Comparison of rheological and colorimetric measurements to determine α-amylase activity for malt used for the beverage Bozo

Figures & data

Figure 1. Production scheme of Bozo.

Table 1. Comparison of amylase activity different malt types from colorimetric method with crossover point G′/G and LVE-range parameters of porridge + malts from amplitude sweep.

	Colorimetric method		Rheological method
Parameters	A* at 55°C	A at 30°C	γ (%)	τ (Pa)	G΄ (Pa)
Porridge			9.01 ± 0.02	542.0 ± 3.2	2400 ± 2.3
Barley malt	10.51 ± 0.05	32.83 ± 0.03	9.187 ± 0.03	151.6 ± 1.3	1168 ± 0.5
Wheat malt	10.04 ± 0.01	32.09 ± 0.06	13.63 ± 0.05	212.4 ± 2.15	1103 ± 6.5
Maize malt	8.71 ± 0.00	10.76 ± 0.00	13.44 ± 0.1	307.4 ± 0.18	1619 ± 1.7
Millet malt	9.14 ± 0.02	10.82 ± 0.01	15.91 ± 0.07	324.8 ± 0.12	1443 ± 2.1
R^2 with A, at 55°C			0.5072	0.9069	0.8786

*A: amylase activity (in Unit/mL), all parameters are reported as mean and standard deviation of three independent measurements.

Table 2. Adjustment of experimental data of millet porridge to the Casson model n = 0.5.

T (°C)	τ0 (Pa)	ηpl (Pa- s^n)	A (Pa/s)	R	ηeff (Pa∙s), = 50 s^–1	SD
25	19.94	1.24	2231	0.996	23.8	1.42
35	19.99	1.13	2019	0.995	22.8	1.30
45	19.51	0.98	1813	0.992	20.6	1.44
55	18.47	0.98	1915	0.993	18.9	1.24
65	17.80	0.85	1688	0.994	16.8	0.93

The rheological parameters are reported as mean and standard deviation of three independent measurements.

Figure 2. Viscosity curves with hysteresis areas of the millet porridge at 25°C (♦) and 65°C ((Ο).

Figure 3. Diagram of viscosity versus time after addition of different malts at 55°C.

Figure 4. Amplitude sweep of millet porridge (P) before and after addition of different malts: a: maize (Ma); b: millet (Mi); c: wheat (W); and d: barley (B).

Figure 5. Temperature-sweep: The relationship between complex viscosity and temperature after addition of malts.

Figure 6. Correlation diagram of the predicted data from rheological oscillation methods and measured data of α-amylase activity from colorimetric method.