Packaging and food should not be considered two separate entities, but as elements that can interact, always with the aim to improve the acceptability of the packaged product. In the last two decades many researchers have placed their attention on the study of new packaging systems that improves food preservation. The most investigated new preservation technologies for fresh meat are new packaging systems such as active packaging (AP) and modified atmosphere packaging (MAP) which use natural antimicrobials for bio preservation. AP is the incorporation of specific compounds into packaging systems that interact with the contents environment to maintain or increase product quality and shelf life. AP functions and technologies include moisture control, O2 scavengers or absorbers, CO2 controllers, odours controllers, antimicrobial and antioxidant agents, either natural or synthetic. By preserving the important nutrients of fresh meat such as proteins, essential amino acids, vitamins of group B and others, AP technology can be useful for enhancing the intake of these nutrients too. Natural extracts and essential oils of plants are extraordinary sources of bioactive molecules mixtures, having important antioxidant and antimicrobial actions. The use of natural extracts categorized as flavourings by the European Union (EU) and generally recognized as safe (GRAS) by the US Food and Drug Administration (FDA), represents an interesting approach in AP technology. Considerable results, especially from a biological point of view, have been carried out on the assessment of the antioxidant activity of many herbs such as rosemary (Rosmarinus officinalis), oregano (Origanum vulgare) and others incorporated in an active packaging film. The Rosemary (Rosmarinus officinalis L.) essential oil (REO) contains bioactive compounds having important antioxidant and antimicrobial activities. In this research work the shelf life of different types of fresh food (chicken and beef meat, raw and cooked ham) was studied by monitoring: biogenic amines (BAs), hexanal, microbial growth (such as psychrotrophics, Brochothrix thermosphacta, Pseudomonas spp., and Enterobacteriaceae), pH, colorimetric measurement (L*, a*, b* values) and sensory analyses. The packaging used were IdeabrillÂ® enriched with REO (called ''AP''), IdeabrillÂ® (NAP) and the common packaging (PP). Fresh food wrapped in different systems, were stored at 4Â°C in different condition: air, under-vacuum and with high-O2 concentration (50:30:20; O2:CO2:N2 %). First of all, more attention was focused on the studies of BAs, that are basic nitrogenous compounds considered important indicator of freshness and quality of food. The active packaging system (AP) that incorporating essential oil of Rosmarinus officinalis at 4% (w/w), inhibits the increase of BAs and the bacteria involved in to their production was developed. BAs were analyzed by a SPE-HPLC-DAD method during the storage time of meat (0-7 days, 4Â°C). Results showed that, in each monitored day, Biogenic Amine Index (BAI) expressed in mg kg-1 is lower in meat wrapped in AP with respect to that packed in polycoupled packaging (PP) (from 19% to 62%). A strong correlation was found between the inhibition of increase of putrescine, cadaverine, histamine and their bacteria producers such as Enterobacteriaceae, Pseudomonas spp., Brocothrix thermospacta. By exploiting antimicrobial and antioxidant action of essential oil of Rosmarinus officinalis, the new APs contributes to increase the shelf life of fresh meat and to preserve its important nutrients. Moreover, the antioxidant action of new AP system was tested by monitoring hexanal as marker of lipidic oxidation of fresh meat. Preliminary results showed good results in favour of food wrapped in AP system in comparison with PP. In collaboration with Ghent University, the shelf life of beef meat wrapped in AP and in NAP under different air conditions were studied. Microbial growth, sensory characteristics, color parameters, and pH were measured. The use of REO has proved to be efficacious in every storage conditions, because the counts of psychrotrophics, Brochothrix thermosphacta, Pseudomonas spp., and Enterobacteriaceae were lower in AP meat compared to NAP meat. Sensorial and colorimetric analysis showed that the best packaging conditions were high-O2 atmosphere in combination with REO. Based on microbiological data, shelf life of beef meat was 5 days for air packaged samples (AP and NAP), 6-7 days for NAP under vacuum condition samples, 8-9 days for AP under vacuum condition samples, 9-10 for NAP in high-O2 condition samples, and until 15 days for AP in high-O2 condition samples. During the last part of the work, a new analytical method for analyzing ten underivatized BAs in meat by HPLC-MS/MS has been developed. The comparison between ion trap and triple quadrupole as mass analyzers elected triple quadrupole for its higher sensitivity and selectivity. The correlation coefficients of calibration curves of the analyzed compounds were in a range 0.987-0.999, and the Limits of Detection (LODs) and Limits of Quantification (LOQs) were in the range 0.002-0.1 mg l-1 and 0.008-0.5 mg l-1, respectively. The validated method was applied to the analysis of sixteen commercial meat samples for evaluating the freshness of food through the study of BA indices, i.e. Biogenic Amine Index (BAI) and the ratio spermidine/spermine (SPD/SPE). Results showed that all analyzed samples presented good freshness quality with a BAI lower than 1.49 mg kg-1 and a SPD/SPE ratio lower than 0.41 in each case. This methodology to test the freshness of meat could have a great potentiality of application along the entire production chain of meat products.
|Titolo:||Development a new active packaging system for fresh food through the studies of chemical and biological markers|
|Data di pubblicazione:||28-mar-2014|
|Appare nelle tipologie:||Tesi di dottorato (Pregresso)|