Non-thermal Technologies for Food Safety and Quality Improvement

A rapid action for emerging nonthermal technologies was a must as a consequence to the high numbers of foodborne diseases worldwide as stated by world health organization. Thus, various non-thermal technologies (such as cold plasma and high pressure) are being developed in order to replace or enhance the performance of the traditional ones. Understanding the mechanisms of these technologies and their reaction with food quality, physically (i.e., color and texture) and chemically (i.e., primary and secondary lipid oxidation products) is highly recommended to meet the growing demand of consumers for fresh-like and minimally processed products. Moreover, expanding the potential use of these technology to form new food products as a delivery system for bioactive compounds such as food emulsions considering their chemical composition (lipid and antioxidants) and physical attributes (droplet size and distribution) to ensure their stability. The overall objective of the thesis is to ensure the application of non-thermal technologies (i.e., cold plasma and high pressure) for safety and quality improvement of high lipid content food (i.e., sardine and pistachio) and to valorize the prospective application of these technologies in shaping novel food systems (i.e., emulsions). To accomplish this, the workflow has been segmented into four sub-objectives as following; 1) assessment of lipid oxidation and microbial decontamination of sardine (Sardina pilchardus) fillets processed by plasma-activated water (PAW); 2) impact of cold atmospheric plasma (CAP) treatments on the oxidation of pistachio kernel lipids; 3) effect of high-pressure processing (HPP) on sardine physicochemical quality: changes in color, texture and volatile markers of lipid oxidation; 4) exploiting technological functionality of pistachio oil for innovative emulsified systems stabilized with high pressure homogenizing (HPH). As results of plasma treatment on sardines, PAW was able to reduce the natural microflora to a very small extent (0.22 and 0.20 log units) for the total number of mesophilic aerobes and Pseudomonas spp, respectively), but no improvements in shelf-life at refrigeration temperatures were observed. At the longest treatment duration (30 min), signs of PAW-induced oxidative degradation of fish lipids were observed (loss of PUFAs; increase in secondary volatile oxidation products derived from the cleavage of FA hydroperoxides). Nevertheless, qualitative and quantitative composition of the cholesterol oxidized products (COPs) fraction was not significantly affected by contact with PAW. When applying plasma on pistachios, CAP treatments did not significantly affect the total fatty acid composition and the amounts of identified unsaponifiable matter constituents (4-desmethylsterols, 4,4-dimethylsterols, 4-methylsterols), except for an unexpected significant increase of γ-tocopherol content. There was an effect of plasma on the non-volatile (hydroperoxides, TBARS, POPs) and volatile (C6-C10 aldehydes and alcohols) key markers of lipid peroxidation. Regarding the application of high pressure, HPP was applied to sardine fillets at 400 and 600 MPa for various holding time and subsequently stored at 4 °C for 14 days. The results showed that HPP has a positive influence on the physical properties of fish muscles including texture and color by increasing the values of hardness and lightness. Aldehydes and ketones were affected by storage and HPP. HPP samples had lower levels of ketones on day 14. While HPP samples exhibited higher aldehyde levels, control samples were characterized by two main oxidation markers (i.e., hexanal and 2,4-hexadienal) by the end of the tested storage period. 4 Furthermore, in this study an exploiting of pistachio oil technological functionality for innovative emulsified systems stabilized with HPH was assessed. Emulsifying properties of pistachio oil were investigated in oil-in-water emulsions using Tween 20 (Tw20) at 0.5 % and 1 % (w/w) and by applying high pressure homogenization (30 MPa). Emulsifying capacities were evaluated determining the oil particle size and distribution. Oils and emulsions were analyzed for fatty acids profile, antioxidants properties (δ, β/γ tocopherols, lutein, total polyphenols) and oxidative state (conjugated dienes and trienes, ΔK, peroxide value). All o/w emulsions showed a monomodal oil droplets distribution with sizes ranging from ca. 1.5 to ca. 2.5 μm (0.5 % Tw20) and 1.1 to 2.1 μm (1 % Tw20) for PO1 and PO2 emulsions, respectively. In agreement with the initial oils’ composition PO1 emulsions showed higher antioxidant compounds contents compared to PO2, ones with differences due to the Tw20 concentration. After 7 days, changes in the D [4,3] values of different entity depending on oil type and Tw20 concentration were observed indicating the occurrence of destabilizing processes (i.e. flocculation and coalescence); the creaming index remained unchanged. This study adopts two-dimensional approach to help the research and food industries in better understanding the impact of CP and HP on food quality and expanding the use of these technologies for new food systems.