Sunflower Oil Composition and Properties

Sunflower Oil: Introduction

• Two basic types of sunflower: oilseed and non-oil
• Oilseed type: small black seeds, thin hull (20-25% of total seed weight), 40% oil content
• Non-oil type: larger seeds, thicker black-and-white striped hull, 30% oil content, used for bird feed and confectionery
• Seed size and position in the head influence the oil content, with seeds in the periphery being larger, containing more oil
• Fatty acid composition changes based on seed position
• Linoleic and palmitic acid increase, oleic acid decreases from the periphery of the head

Sunflower Oil: Composition

• Hull Composition: N-free extract (31%), fiber (61%), protein (3%), ash (3%)
• Kernel Composition: Oil (67%), protein (21%), fiber (3%), ash (3%), N-free extract (6%)

Sunflower Oil: Harvesting and Temperature Effects

• Harvesting time affects oil composition, with linoleic acid increasing after the 14th day post-flowering and oleic acid decreasing.
• Temperature and light affect oil composition: linoleic acid content increases with temperature difference, oleic acid content is lower for seeds sown in August (lowest mean temperature).
• Maturity phase affects oil content: Linoleic acid content decreases and oleic acid increases during this stage. This is also affected by the weather conditions

Sunflower Oil: Chemical and Physical Properties

• Fatty Acids: Linoleic acid (high concentration), followed by oleic acid. Other major fatty acids: palmitic acid and stearic acid.
• SFA: Regular Sunflower oil has less saturated fatty acid content than in cottonseed, peanut, corn, and soybean oils.
• LnA: Low LnA content provides good oxidative stability.
• TAG distribution: Low solidification point (16-19°C) allowing storage of products like mayonnaise in refrigerators.

Sunflower Oil: Nonacylglycerols

• Phospholipid content: 0.5–1.2% in crude sunflower oil; higher in solvent-extracted oils
• Most phospholipids are hydratable and can be removed via water degumming.
• Tocopherol levels: Crude oil contains alpha-tocopherol, beta-tocopherol, gamma toco, delta toco, alpha, gamma and delta tocotrienols as antioxidants (values given)

Sunflower Oil: Other Components

• Aliphatic Compounds and Terpenoids: Squalene is the primary terpenoid, with low concentrations in regular sunflower oil. Aliphatic alcohol level is around 100mg/100g of oil.
• Carotenoids and Chlorophyll: Low content compared to other oils, contributing to its light amber color. The color changes to a pale yellow during the bleaching process.

Sunflower Oil: Chemical Characteristics

• Codex alimentarius: Saponification value (188-194 mg KOH/g oil) and iodine value (118-141)

Sunflower Oil: Physical Characteristics

• Refractive Index: 1.461-1.468 at 40°C
• Density: 0.918-0.923 (20°C/water at 20°C)
• Viscosity: values supplied in a graph related to temperature

Sunflower Oil: Specific Heat and Combustion Heat

• Specific heat: 2.197 J/kg°C
• Combustion heat: a major parameter when using oil as an energy source

Modifications of Fatty Acid Content

• High saturated fatty acid consumption has increased the risk of coronary heart disease.
• Traditional sunflower oil contains 11-12% of saturated fatty acids but attempts to lower this to 6% are ongoing.
• New industrial use of vegetable oils: attempts to increased saturated fatty acid content

High-Oleic Sunflower Oil

• Typical composition: 66-72% linoleic acid, 12% saturated (palmitic and stearic), 16-20% oleic acid, and less than 1% alpha-linolenic acid
• Considered healthy due to high polyunsaturated fatty acids (PUFA) content and relatively low levels of saturated fatty acids
• High-oleic sunflower oil suits the requirements of the processing industry but does not suit nutrition recommendations for the n6/n3 ratio.

Other Characteristics and Uses

• High-oleic sunflower oil is sold under the name Sunola in Australia and used as a salad and cooking oil.
• High oxidative stability makes it preferable to use for industrial frying processes.
• Mid-oleic sunflower oil used in the manufacture of potato chips

Sunflower Seed Modifications

• Semi-dwarf and dwarf sunflower varieties developed for smaller size and better handling, needed in different climates
• Sunola and Sunwheat developed with 25-35% shorter height and adapted to handling requirements

Sunflower Oil Extraction

• Partially dehulled seeds are generally used, with 8% moisture and 10% residual hull.
• Cooking of the seeds is used to adjust the moisture content to 3% - 4.5% and adjust the temperature.

Crude Oil Treatment

• Sunflower oil has moderate quantities of carotenoids and xanthophylls but low levels of chlorophylls
• Bleaching is done with less than 1% bleaching earth

Degumming

• Major phospholipids are phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), and phosphatidic acid (PA).
• Most phospholipids are soluble and can be removed by water degumming.

Dewaxing

• Wax content in crude sunflower oil and waxes crystallize and can cause issues with turbidity
• Winterization technique used to remove wax during cooling and result in crystallized waxes
• Temperature crucial in this process as the solubility of wax in oil changes with temperature.

Physical Refining

• The success of physical refining largely depends on efficient removal of nonhydratable phosphatides and addition of phosphoric or citric acid
• Part of the unsaponifiable matter, volatile oxidation byproducts, and flavor components are also distilled

Deodorization

• Loss of tocopherols in the oil is noteworthy for sunflower oil
• Deodorization does not have significant differences between sunflower and other vegetable oils

Cold-Pressed Sunflower Oil

• Virgin oils (including cold pressed sunflower oil), are appreciated due to their nutritional characteristics and desirable flavor.
• Cold-pressing at low temperatures maintains characteristics

Hydrogenation

• Sunflower oil is hydrogenated in some producer countries to produce shortening and margarine
• The addition of hydrogen affects the trans-fat content in the oil as well as its crystalline structure when cooled. The structure of the hardened oil can be improved using other oils eg. cottonseed oils, and additives

Storage and Deterioration

• Key factors affecting shelf life: extraction method, purification, antioxidants, packaging, time, temperature, light
• Composition of refined oil: degree of unsaturation (oleic, linoleic, SFA) affects oxidative stability and AOM (active oxygen method)

Addition of Antioxidants

• TBHQ (butylhydroxytoluene) proved to be the most effective antioxidant for sunflower oil
• The oil produced via a solvent extraction method presented a lower rate of oxidation than the cold pressed oil. Differences in phospholipids between the two types of oils can explain the differences in oxidation rates.

Uses of Sunflower Oil

• Regular sunflower oil is used extensively as salad oil and cooking oil due to its light flavor, golden-yellow color, and high oxidative stability
• High-oleic sunflower oil is used in non-dairy creamer formulas and other products requiring a long shelf life without refrigeration

Margarines

• The oil's tendency to crystallize as beta form must be controlled to ensure a smooth margarine texture
• Addition of 5-15% of beta'-crystallizing hydrogenated oils in margarine formulations aids in achieving desirable creaminess