Imaging based measurement of density for the determination of dry matter and brix for ‘Hayward’, ‘SunGold’ and ‘RubyRed’ : a thesis presentation in partial fulfilment of the requirements of the degree of Masters in Food Technology and Post-Harvest at Massey University, Manawatu, New Zealand
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2023
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Massey University
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Abstract
This research was conducted at both Massey University and Massey AgriFood Digital Foods, Manawatu, New Zealand. Three-dimensional scanning, volume submergence alongside the destructive experiments were conducted on more than 900 kiwifruit. Approximately 312 kiwifruits (RubyRed, SunGold and Hayward) for each cultivar from three different grower lines were tested and examined. The kiwifruits were all picked at harvest maturity, commercially graded, and placed in 0℃ refrigerator storage to maintain the harvest maturity. With advances in imaging technologies, it is now feasible to measure volume accurately and non-destructively and therefore density. The aim of this project is to revisit the relationship between density, DM, SSC for all three cultivars (RubyRed, SunGold and Hayward). This project will be determining the accuracy to which these can be estimated using imaging-based volume measurement. The results from this research will be able to assess the industrial opportunity for the exploitation of imaging technologies as a means of determining the important parameters of DM and SSC. The objectives of this work include: To see if this relationship exists in the three cultivars and to see if dry matter can be estimated non-destructively through this relationship combined with digital density determination. The literature review explored existing destructive and non-destructive methods for measuring the kiwifruit volume and therefore density. Non-destructive fruit volume estimation can be used as a ripeness index to predict optimum harvest time, yield or to study the relationship between fruit expansion rate and susceptibility to physiological disorders such as fruit softening. In a paper by Jordan, R. B. et. al (2000), the volume was measured through the determination of buoyant force and water being displaced where volume is calculated from the object weight and the force. The results across the three cultivars showed strong correlations between the digital volume and the submerged volume. For RubyRed and SunGold it was observed that volume, DM and density had good correlations with 72% for RubyRed and 77% for SunGold. In comparison Hayward had the weakest correlation with an R value of 42%. This was due to experimental conduct during covid-19, where lab time was limited thus influencing the timetable of experiments for Hayward. For all cultivars, the relationship between density and SSC was weak with R values of 45% (RubyRed), 20% (Hayward) and no correlation for SunGold.
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Figures 1, 3, 6, 7, 8 & 11 were reproduced with permission. Figure 2 was reproduced as it is not copyrighted.