Fan Zhu’s research while affiliated with University of Auckland and other places

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Publications (1)


Red pitaya peel powder
The preparation process for the production of KGM and RPP
Contour graphic plot of thickness (a), TS (b), EAB (c), water solubility (d), opacity (e), lightness (f), redness (g), yellowness (h)
The 3D graphic surface of a thickness (a), TS (b), EAB (c), water solubility (d), opacity (e), lightness (f), redness (g), yellowness (h)
Microstructure of RPP powder (a), optimised KGM/RPP films with magnification 1000x (b) and 2500x (c)

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Optimising the Properties of pH-Sensing Films based on Red Pitaya Peel Powder and Konjac Glucomannan
  • Article
  • Publisher preview available

February 2025

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Food Biophysics

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Real-time quality information on chicken freshness can be obtained using pH-sensing packaging. Real-time quality information on chicken freshness is crucial for ensuring food safety, as chicken is a highly perishable animal product prone to rapid spoilage. This study aimed to develop an pH-sensing film using red pitaya (red dragon) peel (RPP) to monitor chicken freshness. RPP containing 22% pectin, showed promise in forming a film and contains betacyanin, which is commonly used in pH-sensing films. The addition of konjac glucomannan (KGM) as a co-biopolymer to RPP films enhanced their physical and mechanical properties. We utilised Central Composite Design (CCD) within the Response Surface Methodology (RSM) framework, with varying concentrations of KGM from 0.80% to 2.20% and RPP from 0.40% to 1.10%. The optimal treatment involved using 1.74 g of KGM and 0.85 g of RPP powder. The variation in KGM and RPP powder concentrations resulted in the following outcomes: film thickness ranged from 0.11 to 0.15 mm, tensile strength from 2.4 to 7.03 MPa, elongation ranged from 22.50% to 49.17%, opacity from 3.68 to 6.50 mm⁻¹, water solubility from 82.70% to 97.82%, lightness from 61.20 to 74.70, redness from 12.90 to 30.80, and yellowness from 0.20 to 2.80. The incorporation of KGM as a co-biopolymer demonstrably enhanced the physical and mechanical properties of RPP powder-based pH-sensing films. The results highlight RPP/KGM-based films as a novel, sustainable option for intelligent packaging, while promoting red pitaya peel waste as a renewable source of pectin and natural colorants. The freshness of chicken breast is indicated by the color change in RPP/KGM coatings, caused by betacyanin degradation from purple-red to yellow (betalamic acid). Graphical Abstract Schematic illustration of the production of konjac and red pitaya peel pH-sensing films

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