Effect of postmortem aging time on flavor profile of stewed pork rib broth

Figures & data

Table 1. Contents and TAVs of free amino acids (mg/100 mL) in broth.

Compounds	Taste attributes	Chilled storage time of raw ribs at 4°C			Taste threshold^a	TAVs
		1 day	3 days	7 days		1 day	3 days	7 days
Aspartic acid	Umami	0.39 ± 0.07^c	0.49 ± 0.04^b	0.66 ± 0.05^a	100	< 0.01	< 0.01	< 0.01
Glutamic acid	Umami	3.95 ± 0.42^c	4.81 ± 0. 39^b	6.94 ± 0.32^a	30	0.13 ± 0.01^c	0.16 ± 0.01^b	0.23 ± 0.01^a
Threonine	Sweet	1.23 ± 0.10^c	1.47 ± 0.11^b	1.79 ± 0.16^a	260	< 0.01	< 0.01	< 0.01
Serine	Sweet	0.94 ± 0.08^c	1.25 ± 0.10^b	1.67 ± 0.14^a	150	< 0.01	< 0.01	0.01±< 0.01^a
Glycine	Sweet	2.86 ± 0.17^c	3.11 ± 0.22^b	3.84 ± 0.17^a	130	0.02 ± < 0.01^c	0.02 ± < 0.01^b	0.03 ± < 0.01^a
Alanine	Sweet	5.60 ± 0.49^b	6.25 ± 0.52^b	7.28 ± 0.60^a	60	0.09 ± < 0.01^b	0.10 ± < 0.01^b	0.12 ± 0.01^a
Proline	Sweet	2.00 ± 0.20^b	2.20 ± 0.20^b	2.55 ± 0.18^a	300	< 0.01	< 0.01	< 0.01
Lysine	Bitter	0.91 ± 0.09^b	0.94 ± 0.07^b	1.86 ± 0.18^a	50	0.02 ± < 0.01^b	0.02 ± < 0.01^b	0.04 ± < 0.01^a
Valine	Bitter	1.13 ± 0.05^b	1.24 ± 0.10^b	1.51 ± 0.15^a	40	0.03 ± < 0.01^b	0.03 ± < 0.01^b	0.04 ± < 0.01^a
Isoleucine	Bitter	0.59 ± 0.05^c	0.73 ± 0.07^b	0.94 ± 0.09^a	90	< 0.01	< 0.01	0.01 ± < 0.01^a
Leucine	Bitter	1.08 ± 0.10^c	1.29 ± 0.09^b	1.72 ± 0.16^a	190	< 0.01	< 0.01	< 0.01
Tyrosine	Sour/bitter	0.91 ± 0.07^b	0.98 ± 0.06^b	1.29 ± 0.12^a	90.6	0.01 ± < 0.01^b	0.01 ± < 0.01^b	0.01 ± < 0.01^a
Phenylalanine	Bitter	1.03 ± 0.04^b	1.11 ± 0.04^b	1.43 ± 0.12^a	90	0.01 ± < 0.01^b	0.01 ± < 0.01^b	0.02 ± < 0.01^a
Histidine	Bitter	ND	ND	ND	20	–	–	–
Arginine	Bitter	0.62 ± 0.06^c	0.89 ± 0.08^b	1.27 ± 0.20^a	50	0.01 ± < 0.01^c	0.02 ± < 0.01^b	0.03 ± < 0.01^a
Methionine	–	0.20 ± 0.02^c	0.27 ± 0.03^b	0.39 ± 0.06^a	30	< 0.01	< 0.01	0.01 ± < 0.01^a
Cysteine	–	0.33 ± 0.03^b	0.39 ± 0.04^b	0.52 ± 0.05^a	–	–	–	–
Umami AA		4.32 ± 0.48^c	5.01 ± 0.23^b	7.63 ± 0.33^a
Sweet AA		12.01 ± 0.61^c	13.99 ± 0.26^b	17.21 ± 0.65^a
Bitter AA		6.23 ± 0.60^c	7.33 ± 0.63^b	9.78 ± 0.96^a
Total AA		23.96 ± 2.10^b	26.83 ± 1.22^b	34.78 ± 3.44^a

Values are mean ± SD from 8 determinations.

Means in a row with different superscripts (a, b, c) are significantly different (p < 0.05) for chilled storage time.

¹Taste threshold of free amino acids were obtained from Zhuang et al.^[18] and Lou et al.^[28].

–, No taste threshold parameters were found in previous report.

TAV: taste activity value; umami AA: umami amino acids; sweet AA: sweet amino acids; bitter AA: bitter amino acids; total AA: total amino acids; ND: not detected.

Table 2. Contents and TAVs of nucleic acid-related compounds (mg/100 mL) in broth.

Compounds	Chilled storage time of raw ribs at 4°C			Taste threshold^1	TAVs
	1 day	3 days	7 days		1 day	3 days	7 days
5ʹ-CMP	0.49 ± 0.14^a	0.45 ± 0.06^a	0.47 ± 0.03^a	–	–	–	–
5ʹ-GMP	0.83 ± 0.08^a	0.67 ± 0.07^b	0.59 ± 0.05^b	12.5	0.07 ± < 0.01^a	0.05 ± < 0.01^b	0.05 ± < 0.01^b
5ʹ-IMP	6.21 ± 1.82^a	5.47 ± 1.49^ab	3.65 ± 1.15^b	25	0.25 ± 0.07^a	0.22 ± 0.06^ab	0.15 ± 0.05^b
Hx	1.40 ± 0.09^c	2.50 ± 0.43^b	4.03 ± 0.39^a	–	–	–	–
5ʹ-AMP	3.49 ± 0.33^a	2.91 ± 0.26^b	2.42 ± 0.22^c	50	0.07 ± < 0.01^a	0.06 ± < 0.01^b	0.05 ± < 0.01^c
In	8.16 ± 1.66^a	7.35 ± 0.70^a	5.33 ± 0.30^b	–	–	–	–
EUC	42.21 ± 1.59^b	46.25 ± 1.81^a	43.99 ± 2.31^ab	30	1.40 ± 0.05^b	1.54 ± 0.06^a	1.47 ± 0.07^ab

Values are mean ± SD from eight determinations.

Means in a row with different superscripts (a, b, c) are significantly different (p < 0.05) for chilled storage time.

¹Taste threshold of nucleotides and EUC were obtained from Qi et al.^[17].  

–, No taste threshold parameters were found in previous report.

TAV: taste activity value; 5ʹ-CMP: 5ʹ-cytidine monophosphate; 5ʹ-GMP: 5ʹ-guanosine monophosphate; 5ʹ-IMP: 5ʹ-inosine monophosphate; Hx: hypoxanthine; 5ʹ-AMP: 5ʹ-adenosine monophosphate; In: inosine; EUC: equivalent umami concentration.

Table 3. Contents and TAVs of organic acids (mg/100 mL) in broth.

Compounds	Chilled storage time of raw ribs at 4°C			Taste threshold^1	TAVs
	1 day	3 days	7 days		1 days	3 days	7 days
Oxalic acid	606.16 ± 35.36^a	628.11 ± 52.68^a	593.60 ± 53.10^a	–	–	–	–
Tartaric acid	50.29 ± 13.27^a	48.76 ± 10.68^a	48.23 ± 7.10^a	1.5	33.52 ± 8.85^a	32.50 ± 7.12^a	32.15 ± 4.73^a
Malic acid	13.97 ± 0.91^b	16.41 ± 1.76^a	15.77 ± 1.32^a	49.6	0.28 ± 0.02^b	0.33 ± 0.03^a	0.32 ± 0.02^a
Lactic acid	252.66 ± 22.22^a	254.33 ± 21.41^a	252.00 ± 54.64^a	126	2.01 ± 0.18 ^a	2.02 ± 0.17 ^a	2.00 ± 0.43^a
Citric acid	84.46 ± 5.60^a	77.99 ± 7.36^ab	74.78 ± 6.84^b	45	1.88 ± 0.12^a	1.73 ± 0.16^ab	1.66 ± 0.15^b
Succinic acid	546.87 ± 37.74^c	722.35 ± 67.86^b	837.01 ± 75.82^a	10.6	51.59 ± 3.56^c	68.14 ± 6.40^b	78.96 ± 7.15^a

Values are mean ± SD from eight determinations.

Means in a row with different superscripts (a, b, c) are significantly different (p < 0.05) for chilled storage time.

¹Taste threshold of organic acids were obtained from Lou et al.^[28], Zhong et al.^[35] and Weng^[36].

-: No taste threshold parameters were found in previous report.

TAV: taste activity value.

Figure 1. (a) PCA plots and (b) radar plots of the data from the electronic tongue for broth samples at different postmortem aging periods of raw pork (n = 8).

Notes: ZZ, JB, GA, CA, and JE are names of e-tongue sensors.

Table 4. Contents of volatile compounds (μg/L) in broth.

Compounds	LRI	Identification methods	Amount(μg/L broth)
			1 day	3 days	7 days
Aldehydes
Pentanal	980	MS/LRI	2.12 ± 0.33	1.76 ± 0.12	2.27 ± 0.62
Hexanal	1086	MS/LRI	33.48 ± 0.81	42.47 ± 5.64	43.37 ± 5.98
Heptanal	1177	MS/LRI	10.72 ± 1.10^a	7.64 ± 0.41^b	10.35 ± 2.88^a
Octanal	1272	MS/LRI	13.12 ± 2.81	12.26 ± 2.74	13.90 ± 2.06
(Z)-2-Heptenal	1320	MS/LRI	3.21 ± 0.31	3.30 ± 0.66	3.25 ± 1.38
Nonanal	1369	MS/LRI	18.91 ± 5.20	17.21 ± 5.28	18.66 ± 1.35
4-(1,1-Dimethylethyl)-benzenepropanal	1418	MS	−	−	0.31 ± 0.12
Decanal	1447	MS/LRI	−	−	1.73 ± 0.43
Benzaldehyde	1479	MS/LRI	0.45 ± 0.06	0.47 ± 0.03	0.51 ± 0.05
(E)-2-Nonenal	1496	MS/LRI	−	1.08 ± 0.11	1.20 ± 0.25
(E)-2-Decenal	1590	MS/LRI	2.55 ± 0.65	3.01 ± 0.11	3.70 ± 1.05
2-Undecenal	1663	MS/LRI	1.68 ± 0.39	1.46 ± 0.24	1.63 ± 0.11
2,4-Decadienal	1758	MS/LRI	−	−	1.27 ± 0.09
2,6-Dimethyl benzaldehyde	2011	MS	−	1.29 ± 0.16	−
Subtotal			85.30 ± 17.05	81.87 ± 19.42	96.40 ± 8.19
Alcohols
1-Pentanol	1249	MS/LRI	0.57 ± 0.09^b	0.66 ± 0.10^ab	0.83 ± 0.13^a
1-Hexanol	1358	MS/LRI	−	0.44 ± 0.09	0.53 ± 0.09
1-Octen-3-ol	1424	MS/LRI	4.85 ± 0.67	5.64 ± 0.57	5.02 ± 0.80
1-Heptanol	1429	MS/LRI	1.52 ± 0.32	1.69 ± 0.40	1.64 ± 0.14
2-Ethyl-1-hexanol	1493	MS/LRI	1.02 ± 0.12^b	2.76 ± 0.88^a	−
1-Undecanol	1804	MS/LRI	−	−	0.38 ± 0.09
Subtotal			9.69 ± 1.71^ab	11.08 ± 2.12^a	7.63 ± 0.87^b
Ketones
2-Methyl-4,6-octadiyn-3-one	1152	MS	0.34 ± 0.07	0.24 ± 0.04	0.16 ± 0.01
6-Methyl-5-methylene-2-heptanone	1436	MS	−	0.15 ± 0.01	−
1,5-Bis(1,1-dimethylethyl)-3,3-dimethyl-bicyclo[3.1.0]hexan-2-one	2005	MS	0.27 ± 0.05	−	−
Subtotal			0.43 ± 0.15^a	0.23 ± 0.12^b	0.16 ± 0.01^b
Aliphatic hydrocarbon
5,5-Dimethyl-1,3-heptadiene	1542	MS	1.15 ± 0.27	1.29 ± 0.56	1.22 ± 0.16
Pentadecane	1553	MS/LRI	0.95 ± 0.18	−	−
Pentyl-cyclopropane	1587	MS/LRI	1.42 ± 0.55^b	2.03 ± 0.38^a	1.82 ± 0.21^ab
Hexadecane	1590	MS/LRI	4.02 ± 2.25	−	−
Heptadecane	1697	MS/LRI	−	−	0.39 ± 0.04
2,3,6,7-Tetramethyl-4-octene	1779	MS	0.56 ± 0.08	−	−
Subtotal			6.86 ± 1.98^a	3.17 ± 1.16^b	3.65 ± 0.68^b
Heterocyclic compounds				±
2-Pentylfuran	1219	MS/LRI	0.57 ± 0.11^b	1.40 ± 0.17^a	0.47 ± 0.11^b
Subtotal			0.57 ± 0.11^b	1.40 ± 0.17^a	0.47 ± 0.11^b
Esters
Acetic acid, butyl ester	1089	MS/LRI	0.37 ± 0.04	0.37 ± 0.03	−
Acetic acid, hexyl ester	1295	MS/LRI	0.33 ± 0.04	0.38 ± 0.04	0.33 ± 0.07
Phosphoric acid, diethyl pentyl ester	1856	MS	2.15 ± 0.40^b	2.73 ± 0.85^b	4.05 ± 0.99^a
Propanoic acid, 2-methyl-, 1-(1,1-dimethylethyl)-2-methyl-1,3-propanediyl ester	1861	MS	1.42 ± 0.12^a	−	0.15 ± 0.01^b
Subtotal			2.86 ± 0.52^b	2.97 ± 0.52^b	4.88 ± 0.83^a
Others
p-Xylene	1134	MS/LRI	−	−	0.50 ± 0.06
1,4-Dichloro-benzene	1256	MS	1.14 ± 0.25^a	0.53 ± 0.19^b	1.01 ± 0.13^a
Methoxy-phenyl-oxime	1412	MS/LRI	0.62 ± 0.25	0.46 ± 0.21	−
2,4-Bis(1,1-dimethylethyl)-phenol	2044	MS/LRI	3.12 ± 0.61	−	−
Subtotal			3.50 ± 0.92^a	0.81 ± 0.22^b	1.63 ± 0.08^b
Total			109.69 ± 18.02	113.49 ± 17.52	128.41 ± 22.53

Means in a row with different letters (a, b) are significantly different (p < 0.05).

Values are means of eight replicates with duplicate extraction ± standard deviation.

−, The compounds were not detected at least in four replicates.

LRI: linear retention index on DB WAX column.

Identification methods: MS: mass spectrum; LRI: linear retention index (compared with the LRI in the online database, http://www.odour.org.uk; http://www.flavornet.org.).

Figure 2. (a) PCA plots and (b) radar plots of the data from the electronic nose for broth samples at different postmortem aging periods of raw pork (n = 8).

Notes: LY2/LG, LY2/G, LY2/AA, LY2/GH, LY2/gCT1, LY2/gCT, T30/1, P10/1, P10/2, P40/1, T70/2, PA/2, P30/1, P40/2, P30/2, T40/2, T40/1, and TA/2 are names of e-nose sensors.

Table 5. Sensory scores of different broth samples

Index	Chilled storage time of raw ribs at 4°C
	1 day	3 days	7 days
Clarity	5.38 ± 1.85b	7.54 ± 1.26a	6.62 ± 1.38^a
Taste	6.73 ± 0.90b	8.00 ± 0.91a	7.36 ± 1.02^ab
Aroma	7.00 ± 1.00a	7.31 ± 1.31a	7.18 ± 1.25^a

Values are mean ± SD from 10 determinations.

Means in a row with different superscripts (a, b, c) are significantly different (p < 0.05) for chilled storage time.

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