Effect of extraction conditions on composition, surface activity and rheological properties of protein isolates from flaxseed (Linum usitativissimum L)

Abstract

Flaxseed protein isolates were prepared by micellisation (FM) and isoeletric precipitation (FI). The in¯uence of preparation conditions on composition and functional properties was investigated. Contents of 0.6% phytic acid and 2.3% pentosans were found for FI, whereas FM was almost phytic acid-free and had a low content of pentosans (0.6%). Chromatography and electrophoresis identi®ed the 11S globulin (linin) as the main protein fraction in both isolates. Protein solubility, water-and oil-binding capacities, emulsi®cation and rheological properties of dispersions and gels were measured at pH 8 and 3. For the latter, interactions of protein with phytic acid and pentosans are highly probable. FI possesses a lower solubility (about 40±50%) and an overall higher water-binding capacity than FM. For FI dispersions a higher storage modulus G' than loss modulus G@ was measured, clearly pointing to the formation of protein networks. Moreover, FI formed stronger gels than FM (G' about ®vefold). The emulsifying activity, however, was distinctly lower for FI. These results point to enhanced complexation and aggregation of the isoelectric-precipitated protein isolate. INTRODUCTIONRecently, interest in¯axseed or linseed (Linum usitativissimum L) in the food and feed markets has increased owing to the reported health bene®ts attributed to¯axseed components. 1±3 The nutritional value of¯axseed meal and protein isolates has been reported to approach the corresponding data of soybean products, with a slightly lower net protein utilisation and protein ef®ciency ratio of the former. 4,5 Flaxseed protein products contain considerable amounts of mucilage (pentosans) as well as phytic acid, which distinctly in¯uence their functional properties. For example, Dev and Quensel 6±8 studied the functional properties of a¯axseed protein isolate and various protein concentrates with varying pentosan content. The pentosan content, amounting to about 5% in the isolate and between 6 and 9% in the concentrates, exerted a marked effect on the emulsifying and foaming properties and water-and oil-binding capacities as well as on the behaviour in complex food systems. However, the data do not verify that the functional properties can be attributed unambiguously to the pentosan content, owing to the additional effect

Bioactive, functional and edible film-forming properties of isolated hazelnut (Corylus avellana L.) meal proteins

“…The OACs of isolated hazelnut meal proteins were also comparable with those of non-GMO soy protein isolate (OAC: 8.23 g/g) and those of protein isolates from various red and green lentil cultivars (average OAC for 6 cultivars: 8.62 g/g) obtained with the same extraction and purification method (IEP) applied for HPI (Aydemir & Yemenicioglu, 2013). The IEP protein isolates from flaxseed meal (7.97 g/g) also showed similar OAC with the hazelnut meal protein isolates (Krause, Schultz, & Dudek, 2002). However, it is worth to note that the OACs of isolated hazelnut meal proteins were 4e8 fold higher than those of wheat protein isolate (1.73 g/g reported by Ahmedna, Prinyawiwatkul, and Rao (1999)), and those of commercial whey (1.59 g/g) and soy (1.16 g/g) protein isolates reported by Aydemir and Yemenicioglu (2013).…”

Effects of Flaxseed and pH on the Emulsion Properties of Beef by Using a Model System

“…Moreover, hydrophilic and lipophilic properties and the balance between them played a significant role in EC values. These properties of the proteins and polysaccharides reduce the interface tension between oil and water and allow emulsion formation with much lower energy input (Elizalde et al, 1988, Krause et al, 2002. Oomah and Mazza (1993) stated that major flaxseed proteins are more lipophilic than soy proteins due to the effect of the polysaccharide composition.…”

“…Mucilage consists of polysaccharides, such as pentosans, which become viscous when mixed with water (Ayad, 2010). Pentosans had a considerably effect on the rheological properties of emulsified food products (Ayad, 2010, Krause, 2002. A protein complexation with phytic acid and pentosans had significant effects on emulsifying properties (Krause, 2002).…”

“…Pentosans had a considerably effect on the rheological properties of emulsified food products (Ayad, 2010, Krause, 2002. A protein complexation with phytic acid and pentosans had significant effects on emulsifying properties (Krause, 2002). The changes in pH values might have a significant effect on this complex formation and its behaviour.…”

Formulation and Sensory Evaluation of Gluten-Free Muffins Containing Flax

“…This unique texture allows for enhanced viscosity and can be seen as favorable in certain products. Flaxseed products also have an excellent water and oil binding capacity that allows them to maintain moisture and freshness (Krause, Schultz, & Dudek, 2002). Unfortunately, this causes flax to have a relatively short shelf-life.…”