Novel antimicrobial strategies for new food trends

Background: The new food trends are moving in the direction of plant-based foods and circular economy. In this respect, plant-based antimicrobials are considered promising substitutes for conventional food additives. This study focuses on some emerging topics in food product development and proposes sustainable solutions involving the use of plant-based antimicrobials. Aims: The aims of the study were to: 1. develop an active packaging using a cryogel made from starch containing hexanal able to hinder the growth of postharvest pathogens in sweet cherries. 2. evaluate the effectiveness of natural substances as alternatives to traditional additives (e.g. organic acids) for preserving ambient gnocchi. Methods: For the first aim, the in vitro antifungal activity of starch cryogels loaded with 0.1, 0.5, and 1% hexanal was determined against two strains of Botrytis cinerea. Subsequently, the in situ efficacy of the treatment was evaluated on sweet cherries infected with B. cinerea, and finally, the impact of the treatment on the natural microbiota and quality attributes of the fruit was investigated. For the second aim, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and fractional inhibitory concentration (FIC) were calculated to assess the antimicrobial activity of six essential oils (EOs) alone or in combination with each other, against twenty-five Bacillus spp. strains isolated from ambient gnocchi, as well as from raw materials used for gnocchi production. After that, selected EOs together with hydrolates, phenolic compounds, and tinctures were used in ambient gnocchi formulations. Results: The cryogel system showed antifungal activity in vitro. In the presence of hexanal, the lag phase was significantly extended compared to the control, and reductions in the maximum level of growth were detected. The 0.5 % hexanal-cryogel significantly reduced the disease incidence and the disease severity of the sweet cherries during the first days of storage. Moreover, a significant reduction of total mesophilic aerobic bacteria and yeast counts was observed. The study on the effectiveness of biopreservatives against Bacillus spp. revealed MICs values in the range of 0.31-1.25 μL/mL for the most active EOs, which were those with thymol and carvacrol chemotype. According to the FIC index combination, Origanum vulgare or Thymus vulgaris EOs associated with Syzygium aromaticum showed commutative effect, while the same EOs, associated with Ocimum basilicum showed indifferent effects. In different formulations of ambient gnocchi, the biopreservatives were as effective as lactic acid in containing the microbial community, especially when EOs and hydrolates were used. Conclusions: Our findings suggest that the use of novel antimicrobial strategies such as coating with hexanal and biopreservatives are effective solutions to address postharvest decay of fruit and spoilage of ambient gnocchi. However, further studies exploring the hexanal control and release profile in the aerogels and the sensory aspects in gnocchi can be carried out in future.