Measuring perception of acidity and sweetness in kiwifruit

Abstract

Once mature, the titratable acidity of kiwifruit (TA) remains relatively constant, but, as the fruit continues to soften and ripen, the perception of acidity upon consumption differs. The wealth of sensory and consumer research into kiwifruit clearly indicates that the perception of sweetness and acidity, and the resulting sweet/sour balance, are critical factors in achieving consumer acceptance. However, often only sweetness is estimated or controlled for in such studies by measuring ripe soluble solids content (SSC) or dry matter (DM). Typical methods of measuring acidity in kiwifruit often rely on lysing of cells through a freeze/thaw cycle and/or grinding tissue, and hence reflect the maximum amount of TA present. However, this may not represent the relative acidity perceived upon chewing, where only a fraction of the cells may be broken to release their contents into the mouth. Furthermore, the release of cellular contents upon chewing is influenced by fruit firmness, and the perception of acidity is influenced by SSC; hence, fruit quality has a considerable impact on the sweet/sour balance and ultimately consumer acceptance. Data will be presented from a consumer study that explored the relationship between the perception of sweetness and acidity in kiwifruit juices and a corresponding kiwifruit flesh sample. From kiwifruit that ranged in firmness and SSC, juices were prepared using increasingly destructive methods, in an effort to identify the method of sample preparation for measuring acidity and sweetness that best correlated with taste perception from chewed flesh.