A biodegradable film based on sodium alginate–gelatin involving a mulberry anthocyanin extract for fish oil packaging

Figures (5) Tables (3)

Figure 1.
The UPLC chromatograms (520 nm) and mass spectrometry of Peak 1 (S-1, MAE-1) and Peak 2 (S-2, MAE-2) of anthocyanins in MAE and the anthocyanin standard.
Figure 2.
(a) The UV–visible spectroscopy of mulberry pomace anthocyanin extract (MAE) and (b) its free radical scavenging activity against ABTS and DPPH. Different letters on the columns indicate statistically significant differences among MAE concentrations (p < 0.05).
Figure 3.
The (a) rheological properties, (b) Fourier transform infrared, (c) X-ray diffraction, and (d) mechanical properties of SG-MAE films. SG: sodium alginate–gelatin film; SG-(2-10) MAE, sodium alginate–gelatin film with 0.2–1.0 mg/mL MAE.
Figure 4.
The (a) SEM, (b) WCA, (c) transmittance scanning spectra, and (d) free radical scavenging activities of SG-MAE films. SG, sodium alginate–gelatin film; SG-(2-10) MAE, sodium alginate–gelatin film with 0.2–1.0 mg/mL MAE.
Figure 5.
(a) The packaging of fish oil, (b) peroxide values, (c) TBA values, and (d) acid values of fish oil with different packaging methods during storage at 25 °C. Control: Sample of unpackaged fish oil; ziplock bags: Fish oil packaged using ziplock bags; SG: Fish oil packaged using sodium alginate–gelatin (SG) film in the forms of bags and top-covering; SG-4MAE: Fish oil packaged in the forms of bags and top-covering using sodium alginate–gelatin film containing 0.4 mg/mL MAE.

Films	Thickness (μm)	Water solubility (%)	Moisture content (%)	Water vapor permeability (× 10⁻¹¹ g/[m·s·Pa])	Oxygen permeability (g/dm²)
SG	80.12 ± 4.11^c	63.11 ± 0.77^a	19.58 ± 1.62^a	2.21 ± 0.01^a	3.16 ± 0.21^c
SG-2MAE	82.69 ± 3.29^c	62.89 ± 2.31^a	17.83 ± 1.68^b	1.50 ± 0.01^d	5.22 ± 0.54^b
SG-4MAE	80.07 ± 2.71^c	62.31 ± 1.23^a	16.11 ± 1.57^c	1.73 ± 0.03^c	5.43 ± 0.67^b
SG-6MAE	85.61 ± 4.21^b	60.03 ± 0.91^b	16.53 ± 2.36^c	1.85 ± 0.01^b	5.51 ± 0.61^b
SG-8MAE	83.09 ± 2.81^bc	58.21 ± 0.89^c	18.73 ± 0.82^ab	1.97 ± 0.17^ab	5.47 ± 0.35^b
SG-10MAE	89.93 ± 1.01^a	58.11 ± 0.77^c	17.42 ± 0.80^b	1.65 ± 0.01^bc	6.20 ± 0.23^a
SG-MAE, sodium alginate–gelatin film with 0.2–1.0 mg/mL mulberry pomace anthocyanin extract. Different letters in the same column represent significant differences at p < 0.05.

Table 1.

Physical properties of SG-MAE films.

Films	L*	a*	b*	ΔE	T_{(600 nm)} (%)
SG	90.94 ± 0.26^a	−0.75 ± 0.30^f	15.14 ± 0.20^a	−	71.84 ± 0.98^a
SG-2MAE	76.14 ± 1.50^b	10.26 ± 0.33^e	13.87 ± 0.29^b	26.46 ± 1.46^e	58.77 ± 0.55^b
SG-4MAE	64.78 ± 0.61^c	20.23 ± 0.00^d	14.59 ± 0.38^a	40.2 ± 1.33^d	47.63 ± 1.85^c
SG-6MAE	56.28 ± 1.27^d	24.46 ± 0.78^c	15.06 ± 0.29^a	49.89 ± 1.79^c	40.34 ± 0.97^d
SG-8MAE	43.32 ± 3.03^e	30.19 ± 0.53^b	15.26 ± 0.58^a	63.35 ± 2.56^b	28.55 ± 1.60^e
SG-10MAE	36.92 ± 0.05^f	36.29 ± 0.80^a	16.13 ± 0.77^a	71.93 ± 0.57^a	22.3 ± 0.14^f
SG-MAE, sodium alginate–gelatin film with 0.2–1.0 mg/mL MAE. Different letters in the same column represent significant differences at p < 0.05.

Table 2.

Optical properties of SG-MAE films.

Packaging	Kinetic equation	R²	Shelf life (days)
Control	ln(AV) = 0.053t − 0.173	0.97	24.6
Top-cover with SG film	ln(AV) = 0.048t − 0.170	0.97	26.5
Top-cover with SG-4MAE film	ln(AV) = 0.042t − 0.223	0.99	31.6
Ziplock bags	ln(AV) = 0.043t − 0.196	0.96	30.3
SG bag	ln(AV) = 0.033t − 0.315	0.95	42.8
SG-4MAE bag	ln(AV) = 0.022t − 0.282	0.95	62.6
Control: Unpackaged fish oil; ziplock bags: Fish oil packaged in plastic ziplock bags; SG bag and SG-4MAE bag: Fish oil packaged in bags made of sodium alginate–gelatin (SG) film and sodium alginate–gelatin film containing 0.4 mg/mL mulberry pomace anthocyanin extract; top-covering with SG film and SG-4MAE film: Fish oil packaged in glass bottles and covered with SG or SG-4MAE films.

Table 3.

Kinetic analysis and predicted shelf life of fish oil packaged with SG-4MAE films.