Application of coating on dog biscuits for extended survival of probiotic bacteria

Functional biscuits for adult domestic dogs containing probiotic bacteria (Lactobacillus plantarum) and prebiotics (inulin) were developed and characterized. In order to assure a higher bacterial survival, the application of a protective coating was necessary. Two biscuit formulations were prepared, one with wheat flour and the other with soy and whole wheat flour. After baking them at 140 °C for 45 min, hard and crispy biscuits appropriate for adult dogs were obtained. Biscuits were treated either with calcium alginate or starch–glycerol coating. The preferred coating formulation was the starch–glycerol because of a higher survival rate of L. plantarum observed after passing through a simulated gastrointestinal system (HCl pH 1–2). In the case of wheat flour biscuits with coating, the bacteria survival rate after passing through the in vitro system, showed higher survival rate, regardless the presence of inulin while in soy and whole wheat flour biscuits, the presence of coating did not improve bacteria survival. The latter formulation showed a protective effect thus obtaining higher bacteria survival without coating. It is worth mentioning that after one month storage, biscuit formulations with coating maintained viable counts of L. Plantarum higher than 108 CFU/mL. The presence of inulin at 20 g/L did not show a significant effect on the survival rate of bacteria after one month storage period.