|
|
Microbial production of emulsifier for utilization in dairy products
|
|
Abstract: Unpublished Doctor of Philosophy Thesis, Ain Shams University, Faculty of Agriculture, Department of Food Science, 2006.
The main objective of this study was to produce bioemulsifier from yeast that could potentially be used in food and dairy industries and many other applications.
The heat extraction procedure allowed the isolation of emulsifying agent from all of the eleven yeast strains tested.
Saccharomyces cerevisiae EMCC 69 strain produced the highest bioemulsifier yield with superior emulsification activity. Some yeast strains such as Candida utilis EMCC 120 produced higher extracellular bioemulsifier yield and activity, than that recorded for Glycerol monoleate as a control emulsifying agent. For this reason, and due to long history of safe human consumption, Saccharomyces cerevisiae EMCC 69 Candida utilis EMCC 120 were chosen for further studies.
The highest production of intracellular bioemulsifier in modified Czapek, s yeast broth by S. cerevisiae EMCC 69 strain was achieved with initial pH 7, inoculum level of 5%, agitation rate of 200 rpm, fermentation at 30ºC for 72 h.. The highest production of extracellular bioemulsifier in modified Czapek, s yeast broth by C. uti/is EMCC 120 strain was achieved with initial pH 7, inoculum level of 3%, agitation rate of 400 rpm, fermentation at 30ºC for 60 h. Scale-up fermentation enhanced the yield of exteracellular bioemulsifier of Candida uti/is EMCC 120 and intracellular bioemulsifier of Saccharomyces cerevisiae EMCC 69. This means high yield of
exteracellular and interacellular bioemulsifiers with low
production costs.
The pH of aqueous phase had little effect on the amount of the butter oil phase emulsified by Candida emulsifier between pH 2 and 11. Stability of emulsions with S. cereviciae EMCC 69 emulsifier decreased with increasing pH values over 6. In the presence of 1 to 5% (w/v) sodium chloride, there was no loss of emulsion stability occurred. Stable emulsions were formed in the presence of up to 15% (w/v) sucrose. Emulsion for both of S. cereviciae and C. uti/is emulsifier stability was 79% after three cycles of freezing at -18C for 16 hand thawing at 32C for 8h. Emulsions with S. cereviciae EMCC 69 and C. utilis EMCC 120 were not disrupted by pasteurization at 63C for 30 min. Stability of emulsions did not change during storage at 4ºC for 30 days. Much loss in emulsion stability during storage at room temperature 25ºC for 15 days was observed. Emulsifiers extracted from S. cereviciae EMCC 69 and C. utilis EMCC 120 emulsified all oils tested.
High quality ice cream and whipped cream with preferable texture and consistence, were produced with adding 0.2% or 0.3% bioemulsifiers, respectively.
Key words: Yeast, emulsifier, emulsification activity, emulsification stability, ice cream, whipped cream.
|
| Publication year |
2003
|
| Pages |
200p.
|
| Availability location |
مكتبة معهد بحوث الانتاج الحيوانى - شارع نادى الصيد- الدقى - الجيزة
|
| Availability number |
970
|
| Organization Name |
|
| Country |
Egypt
|
| Department |
Dairy Microbiology Research Department
|
| Author(s) from ARC |
|
AGROVOC
TERMS |
Cell culture.
Emulsifiers.
Icecream.
Milk products.
Uses.
Whipping.
Yeasts.
|
| Publication Type |
PhD Thesis
|