Naturally occurring protein–polysaccharide complexes from linseed (Linum usitatissimum) as bioemulsifiers

The use of proteins, polysaccharides, and their mixtures as bioemulsifiers is becoming increasingly important due to their high versatility and environmental acceptability. In this study, three different fractions mainly composed of protein and polysaccharides, extracted from linseed were evaluated as bioemulsifiers. The three fractions showed the same functional groups, and the amino acid profile revealed the presence of apolar amino acids which are important for forming emulsions. All negatively charged fractions were affected at pH values below 6 and above 100 mM NaCl, confirming their ionic character. Fraction 3 formed oil-in-water emulsion (O/W) and its estimated hydrophilic–lipophilic balance (HLB) value was 10–13. A phase diagram was used to produce a long-term stable O/W emulsion using Fraction 3 as a bioemulsifier. The emulsion containing linseed oil Fraction 3 and water of 5:5:90% w/w exhibited 100% stability under a wide pH range (5–11), ionic strengths (0–500 mM NaCl), and temperatures (4–70°C). Based on these results, Fraction 3, composed of 47.20% w/w protein and 37.88% w/w polysaccharide from linseed, can be considered a potential natural emulsifier for improving stability of O/W emulsions in the face of environmental stresses. Practical applications: The increasing customer demand for natural over synthetic ingredients and the rapid growth of functional foods requiring “green” additives represents an opportunity for bioemulsifiers extracted from natural resources. Linseed and the by-products after oil extraction have great potential as a source of ingredients and bioactive molecules for food applications. In this work, the capability of protein/polysaccharide fractions from linseed as bioemulsifiers to form highly stable O/W emulsions containing omega-3 rich oil was demonstrated. The designed emulsion proved to be stable at acidic pH and salt concentrations found in many food products. Moreover, thermal stability exhibited by this emulsion could also be an important characteristic for its use in food products. Phase diagram illustrating the emulsion area with linseed oil-Fraction 3-water and a microscopic image in the zone of 100% emulsion (black shaded area).