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Size, shape, and identity of surface crystals and their relationship to sensory perception of grittiness in soft smear-ripened cheeses

Polowsky, P.J., Kindstedt, P.S., Hughes, J.M.
Journal of dairy science 2018 v.101 no.12 pp. 10720-10732
European Union, X-ray diffraction, calcite, calcium, cheese ripening, cheeses, crystallization, crystals, image analysis, magnesium, magnesium ammonium phosphate, phosphorus, polarized light microscopy, protected designation of origin, sensation, sensory evaluation, sensory properties, texture, traditional technology, wheels, United States
Soft smear-ripened cheeses undergo extensive surface crystallization and radial demineralization of calcium, magnesium, and phosphorus, which likely contributes to radial softening during ripening. Furthermore, anecdotal evidence suggests that grittiness is a common characteristic of smear-ripened cheeses. The primary aims of the present study were to evaluate the intensity of perceived grittiness while assessing other key sensory attributes in US artisanal and European protected designation of origin smear-ripened cheeses, and to relate perceived grittiness to the size, shape, and identity of crystals present in the cheese surface smears. Fully ripened wheels of 24 different varieties of smear-ripened cheeses, 16 produced in the United States and 8 in the European Union, were obtained from retail sources. A trained sensory panel (n = 12) was employed to evaluate intensity of grittiness. Crystals present in the cheese smears were identified by powder X-ray diffractometry and polarized light microscopy, and further evaluated in polarized light microscopy micrographs by image analysis for size and shape characteristics. Mean sensory scores for the 24 cheeses ranged from no perceived grittiness to easily identifiable grittiness. Surface crystals included ikaite, struvite, calcite, and brushite, and mean crystal length and area ranged among cheeses from 27 to 1,096 μm, and 533 to 213,969 μm2, respectively. Panel threshold for grittiness occurred at a mean crystal length of about 66 μm and mean crystal area of about 2,913 μm2. Cheeses with mean values at or below these thresholds displayed negligible perceived grittiness. In contrast, for cheeses with mean values above these thresholds, the mean sensory scores for grittiness were highly correlated with mean crystal length and crystal area (r = 0.93 and 0.96, respectively). Results suggest that surface crystals in soft smear-ripened cheeses influence sensory perception of texture in complex ways that likely include radial softening and grittiness development. A better understanding of factors that govern surface crystal formation may lead to improved control over crystallization and more consistent cheese texture.