Abstract
Abstract Eggs, often used in pastry products, are one of the major transmission vehicles of Salmonella. The main purpose of this study was to evaluate Salmonella Typhimurium thermal resistance, by D and z values determination, in a traditional Portuguese egg-based pastry and its microbial and physical-chemical characterization. Salmonella Typhimurium ATCC 14028 (OXOID C6000L) (Ca. 1.33×108 cfu g-1) was inoculated in a liquid batter consisting of 8 whole eggs, 7 egg yolks, 280 g of wheat flour and 250 g of sugar. D and z values determinations were performed after applying a water bath to vacuum-packed samples of liquid batter (5 g), following thermal treatments: 52 °C (45, 90, 135, 180 and 225 min); 55 °C (15, 30, 45, 60, 70 and 80 min); 58 °C (5, 10, 15, 20, 25 and 30 min) and 61 °C (1, 2, 3, 4 and 5 min). Physico-chemical (aw, pH, moisture, sugar, ashes, protein and free fat) and microbiological determinations (mesophilic microorganisms, psychrotrophic, molds and yeasts, Enterobacteriacea, E. coli; Salmonella spp., Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus) were also conducted in raw liquid batter. It was possible to investigate different combinations of time and temperature for Salmonella Typhimurium inactivation, compared to other studies on egg-based batter, often used to make pastry products. Liquid batter aw before inoculation was 0.94 and pH 7.26. The D values were obtained 53.19 min, 20.45 min, 6.95 min and 1.60 min, at 52 °C, 55 °C, 58 °C e 61 °C, respectively. From the calculated D values, the corresponding z value was 5.96 °C.
Highlights
Salmonella is known as a versatile microorganism, that adapts to pH, aw and temperature conditions beyond its growth range
Optimal temperature growth for Salmonella is about 35 to 37 °C, it can develop between 5 to 47 °C. This microorganism can grow at pH ranges of 3.8 to 9.5 (6.5-7.5 optimal) and aw of 0.94 to 0.99, below 0.94 it can remain at a latency state (D’ Aoust & Maurer, 2007; International Commission on Microbiological Specifications for Foods, 1996; Jay et al, 2005)
The present study aimed to evaluate thermal resistance of S
Summary
Salmonella is known as a versatile microorganism, that adapts to pH, aw and temperature conditions beyond its growth range. Optimal temperature growth for Salmonella is about 35 to 37 °C, it can develop between 5 to 47 °C This microorganism can grow at pH ranges of 3.8 to 9.5 (6.5-7.5 optimal) and aw of 0.94 to 0.99, below 0.94 it can remain at a latency state (D’ Aoust & Maurer, 2007; International Commission on Microbiological Specifications for Foods, 1996; Jay et al, 2005). The presence of Salmonella in bakery products has been a concern in the last years Outbreaks associated with this microorganism have been reported in custards, pies, bread and cakes, among others (Bonner & Schweiger, 1994; Evans et al, 1996; Lathrop et al, 2014; Zhang et al, 2007). Contamination by Salmonella through raw ingredients is a reality, as they are usually used in bakery receipts, such as eggs, chocolate, flour, peanut butter and dairy products (Arvanitoyannis & Bosinas, 2006; Saranraj & Geetha, 2012; Smith et al, 2004)
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