Biomass of the oleaginous yeast Rhodotorula toruloides as feed ingredient in the diet of Arctic char (Salvelinus alpinus): impact on quality; safety and sensory outcome

Figures & data

Table 1. Concentrations of organic pollutants in hydrolysate and yeast samples (mean ± standard deviation, n =  3). Concentrations are reported as the total sum of single compounds quantified in the sample.

	Σ17PAH	Σ20PCB	HCB
Hydrolysate, ng g^−1	<LOQ or n.d.	n.d.	n.d.
Yeast, ng g^−1lipid weight	200 ± 12	n.d	0.21 ± 0.02

n.d.: non-detected.

PAHs, polycyclic aromatic hydrocarbons (sum of naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, perylene, indeno(1,2,3-c,d)pyrene, dibenz(a,h)anthracene, benzo(g,h,i)perylene).

PCBs, polychlorinated biphenyls (CB-28, −52, −77, −81, −101, −105, −114, −118, −123, −126, −138, −153, −156, −157, −167, −169, −170, −180, −189, −209).

HCB, hexachlorobenzene.

Hydrolysate: PAHs LOQ: 14–220 pg g⁻¹, w:w; PCBs LOQ: 1.5–0.26 pg g⁻¹, w:w; HCB LOQ: 3.5 pg g⁻¹, w:w.

Yeast: PAHs LOQ: 2.9–100 ng g⁻¹, l:w; PCBs LOQ: 62–370 pg g⁻¹, l:w; HCB LOQ: 84 pg g⁻¹, l:w.

Table 2. Heavy metal concentration (mg kg⁻¹ or mg L⁻¹) in hydrolysate and in yeast biomass compared with maximum levels for contaminants in foodstuffs by EU legislation (EU leg.), European Food Safety Authority (EFSA) and FAO & WHO.

Element	EU leg., mg kg^−1	Hydrolysate, mg L^−1	Yeast, mg kg^−1	LOQ hydrolysate, mg L^−1	LOQ Yeast, mg kg^−1
Al	1^a	0.336	0.539	0.0100	0.500
As	0.01^b	0.005	<LOQ	0.0030	0.005
Cd	0.05^c	0.006	0.020	0.0001	0.002
Hg	0.50^c	<LOQ	<LOQ	0.0010	0.005
Pb	0.30^c	0.016	0.034	0.0005	0.010

^a . European Food Safety Authority (EFSA), 2008.

^b . FAO & WHO, 1995.

^c . Commission Regulation (EC), 2006.

Table 3. Composition of control and experimental yeast feeds (% of dry matter) for fish in duplicates. Table from Brunel et al. (2022), under Creative Commons Attribution License CC BY 4.0. ‘Vitamin mix’ and ‘Mineral mix’ ingredients were provided by NOFIMA (Norway) and ‘Astaxanthin & vitamin mix’ ingredients were provided by Aller Aqua A/S (Denmark). Further details on vitamin and mineral mixes composition can be found as supplementary materials, Table S4.

Ingredients	Control feed		Experimental feed
Fish meal	52.8		53.5
Fish oil	12.5		12.6
Mineral mix	0.48		0.49
Vitamin mix	0.96		0.97
Astaxanthin & vitamin mix	0.14		0.15
Gelatine	0.48		0.49
Wheat meal	18.7		14.1
Ca2PO4	2.40		2.43
Casein	5.76		-
Vegetable oil	5.76		-
Yeast biomass	-		15.3 (5.8% oil)
Chemical composition
Crude protein (%)	44.8		42.1
Total fat content (%)	19.8		18
Ash content (%)	10.7		11.8
Moisture content (%)	9.92		9.86

Table 4a. Total fat content and fatty acid profile (%) of fish fillet from Arctic char fed with yeast biomass (experimental fish group). Data from Jacobsson (2022) and Brunel et al. (2022) under open access or under Creative Commons Attribution License CC BY 4.0. Data are presented as the mean ± standard deviation, with n sample size per group of fish.

Experimental fish	Small fish (Jacobsson, 2022) n = 4		Large fish (Jacobsson, 2022) n = 4	Fish (Brunel et al., 2022) n = 6
Total fat content (%)	8.28 ± 2.32		9.25 ± 1.13	6.46 ± 1.37
Fatty acid (%)
14:0	3.55 ± 0.19		3.58 ± 0.05	4.07 ± 0.16
15:0	n.d		n.d	0.29 ± 0.10
16:0	14.0 ± 0.48		14.3 ± 0.41	15.2 ± 0.33
16:1(n-9)	6.01 ± 0.45		6.25 ± 0.52	0.29 ± 0.07
16:1(n-7)	n.d		n.d	5.81 ± 0.37
18:0	2.06 ± 0.19		2.08 ± 0.13	2.13 ± 0.10
18:1(n-11)	1.06 ± 0.27		1.15 ± 0.07	n.d
18:1(n-9)	28.2 ± 0.49		28.7 ± 0.86	28.0 ± 0.98
18:1(n-7)	2.79 ± 0.02		2.72 ± 0.11	2.33 ± 0.97
18:2(n-6)	6.93 ± 0.33		6.60 ± 0.29	6.73 ± 0.17
18:3(n-3)	1.81 ± 0.32		1.75 ± 0.06	1.79 ± 0.27
20:1(n-11)	1.07 ± 0.02		1.41 ± 0.57	n.d
20:1(n-9)	6.90 ± 0.33		7.21 ± 0.48	7.01 ± 0.29
20:2(n-6)	0.46 ± 0.07		0.43 ± 0.07	0.43 ± 0.05
20:4(n-6)	0.37 ± 0.17		0.44 ± 0.04	0.40 ± 0.11
22:1(n-11)	7.20 ± 0.14		6.92 ± 0.37	n.d
22:1(n-9)	0.80 ± 0.08		0.75 ± 0.08	n.d
20:5(n-3)	3.84 ± 0.09		3.50 ± 0.98	3.94 ± 0.21
C24:1	n.d		n.d	0.51 ± 0.14
22:5(n-3)	1.01 ± 0.09		0.93 ± 0.05	1.04 ± 0.15
22:6(n-3)	10.2 ± 0.66		9.38 ± 0.53	11.0 ± 1.06
SFA	19.6 ± 0.62		19.9 ± 0.55	21.7 ± 0.31
MUFA	54.0 ± 0.61		55.1 ± 1.19	44.7 ± 1.44
PUFA	24.6 ± 0.67		23.0 ± 0.57	32.3 ± 1.17
n-3	16.9 ± 0.62		15.6 ± 0.65	25.1 ± 1.36
n-6	7.75 ± 0.11		7.47 ± 0.33	7.22 ± 0.38
n-3/ n-6	2.18 ± 0.08		2.09 ± 0.15	3.49 ± 0.34

Abbreviation: SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; n.d, non-detected.

Table 4b. Total fat content and fatty acid profile (%) of fish fillet from Arctic char fed with vegetable oil ingredients (control fish group). Data from Jacobsson (2022) and Brunel et al. (2022) under open access or under Creative Commons Attribution License CC BY 4.0. Data are presented as the mean ± standard deviation, with n sample size per group of fish.

Control fish	Small fish (Jacobsson, 2022) n = 4		Large fish (Jacobsson, 2022) n = 4	Fish (Brunel et al., 2022) n = 6
Total fat content (%)	7.05 ± 3.11		13.0 ± 3.05	5.95 ± 2.06
Fatty acid (%)
14:0	3.45 ± 0.24		3.55 ± 0.20	4.04 ± 0.13
15:0	n.d		n.d	0.33 ± 0.16
16:0	14.1 ± 0.20		15.1 ± 0.28	15.4 ± 0.60
16:1(n-9)	4.98 ± 0.70		5.96 ± 0.31	0.41 ± 0.12
16:1(n-7)	n.d		n.d	5.28 ± 0.44
18:0	2.12 ± 0.10		1.98 ± 0.54	2.18 ± 0.13
18:1(n-11)	1.25 ± 0.01		1.17 ± 0.07	n.d
18:1(n-9)	27.4 ± 1.27		29.0 ± 0.39	26.8 ± 1.39
18:1(n-7)	2.80 ± 0.17		3.05 ± 0.09	2.44 ± 1.19
18:2(n-6)	7.06 ± 0.16		6.19 ± 0.15	6.80 ± 0.30
18:3(n-3)	2.01 ± 0.08		1.76 ± 0.04	1.96 ± 0.21
20:1(n-11)	1.07 ± 0.05		1.07 ± 0.04	n.d
20:1(n-9)	6.83 ± 0.26		7.27 ± 0.31	6.98 ± 0.30
20:2(n-6)	0.49 ± 0.04		0.48 ± 0.03	0.54 ± 0.09
20:4(n-6)	0.40 ± 0.13		0.27 ± 0.22	0.51 ± 0.03
22:1(n-11)	7.27 ± 0.14		7.25 ± 0.26	n.d
22:1(n-9)	0.83 ± 0.06		0.79 ± 0.06	n.d
20:5(n-3)	4.03 ± 0.22		3.29 ± 0.22	4.11 ± 0.31
24:1	n.d		n.d	0.58 ± 0.11
22:5(n-3)	0.88 ± 0.17		0.90 ± 0.05	1.05 ± 0.13
22:6(n-3)	11.7 ± 1.91		8.77 ± 0.55	11.3 ± 0.96
SFA	19.7 ± 0.33		20.7 ± 0.38	22.0 ± 0.82
MUFA	52.4 ± 2.06		55.6 ± 1.22	43.6 ± 1.63
PUFA	26.5 ± 2.13		21.7 ± 0.50	33.2 ± 0.96
n-3	18.6 ± 1.93		14.7 ± 0.53	25.5 ± 1.01
n-6	7.95 ± 0.27		6.94 ± 0.19	7.65 ± 0.35
n-3/ n-6	2.34 ± 0.20		2.12 ± 0.11	3.35 ± 0.24

Abbreviation: SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; n.d, non-detected.

Figure 1. 7-ethoxyresorufin-O-deethylase activity in hepatic microsomes of Arctic char fish after the feeding trial. Enzyme activity is presented as pmol min⁻¹ mg⁻¹ of microsomal protein (mean ± standard error, n = 16 per group).

Table 5. Sensory analysis of fish fillets on untrained volunteers (p < 0.05).¹

Number of volunteers	34
Number of incorrect responses	27
Minimum number of correct answers to validate a difference	17

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Data availability statement

The data supporting the findings of the study are available from the corresponding author upon reasonable request.