Abstract
In the present paper, a novel approach for the development of probiotic baked cereal products is presented. Probiotic pan bread constructed by the application of film forming solutions based either on individual hydrogels e.g. 1% w/w sodium alginate (ALG) or binary blends of 0.5% w/w sodium alginate and 2% whey protein concentrate (ALG/WPC) containing Lactobacillus rhamnosus GG, followed by an air drying step at 60 °C for 10 min or 180 °C for min were produced. No visual differences between the bread crust surface of control and probiotic bread were observed. Microstructural analysis of bread crust revealed the formation of thicker films in the case of ALG/WPC. The presence of WPC improved significantly the viability of L. rhamnosus GG throughout air drying and room temperature storage. During storage there was a significant reduction in L. rhamnosus GG viability during the first 24 h, viable count losses were low during the subsequent 2–3 days of storage and growth was observed upon the last days of storage (day 4–7). The use of film forming solutions based exclusive on sodium alginate improved the viability of L. rhamnosus GG under simulated gastro-intestinal conditions, and there was no impact of the bread crust matrix on inactivation rates. The presence of the probiotic edible films did not modify cause major shifts in the mechanistic pathway of bread staling – as shown by physicochemical, thermal, texture and headspace analysis. Based on our calculations, an individual 30–40 g bread slice can deliver approx. 7.57–8.98 and 6.55–6.91 log cfu/portion before and after in-vitro digestion, meeting the WHO recommended required viable cell counts for probiotic bacteria to be delivered to the human host.
Highlights
Probiotics are defined as live organisms that when administered in adequate amounts (>6e7 log cfu/g) confer health benefits to the host (FAO/WHO 2002)
No significant differences were observed between the control and the samples containing the alginate based films whilst the bread loaves treated with WPC based films and dried at oven temperature were characterised by the highest yellow component of the hue intensity (b*, p < 0.05)
Our results suggest that the direct inoculation and application of edible films with probiotics to bread crust can be considered an appropriate strategy for the production of functional bakery products
Summary
Probiotics are defined as live organisms that when administered in adequate amounts (>6e7 log cfu/g) confer health benefits to the host (FAO/WHO 2002). The growth of the probiotic food segment has been remarkable over the last decade with dairy products i.e. yogurt, ice cream, cheese and milk, juices and beverages and infant formulations being predominant (Euromonitor, 2012). Processing conditions during production can lead to significant losses of probiotic viability due to heat, mechanical or osmotic stress induced cellular injuries (Bustos & Bórquez, 2013; Fu & Chen, 2011). Several strategies have been extensively researched over the last years to overcome these processing obstacles to establish maximum viability of probiotics throughout the entire production cycle including product storage, market distribution and during consumption i.e. under gastric juice and intestine bile salt conditions.
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