Table 3. Experimental data on free amino acids of the dried Gugija (Lycium chinensis Mill) under different conditions based on central composite design for response surface analysis (unit: mg/100 g)

Amino acids	The number of experimental conditions by central composite design
	1	2	3	4	5	6	7	8	9	10
Glycine	0.952 1)	0.782	1.138	1.038	1.176	1.266	0.525	1.183	1.322	1.166
Serine	7.687	7.472	9.544	9.335	12.367	10.894	4.055	9.628	9.868	10.689
Alanine	35.226	33.485	42.379	37.864	44.006	42.788	28.859	41.440	44.705	42.139
Threonine	3.838	3.017	4.548	3.647	6.044	5.544	2.805	3.956	5.161	4.595
Proline	37.999	37.283	45.311	40.548	47.235	46.856	36.722	45.045	54.286	47.508
Valine	3.502	3.159	4.279	3.530	4.273	4.112	3.046	4.420	4.512	4.018
Methionine	1.128	1.019	1.942	1.957	1.485	1.408	1.081	2.180	1.139	1.103
Isoleucine	3.796	3.758	4.527	4.158	4.872	4.980	2.890	4.942	5.106	4.976
Leucine	7.968	7.386	9.332	8.450	10.756	10.361	4.689	11.351	11.639	9.342
Tyrosine	2.670	2.570	2.546	2.499	3.411	3.320	2.245	3.443	3.670	3.206
Tryptophan	5.466	6.331	7.217	6.522	8.206	9.147	4.659	7.964	8.637	8.495
Phenylalanine	2.876	2.644	3.316	2.613	3.325	3.371	2.884	3.752	3.447	3.126
Asparagine	137.434	129.485	180.657	154.911	184.309	188.246	72.773	188.601	198.823	179.654
Lysine	0.000	0.000	0.000	0.000	0.000	3.344	0.417	1.968	1.831	1.754
Arginine	10.675	10.238	14.445	12.436	14.749	14.570	3.538	15.371	15.647	14.718
Histidine	2.439	2.195	3.920	2.948	3.548	3.535	0.762	3.993	3.955	3.088
Carnosine	0.423	0.577	0.875	0.831	0.868	0.815	0.150	0.788	0.744	0.969
Ornithine	0.322	0.325	0.467	0.474	0.425	0.474	0.080	0.408	0.458	0.342
Aspartic acid	17.326	17.967	25.680	21.396	28.121	27.433	5.427	24.590	27.509	26.153
Glutamic acid	11.049	10.080	14.239	13.335	18.010	15.455	6.031	14.158	15.634	16.206
Phospho-serine	2.915	3.293	3.071	3.382	4.037	3.600	1.240	2.721	3.070	4.016
Hydroxy-proline	18.386	19.348	21.495	17.157	21.282	21.039	27.225	22.365	18.161	16.505
γ-Amino-n-butyric acid	7.974	7.974	10.292	9.311	10.870	10.765	4.654	9.013	9.047	8.580
Taurine	11.890	12.211	7.106	5.649	16.365	16.197	4.293	16.140	16.335	17.077
Phospho-ethanolamine	116.327	123.172	143.651	139.262	167.690	165.423	59.577	152.121	160.083	174.814
Citrulline	1.211	1.173	1.360	1.078	1.443	1.074	1.074	1.335	1.449	1.355
β-Alanine	0.019	0.000	0.031	0.000	0.031	0.000	0.000	0.000	0.030	0.000
β-Amino-isobutyric acid	0.068	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
Hydroxy-lysine	0.000	0.000	0.117	0.100	0.000	0.100	0.050	0.118	0.102	0.135
Sarcocine	0.887	0.858	1.078	1.249	5.646	1.082	0.653	1.136	0.903	0.999
Ethanolamine	13.312	12.860	16.500	14.060	16.492	0.440	0.038	0.092	0.088	0.045
Total amino acids	465.762	460.662	581.061	519.740	641.041	617.641	282.439	594.221	627.358	606.770

¹⁾Data were expressed as mean of triplicate determinations.