Hazelnut Meal Research Articles

Comparative evaluation of nutrient composition, in vitro nutritional value, and antioxidant activity of de-oiled meals from walnut, hazelnut, almond, and sesame.

This study aimed to establish a comparative database on the chemical composition, in vitro nutritional value, and antioxidant activity of the de-oiled meals produced from walnut, hazelnut, almond, and sesame seeds from the ruminant nutrition perspective. The meals were provided in dried form after their oil harvest using the cold-pressing oil extraction method. Crude protein (CP) constituted the major component of the meals and was the greatest in walnut and almond (average of 45.6% of dry matter (DM)], intermediate in hazelnut meal (41.4%), and least in sesame meal (33.3%)). Potassium was the most abundant mineral in walnut, hazelnut, and almond meals, followed by phosphorus, calcium, and magnesium. The CP fractions determined using the Cornell Net Carbohydrate and Protein System were largely different across the meals, with fraction A being the greatest in hazelnut (40.9% of CP) and intermediate in almond, sesame, and walnut meals (11.4% of CP). The unavailable CP fraction (fraction C) was the least abundant fraction in all meals, ranging from 0.13% of CP in walnut to 3.30% of CP in hazelnut meal. Oleic and linoleic acids were the predominant unsaturated fatty acids, and palmitic acid was the principal fatty acid in all meals analyzed. The fractional degradation rate (h-1) ranged from 0.043 in almond meal to 0.017 in walnut meal. In vitro intestinal CP digestibility (% of rumen-undegraded protein) ranged from 91.6 in hazelnut meal to 97.2 in almond meal. Total phenolics expressed as milligram tannic acid equivalent/gram DM was greatest in walnut meal (11.9), resulting in the greatest antioxidant activity recorded for walnut meal (83.2%). This study provided a database on the nutrient composition, in vitro nutritional value, and antioxidant capacity of the selected de-oiled meals. Additional investigation is needed to identify the in vivo response of their inclusion in the diet of ruminants.

Influence of pH and ionic strength on the bulk and interfacial rheology and technofunctional properties of hazelnut meal protein isolate

The functional, bulk, and interfacial shear rheological properties of hazelnut protein isolate were studied at different pH values between 3.0 and 8.0 and ionic strength levels between 0.0 and 1.0 M. The results showed that pH significantly affected protein solubility, emulsion properties, water and oil holding capacities, foam stability, surface hydrophobicity, and free -SH groups. The highest surface hydrophobicity, free -SH groups, and better functional properties were observed at pH 8.0. Protein solubility also increased with increasing ionic strength up to 0.6 M. The emulsion and foam stability of hazelnut protein isolate showed similar changes with protein solubility. The flow behavior of hazelnut protein suspensions was found to be shear thinning with the highest consistency index at pH 3.0 and the lowest at pH 6.0, however, the ionic strength did not significantly affect the consistency coefficient but did cause a significant change in the flow behavior index, with the lowest value observed at 0.6 M. The best gel structure in hazelnut proteins was observed at pH 3.0 and 4.0. The addition of ions at 0.4 and 0.6 M concentrations resulted in an improved viscoelastic character. The hazelnut protein isolate was also found to form solid-like viscoelastic layers at both air-water and oil-water interfaces, with the interfacial adsorption behavior affected by both pH and ionic strength. Overall, these results suggest that pH and ionic strength have significant effects on the functional and rheological properties of hazelnut protein isolate, which may have the potential as an auxiliary substance in food systems.

Effect of protein oxidation on the structural characteristics of hazelnut protein isolate

The oxidation and structural properties of hazelnut protein prepared from a low-temperature cold-pressed hazelnut meal were evaluated using three oxidative modification methods: AAPH (2,2'-azo(2-methylpropionamidine)dihydrochloride), MDA (malondialdehyde), and H2O2. The three different oxidants gradually increased the carbonyl content of the proteins, MDA from 1.91 to 8.87 nmol/m, AAPH (from 2.13 to 12.18 nmol/mg, and H2O2 from 2.28 to 13.72 nmol/mg, indicating that the hazelnut protein was oxidized. The carbonyl content of H2O2-modified hazelnut proteins was the highest, implying that the proteins were more susceptible to oxidation by hydroxyl radicals. FT-IR, intrinsic fluorescence spectra, surface hydrophobicity, and protein electrophoresis implied that oxidative modifications altered the secondary structure of hazelnut proteins, and promoted protein aggregation and cross-linking. In addition, the oxidative modification resulted in a larger particle size distribution of hazelnut proteins and a decrease in the zeta potential absolute value, indicating a decrease in the hazelnut proteins stability and the formation of soluble aggregates. Overall, incubation with AAPH, MDA, and H2O2 significantly affected the structure of hazelnut proteins, demonstrating that hazelnut proteins in food processing systems are susceptible to structural and property changes due to different oxidation products.

Combined Neutrase-Alcalase Protein Hydrolysates from Hazelnut Meal, a Potential Functional Food Ingredient.

Consumers' interest in functional foods has significantly increased in the past few years. Hazelnut meal, the main valuable byproduct of the hazelnut oil industry, is a rich source of proteins and bioactive peptides and thus has great potential to become a valuable functional ingredient. In this study, hazelnut protein hydrolysates obtained by a single or combined hydrolysis by Alcalase and Neutrase were mainly characterized for their physicochemical properties (SDS-PAGE, particle size distribution, Fourier-transform infrared (FTIR) spectroscopy, molecular weight distribution, etc.) and potential antiobesity effect (Free fatty acid (FFA) release inhibition), antioxidant activity (DPPH and ABTS methods), and emulsifying properties. The impact of a microfluidization pretreatment was also investigated. The combination of Alcalase with Neutrase permitted the highest degree of hydrolysis (DH; 15.57 ± 0.0%) of hazelnut protein isolate, which resulted in hydrolysates with the highest amount of low-molecular-weight peptides, as indicated by size exclusion chromatography (SEC) and SDS-PAGE. There was a positive correlation between the DH and the inhibition of FFA release by pancreatic lipase (PL), with a significant positive effect of microfluidization when followed by Alcalase hydrolysis. Microfluidization enhanced the emulsifying activity index (EAI) of protein isolates and hydrolysates. Low hydrolysis by Neutrase had the best effect on the EAI (84.32 ± 1.43 (NH) and 88.04 ± 2.22 m2/g (MFNH)), while a negative correlation between the emulsifying stability index (ESI) and the DH was observed. Again, the combined Alcalase-Neutrase hydrolysates displayed the highest radical scavenging activities (96.63 ± 1.06% DPPH and 98.31 ± 0.46% ABTS). FTIR results showed that the application of microfluidization caused the unfolding of the protein structure. The individual or combined application of the Alcalase and Neutrase enzymes caused a switch from the β-sheet organization of the proteins to α-helix structures. In conclusion, hazelnut meal may be a good source of bioactive and functional peptides. The control of its enzymatic hydrolysis, together with an appropriate pretreatment such as microfluidization, may be crucial to achieve the best suitable activity.

Interactions between Hazelnut (Corylus avellana L.) Protein and Phenolics and In Vitro Gastrointestinal Digestibility

In this study, we investigated the formation of protein–phenolic complexes from dephenolized hazelnut meal protein isolates (dHPI) and hazelnut skin phenolic extracts (HSE) and their effects on the bioaccessibility of both hazelnut proteins and phenolics. The dHPI–HSE complexes were of considerable size and were dependent on HSE concentration due to aggregation. Although catechin was the main component of HSE, it did not cause aggregation, except for a slight rise in particle size. According to fluorescence quenching, the hazelnut protein–phenolic extract complex had a linear Stern–Volmer plot expressing static quenching between 0–0.5 mM concentration; the interaction was mainly dependent on hydrogen bonding and van der Waals forces (ΔH < 0 and ΔS < 0), and the reaction was spontaneous (ΔG < 0). According to Fourier transform infrared (FTIR) spectroscopy results, higher phenolic extract concentration caused an increase in irregular structures in hazelnut protein, while the lowest catechin and phenolic concentration altered the regular structure. Skin extracts did not alter the digestibility of dephenolized proteins, but dephenolization reduced the degree of hydrolysis by pancreatin. The formation of the protein–phenolic complex had a beneficial effect on the bioaccessibility of hazelnut skin phenols, predominantly those on the galloylated form of the catechins, such as gallocatechin gallate and epigallocatechin gallate. Thus, the bioaccessibility and antioxidant activity analysis results showed that protein–phenolic complexes obtained from hazelnut meal and skin may promote the transition of phenolic compounds from the gastrointestinal tract without degradation.

Pretreatment effect of osmotic dehydration on ultrasound‐assisted solvent extraction: Functional properties of defatted hazelnut meal

This study aimed to investigate the impact of ultrasound and osmotic dehydration on the functional properties of defatted hazelnut meal. The results showed that osmotic dehydration sample pretreatment did not significantly affect the functional properties of defatted meal based on p-value analysis. However, the parameters in extraction process significantly affect (p < .05) the functional properties of defatted meal. The ultrasound amplitude, solvent-to-solid ratio, and extraction temperature at highest settings in the extraction process could affect the protein content (from 29 to 33%), water-holding capacity (from 1.1 to 1.7%) and emulsifiability (from 1 to 1.4%) but negatively affect the fat-binding capacity (from 74 to 72%) of defatted meal. It was found that defatted meal extracted from higher setting on parameters is suitable for foods with high juiciness and tenderness requirement while defatted meal extracted from lower setting of parameters is suitable for milk-based beverages. Practical applications Most of the reported articles were focused on investigating the effects of processing parameters on oil yield and quality, but only limited information was given about the defatted meal after the oil extraction process. The defatted meal obtained after the extraction process can be considered as another valuable side product due to its high protein content. The meal could be very useful for various applications in food and beverage industry depends on its characteristics. Therefore, this paper aims to investigate the effects of osmotic pretreatment and ultrasound treatment on the functional properties of defatted hazelnut meal.

The Effect of Phytase Enzyme Supplementation to Hazelnut Meal Based Diets on Growth Performance and Nutrient Digestibility of Siberian sturgeon (Acipenser baerii)

This research was carried out to determine that the effects of diets containing 30% hazelnut meal and different proportions of phytase enzymes on the growth performance of Siberian sturgeon (Acipenser baerii) (initial mean weight, 960.23 ± 0.55 g). The trial diets consisted of feeds supplemented with 0.25 g kg-1 (G2), 0.50 g kg-1 (G3), and 1.00 g kg-1 (G4) phytase enzyme, and with no enzyme added to the control group (G1), respectively. Experiment groups were performed in 3 replicates and trials were carried out for 90 days. As a result, adding phytase enzyme to feeds contain 30% hazelnut meal was found to have a positive effect on the weight gain (WG, g), the protein efficiency ratio (PER), feed conversion ratio (FCR), and specific growth rate (SGR, %). Growth performance was found to be more successful in all groups fed feeds supplemented with phytase enzyme compared to the G1 group (P<0.05). The G4 was the best group than the others statistically (P<0.05). In terms of the digestibility effect of enzyme added groups, the highest total digestion rate (77.14 ± 0.07%) was obtained in the G4 enzyme group and the lowest total digestibility (74.32 ± 0.02%) was estimated in the G1.

Angiotensin I-converting enzyme, dipeptidyl peptidase-IV, and α-glucosidase inhibitory potential of hazelnut meal protein hydrolysates

Angiotensin I-converting enzyme, dipeptidyl peptidase-IV, and α-glucosidase inhibitory potential of hazelnut meal protein hydrolysates

Effects of the use of feeds containing phytase enzyme from different protein sources on nitrogen and phosphorus discharge of rainbow trout (Oncorhynchus mykiss) juveniles

In this study, the effects of diets (D1-3) including fish meal (FM), hazelnut meal (HM), soybean meal (SM), and phytase enzyme [- (0),+(1000 FTU)] in varying rates (D1-, D1+; D2-, D2+; D3-, D3+) were examined on nitrogen and phosphorus discharge based on the nutrition of rainbow trout (Oncorhynchus mykiss) juveniles. The study was conducted in tanks with 3 replicates for each group. In this trial, it was found that the differences among total-particle nitrogen, particle phosphorus, and total solid waste values released from the rainbow trout groups were insignificant; however, the differences between the values of total-dissolved phosphorus and dissolved nitrogen released were found significant (p 0.05). Moreover, although there were increases in the total and dissolved phosphorus and dissolved nitrogen discharge in all groups fed with diets including phytase, the particle phosphorus discharge decreased (p<0.05). Based on the decrease in the amounts of hazelnut meal and soybean meal used in the diets, it was determined that there was a decrease in the amount of dissolved phosphorus released to the environment; besides, it was determined that it led to an increase in the amount of released dissolved phosphorus in all groups fed with diets containing phytase enzyme (p<0.05).

Production of a Protein Concentrate from Hazelnut Meal Obtained as a Hazelnut Oil Industry By-Product and Its Application in a Functional Beverage

This study aimed to extract protein from hazelnut meal, to evaluate its functional properties, and to apply it in a functional beverage. Hazelnut meal protein (HMP) was extracted by isoelectric precipitation. Proximate composition as well as solubility and water and oil absorption capacities of HMP were evaluated. Functional beverages with 2% and 4% of HMP were produced and compared to a reference beverage in terms of physicochemical and sensory properties. HMP with 86.8% protein was obtained. Essential amino acid concentration (36.65%) of HMP was considerably higher than many plant-based proteins. Moreover, branched-chain amino acids concentration composed of 12.33% of total protein. Water and oil absorption capacities of HMP was 2.21 ± 0.03 (g water/g protein) and 4.85 ± 0.28 (mL oil/g protein), respectively. 2% and 4% (w/v) HMP beverages (HMPB2 and HMPB4) were prepared and compared with the reference beverage (RB). All physiochemical properties investigated significantly differed except turbidity and viscosity. Sensory evaluation revealed that overall acceptability of the formulations was comparable to each other and that both HMPB2 and HMPB4 were preferred by the panelists. Results suggested that hazelnut meal can be a protein source for functional foods and partially replace the existing sources in a more environmentally friendly, cheap and sustainable manner.

SOĞUK PRES FINDIK POSALARINDAN ÜRETİLMİŞ TRİPTİK PEPTİTLERİN IN VITRO ACE İNHİBE EDİCİ AKTİVİTELERİ ÜZERİNE ÖN INCELEMELER

Hazelnut (Corylus avellana L.) is a rich source of proteins which are concentrated in deoiled meals during hazelnut oil manufacture. Here, an in vitro attempt was made to evaluate the biological functionality of tryptic hazelnut peptides. In our in silico investigations, a specific subset of hazelnut proteins was predicted to demonstrate ACE-inhibitory and DPP-IV-inhibitory activities. Consequently, hazelnut protein concentrates were produced from cold press deoiled meals and subjected to tryptic hydrolysis (37°C). The progress of trypsinolysis was monitored using size exclusion chromatography (SEC), fast protein liquid chromatography (FPLC) and Raman spectroscopy. While the protein hydrolyzates had limited ACE-inhibitory activity, after 240 min of trypsinolysis, ACE-inhibitory activity was approximately 40% at a relatively low protein concentration level. Although further clarifications are necessary, current findings demonstrated hazelnut meal could be considered as a valuable source of ACE-inhibitory peptides that can be utilized in the formulation of functional foods and food supplements.

Effects of the Feeds Containing Hazelnut Meal as Plant Protein Source on Growth Performance and Body Composition of Siberian sturgeon (&lt;i&gt;Acipenser&lt;/i&gt; &lt;i&gt;baeri&lt;/i&gt;) and Economic Profitability Value

In this study, the effects of feeding with the diets containing hazelnut meal (HM) at different levels (0%, 15%, 30%, and 45%) on the growth performance and body composition of Siberian sturgeon were investigated. The study was carried out for 90 days with 3 replicates (n = 15; 283.1 ± 6.52 g fish weight). The highest weight gain (180.62 ± 2.84%) was observed in the control group followed by 15%, 30%, and 45% HM. When the groups were evaluated in terms of SGR, FCR, and PER, the control group was observed to have the best performance. The control group and the 15% HM group, which were statistically similar, were found to be different from the other groups (P < 0.05). The statistical difference between the control group and the 45% HM group of HSI values was significant (P < 0.05). CP, CF, and GE values were found to be similar in the control group and 15% HM groups and different from other groups (P < 0.05). Finally, it was concluded that adding 15% HM to the diet would positively affect fish growth in terms of growth performance, ECR, meat quality, and body composition, but considering the economic performance, it is determined that the rate of HM can be increased up to 45%.

Effect of high pressure homogenization (HPH) on functional and rheological properties of hazelnut meal proteins obtained from hazelnut oil industry by-products

The effect of high pressure homogenization (HPH) on functional and rheological properties of hazelnut meal proteins was investigated. Hazelnut meal proteins were extracted from hazelnut oil industry by-products. Protein patterns remained unchanged up to 75 MPa, and band intensity decreased when pressure reached 100 MPa. HPH treatment decreased particle size, produced higher zeta potential and hence, improved water solubility, which resulted in higher emulsifying and foaming properties. Hazelnut meal protein suspensions displayed shear thinning behavior and higher G′ than Gʹ' which means suspensions had soft-gel network. For better understanding of internal structure, elastic and viscous behavior, creep and recovery tests were explained by Burgers and exponential decay models. Final percentage recovery increased after 100 MPa due to strengthened solid-like structure of protein suspensions. As a result, functional and rheological properties of proteins can be successfully improved by HPH treatment, and thus hazelnut oil industry by-products have added value once processed by HPH.

Effect of ultrasound treatment on the properties of nano-emulsion films obtained from hazelnut meal protein and clove essential oil

Hazelnut meal protein (4% (w/v)) and clove essential oil (CEO) (3% (v/v)) were homogenized with ultrasound (US) at different times (2, 4 and 6 min) and amplitudes (50, 75 and 100%) to obtain nano-emulsion films. Film forming nano-emulsions (FFNs) were analyzed for average particle size (Dz) and zeta potential, and edible film characterization were evaluated depending on US treatment, as well as antibacterial and antioxidant activities. Dz values and zeta potential of FFNs decreased with increasing acoustic energy delivered to nano-emulsion system. Thickness and water solubility of films significantly decreased with increasing US treatment. Films became more transparent depending on US treatment probably due to particle size reduction. Tensile strength (TS) of films significantly increased with US treatment, while elongation at break (EAB) slightly increased. Microstructure of films became more homogeneous after US treatment and caused to lower water vapor permeability. Enrichment with CEO has given the films antibacterial activity against L. monocytogenes, B. subtilis, S. aureus, P. aeruginosa and E. coli, and antioxidant activity, and US application has improved these activities. US technology can be used to improve mechanical, barrier and antimicrobial properties of hazelnut meal protein based edible films enriched with CEO.

Growth Performance and Feed Utilization of Koi Carp (Cyprinus carpio L., 1758) Fed Partial or Total Replacement of Fish Meal with Hazelnut Meal and Soybean Meal

Growth Performance and Feed Utilization of Koi Carp (Cyprinus carpio L., 1758) Fed Partial or Total Replacement of Fish Meal with Hazelnut Meal and Soybean Meal

Nutritional and anti‐nutritional compositions of defatted Nebraska hybrid hazelnut meal

SummaryDefatted meal of hybrid hazelnuts may have potential food and value‐added industrial applications. The proximate composition, mineral elements, amino acid profile and anti‐nutritional factors (total phenolics, tannins, condensed tannins and phytates) of defatted meals of ten Nebraska hybrid hazelnut genotypes were investigated. Excluding the amino acid profile, the nutritional and anti‐nutritional compositions of the meals differed significantly, with high protein, carbohydrate, neutral and acid detergent fibre concentrations and energy value. Mineral concentrations were higher than those previously reported. K was the most abundant mineral element, followed by P, Ca and Mg. Seven essential amino acids accounted for approximately 27.8% of the total amino acid contents. Tryptophan was not detected. All essential amino acid contents were significantly lower than the reference levels recommended for human and animal consumption. The high levels of anti‐nutritional factors, such as total phenolics, tannins, condensed tannins and phytate in the meals, could reduce protein and mineral bioavailability.

EFFECT OF BLANCHING ON STORAGE STABILITY OF HAZELNUT MEAL

ABSTRACT Influence of blanching on storage stability of hazelnut meal was investigated under accelerated storage conditions. Meals were obtained from unblanched and blanched hazelnut kernels, and stored at a relative humidity of 60% at 30C for 50 days. Total free fatty acid content, concentrations of individual free fatty acids, peroxide value and oil stability index were measured in the hazelnut meal samples during storage. No significant difference was found between peroxide values of the samples, however, the values of both samples increased during storage time. The concentrations of free fatty acids increased because of the activity of lipase in both meals, but the levels were lower in the blanched sample. Oil stability index of the unblanched sample was lower than that of the blanched sample. Blanching treatment was found to improve the oxidative stability of hazelnut meal, possibly because of partial inactivation of deteriorative enzymes. PRACTICAL APPLICATIONSHazelnut meal is a product obtained from hazelnut which is used as an ingredient in various food products. Hazelnut meal is more prone to degradation and quality loss during storage via oxidation compared with the whole counterpart. Stability of whole hazelnut has been studied to a great extent in the literature, but there is a scarcity of information regarding stability of processed hazelnut. In addition, there is no information in the literature about the amount of individual free fatty acids in hazelnut where the amounts of total free fatty acids have been reported extensively. This study provides data for quality and stability of hazelnut meal during storage which could be used by the food industry.

ERRATA

Aquaculture ResearchVolume 40, Issue 3 p. 384-384 Free Access ERRATA This article corrects the following: A preliminary study on the utilization of hazelnut meal as a substitute for fish meal in diets of European sea bass (Dicentrarchus labrax L.) Yılmaz Emre, Hüseyin Sevgili, Murat Şanlı, Volume 39Issue 3Aquaculture Research pages: 324-328 First Published online: January 24, 2008 First published: 22 January 2009 https://doi.org/10.1111/j.1365-2109.2008.02090.xAboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat In Aquaculture Research 39:3, the following errors were published on page 325: Was incorrect and should have been feed conversation ratio (FCR)=weight gain/feed consumed Was incorrect and should have been feed conversion ratio (FCR)=dry feed consumed/weight gain On page 327, the following error was published: Because 30% was the maximum incorporation level of HM, this hampered us in estimating the level of HM that can be incorporated into European sea diets instead of FM. This sentence was incorrect and should have read: Because 30% was the maximum incorporation level of HM, this hampered us in estimating the level of HM that can be incorporated into European sea bass diets instead of FM. We apologize for these errors. Reference Emre Y., Sevgili H. & Şanlι M. (2008) A preliminary study on the utilization of hazelnut meal as a substitute for fish meal in diets of European sea bass (Dicentrarchus labrax L.). Aquaculture Research 39, 324– 328. doi: 10.1111/j.1365-2109.2007.01881.x. Wiley Online LibraryCASWeb of Science®Google Scholar Volume40, Issue3February 2009Pages 384-384 ReferencesRelatedInformation

Effects of Replacement of Fishmeal with Hazelnut Meal on Growth Performance, Body Composition, and Nutrient Digestibility Coefficients in Rainbow Trout, Oncorhynchus mykiss

Hazelnut meal was evaluated as an alternative protein source to fishmeal in diets for rainbow trout, Oncorhynchus mykiss (initial wt 57.5±0.1 g). Hazelnut meal was incorporated in the diet at levels of 0% (control), 7.5%, 15%, 22.5%, and 30%. Diets were tested in triplicate for ten weeks. Higher levels of hazelnut meal produced better growth performance, that was sig- nificantly higher in fish fed 30% hazelnut meal than in the control (p&lt;0.05). Feed utilization and protein efficiency ratios followed a similar trend while the level of hazelnut meal did not significantly affect whole body composi- tion. Apparent digestibility of dry matter and energy of fish fed hazelnut meal at all levels was significantly lower than in fish fed the control (p&lt;0.05). Crude and digestible protein, as well as energy retention, were significant- ly correlated with hazelnut meal level. Nevertheless, energy retention declined in fish fed 30% hazelnut meal. Based on growth performance and nutrient retention, the optimal level of hazelnut meal in diets for rainbow trout may be around 30%.

Hazelnut meal in diets for seawater farmed rainbow trout (Oncorhynchus mykiss): effects on growth performance and body composition

A 77-day feeding trial was designed in order to assess the effect of partial or total replacement of soybean meal by hazelnut meal (HNM) on feed intake, growth performance, nutrient utilization and body composition of rainbow trout (initial mean body weight: 80.0±3.5 g) in seawater conditions. A control and three experimental diets were formulated in which soybean meal level (25.5%) in the control diet was replaced by hazelnut meal at 39.2 (HN 39), 78.4 (HN 78) and 100% (HN 100) to provide 44% crude protein and 20% crude lipid diets. Diets were fed to 125 rainbow trout to apparent satiation by hand twice daily at 09.00 and 16.00 hours under natural photoperiod conditions. At the end of the feeding trial, fish of all groups almost tripled their body weight and no significant difference (P>0.05) was revealed in final weight or specific growth rate between treatments. However, feed conversion ratio (FCR) of the HN100 group was significantly higher than other treatments (P<0.05). There was a slightly decreasing trend in protein efficiency ratio (PER) and net protein utilization (NPU) with increasing level of dietary hazelnut meal, but it was only significant in groups of fish fed HN100. All groups of fish displayed similar carcass and muscle compositions. According to the results of the present study, it can be stated that hazelnut meal can replace soybean meal at up to 200 g kg-1 in grow-out diets of rainbow trout without any detrimental effects on growth performance.