Study supports encapsulation in synbiotic ice cream

Probiotics - live bacteria the dwell in the gut and are understood to play a role in maintaining good health - have found popular use in products such as yoghurt and milk. In the last few years food manufacturers have been looking to extend their use into new product types, including chocolate, cheese, breakfast cereals and ice cream. Indeed the researchers of the study, which has been accepted for publication in the journal Food Chemistry, note that probiotic bacteria have already been used in fermented and non-fermented ice cream, which they say is an "ideal vehicle for delivery of these organisms into the human diet". One major problem, however, is that the freezing process can affect the number of live bacteria. A reason for this, the researchers said, could be the effect of the freezing process on the cell wall, or oxygen toxicity. Some positive research has already been done on how encapsulation can boost survival of the bacteria in frozen products. But the researchers said that the survival of free and microencapsulated L.casei and B lactis bacteria has not been reported for synbiotic ice cream - that is, ice cream that also contains resistant starch as a prebiotic substance to help make the gut environment more amenable to probiotic survival. They also found no reports of studies about how the sensory properties of ice cream would be affected by the inclusion of pro- and prebiotic ingredients. Researcher A Homayouni and team therefore set out to evaluate the feasibility of incorporating resistant starch into both the coating of microencapsulation beads and the ice cream formulation. Using freeze dried L case and B lactis cultures obtained from Chr Hansen and Hi-maize resistant starch supplied by Merck, they prepared two samples of symbiotic ice cream. One had the probiotics contained within the prebiotic carriers, and in the other they were free. They found that, in the free state ice cream, the viable cell number of L casei and B lactis reduced from 5.1 x 109 and 4.1 x 10 9 CFU per ml respectively at day one to 4.2 x 106 and 1.1 x 10 7 CFU per ml after 180 days storage at -20 degrees Celsius. In the encapsulated sample, however, the survival rate was seen to be 30 per cent higher under the same conditions. From this, they concluded that, in general, "encapsulation can significantly increase the survival rate of probiotic bacteria in ice-cream over an extended shelf-life". The International Dairy Federation has said that a minimum of 107 bacteria per gram of product should be alive at the time of consumption in order for them to confer a benefit. For the second part of the study the symbiotic ice cream samples were assessed by 32 panellists for their organoleptic properties. They looked at the samples under white fluorescent light and gave them a sensory rating of 1-10 for flavour and taste, 1-5 for body and texture, and 1-5 for colour and appearance. Overall, the panellists reported that all the samples were good in terms of colour, texture and taste, and did not have any marked off-flavour during the storage period. None of the ice creams were deemed "crumbly, weak, fluffy or sandy". Although the researchers said their study indicates that encapsulation can "significantly improve" the survival of probiotic bacteria in ice cream, they said that further studies are needed to investigate how much protection microencapsulation offers in the gastrointestinal tract. Source Food Chemistry (article in press) DOI: 10.1016/j.foodchem.2008.03.036 "Effect of microencapsulation and resistant starch on the probiotic survival and sensory properties of synbiotic ice cream" Authors: A Homayouni, A Azizi, MR Ehsani, MS Yarmand and SH Razavi