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20211
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Subject: Processing and Food Engineering × Author: Sidhu, Jashandeep Singh × Thesis Type: Ph.D ×
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    Mathematical modeling of osmo assisted freeze drying process for strawberries (Fragaria vesca)
    (Punjab Agricultural University, Ludhiana, 2021) Sidhu, Jashandeep Singh; Gupta, . S.K.
    The study entitled “Mathematical modeling of osmo assisted freeze drying process for strawberries (Fragaria vesca)” was undertaken to characterize the effect of process parameters; osmotic solution concentration (40-80 °Brix), solution to fruit ratio (4-8 STFR) and freeze drying temperature (-20 to -40°C) on drying kinetics and quality attributes. The treatments with -20°C freeze drying temperature required more time for drying as compared to -30 & -40°C (2to 4 hours) to reduce the moisture content from 87.2% wb to 4.2±0.1 % wb. The input parameters for osmo-freeze drying process for strawberry halves were optimized by „Multiple Response Optimization‟ technique with optimum operating conditions recorded as freeze drying time temperature: -40°C, osmotic solution concentration: 79.43° Brix and solution to fruit ratio (STFR): 6.61. Corresponding to these values, the value of responses was rehydration ratio: 7.150, shrinkage ratio: 0.627, colour change: 6.661, bulk density: 502.19 kg/m3, % vitamin-c retained: 71.846%, texture (hardness): 8.1871Kg-f, and overall acceptability: 83.431%. The best fit of experimental data for osmotic dehydration was observed in Penetration model followed by GEM model. The overall performance of the mathematical model developed in VISUAL BASIC-6.0 for prediction of freeze drying time for osmo-freeze drying was satisfactory (0.122-7.285 % error) and can be used for predicting the freeze drying time for osmo-freeze drying of strawberries. The osmo-freeze and freeze dried products packed in three types of packaging materials viz. high density polyethylene, laminate aluminium pouches & glass jars were kept under refrigerated and ambient storage conditions. Overall, it was concluded that osmo-freeze drying of strawberry halves at optimized conditions of 79.43°B osmotic solution, 6.61 solution to fruit ratio (STFR) and 40°C freeze drying temperature gave better quality product as compared to freeze drying and can be stored for 5 and 3 months in refrigerated and ambient conditions respectively.