Many authors have described the existence
Many authors have described the existence of correlation between viability and moisture content and therefore, water availability. Sabuquillo et al. (2010) demonstrated that only Penicillium oxalicum conidial formulations whose initial moisture contents ranged between 5 and 14% retained their viability after one-year storage at room temperatures. These values were similar to those obtained for conidial formulations of Penicillium frequentans (Guijarro et al., 2006) and Epicoccum nigrum (Larena et al., 2007), both of which are recognized BCAs against peach brown rot. However, could such values kept stable along the time? Regarding to that, we found that temperature was the most important factor that affects the shelf-life of the CPA-8 formulations here studied. While initial moisture contents were lower than 10% with aw values of 0.292–0.331, such values were considerably affected by the storage temperature, since they substantially changed during the time course of the assay. Storing biological products at low temperatures has been historically recommended to maintain the microorganism in a state of low metabolic activity. However, in this study we found that storage at 4 °C compromise the Caspase-1, human recombinant proteinase and visual aspect of both CPA-8 formulations, mainly associated not only to the increase of RH but also aw. Moreover, it should be pointed out that flasks did not conserve refrigerated BA3 samples in a suitable way, since RH and aw increased noticeably making their visual properties unsightly after 10 months of cold storage. At that time, the BA4 products were better preserved at 4 °C when packaged in flasks. In terms of the viability neither the BA3 nor the BA4 product has been compromised, probably due to the physiology of the microorganism. To successfully formulate CPA-8, the endospore form was used (Gotor-Vila et al., 2017d). The inherent stability of these structures enabled them to remain quiescent, and to withstand extreme environmental conditions such as temperature fluctuations and humidity stress (Gotor-Vila et al., 2017c). However, the physical features of the product were drastically altered, losing homogeneity that would become in an even bigger handicap if the product does not have to be expended in a single dose. Shelf-life is a period of time that corresponds, in appropriate storage conditions, to a tolerable decrease in the quality of a packaged product (Alamprese et al., 2017). This general definition emphasized the commercial significance of the terms and does not necessarily relate to its real life (understood as viability). The end of its marketability is also considered in terms of an unacceptable worsening of its peculiar physical and sensory features (Pergiovanni and Limbo, 2010) and the loss of these characteristics is sufficient to cause the product rejection by consumers. This work revealed that samples avoid caking when stored at room rather than at cold conditions, against the well documented principle that high storage temperatures often affect negatively the survival of different BCAs and biopesticidal products (Melin et al., 2011). It is a very remarkable finding since costs of storage and transportation are significantly reduced due to the needless of refrigeration. These results are in agreement with previous reports on CPA-8, in which spray-dried (Yánez-Mendizábal et al., 2012a), freeze-dried and fluid-bed spray-dried cells proved to be shelf-stable after storage at 22 °C using standard laboratory plastic flasks (Gotor-Vila et al., 2017b; Gotor-Vila et al., 2017d). Taken together all data recorded in this work, higher aw in the samples correlated with poor keeping qualities that mainly appeared in the packaging materials with less protecting barriers. Therefore, PE EVOH plastic flasks (flask02) as well as aluminium bags (less oxygen permeability) with vacuum conditions (bag01) should be considered for further trials for CPA-8 commercialization.