Spray-dried microencapsulation of bean coat flour (Phaselus vulgaris, L.) bioactive compounds: optimization, functional activity, and storage

Figures & data

Table 1. Central composite design for two factors: inlet air temperature (100°C–140°C) and total solids in the mix (20–30%).

Temperature (°C)	Total solids in mix (%)
120	25
120	25
100	25
120	25
140	25
120	25
134	28
134	21
120	30
120	20
120	25
105	21
105	28

Figure 1. Response surface of dependent variables: (a) microencapsulation efficiency (%), (b) total phenolic compounds (mg GAE/g), (c) total flavonoids (mg CE/g), and (d) total monomeric anthocyanins (mg C3GE/g), based on the temperature of drying air and total solids of N-Lok as wall material.

Table 2. Estimated coefficients of the adjusted model and significance level of response variables: microencapsulation efficiency, total phenols, flavonoids, monomeric anthocyanins, radical scavenging capacity (ABTS and DPPH), water activity, and humidity in microencapsulates with bean coat extract.

Responses	Intercept	Linear		Interaction	Quadratic
	bo	b1	b2	b12	b11	b22
Microencapsulation efficiency (ME %)	96.38	−1.28 *(<0.0001)	−0.83 *(0.0008)	−1.68 *(<0.0001)	−0.89 *(0.0024)	−0.18 (0.4581)
Total phenolic compounds (mg GAE/g)	34.76	−0.037 (0.7357)	−0.36 *(0.0022)	−0.80 *(0.0001)	−0.10 (0.3364)	0.82 *(<0.0001)
Flavonoids (mg CE/g)	10.64	−3.503E–003 (0.6945)	0.063 *(<0.0001)	0.021 (0.1025)	−0.042 *(0.0001)	−0.067 *(<0.0001)
Total monomeric anthocyanins (mg CE3G/g)	1.10	0.16 (0.1372)	0.020 (0.8429)	0.22 (0.1278)	−0.26 *(0.0220)	0.76 *(<0.0001)
Free-radical scavenging activity by ABTS (mg TE/g)	36.38	−5.31 *(0.0017)	0.024 (0.8782)	−2.28 (0.3057)	−14.16 *(<0.0001)	−0.016 (0.9239)
Free-radical scavenging activity by DPPH (mg GAE/g)	38.47	−1.82 *(0.0003)	0.64 (0.1643)	4.19 *(<0.0001)	−1.56 *(0.0029)	3.87 *(<0.0001)
Water activity (aw)	0.34	2.435E–003 (0.3356)	−3.769E–003 (0.1400)	0.038 *(<0.0001)	3.504E–003 (0.1988)	−0.033 *(<0.0001)
Humidity (%)	4.97	0.059 (0.2305)	0.016 (0.7427)	0.25 *(0.0007)	0.36 *(<0.0001)	−0.11 *(0.0334)

b₁= inlet temperature in drier; b₂= total solids in mix. *Significant effect p ≤ .05.

Figure 2. Response surface of the dependent variables: (a) Radical scavenging capacity, (b) ABTS (mg/TE/g), (c) DPPH (mg AAE/g), (d) water activity, and E) humidity (%), based on drying air temperature and total solids of N-Lok as wall material.

Table 3. Experimental verification of predicted response variables in microcapsules.

Responses	Predicted value (Software)	Actual value* (Experimental)
Microencapsulation efficiency(ME %) (ME %)	96.3	96.0 ± .03
Total phenolic compounds(mg GAE/g) (mg GAE/g)	35.4	34.4 ± .01
Total flavonoids(mg CE/g) (mg CE/g)	1.62	1.79 ± .01
Total monomeric anthocyanins(mg CE3G/g) (mg CE3G/g)	1.7	2.1 ± .01
Free-radical scavenging activity by ABTS (mg TE/g)	37.3	31.6 ± .03
Free-radical scavenging activity by DPPH(mg GAE/g) (mg GAE/g)	41.9	35.1 ± .02
Water activity (aw)	.28	.22 ± .00
Humidity (%)	4.8	4.69 ± .03

All the experimental were repeated three replicates. Experimental values were expressed as mean + standard error.

Figure 3. Stability of encapsulated compounds (total phenols, flavonoids, and anthocyanins) and bean coat flour analyzed under controlled conditions of temperature and water activities for 40 days: (a, d) total phenolic compounds (mg GAE/g); (b, e) total flavonoids (mg CE/g); and (c, f) total monomeric anthocyanins (mg C3GE/g).

Table 4. Differences (∆) in concentration of bioactive compounds (initial – final) in microencapsulates and bean coat flour under different storage conditions and half-life of the bioactive compounds (t ½).

Sample	Conditions (°C/aw)	Total phenols (mg GAE/g) (∆)	Total phenols t ½ (days)	Flavonoids (mg CE/g) (∆)	Flavonoids t ½ (days)	Anthocyanins (mg C3GE/g) (∆)	Anthocyanins t ½ (days)
Microencapsulated	7/0.329	3.84 ± 0.69	>40	1.98 ± 0.06	>40	1.07 ± 0.00	>40
Microencapsulated	30/0.329	2.84 ± 0.54	>40	1.29 ± 0.08	>40	1.08 ± 0.00	39.10
Bean coat flour	7/0.329	20.76 ± 0.23	38.22	9.67 ± 0.21	28.65	2.01 ± 0.00	12.73
Bean coat flour	30/0.329	19.01 ± 0.12	34.16	9.02 ± 0.14	26.70	2.01 ± 0.00	11.98
Microencapsulated	7/0.765	9.72 ± 0.078	>40	2.96 ± 0.06	>40	1.67 ± 0.00	21.60
Microencapsulated	30/0.765	9.00 ± 0.77	>40	2.47 ± 0.01	>40	1.67 ± 0.00	21.22
Bean coat flour	7/0.765	20.82 ± 0.07	34.46	7.88 ± 0.14	28.55	2.18 ± 0.00	11.28
Bean coat flour	30/0.765	20.26 ± 0.15	35.17	8.3 ± 0.00	32.41	2.01 ± 0.00	11.83

Experimental values are expressed as mean + standard error, mg gallic acid equivalents (mg GAE), mg of catechin equivalents (mg CE), mg of cyanidin-3-glucoside equivalent (mg C3GE); all per g of sample.

Figure 4. Micrograph of microcapsules with extract of bean coat flour and N-Lok starch obtained by spray drying using inlet air temperature of 115°C and 28.5% solids in wall material: (a) After spray drying (zero time) 300×; (b) (zero time) 500×; (c) After 40 days at 7°C and 0.329 aw; (d) After 40 days at 7°C and 0.765 aw; (e) After 40 days at 30°C and 0.329 aw, and (f) After 40 days at 30°C and 0.765 aw.