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A laboratory evaluation of the efficiency of spray drying for encapsulation of functional ingredients

S. Birch1, L. Bui2 and D.M. Small1

1School of Applied Sciences, RMIT University, Melbourne, Victoria
2
Defence Science and Technology Organisation, Scottsdale, Tasmania

Introduction

The incorporation of selected vitamins, antioxidants and other ingredients offers the potential to enhance the well being of consumers. However the stability of such components limits the delivery of the benefits, particularly where long shelf life is desired. The term microencapsulation describes the coating of an active ingredient with a protective layer. This is typically selected to allow release under particular conditions which may be during processing, storage or even digestion of the food product. For this purpose, a range of food ingredients, known as encapsulating agents are available. The purpose of this study has been to evaluate the small scale microencapsulation of food ingredients by spray drying.

Materials and methods

Preparation of microcapsules by spray drying

Solutions of various hydrocolloid gums (0.5 to 1%) were stirred overnight before rice starch was added. Prior to spray drying, B-group vitamins were dissolved and pH adjusted to 4.0. A Niro Atomiser minor (Niro, Copenhagen) unit was used and the drying conditions were: flow rate 7mL/min, air pressure 5kg/m2, inlet temperature 120C, and outlet 80-90C (Uddin et al 2001; Zhao & Whistler, 1994).

Calculation of yield and recovery

Yield is the amount of solid capsule material obtained during spray drying divided by the total amount of solid ingredients delivered to the chamber of the spray drier, expressed as a percentage. Recovery is the proportion of the vitamin found in the capsules by analysis in relation to that initially weighed and dissolved in the feed stock, as a percentage.

Extraction and analysis of B-vitamins

These were based on the procedure of Esteve et al, 2001. Flour, dough and bread (1g) were extracted with 0.1M HCl by autoclaving. For thiamin, an aliquot was oxidized with potassium ferrocyante solution. After neutralisation and filtration samples were analysed by HPLC using a C-18 column and fluorescence detection.

Results and discussion

A variety of different gums were used in preliminary trials to microencapsulate riboflavin by spray drying (Table 1). In each case the capsule preparations were free-flowing fine powders. The yields varied, possibly reflecting the small scale of these evaluations (Table 2) with yields ranging up to 92%. The highest recoveries were for microcapsules prepared with rice starch and equal amounts of alginate and low methoxy pectin. Electron microscopy demonstrated that these had relatively uniform particles with diameters in the range of 15-50μm. In addition the appearance of the capsules was typically spherical although the granular structure was apparent on the outer surface of the capsules, confirming that the spray drying conditions were mild enough to avoid gelatinization of the granules.

Table 1 Description of the ingredients used in spray drying trials for preparation of microencapsulated riboflavin

Batch

Vitamin

Encapsulating agent

Hydrocolloid

R1

Riboflavin (1.5g)

Rice starch (10%)

κ -carrageenan (1%)

R2

Riboflavin (1.0g)

Rice starch (15%)

Low methoxy pectin (0.5%)

R3

Riboflavin (1.0g)

Rice starch (30%)

Sodium alginate (1.0%)

R4

Riboflavin (1.5g)

Rice starch (15%)

Sodium alginate (2.0%)

R5

Riboflavin (1.5g)

Rice starch (15%)

Sodium alginate (0.5%) and
Low methoxy pectin (0.5%)

R6

Riboflavin (2.0g)

Gum acacia (15%)

κ -carrageenan (0.5%)

R7

Riboflavin (1.0g)

Gum acacia (15%)

Low methoxy pectin (1.0%)

R8

Riboflavin (1.0g)

Maltodextrin (15%)

Sodium alginate (0.5%)

R9

Riboflavin (1.5g)

Maltodextrin (10%)

Sodium alginate (1.0%)

Note: R refers to riboflavin

Table 2 The yields and recovery of riboflavin during spray drying trials

Batch

Weight of product (g)

Capsule yield (%)

Vitamin recovery (%)

R1

20.68

40%

77%

R2

118.42

76%

85%

R3

43.89

28%

100%

R4

89.96

66%

93%

R5

117.19

91.9%

93%

R6

113.26

71%

nd

R8

64.23

81%

nd

R9

101.93

57%

nd

Note: nd indicates not determined

Analysis of riboflavin on HPLC with spectroflourimetric detection provided a relatively sensitive method and the results indicate that very little of the vitamin was lost at the pH and temperature conditions used in these trials. Thiamin microcapsules were also prepared and analysed (Tables 3 and 4).

Table 3 Description of the ingredients used in spray drying trials for preparation of microencapsulated thiamin

Batch

Vitamin

Encapsulating agent

Hydrocolloid

T1

Thiamin (1.0g)

Rice starch (15%)

Xanthan gum (0.175%)

T2

Thiamin (1.0g)

Rice starch (15%)

Locust bean gum (0.5%)

T3

Thiamin (1.0g)

Rice starch (15%)

κ -carrageenan (1.0%)

T4

Thiamin (1.55g)

Rice starch (30%)

Low methoxy pectin (1.0%)

T5

Thiamin (1.0g)

Rice starch (15%)

Sodium alginate (0.5%) and
Low methoxy pectin (0.5%)

Note: T refers to thiamin

Table 4 The yields and recovery of thiamin during spray drying trials

Batch

Weight of product (g)

Capsule yield (%)

Vitamin recovery (%)

T1

62.94

81%

99%

T2

56.3

72%

79%

T3

51.64

67%

86%

T4

112.22

72%

6%

T5

55.23

67%

53%

In most cases the yields as well as the thiamin recoveries were good. The reasons for the low recovery with the low methoxy pectin are not apparent, particularly when the corresponding capsules containing riboflavin showed satisfactory results.

Conclusion

The encapsulation of the B-vitamins by spray drying using hydrocolloid gums and rice starch gave good product yields. The form of capsules was suitable for incorporation into dough formulations as well as other food products. Of the encapsulating agents evaluated here, the most effective appeared to be alginate and pectin. Further studies to optimise the conditions for encapsulation are warranted and work is underway to encapsulate other functional food molecules and utilise these in food products in order to establish their protective properties, release characteristics, as well as overall potential as food ingredients.

Acknowledgement

A special thanks to staff of the pilot plant (RMIT Food Science and Technology) particularly Michael Kakoullis for help and support with the spray drier.

References

Augustin, M.A., Sanguansri, L., Margetts, C., & Young, B. (2001). Food Australia, 53: 220 - 223.

Esteve, M.J., Farre, R., Frigola, A. & Cantabella-Garcia, J.M. (2001). Journal of Agricultural and Food Chemistry, 49: 1450-1454.

Uddin, M.S., Hawlader,M.N., & Zhu, H.J. (2001). Journal of Microencapsulation, 18: 199 - 209.

Zhao, J. & Whistler, R.L. (1994). Food Technology, 48: 104-105.

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