Development of a Novel Whey Date Beverage Fermented with Kefir Grains Using Response Surface Methodology

Table 2

Matrix of the central composite design (CCD) and observed responses for the response variables (pH, LAB, and yeasts).

Exp. no.	X1 (whey permeate % w/v)	X2 (date syrup % w/v)	X3 (kefir grains % w/v)	Response variables
				pH (Y1)	LAB (log10 CFU/mL) (Y2)	Yeasts (log10 CFU/mL) (Y3)
1	1.0	18	2.6	4.02 ± 0.01	6.77 ± 0.10	4.35 ± 0.23
2	4.0	18	2.6	4.19 ± 0.02	5.47 ± 0.02	4.77 ± 0.31
3	1.0	42	2.6	4.53 ± 0.02	5.10 ± 0.16	4.50 ± 0.24
4	4.0	42	2.6	4.60 ± 0.02	7.00 ± 0.16	5.20 ± 0.28
5	1.0	18	4.4	4.00 ± 0.02	6.47 ± 0.07	5.70 ± 0.14
6	4.0	18	4.4	4.23 ± 0.02	3.27 ± 0.21	2.10 ± 0.02
7	1.0	42	4.4	4.08 ± 0.02	2.32 ± 0.14	2.60 ± 0.28
8	4.0	42	4.4	4.44 ± 0.07	2.38 ± 0.10	2.10 ± 0.01
9	−0.0	30	3.5	4.11 ± 0.17	4.27 ± 0.12	2.90 ± 0.26
10	5.0	30	3.5	4.37 ± 0.04	2.32 ± 0.10	2.10 ± 0.09
11	2.5	10	3.5	4.02 ± 0.17	5.90 ± 0.18	4.10 ± 0.28
12	2.5	50	3.5	4.64 ± 0.08	3.39 ± 0.15	2.21 ± 0.22
13	2.5	30	2.0	4.32 ± 0.04	8.70 ± 0.14	6.56 ± 0.38
14	2.5	30	5.0	4.19 ± 0.01	5.30 ± 0.28	5.78 ± 0.24
15	2.5	30	3.5	4.10 ± 0.01	4.07 ± 0.19	3.56 ± 0.41
16	2.5	30	3.5	4.19 ± 0.28	3.38 ± 0.20	3.31 ± 0.06
17	2.5	30	3.5	4.21 ± 0.14	3.56 ± 0.16	3.49 ± 0.12
18	2.5	30	3.5	4.20 ± 0.02	4.01 ± 0.12	3.41 ± 0.19
19	2.5	30	3.5	4.17 ± 0.02	3.92 ± 0.09	3.39 ± 0.28

Whey permeate fortification ranged from 0 to 5% (w/v); date syrup ranged from 18 to 50% (w/v); kefir grains ranged from 2 to 5% (w/v).