Edible Clusteroluminogenic Films Obtained from Starch of Different Botanical Origins for Food Packaging and Quality Management of Frozen Foods

Abstract

Starch is a naturally occurring material showing high potential for use in food packaging because of its low cost, natural abundance and high biodegradability. Over the years, different starch-based packaging films have been developed, but the impact of botanical sources on film performance has rarely been exploited. Efforts devoted to exploiting the role played by the clusteroluminescence of starch in food packaging are also lacking. This study fills these gaps by comparing the properties of edible starch films generated from different botanical sources (including water chestnuts, maize and potatoes) in food packaging. Such films are produced by solution casting. They are highly homogeneous, with a thickness of 55-65 μm. Variations in the botanical sources of starch have no significant impact on the color parameters (including L*, a* and b*) and morphological features of the films but affect the water vapor permeability, maximum tensile strength and elongation at break. Starch films from water chestnut show the highest percentage of transmittance, whereas those from potatoes are the opaquest. No observable change in the intensity of clusteroluminescence occurs when a packaging bag generated from starch is used to package fresh or frozen chicken breast meat; however, a remarkable decline in the intensity of luminescence is noted when the frozen meat is thawed inside the bag. Our results reveal the impact of starch sources on the performance of starch films in food packaging and demonstrate the possibility of using the clusteroluminescence of starch as an indicator to reveal the state of packaged frozen food.

Keywords: clusteroluminescence; films; food packaging; quality management; starch.

Figure 1

(A) Images of (a,b) water chestnut starch (WS), (c,d) maize starch (MS) and (e,f) potato starch (PS) under (a,c,e) white light and (b,d,f) UV light. The wavelength of UV light is at 365 nm. (B) Amylose content of starch obtained from different botanical sources. * p < 0.05. (C) ¹H-NMR spectra (400 MHz) of WS, MS and PS. The solvent used is DMSO-d6, and the spectra are recorded at 80 °C. (D) Fourier-transform infrared (FTIR) spectra, (E) thermogravimetric analysis (TGA) curves and (F) derivative thermogravimetry (DTG) curves of WS, MS and PS.

Figure 2

(A) Photos of the films generated from (a) WS, (b) MS and (c) PS. (B) Thickness and (C) tensile strength of the water chestnut starch film (FWS), maize starch film (FMS) and potato starch film (FPS). (D) Photoluminescence (PL) spectra of dry and swollen films. (E) Images of (a,b,g,h) FWS, (c,d,i,j) FMS and (e,f,k,l) FPS under (a,c,e,g,i,k) white light and (b,d,f,h,j,l) UV light. The wavelength of UV light is at 365 nm. Scale bar = 1 cm.

Figure 3

(A) Optical images showing the transparency of (a) FWS, (b) FMS and (c) FPS. (B) UV-Vis transmittance spectra of different films. (C) (a) Haze values, (b) lightness values (L*), (c) redness/greenness values (a*) and (d) yellowness/blueness values (b*) of different films. * p < 0.05. (D) Viability of (a,b) HEK293 and (c,d) 3T3 fibroblasts after 5 h of treatment with different samples (viz., WS, MS, PS, FWS, FMS, and FPS) (a,c) before and (b,d) after 24 h of post-treatment incubation.

Figure 4

(A) Photos of packaging bags generated from (a,d) FWS, (b,e) FMS and (c,f) FPS under (a–c) white light and (d–f) UV light. The wavelength of UV light is at 365 nm. Scale bar = 1 cm. (B) Scanning electron microscopy (SEM) images of the morphology of (a) FWS, (b) FMS and (c) FPS. Scale bar = 10 μm. (C) Erosion susceptibility and (D) water vapor permeability of different films. * p < 0.05. (E) Measurement of the static contact angle of a water droplet on (a) FWS, (b) FMS and (c) FPS.

Figure 5

(A) Photos of an apple piece stored in a tube with the hole either (a–c) uncovered or (d–l) protected by different films ((d–f) FWS, (g–i) FMS and (j–l) FPS) at 4 °C for (a,d,g,j) 0 days, (b,e,h,k) 3 days and (c,f,i,l) 6 days. (B) Changes in the weight of an apple piece stored in a tube with the hole either uncovered (control) or protected by different films. (C) Photos of a starch-based packaging bag containing (a,b) fresh chicken meat, (c,d) frozen chicken meat and (e,f) thawed frozen chicken meat under (a,c,e) white light and (b,d,f) UV light. (D) Time-dependent changes in the water content of the meat stored inside an FMS-generated packaging bag. Meat stored in open air is used as a control.