Stability enhancement of mulberry-extracted anthocyanin using alginate/chitosan microencapsulation for food supplement application

Figures & data

Table 1. Characteristics of mulberry extracts obtained from Chul Thai Silk Co., Ltd. (Petchaboon Province, Thailand).

Characteristics of mulberry extracts
pH	4.02 ± 0.01
Solubility (% Brix)	6.04 ± 0.27
Anthocyanin content (mg/g dry weight)	4.04 ± 0.38
IC50 (mg/ml)	0.45 ± 0.02

Figure 1. (A) Model of alginate/chitosan beads prepared by different processes without and with anthocyanin encapsulation. (B) Chemical structure of an anthocyanin, R1 and R2 are functional groups, and R3 is a sugar molecule.

Table 2. Formulation and nomenclature of alginate/chitosan beads prepared by different processes.

			Step 2: spraying
Bead formulation	Name	Step 1: solution preparation1.5% Alginate	0.1M CaCl2 bath	0.1M CaCl2 + Chitosan(% w/v) bath	Step 3: coatingChitosan (% w/v)
Alginate beads	A0	×	×
Alginate/chitosan beads	A1	×		× (0.05)
	A2	×		× (0.10)
	A3	×		× (0.15)
	A4	×		× (0.20)
Alginate/chitosan beads	A5	×	×		× (0.05)
	A6	×	×		× (0.10)
	A7	×	×		× (0.15)
	A8	×	×		× (0.20)

Figure 2. Microscopic images of different formulations of alginate/chitosan beads prepared by different processes before (upper row) and after encapsulation with mulberry-extracted anthocyanin (lower row) (scale bar = 500 μm).

Figure 3. Amount of anthocyanin in alginate/chitosan beads encapsulating mulberry-extracted anthocyanin (*significant difference at p < .05 when compared to A0, †significant difference at p < .05 when compared to A1 within the same preparation group, A1–A4).

Figure 4. Dynamic water swelling ability of alginate/chitosan beads (A0, A1, and A5) when incubated at different pH (♦ pH 1, ▪ pH 4, ◆ pH 6, • pH 7.4).

Figure 5. Microscopic images of alginate/chitosan beads (A0, A1, and A5) when incubated at different pH (1.0, 4.0, 6.0, and 7.4) for 6 h (scale bar = 500 μm).

Figure 6. Percentage of weight remaining of alginate/chitosan beads (A0, A1, and A5) when incubated in (A) simulated gastric fluid (SGF) condition (pH 1.2) and (B) simulated intestinal fluid (SIF) condition (pH 6.8) at 37 °C (♦ A0, ◆ A1, ▪ A5).

Figure 7. Cumulative release of anthocyanin from alginate/chitosan beads (A0, A1, and A5) encapsulating mulberry-extracted anthocyanin when incubated in (A) simulated gastric fluid (SGF) condition (pH 1.2) and (B) simulated intestinal fluid (SIF) condition (pH 6.8) at 37 °C (♦ A0, ◆ A1, ▪ A5).

Figure 8. Stability of anthocyanin in alginate/chitosan beads (A0, A1, and A5) encapsulating mulberry-extracted anthocyanin after (A) freeze–thaw for 0

, 1

, 2

, 3

, and 4

cycles, (B) incubated at 45° for 0

, 7

, 14

, 30

, and 60

days (*significant difference at p < .05 comparing to 0 day within the same preparation group).

Figure 9. FTIR spectra of alginate/chitosan beads (A0, A1, and A5) encapsulating mulberry-extracted anthocyanin after (A) freeze–thaw for 0 (C0), 1 (C1), 2 (C2), 3 (C3), and 4 (C4) cycles.

Figure 10. Electrostatic charges of freeze-dried mulberry-extracted anthocyanin (A) and mulberry-extracted anthocyanin-encapsulated alginate/chitosan beads (A0, A1, and A5) when filling into capsule.