The potential of soapstock‐derived film: Cottonseed and safflower

Oilseed soapstock is seldom used today for the recovery of fatty acids, but it is often added to oilseed meal. The energy value of oilseed meal is marginally increased by the addition of soapstock. To find alternative uses for oilseed by‐products, cottonseed and safflower soapstock samples from industrial plants were characterized using American Oil Chemists’ Society recommended and modified methods. The characterization included moisture and volatiles, phosphorus and nitrogen, neutral oil, total fatty acid amount and individual fatty acid profile, and total gossypol for cottonseed soapstock samples. The characterization indicated that cottonseed soapstock samples contained a slightly larger amount of neutral oil than safflower. These soapstock samples were frozen to −40°C at 40 mm Hg for more than 8 h, thawed, and the low‐boiling compounds were removed by evaporation under reduced pressure. The freeze‐dried soapstocks were mechanically pulverized in an inert atmosphere until able to pass through a 50‐mesh screen. When these freeze‐dried soapstock particles were rehydrated with deionized water, the formation of a gel phase was observed. Casting of this gel phase onto a substrate and subsequent drying without heating resulted in a thin film, a liposomelike material, with a uniform thickness of about 0.01”. The lamination capability of freeze‐dried oilseed soapstocks by rehydration may be attributed to the formation of multiple bilayer lamellae by phospholipids from the oilseed soapstock. Due to its biodegradable nature, the use of soapstock‐derived film as a composite or by itself as an encapsulating agent is highly attractive. The potential of this liposome‐like material as a chemical carrier is discussed.