Effect of different freezing rates on the texture and quality parameters of selected fruit and vegetable

Bulut, Merve
The freezing rates of strawberry and green bean were determined at -23, -26 and -27°C in a home type freezer. For the estimation of freezing rate, the temperature-time data was obtained with a thermocouple embedded inside the sample. The freezing rates of strawberry were 0.75, 0.93 and 1.02 cm/h at -23, -26, and -27°C, respectively. For green bean, the freezing rates were 0.36, 0.50, 0.57 cm/h at -23, -26, -27°C, respectively. In three freezing rates studied, cellular integrity was examined with NMR relaxometry analysis. NMR relaxometry analysis showed that the freezing rates studied did not keep the cellular integrity in strawberries. However, cell integrity of green bean was kept better after freeze-thawing in comparison to strawberry. Packaged strawberries and green beans were frozen stored at -27°C for 3 months to determine some quality parameters such as L-ascorbic acid, total phenolic content, antioxidant activity and color change. Total phenolic content and antioxidant activity change of selected samples did not decrease a value lower than 80% during the frozen storage at -27°C. L-ascorbic acid losses were approximately 42 and 27 % for 13 weeks of frozen storage of strawberry and green bean, respectively. The degradation rate of ascorbic acid was lower in green bean in comparison to strawberry. A significant change in color was not observed for the selected samples. Home freezing should be done appropriately to preserve the nutritional content and texture of fruits and vegetables. The approximations and analyzes used in this study, can be a base to design and produce a convenient deep freezer systems.


Effect of freezing rate and storage on the texture and quality parameters of strawberry and green bean frozen in home type freezer
Bulut, Merve; Bayer, Özgür; Kırtıl, Emrah; Bayındırlı, Alev (2018-04-01)
The focus of interest of this research was freezing preservation of green bean and strawberry in a home type freezer. Freezing time and freezing rates were determined from the cooling curves obtained experimentally. Home type freezing provided slow freezing rate. NMR Relaxometry measurements showed that freezing did not keep the cellular integrity in strawberries and green beans due to structural damage and extracellular ice formation. Packaged samples were stored at -27 degrees C for approximately 3 months...
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Effects of nickel, chromium and substrate concentration on the microbial growth of acclimatized and unacclimatized microbes of sewage origin were studied in batch cultures at a constant temperature of 25 °C, at pH 7.0. A synthetic medium supplemented with Ni(II) (5 and 10 mgl‐1) or Cr(VI) (1 and 50 mgl‐1) or with their combinations and at various feed concentrations (650, 975, 1300 mgl‐1) was employed to investigate the effects on the specific growth rate (μm) of the microbial culture. The experimental resu...
Citation Formats
M. Bulut, “Effect of different freezing rates on the texture and quality parameters of selected fruit and vegetable,” M.S. - Master of Science, Middle East Technical University, 2015.