Hazelnuts and walnuts spreads with probiotics: development, characterization, and storage stability.

Aim: The aim of this work was the development of two different kinds of nuts spreads added with probiotics. Tree nuts are widely consumed for their taste and healthy properties, whereas probiotics are one of the most used functional ingredients for the production of innovative and nutraceutical confectionery products. For this purpose a strain of Bifidobacterium animalis subsp. lactis (BB-12®) was selected to be added to the spreads, due to its most documented beneficial effects. Method: Walnuts and hazelnuts were selected as base-ingredients for nut butters preparation in order to maximize the sensorial and nutritional profile of final products, thanks to their typical bioactive compounds (vitamins, antioxidants) and macronutrient compositions (fibre, proteins, PUFAs). Freeze-dried BB-12® was added to the nut pastes in calculated amount to guarantee an initial viability of 1010 UFC/g for serving portion (15g). In addition, a mixture of oligo- and polysaccharides (maltodextrin and tragacanth gum) and sugar alcohols (maltitol) was expected to be used for preserving and/or enhancing chemical, physical, and microbial properties. Based on an estimated activation energy of about 90 kJ/mol for nut lipid oxidation, it was possible to simulate sample storage at 21 °C for more than one year in a shorter period: samples were stored at 40 °C for 40 days and characterized once a week for rheological properties, microbiological, and oxidative quality. Results: Both nut spread formulations exhibited an excellent nutritional profile and resulted also stable to the oxidative stress. The probiotic strain kept a viability of 109 UFC/g through all the considered shelf life in both samples allowing to use the claim that the products “promote the balance of intestinal flora”. Conclusion: BB-12® probiotics showed a good adaptability and resistance to survive inside the walnuts and hazelnut spread formulations both during processing and storage: their viability was maintained, making possible to obtain a nutraceutical product. The addition of different ingredients that can contribute on creating an appealing product for new consumers, also approaching the industries, is being evaluated.