Optimising the Properties of pH-Sensing Films based on Red Pitaya Peel Powder and Konjac Glucomannan

Abstract

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

Full text

Vol.:(0123456789)
Food Biophysics (2025) 20:41
https://doi.org/10.1007/s11483-025-09929-y
RESEARCH
Optimising theProperties ofpH‑Sensing Films based onRed Pitaya
Peel Powder andKonjac Glucomannan
RizkaAuliaRahma1· WidyaDwiRukmiPutri2· AtaAdityaWardana3· FanZhu4· IsminaDwiPurwati2·
AhmadZakiMubarok2· MokhamadNur2
Received: 7 October 2024 / Accepted: 9 January 2025 / Published online: 4 February 2025
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025
Abstract
Real-time quality information on chicken freshness can be obtained using pH-sensing packaging. Real-time quality infor-
mation 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).
Keywords Environment· Food freshness indicator· PH-sensing film· Sustainable materials· Waste
Introduction
Red pitaya peel (RPP) as a food waste constitutes 22% of the
total red pitaya fruit [1]. RPP waste is valuable and is rich in
bioactive compounds, including betacyanin pigment, pectin,
and fiber [2]. Nurliyana [3] found that RPP exhibited higher
antioxidant activity than fruit flesh. Betacyanin contained in
RPP can be used to indicate meat freshness [4]. Moreover,
RPP peel possesses a range of health-promoting properties,
including antidiabetic, antihyperlipidemic, anti-inflamma-
tory, antiobesity, anticancer, antiviral, antimicrobial, wound-
healing, and prebiotic effects, as well as anti-aging benefits
[5, 6]. This research builds on previous studies utilising fruit
peel waste as pH-sensing film materials. For example, Tran
[7] focused on shallot waste powder, Yaradoddi [8] on Citrus
sinensis peel powder, Kevij [9] on orange peel powder, and
Rojas-Bravo [10] on mango peel powder. These studies uti-
lised all the peeled pieces without extracting pectin or starch.
Yaradoddi [8] highlighted the benefits of using whole fruit
peel waste, including cellulose, pectin, and starch, which
distinguished this research from previous studies that often
focused on specific extracts such as RPP extract or pectin
extract [11–15].
* Widya Dwi Rukmi Putri
widya2putri@ub.ac.id
1 Food Science Study Program, Faculty ofAgricultural
Technology, Universitas Brawijaya, Malang,
Indonesia65145
2 Food Science andBiotechnology Department, Faculty
ofAgricultural Technology, Universitas Brawijaya, Malang,
Indonesia65145
3 Food Technology Department, Faculty ofEngineering, Bina
Nusantara University, Jakarta, Indonesia11480
4 Chemical Sciences, Faculty ofScience, The University
ofAuckland, Auckland, NewZealand
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