Comparison of sensory attributes of fresh and frozen wine grape berries using Berry Sensory Assessment

Abstract

Background and Aims: We examined whether a sensory difference between fresh and frozen berries could be detected using Berry Sensory Assessment (BSA). If no sensory difference was detected, then fresh berries could be frozen and assessed later, thus reducing the problem of palate fatigue for assessors. Methods and Results: Twenty-five sensory attributes of fresh and frozen Shiraz berries were evaluated by Descriptive Analysis at three times of harvest, ‘before harvest’, ‘harvest’ and ‘after harvest’. In addition total soluble solids (TSS), pH, titratable acidity (TA) and berry mass were measured for all berry samples. Five sensory attributes were consistently different at the three times of harvest – pulp sweetness, pulp fresh fig flavour, skin colour extraction, skin bitterness and seed astringency. Frozen berries were characterised by having pulp sweetness, pulp fresh ripe fig flavour and seed astringency higher than that of fresh berries. Whereas fresh berries had skin colour extraction and bitterness higher than that of frozen samples, freezing did not affect TSS, but pH in frozen berries was higher than that in fresh berries at each harvest. Titratable acidity was lower in frozen berries at harvest and at after harvest. Freezing reduced berry mass before harvest and at each harvest compared with that of fresh berries. Conclusions: Shiraz berries that are frozen and thawed have a sensory profile different to that of fresh berries. Time of harvest affects the sensory attributes of Shiraz berries, whether they have been frozen or assessed when fresh. Significance of the Study: Freezing and thawing affect grape berry sensory attributes as assessed by BSA and berry composition and, therefore, comparing results from frozen and fresh berries may not be valid. Further work is required to determine the effect of freezing temperature, storage period and thawing procedure