It is estimated that the papaya postharvest losses due to microbiological diseases account for almost 93% of the losses. Given the susceptibility of papaya to postharvest diseases is high, a careful management is fundamental.
Several methods are investigated to avoid the postharvest losses of papaya and to extend its shelf life, such as, use of fungicides, heat treatment, irradiation, biocontrol agents, natural coatings (essential oils, chitosan) and others.
Brazilian scientist have tested chitosan solutions with different molecular weights (150 and 300 kDa) as a method to extend the microbiological shelf life of papaya fruits during its storage at room temperature.
Chitosan solutions (150 and 300 kDa) were prepared by diluting 5.0 g of chitosan powder in 1.0 L of 0.5 mol/L acetic acid, using moderate magnetic stirring at room temperature for 5 h.; then, solutions were centrifuged to remove the supernatant.
For the study, whole fruits were separately immersed in chitosan solutions for 5 min, and after, solutions were removed by using a sterile rod. In this way, it was estimated that the amount of chitosan applied per unit area was of 10 g/m2. Then, fruits were stored at room temperature (18-24 °C) up to 20 days.
Evolution curves of mesophilic bacteria, yeasts and molds on papaya fruits during the storage period were constructed for coated and uncoated samples. These curves were represented by the Gompertz model, in order to estimate the shelf life of papaya fruits.
The results showed that the 150 kDa chitosan solution was more suitable to preserve the papaya fruits. After 10 days of storage, the Log (CFU/g) of mesophilic bacteria and yeasts and molds were, respectively, 1.3 and 2 times lowest for coated fruits.
Scientists conclude that the 150 kDa chitosan solution was more suitable than the 300 kDa chitosan solution. The use of 150 kDa chitosan solutions extended in about 4-7 days the microbiological shelf life of papaya fruits, during the storage at room temperature.
Study is available online since June 3rd 2015 at:
http://www.sciencedirect.com/science/article/pii/S0023643815004053
Source: Guilherme L. Dotto, Mery L.G. Vieira, Luiz A.A. Pinto, 'Use of chitosan solutions for the microbiological shelf life extension of papaya fruits during storage at room temperature', November 2015, LWT - Food Science and Technology, Vol. 64, pages 126-130.
Contacts:
Guilherme L. Dotto
Environmental Processes Laboratory (LAPAM), Chemical Engineering Department, Federal University of Santa Maria-UFSM
Santa Maria, RS, Brazil
Phone: +55 55 3220 8000.
Email: [email protected]
