript (P3), spoilage of Atlantic cod (Gadus morhua) was examined with microbiological, chemical and sensory analyses. Selected-ion flow-tube mass spectrometry was used for real-time quantification of volatile organic compounds in the package headspace throughout storage time. Cod microbiota was examined with 16S rRNA sequencing.<br/><br/>In the fourth manuscript (P4), multivariate statistical analyses were applied for determining potential spoilage indicators of Atlantic cod and brown shrimp (Crangon crangon). Evolution of volatile organic compounds over storage time was explored with hierarchical cluster analysis, principal components analysis and partial least squares regression. Consequently, partial least squares regression was used as a selective tool for identifying most potential spoilage indicators.<br/><br/>Results of the present dissertation provide with new insights into the food quality characterization process as well as into the spoilage of packaged muscle food products. The requirements of packaging technology development and the characteristics of food quality information were identified as the main aspects of the characterization process and their impact on the experimental setup and methodology was examined. Efficiency of antimicrobial packaging solutions was found to be highly dependent on food product properties, antimicrobial activity mechanisms and material preparation techniques. Even though nanoscale silver showed high efficiency against typical spoilage bacteria in vitro, they were not effective in situ meat. The impact of varying oxygen levels on pork properties was demonstrated, suggesting that anoxic packaging could have benefits in pork packaging. On the other hand, a systematic procedure was developed for identifying and quantifying volatile organic compounds that could be used as food spoilage indicators. Several compounds were identified as potential spoilage indicators for both Atlantic cod and brown shrimp and their critical concentration levels were defined.<br/><br/>Overall, the present dissertation highlights the importance of a multidisciplinary approach and novel methods in food quality characterization when aiming at improving food quality, combining different aspects of microbiology, (bio)chemistry, materials science and multivariate statistical analysis.