Extraction is a mandatory process for most of the industries, especially in the food processing industry to obtain the targeted compounds from various sources such as plant or seed samples. This review paper provides information about various extraction techniques that are normally used in the edible oil extraction industry. Five extraction techniques are presented in this paper. Among all the techniques presented in this paper, pressing and solvent extraction methods are considered as traditional techniques while supercritical fluid extraction, microwave assisted extraction, and ultrasound assisted extractions are considered as advanced techniques. Both advantages and disadvantages of supercritical fluid extraction, microwave assisted and ultrasound assisted extractions are discussed. Furthermore, the parameters that would affect the output of each technique are included in each section. Nowadays, research is going on to further enhance the extraction method to obtain a higher extraction yield or increase the quality of the extraction product. The enhancement can be either combining two or more extraction techniques into one complete process or modifying the available technique alone. Therefore, the theoretical knowledge provided in this review will be useful for future researchers who are interested in enhancing the extraction techniques. Practical Applications: Extraction is a mandatory process in edible oil extraction industry. Extraction industry is always looking for a process which is high efficiency and low extraction cost. Therefore, various advanced techniques or treatments are applied to optimize the oil yield and shorten the extraction time. This paper provides a review on various techniques by summarizing both advantages and disadvantages of each technique. The information can be very useful for improving the current extraction technique to further optimize the oil yield or enhance the quality of oil.

This study aims to increase the hazelnut oil yield using ultrasound as initial treatment in hexane solvent extraction. A Box–Behnken design was applied to optimize the ultrasound amplitude (30%, 60%, and 90%), solvent to solid ratio (6:1, 8:1, and 10:1) and extraction temperature (28, 38, and 48°C). The results showed that increasing all these variables would increase the oil yield. The oil extraction were optimum at 90% ultrasound amplitude, 10:1 solvent to solid ratio, and 48°C of extraction temperature. Effect of extraction time on oil yield was studied at optimum conditions. The maximum oil yield was achieved at 75 min of extraction time with 15‐min initial sonication. The maximum oil yield in ultrasound‐assisted extraction was around 88%. Ultrasound treatment had increased 4% of oil yield from the control. Fourier‐transform infrared spectroscopy results showed that the extracted hazelnut oil has the similar functional groups as other edible oils. Practical applications Hazelnut oil is one of the edible oils that widely been used in food processing. Besides, hazelnut oil has specific contribution in addressing health issues, where it can reduce cholesterol level in human body. This research introduces the optimized extraction process on hazelnut oil to the food manufacturer. With the presence of ultrasound treatment, hazelnut oil can be extracted in shorter time. Therefore, it tends to introduce low cost and healthy hazelnut oil to the consumer.

In this study, ethanol was used as a polar solvent to extract hazelnut oil, with ultrasound aid in the first 15 min of extraction. A Box–Behnken design was used for optimization in term of ultrasound amplitude (30%, 60%, and 90%), extraction temperature (28, 38, and 48°C), and extraction time (30, 60, and 90 min). All three factors showed positive effects on the oil extraction. The results showed that the oil yield and quality of extracted oil were significantly affected by the application of ultrasound. Ultrasound treatment had increased the oil yield from 38.93% up to 79.88%. The optimum conditions were identified at 90% of ultrasound amplitude, 29°C of extraction temperature, and 51 min of extraction time. Under these conditions, the predicted maximum oil yield was 55.39% with the minimum FFA value, iodine value and peroxide value of 1.75%, 14.52 g/100 g, and 10.50 meq g O2/kg, respectively. Practical applications Plant oil has become the first choice for edible oil due to large percentage of unsaturated fatty acid, which has been reported that it could help to reduce the bad cholesterol in human body. Hexane is the solvent that commonly used in solvent extraction stage but it is highly volatile and might cause safety issue for extraction plant. Therefore, this study aims to use ethanol to replace hexane. This research introduces the optimized ultrasound‐assisted ethanol solvent extraction process to the manufacturer. Ultrasound could enhance the oil yield which can produce low‐cost hazelnut oil to the consumer.

Nowadays, most of the researches focus on enhancing the oil yield by adjusting the various process parameters or searching for alternative techniques. There is only limited information on investigating the effects of various extraction parameters on kinetic mechanism during oil extraction. The mechanism data can provide additional information to the industry when optimization is needed. Previous work had investigated the effect of ultrasound in extraction process. The main purposes of this study are to apply osmotic dehydration as pretreatment and to investigate the effects of ultrasound amplitude, concentration of osmotic dehydration, and dehydration time on extraction mechanism of hazelnut oil. The kinetic modeling showed that So and Macdonald model was more suitable to describe the mechanism of hazelnut oil extraction with higher R 2 values ranged from 0.944 to 0.987 as compared with Perez et al. model. The results showed that applying 30% ultrasound amplitude in dehydration stage could increase the mass transfer coefficient for diffusion step (k d ) from 0.019 to 0.044 min −1 due to cavitation effect. Besides, 15% concentration of osmotic solution could limit the diffusion step with lowest k d value of 0.055 min −1 as compared with 5 and 10% concentrations due to blocking of surface by solute in higher concentration of osmotic solution. Lastly, increasing the dehydration time from 45 to 150 min could enhance the oil diffusion process with k d values increased from 0.058 to 0.075 min −1 due to lower moisture content in sample.

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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 applicationsMost 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.

In this study, ultrasound treatment was used to enhance the oil yield of hazelnut oil. The oil was extracted by using hexane with 15 min ultrasound treatment initially. Ultrasound amplitude (30, 60 and 90%), solvent to solid ratio (6:1, 8:1 and 10:1 mL/g) and extraction temperatures (28, 38 and 48°C) gave positive effect on oil yield. Higher oil yield of 88.78% was achieved at highest settings of ultrasound amplitude, solvent to solid ratio and temperature as compared to 69.57% obtained from the lowest settings of those parameters. Characterization of extracted oil in terms of iodine value, acid value, and peroxide value were carried out in this study. The results showed that ultrasound treatment would not significantly (p>0.10) affect those values. All the values obtained were in the range of acceptable levels for edible oil. In term of fatty acid, gas chromatograph analysis results showed that around 9% of saturated and 91% of unsaturated fatty acids were observed in hazelnut oil for all the amplitudes applied. More crack structures were observed on the surface of hazelnut samples after ultrasound treatment under scanning electron microscopy images, which could enhance the oil yield. This concluded that extraction with ultrasound aid could be used as an alternative extraction method for hazelnut oil with no negative impact on oil quality.

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