Study of different antifungal systems to preserve strawberry jams against fungi spoilage

Abstract

New tendencies in the development of innovative food packages could affect product microbial stability during storage. In this sense, antifungal systems such as emulsions, nanoemulsions and mesoporous silica supports, may be promising alternatives to preserve the product quality without having to apply further thermal treatments. The formulation of stable antifungal systems and the optimisation of the methodology to be employed to prepare these systems play an important role in: i) their antifungal effectiveness; ii) bioactive compounds losses during their preparation; and iii) their impact on the food product's sensory profile. Nanoemulsions prepared with essential oils generally presented higher antifungal effect than free essential oils applied at the same concentrations. Furthermore, the emulsifier played a key role in the resulting antifungal activity. Whey protein isolated-based nanoemulsions were more effective in inhibiting mycelial mould growth and spore germination than Tween 80-based ones. The great in vitro effectiveness of nanoemulsions to control mould development allowed to check their application to food products, and strawberry jam was selected as the food matrix. To this end, clove and cinnamon leaf emulsions were incorporated into strawberry jams to control fungal decay. Although these emulsions were able to reduce jam spoilage, their incorporation negatively affected the aroma, taste and the overall acceptance of the jam. Regarding the methodology employed to prepare oil-in-water emulsions, the magnetic stirring and high pressure homogenisation combination was the most effective to reduce essential oil losses. Moreover, stable cinnamon bark-xanthan gum emulsions with good in vitro antifungal properties against the target fungi were obtained. Despite the promising use of cinnamon bark emulsions to control fungi decay in strawberry jam, their incorporation negatively affected the product's aroma, taste and overall acceptance. Given the strong impact of essential oils on the food product's sensory profile, two new approaches were investigated: i) combinations of different antifungal compounds in emulsions; and ii) immobilisation of bioactive compounds on mesoporous silica surfaces. The cinnamon bark essential oil, zinc gluconate and trans-ferulic acid combination allowed the obtention of a product considered microbiologically acceptable and with good organoleptic characteristics. However, total mould inhibition was not achieved. Consequently, the antifungal and sensory properties of the bioactive agents (eugenol and thymol) immobilised on mesoporous silica surfaces were studied. The preparation of jams with eugenol immobilised on MCM-41 microparticles induced better control of the fungal inhibition compared with the samples functionalised with thymol. The sensory analysis of the jams after incorporating the solids revealed that eugenol and thymol immobilisation cushioned the impact of these compounds on the jam flavour profile.; Las nuevas tendencias en el desarrollo de envases alimentarios…