Abstract
Bread and intermediate moisture bakery products are mainly spoiled by yeasts and filamentous fungi. The inoculum load and preservation system used determines their shelf life. To extend the shelf life of such commodities, the use of chemical preservatives is the most common way to try and control the initiation of mold spoilage of bread. This study has utilized a rapid turbidimetric assay system (Bioscreen C) to examine the temporal efficacy of calcium propionate (CP) and potassium sorbate (PS) for controlling the growth of important bread spoilage fungi. The objectives were to compare the temporal growth of strains of three important spoilage fungi Hyphopichia burtonii (HB17), Paecilomyces variotii (PV11), and Penicillium roqueforti (PR06) isolated from visibly molded bread to (a) different concentrations of CP and PS (0–128 mM), (b) temperatures (25°C, 30°C), (c) water activity (aw; 0.95, 0.97), and (d) pH (5.0, 5.5). All three abiotic factors, pH, aw, and temperature, and preservative concentrations influenced the relative growth of the species examined. In general, PS was more effective than CP in inhibiting the growth of the strains of these three species. In addition, the Time to Detection (TTD) for the efficacy of the preservatives under the interacting abiotic factors was compared. The strain of Paecilomyces variotii (PV10) was the most tolerant to the preservatives, with the shortest TTD values for both preservatives. P. roqueforti was the most sensitive with the longest TTD values under all conditions examined. These results are discussed in the context of the evolution of resistance to food-grade preservatives by such spoilage fungi in bakery products.
Highlights
Bakery products are intermediate moisture foods and are prone to mold spoilage without the addition of control strategies, such as food-grade preservatives, modified atmosphere packaging, and storage, and the use of humectants (Magan and Aldred, 2006; Pitt and Hocking, 2009; Dagnas and Membré, 2013; Rodríguez et al, 2016; Garcia et al, 2019a).Preservatives, Bread Spoilage Mold ControlThese are combined to develop effective shelf life for products that are stored under ambient conditions
The P. roqueforti strain was sub-cultured on Malt Extract Agar (MEA) [20 g malt extract (Difco), 2 g peptone (Difco), 15 g agar (Sigma Aldrich, Dorset, UK)] for 7 days at 25°C in the dark, while H. burtonii and P. variotii strains were cultured in the same medium, but at 30°C, for 7 days (Pitt and Hocking, 2009)
This study has shown that the strains of H. burtonii and P. variotii have developed very good resilience to the existing preservatives, even at concentrations much higher than those allowed in the EU and many other countries
Summary
Bakery products are intermediate moisture foods (approx. 0.95 aw; pH 5.0–6.0) and are prone to mold spoilage without the addition of control strategies, such as food-grade preservatives, modified atmosphere packaging, and storage, and the use of humectants (Magan and Aldred, 2006; Pitt and Hocking, 2009; Dagnas and Membré, 2013; Rodríguez et al, 2016; Garcia et al, 2019a).Preservatives, Bread Spoilage Mold ControlThese are combined to develop effective shelf life for products that are stored under ambient conditions (e.g., bread products, cakes). 0.95 aw; pH 5.0–6.0) and are prone to mold spoilage without the addition of control strategies, such as food-grade preservatives, modified atmosphere packaging, and storage, and the use of humectants (Magan and Aldred, 2006; Pitt and Hocking, 2009; Dagnas and Membré, 2013; Rodríguez et al, 2016; Garcia et al, 2019a). It is difficult to obtain estimates of the losses in the bakery product industry attributed to fungal spoilage and product wastage. This is influenced by season, product formulation and processing methods, and the hygiene status of the production and processing areas (Legan, 1993; Magan and Aldred, 2006). Updated data were not available, Killian and Krueger (1983) estimated losses of around 5% in the USA and 1–5% in Europe (Abellana et al, 1997), while Freire (2011) showed that losses could exceed 10% in Brazil
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