A three-step approach to assess efficacy of alternative chemical treatments to preserve fresh fruit juices: Application to pineapple (Ananas comosus ‘Queen Victoria’)

International audienceFresh pineapple juice exhibits a shelflife of a few days limited by the development of yeasts and molds. An approach was implemented to assess the efficacy of treatments of juice, based on three successive steps. The first step was to validate the use of a microbial cocktail which leads to juice spoilage. In a second step, the efficacy of treatments was assessed on the growth of fungi in two conditions. The treatment chosen was the addition of Thymus leptobotrys (Tl) and Thymus maroccanus (Tm) essential oils (EO). These extracts were mainly composed of the monoterpene carvacrol, and inhibited fungal growth in culture medium. The addition of EO to pasteurized juice inoculated with a fungal cocktail limited fungal population below 4.6 log CFU/mL during 14 days. The low pH of pineapple juice probably strengthened the effect of antifungal compounds acting on proton gradient across plasma membrane. Lastly, the efficacy of the treatments was assessed in fresh pineapple juice harboring its natural microbial population. The extracts TlEO at 0.25%o or TmEO at 0.05%o limited fungal growth below 5 log CFU/mL during 14 days. Thyme scent was detected after EO addition but the characteristic descriptors of pineapple and sugary were maintained

Effect of Adding Thymus leptobotrys on Extra Virgin Olive Oil’s Quality and Physicochemical Parameters

The present study aimed to evaluate the changes in extra virgin olive oil (EVOO) after enrichment treatments with Thymus leptobotrys, a Moroccan endemic aromatic plant. The EVOO sample was supplemented with two materials obtained from the aerial parts of T. leptobotrys: powder (2.5 and 5%) or essential oil (100 and 200 ppm). The chemical composition analysis of T. leptobotrys extracts (essential oil and powder methanolic extract) allowed the determination of its phenolic profile. Quality parameters (acidity, peroxide value, and specific extinction coefficients), color, fatty acids composition, minor components (pigments and phenol), and Rancimat oxidative stability of the control and enriched oils were measured. Rosmarinic acid and thymusin were the main identified compounds in the powder; thymusin was identified for the first time in the essential oil where it was predominant. Generally, the enrichments did not downgrade the oil from its initial category (EVOO), according to quality indexes. Adding T. leptobotrys to EVOO, especially the essential oil, enriched its phenolic profile by allowing the migration of thymusin, a lipophile flavone, without affecting its quality parameters or color