103: Classification of Fruit Samples for Understanding Supercooling Behaviors Using Oscillating Magnetic Field (OMF) Protocols

Introduction

Fresh-cut fruits are a popular grocery item; however, their perishability can lead to food and monetary waste. Supercooling using OMF technology offers the potential for extending the lifetime of fruits and preserving their quality by storing foods in sub-zero temperatures while inhibiting ice crystal formation. This study shows how fruit classification can provide a useful framework for the understanding of the supercooling factors underlying ice nucleation and inhibition, as well as OMF intensities and frequencies to control water molecule movements inside fruit matrices.

Methods

Fruits were categorized based on moisture (dry weight basis, MCdw) and sugar content (°Brix), and prepared into 10-15 gram samples (peeled/ seeded where appropriate). Fruits were supercooled using a commercial freezer and our proprietary multi-tray supercooling module (up to 15 mT, 30 Hz). Fruits were divided into four categories, depending upon whether their moisture content exceeded 85% MCdw and their sugar content exceeded 13° Brix, with each factor being classified as either high or low. Five trials were run at -5°C for 1-3 days using different OMF intensities (5 - 15 mT) and frequencies (0 - 10 Hz) to access the supercooling probabilities, in comparison with control trials (no OMF).

Results

All classified groups achieved supercooling probabilities of at least 60% during the 1-3 day testing periods. It was found that the fruit groups with higher moisture content were able to achieve higher supercooling probabilities under OMF at stronger magnetic field and lower frequency (15 mT, 1 Hz), whereas groups containing high sugar/low moisture samples had greater success when exposed to OMF at lower magnetic strength and frequency (5 mT, 1 Hz). Low moisture/sugar samples maintained supercooling well under conditions of higher field strength and frequency (15 mT, 10 Hz).

Significance

This classification study contributed to optimization of supercooling conditions of fruits on the basis of their moisture and sugar contents, adding the value of commercialability to OMF-based-supercooling-technology. These findings would offer potential for applications in the fruit supply chain, including storage and transport. Future studies can focus on in-depth investigation of the wider range of OMF, control parameters, sample dimensions, and scaling up factors.

Authors: Abigail Zaehler, Socheatha Tork, Soojin Jun