Characterization of volatile compounds and organic acids in ultra-high-temperature milk packaged in tetra brik cartons

Figures & data

Table 1. Nutritional composition (g/100 mL milk) of UHT milk samples.

Properties	Min	Max	Mean	SD	%CV
Non-fat solid matter	7.94	8.67	8.14	0.24	2.91
Fat	3.00 (3.00)	3.35 (3.40)	3.12 (3.09)	0.12 (0.15)	3.95 (4.68)
Protein	2.78 (2.90)	3.03 (3.39)	2.92 (3.03)	0.10 (0.16)	3.54 (5.33)
Lactose	2.41	5.34	4.01	0.84	20.87
Glucose	0.12	0.26	0.17	0.04	23.50
Galactose	0.02	0.04	0.03	0.01	18.55
Total carbohydrate	2.95 (2.44)	5.61 (4.80)	4.21 (4.34)	0.87 (0.72)	20.60 (16.56)
Ash	0.63	0.87	0.72	0.08	11.12
Dansidity (as g/mL)	1.0293	1.0328	1.0316	0.001	0.13
Titratable acidity (as lactic acid)	0.16	0.21	0.18	0.02	8.59
pH	6.48	6.91	6.67	0.12	1.82

SD: standard deviation; CV: coefficient of variation.

Values in parentheses are data on package.

Table 2. Organic acids (mg/100 mL milk) identified in UHT milk samples.

Acids	Min	Max	Mean	SD	%CV
Oxalic	6.22	14.30	9.17	2.24	24.46
Orotic	2.23	17.14	7.52	4.22	56.16
Citric	94.74	203.26	132.99	30.69	23.08
Pyrüvic	4.42	9.70	5.94	1.55	26.15
Uric	1.16	1.87	1.52	0.28	18.36
Succinic	23.03	71.70	44.69	15.61	34.92
Lactic	73.77	108.68	97.90	9.85	10.06
Formic	84.90	141.17	114.42	19.37	16.93
Acetic	4.76	9.52	8.69	1.34	15.37
Propionic	0.87	15.42	6.80	4.06	59.73
Hippuric	2.27	5.42	3.63	1.04	28.68

SD: standard deviation; CV: coefficient of variation.

Table 3. Volatile compounds identified in UHT milks according to chemical classes.

Ketones (10)	Acids (9)
2-Butanone	Acetic acid
2-Heptanone	Butanoic acid
3-Hydroxy-3-Methyl-2-Butanone	Hexanoic acid
3-Hydroxy-2-Butanone (acetoin)	Octanoic acid
2-Nonanone	Decanoic Acid
Dihydro-2(3H)-Furanone (Butyrolactone)	Dodecanoic acid
Delta-Decalactone	Tetradecanoic acid
2-Undecanone	Hexadecanoic acid
2-Tridecanone	Stearic acid
2-Pentadecanone	Alcohols (5)
Aromatic compounds with benzene ring (10)	Etanol
2-Amino-5-Ethoxycarbonylbenzophenone	2-Ethyl-1-Hexanol
Benzaldehyde	1-Tridecanol
Carvone	2-Furanmethanol
2-Methyl-Benzenethiazole	2-Pentanol
Phenol	Aldehydes (4)
Ethenylbenzene (Styrene)	Pentanal
N-ethyl-1.3-dithioisoindoline	Hexanal
6-Methyl-2-Phenylindole	Nonanal
Alpha-Terpinolene	Heptanal
Alken	Nitrogenous compounds (3)
Pentadecane. 2.6.10.14-tetramethyl (Pristane	Piperazine
Sulfo compounds (2)	Oxime-Methoxy-Phenyl
Dimethyl disulfide	2-Hydroxy-Propanamide (Lactamide)
2-Mercapto-4-Phenylthiazole

Figure 1. Changes in chemical groups of volatile compounds.

Table 4. The percentages of volatile compounds identified in most UHT milk samples.

Compounds	RT	RI	Mean	SD	Min	Max	%CV^1
Etanol	5.76	911.18	1.04	0.53	0.87	1.81	50.86
2-Heptanone^a	13.68	1289.2	16.75	7.50	8.15	32.70	44.77
2-Nonanone^a	20.91	1736.9	4.29	2.92	1.77	11.14	68.16
2-Undecanone	26.69	2204	1.13	0.62	0.26	2.41	54.33
2-Tridecanone	31.62	2300<	0.51	0.12	0.31	0.75	23.17
2-Pentadecanone^a	36.04	2300<	0.37	0.11	0.30	0.68	28.67
δ-Decalactone	39.87	2300<	1.04	0.40	0.62	1.49	38.01
Acetic acid^a	22.88	1906.9	5.87	5.16	1.02	18.35	87.96
Butanoic acid^a	27.42	2262.9	2.41	1.37	0.00	4.32	56.90
Hexanoic acid^a	32.39	2300<	2.92	0.75	1.44	4.22	25.78
Octanoic acid^a	36.78	2300<	2.53	1.30	0.64	4.48	51.66
Decanoic acid^a	40.74	2300<	1.74	1.45	0.31	3.15	83.07
Oxime-methoxy-phenyl	30.02	2300<	46.07	8.09	33.38	58.10	17.56
Dimethyldisulfide	9.15	1108.2	1.19	1.11	0.00	3.48	93.27
2-Mercapto-4-phenylthiazole	23.95	2007.6	7.41	4.76	0.00	13.52	64.33
Benzaldehyde	25.1	2080.9	1.28	0.91	0.62	3.29	70.88
Phenol	35.94	2300<	0.32	0.07	0.24	0.43	22.17
2-Amino-5-ethoxycarbonylbenzophenone	24.24	2026.1	6.11	3.58	0.00	11.78	58.55
2,6,10,14-Tetramethyl pentadecane (Pristane)	24.42	2037.6	5.37	4.05	0.00	11.60	75.30

¹The coefficient of variance (CV) for 11 UHT milk samples.

^aCompounds verified with authentic standards. All compounds were also considered to be tentative (based on the MS library Wiley7n.1/Nist 02.L).

RT: retention time; RI: retention index based on identified compound retention times (RTs). Calculated from linear equation between each pair of straight alkanes (C5–C25 and C7–C40).