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The influence of industrial refining stages on the physico-chemical properties, fatty acid composition and sterol contents in hazelnut oil

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O R I G I N A L A R T I C L E

The influence of industrial refining stages on the physico-chemical

properties, fatty acid composition and sterol contents in hazelnut

oil

Erman Duman1• Mehmet Musa O¨ zcan2

Revised: 23 January 2020 / Accepted: 29 January 2020 / Published online: 3 February 2020 Ó Association of Food Scientists & Technologists (India) 2020

Abstract In this study determined influence of industrial refining stages on the physico-chemical properties, fatty acid composition and sterol contents in hazelnut oil. According to this, while acidity values of hazelnut oil obtained from refining stages change between 0.11 (deodorized) and 1.44 (crude), peroxide values of oil samples were determined between 10.4 meqO2/kg (win-terized) and 12.5 meqO2/kg (crude oil). In addition, iodine values of oils taken from each refining stages varied between 85.06 (no¨tralized) and 87.45 (deodorized). While oleic acid contents of hazelnut oils taken from refining stages change between 84.08% (winterized) and 84.68% (neutralized), linoleic acid contents of oil samples ranged from 6.79% (neutralized) to 8.56% (winterized). Total saturated and unsaturated fatty acids of oil samples chan-ged between 6.84% (deodorized) and 8.00% (neutralized) to 92.00% (neutralized) and 93.16% (deodorized), respec-tively. While campesterol contents of oil sample change between 3.56% (deodorized) and 4.87% (crude), d-5,23-stigmastadienol contents of oil varied between 0.48% (deodorized) and 2.87% (neutralized). The highest sterol had b-sitosterol, its amount changed between 54.98% (deodorized) and 73.96% (crude oil). In addition, d-7-avenasterol contents of hazelnut oil obtained from refining stages varied between 4.85% (crude oil) and 28.33% (deodorized).

Keywords Hazelnut oil Refining  Physico-chemical properties Fatty acids  Sterols  GC

Introduction

Refining is eliminating process of impurities in oils. These impurities are gums, soap-stock, color agents, wax, alde-hyde and ketones. The same time during the refining pro-cess are degraded or reduced at certain rates vitamins, sterols and antioxidants useful for human health (Ortega-Garcia et al. 2006; El-Mallah et al. 2011; Gu¨nc¸ and Ko¨seog˘lu2014). Hazelnut oil is a good source for its high oleic acid and tocopherol contents. Since tocopherols are beneficial compounds in human diet, preservation of tocopherols in oil plays a great role in refining process (Altuntas et al. 2018). Tocopherols are beneficial com-pounds the most decrease (10–20%) during chemical refining (Karabulut et al. 2005). Phytosterols in veg-etable oils have inhibite property of oxidation of oils. A quantity of phytosterols are separated from the oil during refining. Especially during neutralization most of the phytosterols pass through the soap stock. (Sciancalepore 1981; Karaali1985). The refined vegatable oils are rich in terms of tocopherols and phytosterols (Homberg and Bielefeld 1982; Verleyen et al.2001). Viscosity is one of the most important parameter which characterizes rheo-logical properties of liquid foods (Abramovic and Klofutar 1998). The estimation of viscosity of a vegetable oil is essential in the design, piping and reactors (Rodenbush et al. 1999). Vegetable oils are regarded as an important component of the human diet (Okorie and Nwachukwu 2014; Onyema and Ibe2016). The impurities are separated from the crude oil by different refining methods and sep-arated impurities can affect stability of the oil. (Hamm and

& Mehmet Musa O¨zcan mozcan@selcuk.edu.tr

1 Department of Food Engineering, Faculty of Engineering,

University of Afyon Kocatepe, Afyonkarahisar, Turkey

2 Department of Food Engineering, Faculty of Agriculture,

University of Selc¸uk, 42031 Konya, Turkey https://doi.org/10.1007/s13197-020-04285-w

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Hamilton 2000; Gu¨nc¸ and Ko¨seog˘lu 2014). Refined parameters greatly can vary from one process or to another. These parameters are time, temperature, pressure and steam flow and these parameters effect lost total and individual tocopherol during refining process (Hamm and Hamilton2000). In other compounds separated at different stages of refining are free fatty acids, phospholipids, pig-ments and volatile components (Ruiz-Mendez et al.1997). The aim of current study was to determine the effect of industrial refining stages on the physico-chemical proper-ties, color values, fatty acid composition and sterol con-tents in hazelnut oil.

Materials and methods

Material

Hazelnut oil samples used in the research, provided that the same batch product, starting from crude hazelnut oil to refined hazelnut oil in refining process and samples obtained from the exits of crude, neutralization, bleaching, winterization and deoderization stages of refined process. After each stage, 13 different physico-chemical properties and changes at all stages of refining process of hazelnut oil were investigated.

Methods

Physico-chemical methods

Some physico-chemical analyzes were analysed according to AOCS methods (Anonymous 1990). These analyzes made specific gravity, viscosity, melting point, peroxide value, free fatty acidity, soap number, iodine value, saponification value and unsaponification matter value respectively.

Determination of colour

In current study, About 10 mL hazelnut oil was filtered by using Whatman (No. 22) paper, and placed into separate containers of 1ııand 5.25ıı. The color of oils were measured by Lovibond PFX tintometer 880 for 22°C. The mea-surements of the color of each oil was carried out through three different reading (Anonymous1989).

Analysis of fatty acids composition

For determine fatty acid compositions of hazelnut oils were applied a modified method as described by Anonymous (1990) and Hıs¸ıl (1998).

Working conditions of Gas Chromotography; Instrument: SHIMADZU GC-2025

Constant phase: % 10’luk DEGS (Dietilen Glikol Suksinat)

Support material: Chromosorb W(AW-DMCS) (60–80 mesh)

Dedector: FID (Flame Ionization Detector) Temperature

Colon: 180°C (RTX-2330, 60 m 9 0.25 mm i.d.; film thickness 0.20 lm)

Enjection: 200°C Dedector: 200°C Flow

Carrier gas (N2): 30 mL/min. Combustible gas (H2): 28 mL/min. Dry air: 220 mL/dak.

Printer/Entegarto¨r: Chromatopac CR 6A (Shimadzu) Enjection: 1 ll

Vitamin E analysis

For determine vitamin E analysis of hazelnut oils were applied analysis method developed by Balz et al. (1992). The mobile phase comprised 970 mL L-1 hexane and 30 mL L-1 1,4-dioxan at a flow rate of 1 mL min-1. Maxsil 5 (250 mm 9 400 mm, 5 lm), PINO OOG-0053.DO Phenomenex and Chromosorb 5160 (250 mm 9 400 mm, 5 lm) columns were used. Excitation and emission wavelengths of 293 and 326 nm respectively were employed in the fluorescence detector in high pres-sure liquid chromatography (HPLC) (Balz et al.1992). Sterol analysis

Sterol compositions for hazelnut oils were determined using a method as described by Phillips et al. (2005). SGE BP-5 column (30 m length 9 0.25 mm i.d., 0.25 lm film thickness) and a Perkin Elmer Boston, MA, USA GC autosystem were used. All gas (He, He-2 and air) flow rates were 45 mL min-1. The column temperature was increased from 0 to 60°C (2 min) and then from 60 to 220 °C (18 min) and finally held at 220 °C (35 min) (Phillips et al. 2005).

Results and discussion

The physico-chemical properties of hazelnut oil taken from refining stages are given in Table 1. While acidity values of hazelnut oil change between 0.11 (deodorized) and 1.44% (crude), peroxide values of oil samples were determined between 10.4 meqO2/kg (winterized) and

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12.5 meqO2/kg (crude oil). In addition, iodine values of oils taken from each refining stages varied between 85.06 (neutralized) and 87.45 (deodorized). Zhu et al. (2016) determined that acid value and peroxide value were sig-nificantly changed (p \ 0.05) after the complete peanut refining process. Also, saponification values of oil range from 197.53 mgKOH/g (winterized) to 200.02 mhKOH/g (neutralized), unsaponifiable matter values of hazelnut oil samples changed between 0.20% (deodorized) and 1.15% (neutralized). Vitamin E values of oils ranged from 16.26 mg/100 g (deodorized) to 25.11 mg/100 g (neutral-ized). While cold point values of oils taken from refining stages change between - 4.3°C (crude) and - 9.5 °C (deodorized), viscosity values of oil samples ranged from 67.30 mPA (winterized) to 82.60 mPA (neutralized). It was observed significantly differences between the physi-cal and chemiphysi-cal properties of hazelnut oils obtained from refining stages (p \ 0.05). Durmaz and Go¨kmen (2019) were determined that phenolic compounds and tocopherols were also partly removed from hazelnut oil to a degree. Free fatty acids appear as lipids breakdown and are therefore good indicators of degradation. Lipid peroxides are the primary product of oxidized oils or fats (Anony-mous 2018). Iodine value or number is the number of grams of iodine consumed by 100 g of fat. A higher iodine value indicates a higher degree of unsaturation (Beedu and Vijay 1981). Saponification value is expressed by potas-sium hydroxide in mg required to saponify 1 g of fat. It depends on the kind of fatty acid contained in the fat

(Anonymous 2012. There are sterols in fats and oils and these substances are in the non-saponifying substances in fats and oils (Hartman et al.1994). The refractive index of a vegetable oil is an easy test fort he identify or purity of an oil. Both density and viscosity of oil tend to decrease with increase temperature (Dowd2011).

Viscosity of vegetable oils is affected by some physical and chemical factors such as temperature, oil density, molecular weight, melting point and degree of unsatura-tion. Viscosity is known to be variable due to the fatty acid composition (Ergo¨nu¨ 2013). Color is important in veg-etable oil technology. The color of the refined hazelnut oil is rich in terms of yellow, also refined hazelnut oil color is darker from soybean oil and sunflower oil, dark and corn oil, but lighter than corn oil. FFA content is drop off from 1.24 to 0.23% (w/w) in refined stages (Kreps et al. 2014). Neagu et al. (2014) determined 2.588, 0.536, 0.468 and 0.366 acid values in crude sunflower, washed, bleached and deodorized sunflower oils, respectively. Neagu et al. (2014) reported that experimental density (g/cm3) of crude, washed, bleached and deodorized sunflower oil decreased with temperature increasing. While saponification values of crude sunflower, washed, bleached and deodorized sun-flower oils is determined as 212.143, 209.776, 209.476 and 209.448, respectively, iodine values of crude oil,washed, bleached and deodorized oils were determined as 85.916, 82.752, 83.562 and 83.824, respectively (Neagu et al. 2014). Another a study, free fatty acid of groundnut oil decrease after refining from 2.82 to 2.02% (Aluyor et al.

Table 1 Physico-chemical properties of hazelnut oil obtained from refining stages Process

Stages

Acidity (%) Peroxide Value (meqO2/kg) Iodine value (mgI2/100 g) Vitamin E (mg/ 100 g) Saponification number (mg KOH/ g) Unsaponifiable matter (%) Density (mL/ cm3)

Crude 1.44 ± 0.09*a 12.5 ± 0.21a 85.53 ± 1.15bc 23.78 ± 0.76ab 198.6 ± 2.34b 1.09 ± 0.13ab 0.915 ± 0.009a Neutralized 0.14 ± 0.01b** 11.7 ± 0.32b 85.06 ± 1.21c 25.11 ± 0.81a 200.2 ± 1.18a 1.15 ± 0.21a 0.910 ± 0.005b Bleached 0.14 ± 0.01b 10.9 ± 0.54c 85.93 ± 0.98b 22.65 ± 0.64b 200.0 ± 1.36a 1.12 ± 0.27a 0.910 ± 0.07b Winterized 0.12 ± 0.03c 10.4 ± 0.27c 87.44 ± 1.17a 18.14 ± 0.87c 197.5 ± 2.53c 0.42 ± 0.09c 0.905 ± 0.03c Deodorized 0.12 ± 0.01c –*** 87.45 ± 1.57a 16.26 ± 0.98d 197.8 ± 3.65c 0.20 ± 0.05d 0.905 ± 0.03c Process Stages Refractive index Cold point (oC) Viscosity (mPA) Colour

Red Yellow Blue Dark Crude 1.457 ± 0.009c - 4.3 ± 0.0e 67.95 ± 0.16d 3.9 (100) 70 0.0 B 0.8 N Neutralized 1.466 ± 0.005bc - 5.5 ± 0.0d 82.60 ± 0.11a 5.1 (5.2500) 70 0.0 B 0.0 N Bleached 1.469 ± 0.003a - 6.5 ± 0.0c 68.15 ± 0.19c 1.3 (5.2500) 14 0.0 B 0.1 N Winterized 1.467 ± 0.005b - 7.7 ± 0.0b 67.30 ± 0.17d 1.4 (5.2500) 8.6 0.0 B 0.1 N

Deodorized 1.467 ± 0.009b - 9.5 ± 0.0a 69.85 ± 0.15b 1.6 (5.2500) 11 0.0 B 0.0 N

* Each value is expressed as mean ± standard deviation

**Values in each column with different letters are significantly different (p \ 0.05) ***Undetermined

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2009). In addition, saponification, iodine value, refractive index and specific gravity values decrease after refining from 192.00 mgKOH/g to 188.00, 91.00 to 86.00 mg/ 100 g, 1.462 to 1.460 and 0.916 to 0.915, respectively (Aluyor et al.2009). No significant variation (p [ 0.05) in the iodine value was observed among all the peanut oil samples in refining process (Zhu et al.2016). Onyema and Ibe (2016) indicated that there were decrease in some chemical properties (FFA, peroxide value and saponifica-tion value). Onyema and Ibe (2016) also determined to increase of unsaponifiable matter from crude oil to refined oil. They have found to increase from 24.8% to 31.9%, 25.05% to 33.15%, for crude and refined respectively palm oil and soybean oil but decrease of 32.3% to 30.55% for crude and refined palm kernel oil. Viscosity values of chemically refined sunflower oil (crude, neutralized, bleached, winterized, deodorized) were 7.03 Pa.s, 7.18, 8.00, 6.67 and 6.58 Pa.s, respectively (Ergo¨nu¨ 2013). Ergo¨nu¨ and Ko¨seog˘lu (2014) determined to change of tocopherol amounts during chemical and physical refining process of varied vegetable oils. Ruiz-Mendez et al. (1997) reported free fatty acids are high ration decreased in neu-tralization phase. Similar results were obtained on indus-trial refined oils (Hopia 1993). In addition, while unsaponifiable matter of olive oil decrease during alkali-refined and physically-alkali-refined compared to crude olive oil, unsaponifiable matter of alkali and physically-refined sunflower and soybean oil partly increased (Ruiz-Mendez et al.1997).

Fatty acid compositions of hazelnut oil taken from each refining steps are presented in Table2. While palmitic acid contents of oil samples change between 4.39%

(deodorized) and 5.08% (bleached), stearic acid contents of oil samples varied between 2.24% (deodorized) and 2.74% (neutralized). In addition, while oleic acid contents of hazelnut oils taken from refining steps change between 84.08% (winterized) and 84.68% (neutralized), linoleic acid contents of oil samples ranged from 6.79% (neutral-ized) to 8.56% (winter(neutral-ized). Also, while total saturated fatty acids of oil samples change between 6.84% (deodorized) and 8.00% (neutralized), total unsaturated fatty acid contents of refined hazelnut oils varied between 92.00% (neutralized) and 93.16% (deodorized). While oleic acid contents of groundnut oil decrease from 58.6871 to 57.6784% during refining, palmitic acid content of oil sample increased from 8.2280 to 11.7378% (Aluyor et al. 2009). Achinewhu and Akpapunam (2005) and Aluyor et al. (2009) reported that there is a decline at least in fatty acid composition from its crude form to refined form. Zhu et al. (2016) said that peanut chemical refining did not have much effect on the fatty acid composition, except for cer-tain changes of several individual fatty acids.

Sterol contents of hazelnut oil samples obtained from refining steps are shown in Table3. While campesterol contents of oil sample change between 3.56% (deodorized) and 4.87% (crude), delta-5,23-stigmastadienol contents of oil varied between 0.48% (deodorized) and 2.87% (neu-tralized). The highest sterol had b-sitosterol, its amount changed between 54.98% (deodorized) and 73.96% (crude oil). In addition, while delta-7-stigmasterol contents of hazelnut oil are determined between 1.85% (neutralized) and 4.01% (winterized), delta-7-avenasterol contents of hazelnut oil obtained from refining stages varied between 4.85% (crude oil) and 28.33% (deodorized).). It was

Table 2 Fatty acid composition of hazelnut oil obtained from refining stages (%)

Fatty acids Crude oil Neutralized Bleached Winterized Deodorized Palmitic 4.86 ± 0.21*b 5.03 ± 0.13a 5.08 ± 0.09a 4.50 ± 0.07c 4.39 ± 0.17d Palmitoleic 0.12 ± 0.03c** 0.13 ± 0.01b 0.14 ± 0.01a 0.12 ± 0.03c 0.12 ± 0.03c Margaric Asit 0.04 ± 0.01a 0.04 ± 0.01a 0.04 ± 0.01a 0.03 ± 0.01ab 0.04 ± 0.01a Heptadesenoic 0.04 ± 0.01ab 0.04 ± 0.01ab 0.04 ± 0.01ab 0.05 ± 0.01a 0.05 ± 0.01a Stearic 2.72 ± 0.23a 2.74 ± 0.09a 2.63 ± 0.17b 2.25 ± 0.11c 2.24 ± 0.19c Oleic 84.30 ± 0.34a 84.68 ± 0.21a 83.76 ± 0.28b 84.08 ± 0.31a 84.26 ± 0.13a Linoleic 7.43 ± 0.09b 6.79 ± 0.11c 7.80 ± 0.19b 8.56 ± 0.15a 8.47 ± 0.28a Linolenic 0.06 ± 0.03a 0.06 ± 0.01a 0.06 ± 0.03a 0.03 ± 0.01b 0.03 ± 0.01b Aras¸idic 0.16 ± 0.03a 0.15 ± 0.07b 0.14 ± 0.03c 0.13 ± 0.01d 0.13 ± 0.05d Eicosenoic 0.13 ± 0.05c 0.13 ± 0.03c 0.13 ± 0.01c 0.15 ± 0.07b 0.16 ± 0.09a Behenic 0.05 ± 0.01a 0.04 ± 0.01c 0.05 ± 0.03a 0.04 ± 0.01c 0.04 ± 0.01c Total saturated fatty acid 7.83 8.00 7.94 6.95 6.84 Total unsaturated fatty acid 92.17 92.00 92.06 93.05 93.16 * Each value is expressed as mean ± standard deviation

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observed significantly differences between the sterol con-tents of hazelnut oils obtained from refining stages (p \ 0.05). Especially during neutralization most of the phytosterols pass through the soap stock. (Sciancalepore 1981; Karaali 1985). During refined minor composition (Vitamin E and sterol) results are compatible with the findings of other researchers (El-Mallah et al. 2011). During physical refining, the effect of both oil type and refining steps were significantly important, whereas in chemical refining only the effect of oil type was found statistically important (Ergo¨nu¨ 2013). In terms of fatty acids composition were found to very low loss but linoleic and linolenic were nearly kept constant. The cause of fatty acids composition loss reported as bleaching soil absorp-tion and oxidaabsorp-tion (El-Mallah et al.2011).

Conclusion

While acidity, peroxide value, color (red, yellow and dark), vitamin E, unsaponifiable matter, density of hazelnut oil decrease during refining stages, iodine value, cold point and viscosity values increased. No change in the fatty acid composition of the hazelnut oil during refining was observed. However, there was a statistical differences (p \ 0.05). Palmitic, stearic and oleic acids showed con-stant values at the refinement stages. Sterol contents of oils varied depending on refinement stages. While the b-sitos-terol, d,5-avenasb-sitos-terol, d-5,24-stigmastadienol contents of hazelnut oil decreased while the d-7-stigmasterol and avenasterol contents increased.

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Table 3 Sterol contents of of hazelnut oil obtained from refining stages (%)

Sterols Crude oil Neutralized Bleached Winterized Deodorized Campesterol 4.87 ± 0.37*a 3.96 ± 0.48b 3.74 ± 0.27b 4.59 ± 0.16a 3.56 ± 0.13b Stigmasterol 1.23 ± 0.09a** 0.93 ± 0.07b 0.90 ± 0.11b 1.22 ± 0.09a 0.83 ± 0.13c d-5,23-Stigmastadienol 2.77 ± 0.23a 2.87 ± 0.31a 2.25 ± 0.27c 2.49 ± 0.19b 0.48 ± 0.07d Clerosterol 0.91 ± 0.03b 0.99 ± 0.18a 0.29 ± 0.21d 0.41 ± 0.03 cd 0.42 ± 0.09c b-sitosterol 73.96 ± 1.68a 67.30 ± 1.71c 58.64 ± 1.86d 71.09 ± 1.54b 54.98 ± 1.41e d-5-Avenasterol 7.85 ± 0.61a 7.37 ± 0.13d 7.20 ± 0.27de 7.69 ± 0.58b 7.46 ± 0.39c d-5,24-Stigmastadienol 1.24 ± 0.05b 0.66 ± 0.07e 1.08 ± 0.09c 1.45 ± 0.31a 0.68 ± 0.09d d-7-Stigmastenol 2.33 ± 0.18d 1.85 ± 0.13e 3.18 ± 0.31c 4.01 ± 0.37a 3.27 ± 0.26b d-7-Avenasterol 4.85 ± 0.98e 14.06 ± 0.51c 22.72 ± 1.49b 7.05 ± 0.38d 28.33 ± 1.21a * Each value is expressed as mean ± standard deviation

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Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Şekil

Table 1 Physico-chemical properties of hazelnut oil obtained from refining stages Process
Table 2 Fatty acid composition of hazelnut oil obtained from refining stages (%)
Table 3 Sterol contents of of hazelnut oil obtained from refining stages (%)

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sorusuna verilen cevaplar ve yürüme testi sonuçları arasında istatistiksel olarak anlamlı bir fark olduğu tespit edilmiĢtir (p=0. „‟Tamamen‟‟ cevabı

3095 Sayılı Kanuni Faiz ve Temerrüt Faizine İlişkin Kanun Hükümleri 3095 sayılı Kanun, (e) BK ve (e) TTK’da yer alan oranlara dair hükümlerin uygulanma

Linezolidin doku penetrasyonunun son derece iyi oluşundan dolayı; tedavisi oldukça zor olan, bakteriyemik veya bakteriyemik olmayan endokarditte, santral sistem