Porosity and Water Activity Effects on Stability of Crystalline β-Carotene in Freeze-Dried Solids

Authors

  • Nathdanai Harnkarnsujarit,

    1. Author Harnkarnsujarit is with Dept. of Food Science and Technology, Kasetsart Univ., Thailand; and School of Food and Nutritional Sciences, Univ. College Cork, Ireland. Author Charoenrein is with Dept. of Food Science and Technology, Kasetsart Univ., Thailand. Author Roos is with School of Food and Nutritional Sciences, Univ. College Cork, Ireland. Direct inquiries to author Roos (E-mail: yrjo.roos@ucc.ie).
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  • Sanguansri Charoenrein,

    1. Author Harnkarnsujarit is with Dept. of Food Science and Technology, Kasetsart Univ., Thailand; and School of Food and Nutritional Sciences, Univ. College Cork, Ireland. Author Charoenrein is with Dept. of Food Science and Technology, Kasetsart Univ., Thailand. Author Roos is with School of Food and Nutritional Sciences, Univ. College Cork, Ireland. Direct inquiries to author Roos (E-mail: yrjo.roos@ucc.ie).
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  • Yrjö H. Roos

    1. Author Harnkarnsujarit is with Dept. of Food Science and Technology, Kasetsart Univ., Thailand; and School of Food and Nutritional Sciences, Univ. College Cork, Ireland. Author Charoenrein is with Dept. of Food Science and Technology, Kasetsart Univ., Thailand. Author Roos is with School of Food and Nutritional Sciences, Univ. College Cork, Ireland. Direct inquiries to author Roos (E-mail: yrjo.roos@ucc.ie).
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Abstract

Abstract:  Stability of entrapped crystalline β-carotene as affected by water activity, solids microstructure, and composition of freeze-dried systems was investigated. Aliquots (1000 mm3, 20% w/w solids) of solutions of maltodextrins of various dextrose equivalents (M040: DE6, M100: DE11, and M250: DE25.5), M100-sugars (1:1 glucose, fructose and sucrose), and agar for gelation with dispersed β-carotene were frozen at −20, −40, or −80 °C and freeze-dried. Glass transition and α-relaxation temperatures were determined with differential scanning calorimetry and dynamic mechanical analysis, respectively. β-Carotene contents were monitored spectrophotometrically. In the glassy solids, pore microstructure had a major effect on β-carotene stability. Small pores with thin walls and large surface area allowed β-carotene exposure to oxygen which led to a higher loss, whereas structural collapse enhanced stability of β-carotene by decreasing exposure to oxygen. As water plasticized matrices, an increase in molecular mobility in the matrix enhanced β-carotene degradation. Stability of dispersed β-carotene was highest at around 0.2 aw, but decreasing structural relaxation times above the glass transition correlated well with the rate of β-carotene degradation at higher aw. Microstructure, aw, and component mobility are important factors in the control of stability of β-carotene in freeze-dried solids

Practical Application:  β-Carotene expresses various nutritional benefits; however, it is sensitive to oxygen and the degradation contributes to loss of nutritional values as well as product color. To increase stability of β-carotene in freeze-dried foods, the amount of oxygen penetration need to be limited. The modification of freeze-dried food structures, for example, porosity and structural collapse, components, and humidity effectively enhance the stability of dispersed β-carotene in freeze-dried solids.

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