Seafood flavourings characterization as prepared from the enzymatic hydrolysis of Undaria pinnatifida sporophyll by-product

Figures & data

Table 1. Regression coefficients of a quadratic model estimated by multiple linear regressions for the yield and DH of HUPSB.

	Regression coefficient
Factors	Yield (g/100g dry-solids)	DH (g α-amino nitrogen/100 g total nitrogen)
Constant	21.21**	1.31**
Linear
x1	0.25	0.28*
x2	1.00**	0.42**
Quadratic
x1^2	–0.011	–0.022
x2^2	–0.026	–0.013**
Interaction
x1x2	–0.0015	0.00065
Statistical analysis for the model
r^2	0.8125	0.845
Adjusted r^2	0.7631	0.8042

** Significant at p<0.01; * Significant at p<0.05.

Figure 1. Response surfaces for the effect of enzyme concentration and hydrolysis time on (A) yield (g/100 g dry-solids) and (B) degree of hydrolysis of HUPSB (g α-amino nitrogen/100 g total nitrogen).

Table 2. Predicted and experimental values of HUPSB.

	Yield (g/100 g dry-solids)		DH (g α-amino nitrogen/100 g total nitrogen)
	Observed^a	Predicted	Observed^a	Predicted
x1 = 7.31%, x2 = 17.78 h	–	31.93^ns	–	5.699^ns
x1 = 7%, x2 = 18 h	32.52 ± 0.46^ns		5.63 ± 0.27^ns

ns means of yield and DH compared by t-test are not significantly different (p > 0.05), a Observed yield and DH values are expressed as means ± SD (n = 3)

Table 3. Free amino acid composition in UPSB and HUPSB.

Amino acids^a	Amino acid content(mg/100 g of protein)*
	UPSB	HUPSB
Essential amino acid
Threonine	320 ± 110	2000 ± 370
Tryptophan	0	270 ± 10
Valine	30 ± 0	100 ± 0
Tyrosine	70 ± 10	630 ± 130
Non-essential amino acid
Aspartic acid	800 ± 70	3900 ± 580
Glutamic acid	1210 ± 130	3950 ± 380
Glycine	470 ± 50	2110 ± 360
Alanine	2760 ± 280	5080 ± 760
Arginine	250 ± 30	1460 ± 240
Serine	320 ± 30	1640 ± 290
Proline	430 ± 50	2240 ± 260
Total	6640 ± 80	23380 ± 230
Taste component
Bitter^b	500	2480
Umami^c	2010	7850
Sweet^d	4060	12420
Tasteless^e	70	630
Total	6640	23380

^aAmino acids in the seaweed by-products were in free amino acid form。

^bBitter was calculated from the sum of valine + glycine + tryptophan.

^cUmami was calculated from the sum of aspartic acid + glutamic acid.

^dSweet was calculated from threonine + serine + arginine + alanine + proline.

^eTasteless was calculated from tyrosine.

*Values are means and standard deviations of triplicate measurements.

Figure 2. GC-MS chromatogram of HUPSB by 7% flavourzyme for 18 h.

Figure 3. Sensory profiles of HUPSB by 7% flavourzyme for 18 h.

Table 4. Volatile compounds in HUPSB by 7% flavourzyme for 18 h.

Volatile compound^a	RI^a,b	Relative content (%)	Door description^c	Positive relation to
Acetoin	1352.5	9.17 ± 1.29	Butter, cream
Hexanal	1534.7	20.20 ± 1.58	Resin, flower, green	Seaweed^A,crab^B
Heptanal	1973.4	6.97 ± 0.50	Fat, citrus, rancid	crab^B
2-Heptenal	2227.9	10.39 ± 0.11	Green
2-Octanone	2360.2	3.23 ± 0.21	Sour
4-Cyanocyclohexene	2453.3	1.06 ± 0.04	Scent
D-Limonene	2487.4	2.15 ± 0.06	Lemon
Benzyl alcohol	2520.7	0.81 ± 0.29	Sweety, fruit, flower
2-Octenal	2574.6	5.29±0.27	Green, nut, fat
Nonanal	2697.8	11.97 ± 1.11	Citrus, fatty	crab^B
2-Nonenal	2830.9	3.22 ± 0.12	Orris, fat, cucumber
2,4-Decadienal	3101	2.63 ± 0.05	Chicken like
Tridecanal	3121.8	1.60 ± 0.04	Irritant
Naphthalene, 1,7-dimethyl-	3300.5	1.16 ± 0.45	Fume like
Pentadecane	3435	3.42 ± 0.12	Fume like
Eicosane	3558.8	1.25 ± 0.01	Fume like
Hexadecane	3582.7	1.60 ± 0.19	Fume like
Cedrol	3629	13.89 ± 0.21	Warm fire like

^aAll compounds were identified by comparison with mass spectra and retention index database.

^bRI (retention index) calculated with a DB-Wax stationary phase using a series of alkanes between C₈ and C₂₀ as reference standards.

^cOdour descriptions were cited from www.flavornet.org and recent reports.

^ANatta et al. (2014).

^BYu and Chen (2010).