Yogurt enrichment with functional asparagus fibre.: Effect of fibre extraction method on rheological properties, colour, and sensory acceptance

In the asparagus-processing industry, the by-products constitute around 50% of the total weight. These by-products are rich in fibre and bioactive compounds which could be advantageously employed in human nutrition. In the present work, yogurts were enriched with fibre obtained from the non-edible part of asparagus shoots to assess how the method of extraction (water or ethanol) and then drying (oven or lyophilisation) affects its performance. Fibre incorporation increased the consistency of the yogurts (higher eta, G', G ''), especially if the fibres had been extracted in ethanol and lyophilised. However, there were no significant changes in the viscoelastic behaviour (tan delta) for any of the fibre types. Fibres diminished the clarity and imparted a yellow-greenish colour to the yogurt, which also varied depending on the method of extraction and drying, the yogurts with water-extracted fibres being more colourful. The sample more liked according to a consumer test was the yogurt containing water-extracted and oven-dried fibre for aroma, taste, texture, and overall acceptance, and ethanol-extracted and lyophilised for colour. The consumer panel scored all the samples around to the neutral point neither like nor dislike, demonstrating that fibre obtained by all methods were equally compatible with yoghurt enrichment.