Dados do Trabalho

Título

MECHANICAL PROPERTIES OF HEAT-SET AND COLD-SET GELS PREPARED FROM LUPIN PROTEIN ISOLATE

Introdução

Lupin is a vegetable with a high protein content, (~40% w/w), similar to soybeans. Despite the known emulsifying property and some studies on the gelling capacity, a deeper understanding of the gel formation of lupin protein isolate (LPI) is still necessary. The objective of this study was to evaluate the influence of different gelation methods (heat-set - HS and cold-set via transglutaminase crosslinking - CS) on the viscoelastic properties of the gels formed.

Material e Métodos

For that, the isolate was obtained through alkaline extraction (pH 9.0), followed by isoelectric precipitation (pH 4.5). Oscillatory rheological properties within the linear viscoelastic domain were evaluated by producing the gels in a rheometer (TA Instruments, AR1500ex) in the concentration range of 7.5 – 15% (w/w). HS gels were formed using a temperature sweep from 25 to 90 ºC, maintaining the temperature at 90 ºC for 30 minutes, followed by a second temperature sweep to return to 25 ºC. For CS gels, the protein suspensions were initially pretreated in a water bath at 90 ºC for 1 minute to expose enzyme action sites. Subsequently, the samples were placed in the rheometer for oscillatory tests and the temperature was raised from 25 to 45 ºC.

Resultados e Discussão

A time sweep was performed for 4 hours to observe enzymatic action during gel formation. Rheological tests showed that gel formation occurred after 4000 seconds for the CS samples. The HS gels were formed within the lupin protein denaturation temperature range (80~85 ºC). As expected, after the crossover point (G' = G'') a significant increase in the storage modulus was observed. An important highlight is that CS gels were formed even at the lowest protein concentration of 7.5% (w/w), while for HS no gelation was observed in this condition.

Conclusão

Therefore, it is evident that the action of the transglutaminase enzyme made it possible to reduce the amount of protein required to form gel, in addition to being an alternative for thermosensitive components.