DOROTHEE JACOBS*, MICHAEL STEPHANY, PETER EISNER, SIMONE TOELSTEDE

*Corresponding author

Fraunhofer- Institute for Process Engineering and Packaging IVV,

Giggenhauser Str. 35, 85354 Freising, Germany

Abstract

Pasteurised (80°C, 10 min) and ultra-high temperature (UHT) treated (140°C, 10 s) lupin protein based milk alternatives were evaluated regarding their lipoxygenase activities and sensory qualities. The sensory profiles were characterised by oat-like (orthonasal), nutty and cereal-like (retronasal) aroma attributes and sweet, bitter and astringent impressions. Thereby, the type of heat treatment did not affect the sensory profile significantly. LOX activity was reduced by about 72% after pasteurisation and by 90% after UHT treatment. The LOX associated undesired pea-like and green/grassy flavours were scored with low intensities in pasteurised and UHT lupin milk. Storage of UHT lupin milk up to 17 days showed that the residual LOX activity did not lead to any further off-flavour formation. Instead, a decrease in relevant aroma and taste attributes was detected.

INTRODUCTION

After tremendous research efforts in flavour improvement, soymilk offers an excellent milk alternative for the increasing number of lactose intolerant persons and milk allergy suffering people (1, 2). However, as soy beans are
still accompanied by negative aspects due to
genetically modified seeds and rainforest clearance, the demand for other plant-based milk alternatives has increased.

One promising raw material for the production of a plant-based milk product are lupin seeds. With a protein content of about 35% of the dry weight (3) possess lupin seeds an excellent composition for the development of plant-based protein rich products. In addition, numerous human intervention studies have demonstrated several physiological benefits like hypocholesterolemic as well as beneficial cardiovascular effects of sweet lupin (4) underlining the potential of this protein plant (5).

Soymilk flavour research revealed lipoxygenase (LOX) as a biocatalyst strongly decisive for the sensory quality (6). LOX (linoleate oxygen oxido-reductase, EC 1.13.11.12), which is prevalent in legumes, catalyses the oxidation of polyunsaturated fatty ...