Stability of anthocyanins in frozen and freeze-dried raspberries during long-term storage: In relation to glass transition

• Author(s) / Creator(s)

  • Syamaladevi, Roopesh M.
  • Sablani, Shyam S.
  • Tang, Juming
  • Powers, Joseph
  • Swanson, Barry G.

• Abstract: Anthocyanins, natural plant pigments in the flavonoid group, are responsible for the red color and some of the nutraceutical benefits of raspberries. This study explores anthocyanin degradation in frozen and freeze-dried raspberries during storage in relation to glass transition temperatures. Frozen raspberries were stored at −80, −35, and −20 °C, while freeze-dried raspberries were stored at selected water activity (aw) values ranging from 0.05 to 0.75 at room temperature (23 °C) for more than a year. The characteristic glass transition temperatures (T′g) of raspberries with high water content and glass transition temperature (Tg) of raspberries with small water content were determined using a differential scanning calorimeter. The pH differential method was used to determine the quantity of anthocyanins in frozen and freeze-dried raspberries at selected time intervals. The total anthocyanins in raspberries fluctuated during 378 d of storage at −20 and −35, and −80 °C. Anthocyanin degradation in freeze-dried raspberries ranged from 27% to 32% and 78% to 89% at aw values of 0.05 to 0.07 and 0.11 to 0.43, respectively, after 1 y. Anthocyanins were not detectable in freeze-dried raspberries stored at aw values of 0.53 to 0.75 after 270 d. First order and Weibull equations were used to fit the anthocyanin degradation in freeze-dried raspberries. The 1st-order rate constant (k) of anthocyanin degradation ranged from 0.003 to 0.023 days−1 at the selected water activities. Significant anthocyanin degradation occurred in both the glassy and rubbery states of freeze-dried raspberries during long-term storage. However, the rate of anthocyanin degradation in freeze-dried raspberries stored in the glassy state was significantly smaller than the rate of anthocyanin degradation in the rubbery state.

• Date created

  2011-01-01

• Subjects / Keywords

  • Maximally Freeze-Concentrated Matrix
  • Weibull Equation
  • Glass Transition
  • Water Activity

• Type of Item

  Article (Draft / Submitted)

• DOI

  https://doi.org/10.7939/r3-sfnr-4s63

• License

  © 2011 Institute of Food Technologists®. This is the peer reviewed version of the following article: "Syamaladevi, R. M., Sablani, S. S., Tang, J., Powers, J., & Swanson, B. G. (2011). Stability of anthocyanins in frozen and freeze-dried raspberries during long-term storage: In relation to glass transition. Journal of Food Science, 76(6), E414-E421.", which has been published in final form at http://doi.org/10.1111/j.1750-3841.2011.02249.x. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.