Università degli studi di Modena e Reggio Emilia

Nowadays about 31% of the food packaging world global market is represented by paper and paperboard packaging solutions. However, these types of materials show some limits and critical issues (migration of Mineral Oil Hydrocarbons-MOH, poor barrier towards gas, water and grease, no sealability). To overcome these limits, paper, cardboard and paperboard are often treated and lacquered with synthetic polymers. Given the interest in using sustainable processes and recyclable, biodegradable and/or compostable materials, this study aims to develop a biobased coating, as a sustainable alternative to current solutions. The coating is made up of water suspension of micro/nano cellulose fibrils together with some natural functional ingredients. To produce the coating suspension, a plant biomass rich in cellulose was subjected to various high-pressure homogenization cycles and properly formulated. The diluted suspension obtained was first observed under optical microscope to verify the cellulose defibrillation, then chemically e dimensionally characterized, finally applied on commercial cardboards with an automatic coating applicator. On the coated cardboards, we evaluated the grammage of the coating applied in different experimental conditions, then we tested the grease resistance with the TAPPI official method (Kit test), the MOH transmission, the water vapor transmission rate (WVTR) and the contact angle to water and vegetable oil, compared to uncoated samples. The results showed that a coating of 3 g/m2 guarantees excellent resistance to grease, achieving the highest Kit test rating, In addition, the coating significantly reduces MOH transmission compared to uncoated samples. Given the good lab-scale applicability, the research is moving towards industrialization with the optimization of coating applications and towards the possible use of recycled paperboard in food packaging applications.

The food industry is experiencing an increasing demand for clean-labeled and minimally processed foods with high nutritional and health value. In this scenario, high- pressure processing (HPP) stands out among non-thermal treatments as a stabilization method that induces limited changes to the nutritional value, color, and flavor of the food, ensuring food safety and extending shelf life. This study assessed the potential of HPP as an alternative to thermal pasteurization for stabilizing prickly pear puree. To this aim, one batch of prickly pear puree was submitted to a HPP cycle (600 MPa for 180 s at 5°C), while another batch was pasteurized (80 °C for 30 s). After treatment, the samples were stored at 4°C for 42 days. The untreated (NT), pressurized (HP), and pasteurized (PAST) prickly pear purees were first compared on day 0 to evaluate the impact of treatments. Additionally, the stabilized purees (HP and PAST) were monitored weekly for 42 days to evaluate microbiological growth, pH and color change, bioactive compounds content (ascorbic acid, phenolic compounds), antioxidant activity, enzymatic activity (pectin methyl esterase, lipoxygenase, and polyphenol oxidase), and volatile organic compounds. Both treatments ensured microbial stabilization for 42 days under refrigeration. HPP ensured better color preservation, enhanced retention of ascorbic acid and did not significantly impact the total phenolic content. Our study highlighted similar inactivation levels for pectin methyl esterase and lipoxygenase following both treatments, while HPP was less effective at inactivating polyphenol oxidase: despite this, no negative impacts of HPP on color, sensory perception, or aromatic profile were observed. On the contrary, the volatile profile was better preserved with HPP, resembling the characteristics of fresh puree more closely than pasteurization.

The effect of hyperbaric storage (HS) on food packaging materials was evaluated. PA/PE, PP/EVOH/PE, PET and PLA pouches filled with hydroethanolic simulant (D1) were stored at 0.1 and 200 MPa for up to 35 days and analyzed for optical, structural, mechanical and diffusional properties. HS weakened PLA seals, which easily failed after 7 days releasing the simulant. Both PET and PLA films swelled during HS, reducing PET physical ageing and PLA crystallinity. These structural effects caused PET and PLA mechanical properties to vary during HS, and a slight WVTR increase in PLA. Optical, structural and mechanical properties of multi-material films did not change upon HS. Nevertheless, both PA/PE and PP/EVOH/PE released critical amounts of adhesives after 7 and 35 days under pressure, respectively. Results indicate the critical role of the packaging material of foods intended for HS, and the need for its careful selection in future studies on the topic.

Hyperbaric storage (HS) consists in storing foods packaged in flexible plastic pouches under moderate hydrostatic pressure (P < 250 MPa) inside steel vessels for prolonged periods (i.e., up to months). When applied at room temperature, HS guarantees food safety for up to several months with near-zero energetic expenditure. However, the technological readiness level (TRL) of HS is still very low, primarily due to a scarce understanding of the technical framework of the technology. Within the latter, the capability of flexible packaging materials to withstand HS conditions without losing performance is a mandatory, yet untested, requirement. Therefore, the aim of this work was to explore the effects of HS on PA/PE, PP/EVOH/PE, PET and PLA films, selected as packaging materials typically employed in the food industry. To this aim, each film was formed into 10 x 10 cm pouches, filled with simulant (50 % (v/v) hydroalcoholic solution), and subjected to HS (200 MPa, 20 ± 1 °C) for up to 35 days. Control samples were stored at room conditions (0.1 MPa, 20 ± 1 °C). Samples were evaluated for optical (colour, UV-Vis spectroscopy), mechanical (tensile properties) and barrier (overall migration, water vapor transmission rate -WVTR) properties during storage. Storage under pressure caused some modification in the film properties: in PLA film, a significant decrease in WVTR was detected in concomitance with an increase in elongation at break (E%); PET film showed an opposite trend. Results suggest that the effect of HS on film properties is material-specific and time-dependent. The occurrence of changes in packaging film properties upon pressurization should be carefully considered to assess their suitability for HS. To this regard, deeper structural investigation might be performed to obtain sound information driving the choice for optimal HS packaging solutions.

Chia (Salvia hispanica L.) seed mucilage (CSM) is a water-soluble gel consisting in a mixture of polysaccharides (xylose, glucose and methyl glucuronic acid). During hydration of chia seeds, mucilage is released which strongly binds to the seed surface. CSM has film forming capacity, which can be exploited for the development of edible films and coatings. The aim of this study was the optimization of the extraction procedure of CSM and the development and characterization of a biobased film for food application. The time of extraction was set at 1 h for all the conditions, while the extraction yield was optimized through an experimental design (factorial design, LF) with 3 levels and 3 factors. The independent variables were extraction temperature (25, 55 and 80 °C), seed:water ratio (1:10, 1:20, 1:40) and sonication (0, 5 and 10 minutes). The optimum conditions were extraction temperature 80°C; seed:water ratio 1:40. At every condition, no significant effect of sonication was observed. After hydration, the aqueous suspension was oven dried at 55°C overnight and the dried mucilage was separated by rubbing over a sieve. The dried mucilage was used for the preparation of a CSM film forming solution (2 % in water), used to prepare control films and blend films, obtained by mixing CSM with Hydroxypropyl methylcellulose (HPMC) at different ratios. The films were characterized for their mechanical (tensile properties), optical (colour and UV-Vis analysis) and barrier (water vapor transmission rate, WVTR) properties. A significant improvement of the main properties of the blend films was achieved, compared to the control, thus paving the way towards the potential use of CSM as the base for coatings or films for food applications.