Sensory and Chemical Properties of Protein Hydrolysates Based on Mackerel (Scomber scombrus) and Salmon (Salmo salar) Side Stream Materials

Figures & data

Table 1. Overview of the hydrolysates and enzyme dose used

Raw material	Enzyme added (wt %)	Product coding
Mackerel backbones	0.22	MB
Mackerel heads	0.17	MH
Mackerel viscera	0.18	MV
Salmon backbones	0.19	SB
Salmon heads	0.17	SH
Salmon viscera	0.13	SV

Table 2. Sensory attributes determined in the hydrolysates and their respective descriptions

Attribute	Description of tastes/flavors related to the attributes
Total flavor intensity	Strength of all flavors in the sample
Sweet taste	Basic sweet taste (sucrose)
Salty taste	Basic salt taste (sodium chloride)
Acidic taste	Basic sour taste (citric acid)
Bitter taste	Basic bitter taste (caffeine)
Umami taste	Basic umami taste (mono sodium glutamate)
Fish flavor	Flavor of boiled white fish
Shellfish flavor	Flavor of shellfish and shrimp
TMA flavor	Flavor of trimethylamine
Burned flavor	Processed and burned flavors
Rancid flavor	All rancid flavors (grass, hay, stearin, paint)
Flavorless flavor	Related to the flavor of water from boiled potato
Cloying flavor	Related to an un-fresh and nauseating flavor
Astringent (mouthfeel)	Related to complex feeling of contractions and dryness in the mouth
Fatness (mouthfeel)	Surface textural property related to perception of fat in a product

Table 3. Chemical composition (g/100 g) of mackerel and salmon backbones, heads, and viscera

	Mackerel			Salmon
	Backbones	Heads	Viscera	Backbones	Heads	Viscera
Protein (N × 6.25)	17.5	12.3	13.5	14.9	14.2	9.9
Dry matter	35.1	41.1	32.5	44.0	38.1	48.8
Ash	3.5	7.2	2.2	3.9	3.3	0.9
Fat	14.5	21.0	15.9	25.4	26.9	34.5

Table 4. Amino acid composition (g/100 g sample) of backbones, heads, and viscera from mackerel and salmon

	Mackerel			Salmon
	Backbones	Heads	Viscera	Backbones	Heads	Viscera
EAA^1
Arginine	1.0	0.8	0.8	0.9	0.9	0.6
Histidine	0.8	0.3	0.4	0.3	0.4	0.3
Isoleucine	0.7	0.4	0.5	0.5	0.5	0.4
Leucine	1.3	0.7	0.9	0.8	0.9	0.7
Lysine	1.5	0.7	0.9	0.9	1.1	0.7
Methionine	0.5	0.3	0.3	0.4	0.4	0.3
Phenylalanine	0.6	0.4	0.5	0.4	0.5	0.4
Threonine	0.7	0.5	0.5	0.5	0.6	0.5
Valine	0.8	0.5	0.6	0.5	0.6	0.5
Sum EAA	7.9	4.7	5.3	5.4	5.8	4.1
NEAA^2
Alanine	1.0	0.8	0.7	0.9	1.0	0.6
Aspartic acid	1.5	1.0	1.1	1.1	1.2	0.9
Glutamic acid	2.2	1.4	1.5	1.8	1.9	1.3
Glycine	1.1	1.4	0.9	1.8	1.6	0.8
Hydroxyproline	0.2	0.6	0.2	0.5	0.4	0.2
Proline	0.6	0.7	0.5	0.9	0.8	0.4
Serine	0.7	0.6	0.6	0.6	0.6	0.5
Tyrosine	0.6	0.3	0.3	0.3	0.4	0.3
Sum NEAA	7.9	6.7	5.9	8.0	7.9	4.9
Sum protein AA	15.8	11.4	11.2	13.3	13.7	9.0

¹EAA = Essential amino acids

²NEAA = Nonessential amino acids

Table 5. Chemical composition (g/100 g) of protein hydrolysates based on mackerel (M) and salmon (S) backbones (B), heads (H), and viscera (V)

	MB	MH	MV	SB	SH	SV
Protein (N × 6.25)	82.4	59.3	75.5	89.8	89.3	82.8
Total dry matter	96.3	96.4	94.9	96.3	98.0	97.3
Ash	15.7	38.3	11.9	9.3	12.6	8.5
Yield (%)*	5.0	1.5	5.0	4.0	3.3	1.8

*Calculated by dividing the mass of spray-dried hydrolysate by the mass of raw material. No effort was made to optimize these yields as the focus of this study is the chemical and sensory properties of the products.

Table 6. Amino acid composition (g/100 g crude protein) of protein hydrolysates based on mackerel (M) and salmon (S) backbones (B), heads (H), and viscera (V)

Amino acids	MB	MH	MV	SB	SH	SV
EAA^1
Arginine	5.5	6.2	6.1	5.9	6.3	6.6
Histidine	6.1	3.0	2.5	2.0	1.9	1.8
Isoleucine	2.9	2.5	4.1	2.9	2.4	3.6
Leucine	6.1	5.4	7.0	5.6	4.8	6.3
Lysine	8.4	7.3	7.7	7.2	6.2	6.6
Methionine	2.3	2.4	2.8	2.6	2.7	2.5
Phenylalanine	2.3	2.5	3.4	2.6	2.6	3.3
Threonine	3.5	3.4	4.4	3.6	3.2	3.9
Valine	3.8	3.4	5.0	3.6	3.1	4.6
Sum EAA	40.8	36.1	43.0	35.9	33.1	39.3
NEAA^2
Alanine	5.6	7.1	5.4	6.2	6.7	5.6
Aspartic acid	7.9	7.4	8.9	7.8	7.6	7.7
Glutamic acid	13.0	12.5	12.8	12.1	12.1	11.7
Glycine	6.4	10.5	6.9	9.8	13.5	7.4
Hydroxyproline	1.7	3.2	2.1	3.3	4.6	2.2
Proline	3.6	5.2	4.2	5.0	6.8	4.6
Serine	3.8	4.2	4.8	3.8	4.3	4.2
Tyrosine	2.1	1.9	2.0	1.9	1.6	3.1
Sum NEAA	44.1	51.9	47.2	50.0	57.2	46.5
Sum protein AA	84.8	88.0	90.2	85.9	90.4	85.7

¹EAA = Essential amino acids

²NEAA = Nonessential amino acids

Table 7. Molecular weight distribution (wt%) of hydrolysates based on mackerel (M) and salmon (S) backbones (B), heads (H), and viscera (V)

MW (Da)	MB	MH	MV	SB	SH	SV
> 20000	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1
20000–15000	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1
15000–10000	0.1	0.1	<0.1	0.1	0.1	<0.1
10000–8000	0.1	0.3	<0.1	0.2	0.2	<0.1
8000–6000	0.5	1.0	0.1	0.9	1.0	0.1
6000–4000	1.9	3.7	0.2	3.3	3.6	0.5
4000–2000	8.2	13.9	0.8	12.9	15.9	2.3
2000–1000	14.5	17.7	1.9	18.4	22.2	5.6
1000–500	17.7	16.6	5.5	18.9	19.0	10.1
500–200	19.7	16.9	16.8	20.3	17.3	16.6
200-	37.3	29.7	74.5	24.9	20.7	64.7

Table 8. Levels of free amino acids (g/100 g protein) in hydrolysates based on mackerel (M) and salmon (S) backbones (B), heads (H), and viscera (V)

	MB	MH	MV	SB	SH	SV
Aspartic acid	0.07	0.12	1.85	0.10	0.11	1.21
Glutamic acid	0.47	0.46	2.12	0.40	0.36	1.81
Hydroxyproline	0.01	0.02	0.07	0.02	0.03	0.06
Serine	0.11	0.20	1.46	0.13	0.18	1.45
Asparagine	0.02	0.02	0.19	0.02	0.02	0.40
Glycine	0.18	0.35	0.94	0.17	0.24	1.01
Glutamine	0.25	0.73	3.18	0.48	0.50	4.59
Histidine	3.88	1.37	1.22	0.24	0.22	0.76
Threonine	0.12	0.17	1.46	0.16	0.16	1.33
Alanine	0.35	0.46	2.25	0.49	0.45	2.78
Arginine	0.30	0.57	3.84	0.21	0.24	3.99
Proline	0.07	0.15	0.99	0.11	0.08	0.72
Tyrosine	0.22	0.44	1.13	0.20	0.16	2.17
Valine	0.12	0.24	2.25	0.26	0.21	2.29
Methionine	0.35	0.61	3.18	0.52	0.41	2.78
Cysteine	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
Isoleucine	0.10	0.22	2.12	0.27	0.21	1.93
Leucine	0.51	1.32	4.50	0.92	0.81	4.23
Phenylalanine	0.36	0.73	2.38	0.53	0.75	2.05
Tryptophan	0.08	0.12	0.86	0.13	0.11	0.70
Lysine	0.68	0.66	3.84	0.45	0.34	3.38
Sum protein amino acids	8.29	8.92	39.83	5.82	5.59	39.65
Non-protein amino acids
Creatinine	1.14	0.25	<0.01	0.45	0.38	<0.01
β-alanine	<0.01	<0.01	0.03	0.16	0.24	0.16
Taurine	1.03	2.36	2.38	0.51	1.46	3.26
4-aminobutanoic acid	<0.01	<0.01	<0.01	<0.01	0.01	0.01
Citrulline	<0.01	<0.01	0.20	<0.01	0.01	0.07
Carnosine	0.07	0.05	0.25	0.09	0.03	0.17
Anserine	0.13	0.08	0.15	2.56	0.72	0.13
L-Ornithine	0.02	0.03	0.08	0.02	0.02	0.18
Sum non-protein amino acids	2.40	2.78	3.09	3.79	2.87	3.99

Table 9. Levels of trimethylamine (TMA), trimethylamine-oxide (TMAO) (mg N/100 g), and biogenic amines (mg/kg) in spray-dried protein hydrolysates based on mackerel (M) and salmon (S) backbones (B), heads (H), and viscera (V)

	MB	MH	MV	SB	SH	SV
TMA	17	15	23	14	<1	250
TMAO	162	53	<1	125	<1	<1
Putrescine	63	44	78	110	180	410
Cadaverine	<20	<20	<20	<20	<20	380
Histamine	74	38	<20	67	68	22

Table 10. Mean sensory values of protein hydrolysates based on mackerel (M) and salmon (S) backbones (B), heads (H), and viscera (V). Different letters indicate statistical difference (p < 0.05) among the hydrolysates by two-way ANOVA and Tukey’s multiple comparison test

	Total flavor intensity	Sweet	Salty	Acidic	Bitter	Umami	Fish	Shellfish	TMA	Burned	Rancid	Flavorless	Cloying	Astringent	Fatness
MB	5.7^bc	2.8	3.3^b	2.3	3.8^cd	4.2^ab	4.3^ab	2.1	3.1^ab	2.1^b	1.2	3.2^a	3.1^abc	3.3^abc	2.3^ab
MH	6.7^a	2.6	5.8^a	2.4	3.8^cd	3.9^abc	4.9^a	2.8	4.6^a	2.4^b	1.5	1.7^b	4.7^a	3.5^abc	2.6^a
MV	6.1^ab	3.1	3.0^bc	2.6	4.7^ab	4.6^a	3.7^abc	2.9	3.7^ab	3.2^b	1.4	2.8^ab	4.1^abc	3.8^ab	2.4^ab
SB	4.9^cd	2.4	2.3^c	2.6	4.2^bc	2.8^c	3.2^bc	2.1	2.5^b	2.8^b	1.1	2.7^ab	2.6^bc	3.2^bc	1.7^c
SH	4.2^d	2.5	2.3^c	2.1	3.1^d	3.0^bc	2.8^c	2.0	2.3^b	2.1^b	1.1	2.7^ab	2.4^c	2.6^c	2.0^bc
SV	6.9^a	3.0	2.8^bc	2.8	5.7^a	3.7^abc	3.8^abc	2.6	4.2^a	4.5^a	1.3	2.4^ab	4.6^ab	4.3^a	2.2^ab
p-value	<0.001	0.099	<0.001	0.052	<0.001	0.001	<0.001	0.079	<0.001	<0.001	0.133	0.014	0.003	<0.001	<0.001

Figure 1. Mean intensity of sensory attributes based on (a) backbones, heads, and viscera and (b) mackerel and salmon. Different letters indicate statistical difference (p < 0.05) based on mixed model ANOVA and Tukey’s multiple comparison test