Common Problems in Soybean Oil Refining: Effective Solutions for Dark Color and Odor in Crude Oil

Analysis of common problems in soybean oil refining: How to solve the problems of dark color and off-odor in crude oil?

As a mainstay product in the edible oil market, soybean oil's quality control during the refining process is particularly crucial. Excessively dark color and off-odors are major issues affecting finished product quality and consumer acceptance. This article will analyze the causes and optimization measures of these problems from a rational technical perspective, combining real-world factory operation cases, focusing on four key stages: degumming, deacidification, decolorization, and deodorization. This aims to help oil producers improve their refining processes and enhance their product market competitiveness.

I. Causes and Improvement Strategies for Dark Crude Oil Color

The dark color of crude oil is mainly affected by the quality of raw materials and preliminary processing techniques. Common causes include high levels of impurities and natural pigments in the raw materials, insufficient degumming, and improper use of activated carbon for decolorization.

Refining degumming conditions to avoid colloidal residue is the first step in preventing crude oil from turning black. Furthermore, precise selection and control of decolorizing agents have a significant effect on removing pigments and oligomers.

II. Causes of Odor Generation and Optimization of Deodorization Process

The off-odor of soybean oil mainly originates from the release of free fatty acids, oxidation products, and volatile substances that are not completely removed. The off-odor is particularly noticeable when the free fatty acid (FFA) content exceeds 0.5%, and the oil's storage stability decreases. The deacidification and deodorization steps specifically address this challenge.

Deacidification control: Reasonably control the alkali refining reaction conditions, separate soap stalks in a timely manner, and keep the free fatty acid content below 0.3%. It is recommended to control the temperature at 70-80℃ and adjust the pH range to 7-8 to ensure that the reaction is sufficient but not over-saponified, and reduce the quality fluctuations caused by the return of soap stalks to oil.

Deodorization process: High vacuum conditions (2-5 mbar) and high-temperature steam injection are used, with the temperature generally controlled within the range of 200-230℃, to remove volatile odor substances such as free fatty acids and aldehydes. A sufficient steam soaping process is included to ensure that odor substances are efficiently removed, improving the sensory quality of the oil.

III. Key Points for Maintaining the Storage Stability of Edible Oils

The oxidative stability of oils is directly related to their color, aroma, and flavor. In industry standards (such as GB/T International Standard for Oils and Fats), peroxide value (POV) and acid value (AV) are key indicators. It is recommended to strictly control storage temperature and humidity, avoid high temperatures and strong light exposure, and choose food-grade packaging that is opaque and does not easily allow oxygen to permeate.

Actual factory trials show that adding appropriate amounts of natural antioxidants such as tocopherol (vitamin E, 50-100 ppm) can effectively improve end-storage stability, reduce peroxide value, and extend shelf life.

IV. Industry Standards and Operational Self-Inspection Suggestions

In accordance with the Chinese national standard GB 15680-2009 "Technical Specifications for Refining Edible Vegetable Oils" and the international Codex Alimentarius standard, the production operation should strictly monitor the key points of refining and implement process quality tracking.

It is recommended that production line managers conduct regular self-inspections, including but not limited to:

• Raw material crude oil quality inspection (including impurities, color value, acid value)
• Degumming pH and temperature fluctuation monitoring
• Evaluation of the efficiency of deacidified soap residue separation
• Decolorization time and adsorbent quality testing
• Deodorization temperature, vacuum level and steam parameters recorded

These measures can effectively reduce the quality decline caused by over-processing, making the finished oil products more stable and in line with market demand.