12 January - 20 June 2016

Breakthrough in the production of dried apple snacks enriched with probiotics

A study published in the Journal of Functional Foods by a group of researchers at the Universitat Politènica de València in Spain, and the Universidade Federal do Caeará in Brazil, has investigated the incorporation of probiotics into a dried apple snack. Using different drying temperatures, and the use and absence of ultrasound to enhance, they were able to produce a snack with a concentration of Lactobacillus casei similar to current probiotic dairy products.

A study published in the Journal of Functional Foods by a group of researchers at the Universitat Politènica de València in Spain, and the Universidade Federal do Caeará in Brazil, has investigated the incorporation of probiotics into a dried apple snack. Using different drying temperatures, and the use and absence of ultrasound to enhance, they were able to produce a snack with a concentration of Lactobacillus casei similar to current probiotic dairy products.

Probiotic-fortified foods have been suggested to have a variety of health benefits, including mitigating “risk of cardiovascular disease and type 2 diabetes, anti-inflammatory potential, protection against colitis and epithelial cell damage, reduction of insulin resistance and steatosis”, according to Rodrigues et al. in the current study. They also identified the growing market for probiotic foods, citing the lucrative €40bn market estimated in 2016, and projected 38% growth increase by 2021. This market is predominantly filled with dairy based products, as these are stored at temperatures at which the bacteria strains can survive for long periods of time. The researchers note that there are a number of drawbacks to largely only being present in dairy products including the inability to be ingested by lactose intolerance sufferers, people with diets necessitating a control of cholesterol, as well as people who do not enjoy eating dairy. The researchers identified the increased desire for customers to consume fruit and vegetables, the existing popularity of apples, their ability to be dried, along with all the benefits of reduction in size, increased shelf-life etc. that come with dried foods compared with fresh, and the proven ability to add probiotics to dried foods, as a premise for this study. Ultrasound has been shown not to cause destruction of microorganisms, at least up to a temperature of 60°C, and so it was considered a potential enhancer to dry the apple samples.

Granny Smith apples were purchased from a local market in Valencia, Spain, and cut into identical sized cubes. The Lactobacillus casei strain NRRL B-442 was prepared in MRS broth, with pH adjusted, and maintained until an initial cell concentration of 9.0 log counting forming units (CFUs) per ml was established. The cells were then removed from the broth and suspended in a neutral solution where the fresh apple samples were suspended for 2 minutes with gentle stirring to achieve an even incorporation of the bacteria into the cubes. The inoculated samples were dried at temperatures of 10, 40 or 60°C, and with or without the aid of ultrasound. A mathematical model was developed and used by the group to predict drying kinetics, as well as the viability of the bacterial cells.

Initially, and as expected, the samples at higher temperature dried faster, as did the ones with ultrasound enhancement. The higher temperatures and ultrasound-assisted tests did however show a higher inactivation rate of live cells per minute than at 10°C as Lactobacillus casei is heat-sensitive. The aim therefore was to strike the optimal balance in terms of drying speed and maintenance of live cells, to achieve the highest cell viability after the drying process (defined as a reduction in sample weight by 80% and a water activity of 0.35 ± 0.05) to qualify as a probiotic product (106 CFU/g). Ultrasound-assisted drying at 10°C was shown to retain 87 ± 2% of the original probiotic count, and slightly lower at 60°C.

In conclusion therefore, Rodrigues et al. note that ultrasound-assisted drying was shown to have advantages over conventional drying in both drying times and in cell viability after completion of the drying process. They note that their research highlights the potential of apple cubes dried with a combination of conventional and ultrasound-assisted drying to be used as a new form of probiotic snack.

RSSL's Product and Ingredient Innovation Team, has considerable experience in re-formulating products to provide more healthy options including low salt, low sugar versions and using pre- and probiotics.  Using RSSL can help speed up your development cycle considerably. To find out more please contact Customer Services telephone 0118 918 4076 or e-mail enquiries@rssl.com

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