THE POTENTIAL OF THE MICROWAVE-VACUUM TECHNIQUE IN DRYING OF PROBIOTIC AND STARTER CULTURES
The demand on probiotic and starter cultures has been increasing the last years.To satisfy this need,more energy-efficient processes than freeze drying or shipping of frozen cultures are required.For various foods,in particular vegetables and fruit,microwave-vacuum drying showed promising results.However,up to date poor information is available on drying microorganisms with the aid of microwaves.So in this work,the aim was to find out if this drying technique is generally applicable for drying microbial cultures.Therefore,the probiotic lactic acid bacteria Lactobacillus paracasei ssp.paracasei F19 was used as model strain.In a first step,screening tests were conducted in order to find an applicable range of the drying process parameters microwave power input and chamber pressure.Continuous energy input was shown to act detrimentally to the cells due to extreme temperature rise in the second drying stage.To overcome this handicap,pulsed microwave energy input was applied according to certain maximum product temperatures.Here the influence of the most promising settings was studied for drying performance and product quality,such as survival rate and metabolic activity of the cells.The application of 100 W microwave power,5 mbar chamber pressure and a maximum product temperature of 30 °C yielded the best quality.Consequently,pulsed microwave-vacuum drying leads to high numbers of viable cells and metabolically active products produced in a fraction of time compared to the standard drying techniques.A decrease in drying time of up to 90% compared to freeze and vacuum drying can be achieved by this method.Thus,microwave-vacuum drying comes up as promising alternative drying technique in the field of preservation of microbial cultures.
L.paracasei microwave-vacuum drying pulsed energy input metabolic activity survival
S.Ambros S.A.W.Bauer U.Kulozik P.Foerst
Chair for Food Process Engineering Weihenstephaner Berg 1 Freising,D-85354,Germany
国际会议
The 18th International Drying Symposium Conference(第十八届国际干燥学术大会(IDS2012))
厦门
英文
1-8
2012-01-11（万方平台首次上网日期，不代表论文的发表时间）