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Freezing of Palletized Food and Time-to-freeze Prediction

Cai, Hongchang
http://rave.ohiolink.edu/etdc/view?acc_num=osu1563463782014162

Abstract Details

2019, Master of Science, Ohio State University, Food Science and Technology.
Food freezing is one of the more important food preservation methods and extends the shelf-life of food products as well as the safety of food. Efficient and effective way to freeze the food products keeps ice crystals small during freezing and maintain the high quality of food. The need for prediction of time-to-freeze is important to ensuring uniformity of frozen food quality. There are several methods to predict the time-to-freeze of food products in the previous research, but none of them consider the freezing of food products on a larger scale. In the commercial situation, the food products may be packaged as palletized food products in the warehouse during freezing and some modifications might need to be made on the previous methods. The overall objective of this research was to compare and analyze different methods of predicting time-to-freeze with the real experimental data. The initial freezing temperature and thermo-physical properties of products are predicted by the food composition from USDA Composition Data Base. The freezing of food products after being placed on a pallet is influenced by several process parameters. The time-to-freeze is a function of dimensions of the containers holding the product, the vertical space between layers of product packages and the velocity of cold air within the space between layers of product containers. The unique parameters are in addition the typical parameters such as initial product temperature, cold air temperature, and the thermo-physical properties of the food product. Time-to-freeze was predicted based on the computation of convective heat transfer coefficients and four different expressions of estimation: Pham’s equation, modified Pham’s equation, Cleland and Earle’s equation, and numerical method. Then comparing the results from all methods against the experimental results. In the experiment, the pallet (132 x 107 x 114 cm) filled with gel packs which had an initial freezing temperature at -0.5˚C was frozen in the warehouse with the help of a blast cell inhaling air passing through it. When considering the freezing process, the pallet experienced 3 different freezing conditions and 21 temperatures thermocouples were used to record the temperature history in the pallet during freezing. Due to the characteristics of gel packs, they were stable under repeatable freezing process. The results indicated that Pham’s and Modified Pham’s methods provided relatively accurate time-to-freeze comparing to the numerical simulation and experimental results. During freezing, the different positions in the pallet experienced freezing in different rates and the time-to-freeze for the geometric center was longest. The results from application of the prediction models to a food product indicated that a decrease in cold medium temperature from -18˚C to -40˚C decreased the time-to-freeze by one-third. to the time-to-freeze decreased slightly as the cold medium temperature decreased. As for the impact of convective heat transfer coefficient, an increase in the convective heat transfer coefficient from 10-50W/m2K caused a decrease in time-to-freeze by one-third and reached plateau when the convective heat transfer coefficient became higher than 50W/m2K. When the vertical height of the container on the pallet with spacer increased 10 times, the time-to-freeze increased 15 times. Time-to-freeze increased as the volume fraction of air within the container holding the product being frozen on a pallet increased and it increased dramatically when the volume fraction of air was 80% or higher. The conclusions from this research could be helpful for the warehouse to predict the time-to-freeze more precisely and reach higher efficiency in freezing of palletized food products.
Dennis Heldman (Advisor)
Knipe Lynn (Committee Member)
Sastry Sudhir (Committee Member)
101 p.
Food Science

Recommended Citations

Citations

  • Cai, H. (2019). Freezing of Palletized Food and Time-to-freeze Prediction [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563463782014162

    APA Style (7th edition)

  • Cai, Hongchang. Freezing of Palletized Food and Time-to-freeze Prediction . 2019. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1563463782014162.

    MLA Style (8th edition)

  • Cai, Hongchang. "Freezing of Palletized Food and Time-to-freeze Prediction ." Master's thesis, Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563463782014162

    Chicago Manual of Style (17th edition)

osu1563463782014162
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This open access ETD is published by The Ohio State University and OhioLINK.