INFLUENCE OF SEED MOISTURE OF AILANTHUS ON COLD-PRESSED OIL YIELD

ABSTRACT

This article is devoted to the study of the effect of the initial seed moisture content of Ailanthus altissima on oil yield during cold pressing. Ailanthus altissima is a fast-growing tree whose seeds represent a promising raw material for the production of vegetable oil rich in biologically active components. The study investigates the impact of pre-treatment of seeds with varying moisture levels (5%, 8%, 10%, 12%, and 15%) on the quantitative indicators of oil yield. The results demonstrate that increasing seed moisture content up to an optimal level promotes higher oil yield due to the softening of cell walls. However, excessive moisture reduces the efficiency of the pressing process. The obtained data can be applied to optimize the industrial-scale production technology of Ailanthus altissima seed oil.

АННОТАЦИЯ

Настоящая статья посвящена изучению влияния начальной влажности семян айланта высочайшего (Ailanthus altissima) на выход масла при холодном прессовании. Айлант высочайший — быстрорастущее дерево, семена которого являются перспективным сырьём для получения растительного масла с биологически активными компонентами. В работе проведено исследование влияния предобработки семян с различной влажностью (5%, 8%, 10%, 12%, 15%) на количественные показатели выхода масла. Результаты показывают, что повышение влажности до оптимального значения способствует увеличению выхода масла за счёт размягчения клеточных оболочек, однако чрезмерное увлажнение снижает эффективность прессования. Полученные данные могут быть использованы для оптимизации технологии получения масла семян айланта в промышленном масштабе.

Keywords: seed moisture, cold pressing, Ailanthus altissima, oil yield.

Ключевые слова: влажность семян, холодный отжим, Ailanthus altissima, выход масла.

Introduction

Ailanthus altissima (Mill.) Swingle, commonly known as the tree of heaven, belongs to the family Simaroubaceae and is widely recognized for its remarkable adaptability to diverse environmental conditions and rapid growth rate. Despite its classification as an invasive species in numerous regions, Ailanthus altissima has attracted growing scientific interest owing to its rich content of biologically active compounds present in various plant parts, particularly in the bark, leaves, and seeds [1,2].

Among these, the seeds of Ailanthus altissima are considered a promising source of plant-based oil, which is known to possess significant antioxidant potential and possible pharmacological properties. Due to the increasing demand for natural bioactive oils, it becomes crucial to explore efficient methods for oil extraction, with a particular focus on the key factors that influence oil yield [1,3].

One of the most critical parameters affecting the efficiency of oil extraction is the initial moisture content of the raw material. Previous studies have demonstrated that optimal seed moisture levels contribute to enhanced oil recovery by softening cell walls and decreasing the viscosity of intercellular substances, thus facilitating oil release during pressing. However, excessive seed moisture can have adverse effects, such as the formation of emulsions, increased oil retention within seed cake, and difficulties in oil separation [4,6].

This study aims to determine the optimal initial moisture content range for Ailanthus altissima seeds that ensures the highest oil yield during cold pressing. Additionally, the study seeks to investigate how variations in seed moisture levels influence the quantitative oil yield and potentially affect the quality of the extracted oil.

Materials and methods

Plant Material

For this research, mature seeds of Ailanthus altissima were collected from wild populations in the Andijan region of Uzbekistan during September 2024. The seeds were carefully cleaned by removing mechanical impurities, dust, and plant debris, ensuring that only healthy and intact seeds were used in subsequent experiments.

Sample Preparation and Moisture Adjustment

The cleaned seeds were divided into five experimental groups, each weighing 500 grams. To achieve different moisture contents, the seeds were moistened with distilled water to attain target moisture levels of 5%, 8%, 10%, 12%, and 15%. Water was applied via uniform spraying, and the seeds were thoroughly mixed and sealed in airtight containers. The samples were conditioned at room temperature (22–25°C) for 24 hours to allow for uniform moisture distribution within the seed tissues.

Moisture content of the seeds was determined using two complementary methods: (1) the standard gravimetric method involving drying the samples in a laboratory oven at 105°C until a constant weight was achieved; and (2) instrumental analysis using the electronic grain moisture meter ‘LDS-1G,’ which is calibrated for accurate moisture determination in cereal grains.

Cold Pressing Procedure

Oil extraction was performed via cold pressing using a laboratory-scale screw press. All samples were processed under identical and controlled technological conditions: pressing temperature was maintained at 25°C, and the screw shaft rotation speed was set at 30 revolutions per minute (rpm). The extracted oil was collected immediately, followed by filtration through standard filter paper to remove solid residues [8,9].

Calculation of Oil Yield

The oil yield was quantitatively expressed as the percentage ratio of the mass of extracted oil to the initial mass of raw seeds. Each experiment was repeated in triplicate, and average values were calculated to ensure the reliability of the results.

Oil Extraction Method and Its Rationale

Oil extraction from Ailanthus altissima seeds was performed using the cold pressing method on a laboratory screw press. This method was chosen as the most suitable approach due to its significant advantages in preserving the natural biochemical composition of the extracted oil. Cold pressing is a mechanical extraction technique that operates at low temperatures, typically not exceeding 40–45°C, which is critical for preventing the thermal degradation of biologically active substances such as polyunsaturated fatty acids, polyphenols, and vitamins. Compared to alternative extraction methods, including solvent extraction or hot pressing, cold pressing is considered more environmentally friendly, as it excludes the use of chemical solvents and does not leave harmful residues in the final product. It also ensures a simpler and safer technological process with lower energy consumption, which is beneficial for both laboratory studies and industrial production [10,11]. Furthermore, cold pressing aligns with current consumer preferences for natural and minimally processed oils, which are valued for their superior organoleptic properties, higher nutritional value, and overall safety. These multiple advantages made cold pressing the optimal method for this study, allowing for an accurate assessment of the influence of seed moisture content on oil yield while maintaining the natural quality and purity of the product. All pressing procedures were carried out under identical standardized conditions, with a pressing temperature of 25°C and a screw rotation speed of 30 revolutions per minute (rpm). The oil obtained after pressing was immediately filtered through paper filters to remove any residual seed particles before analysis.

Results and discussion

The experimental results revealed a pronounced dependence of oil yield on the initial moisture content of Ailanthus altissima seeds. At the lowest tested moisture level of 5%, the oil yield was the lowest, amounting to 22.4%. As seed moisture increased, a progressive improvement in oil yield was observed, reaching a peak of 29.8% at a moisture content of 10%. This can be attributed to the optimal hydration of seed tissues, facilitating cell wall rupture and oil release.

Further elevation of moisture content to 12% resulted in a slight reduction in oil yield (28.7%), which could be explained by the onset of emulsion formation and reduced pressing efficiency. A sharp decline in oil yield was recorded at 15% moisture content, where oil recovery dropped to 25.1%, likely due to excessive water content hampering oil separation during pressing.

Additional analysis, conducted according to the manufacturer's guidelines using the LDS-1G grain moisture meter, confirmed that the optimal moisture level corresponded to approximately 11.7%. When measured on 118 g seed samples, the total bulk density reached 518 g/L, further indicating optimal seed preparation conditions. (Fig. 1).

Figure 1. Moisture content, mass, and bulk density values of Ailanthus altissima seeds

The obtained results are consistent with data from studies on other oilseed crops such as soybean and sunflower, where optimal raw material moisture promotes the swelling of cell walls and facilitates the rupture of seed coats under mechanical pressure. However, excessive moisture leads to the formation of hard-to-separate emulsions and increases the viscosity of the seed cake, thereby reducing the efficiency of oil filtration [12,13].

Thus, it can be concluded that the optimal moisture range for Ailanthus altissima seeds to achieve maximum oil yield through cold pressing is 8–10%.

Conclusion

This study established that the initial moisture content of Ailanthus altissima seeds has a significant impact on the efficiency of oil extraction. The optimal moisture level is in the range of 8–10%, which ensures the highest oil yield while preserving its quality. The obtained findings can be applied in the development of technological processes for the industrial processing of Ailanthus altissima seeds in the oil and fat industry.

Further research may focus on investigating the influence of seed moisture on the chemical composition and antioxidant properties of the extracted oil.

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