Depending on the needs of
Depending on the needs of the product to be preserved, there are several levels of barrier packaging. Usually they are classified into low and high barriers. High barriers have a low oxygen transmittal rate, low moisture vapor transmission rate, and a high tensile strength, or puncture resistance. When high barrier packaging is paired with an oxygen absorber or desiccant, products enjoy even greater shelf-life and stability. Therefore, low barrier bags seem to be the least effective method of packaging compared to high barrier bags, flasks or vials, so formulated cells could be partially rehydrated and could begin respiration and other degradation processes (Costa et al., 2002).
An essential parameter in the study of dried microorganisms is water activity (aw) rather than moisture content (relative humidity, RH) (Fasoyiro et al., 2016; Teshler et al., 2007). Though they are much correlated, aw indicates how much free water is available to microorganisms opposed to water that is strongly bound to formulation components. Moreover, the PKR Inhibitor conditions inside the package (different combinations of oxygen, carbon dioxide and nitrogen) as well as the temperature of storage also play an important role in the shelf-life of the product (Alamprese et al., 2017).
Continuing with the development of the BCA CPA-8, this work aimed to study the potential use of different types of packaging to prolong bacterium viability and preservation. In order to do this, we studied the following: (i) the effect of different materials (bags or flasks), atmosphere conditions, and storage temperatures on the viability and stability of fluid-bed spray-dried CPA-8 formulations, (ii) the dispersion in water of the CPA-8 packaged formulations and (iii) the efficacy of CPA-8 after packaging and long-term storage against Monilinia fructicola in nectarines.
Materials and methods
Discussion In this study, we stored formulated samples in two types of polyethylene flasks which provide excellent barrier properties to gases, water vapour and aromas (Lee et al., 2008). Moreover, they also have high resistance to fats, oils and chemicals with excellent impact resistance and good sealability (manufacturers' recommendations, Table 1). Some of the samples were also recovered with EVOH (copolymer of polyvinyl alcohol) that gives the complex magnificent properties barrier to gases. As part of the different packaging evaluated, two kind of bags were also evaluated with different barrier materials: an aluminium bag including overlapped layers composed by polyester plus polyethylene and a polyethylene coextruded film (0.76 cm3 m−2 day−1 oxygen permeability), and an impermeable transparent bag composed by polyamide and polyethylene (8.0 cm3 m−2 day−1 oxygen permeability). Other viable solutions to extend the shelf-life of the products are related to the use of modified atmospheres that can exert a barrier effect against light, moisture and oxygen (Alamprese et al., 2017; Gallagher et al., 2003). Vacuum packaging could be an attractive option for maintaining adequate shelf-life of bioproducts. It is a preservation technique which lowers the oxygen in the package atmosphere to levels in which metabolic processes are minimized and the rates of chemical and biochemical reactions reduced (Elzein et al., 2009). Costa et al. (2002) enhanced the survival of the freeze-dried Pantoea agglomerans cells (BCA against postharvest diseases in pome and citrus fruit) stored under vacuum conditions. This is in agreement with the results obtained in this study for CPA-8, in which a vacuum atmosphere seem to better prevent the gain of moisture and aw thus maintaining the physical homogeneity and consistency of the product (although it did not result in a crucial factor, compared to the temperature of storage). It is also worth mentioning that some vacuum packaged samples were discarded because they did not resist long-term storage (probably due to either, the material of the bag, the sealing condition or even the sealing system applied), which suppose a drawback in a large-scale package system.