Sensory and textural changes in maturing Omani dates

The astringency and texture of the Omani date variety khalas were examined at progressive levels of maturity. Astringency was measured using descripti ve sensory analysis, while texture was measured with a texture meter. The p henolic (referred to as 'tannin') and polygalacturonic acid (referred to as 'pectin') contents of the dates were measured by colorimetry. It was found that astringency closely followed levels of tannin content measured on a f resh weight basis. The most astringent dates were at the kimri and tamar st ages of maturity, which also had the highest fresh weight tannin content of 2.8 and 1.5 g kg(-1) respectively. The least astringent dates were at the rutab stage of maturity, which also had the lowest fresh weight tannin cont ent (1.0 g kg(-1)). On a dry weight basis the tannin content decreased as t he dates matured. The texture of the dates closely followed the degree of m ethylation of the date pectin. The softest dates were at the tamar stage of maturity, with a degree of methylation of 39%, while the hardest dates wer e at the kimri stage, with a degree of methylation of 72%. The polygalactur onic acid content did not appear to affect the texture, since the fresh wei ght polygalacturonic acid content was higher at the tamar stage (11-13 g kg (-1)) than at the kimri stage (6-9 g kg(-1)) of maturity. Traditionally, da tes at the rutab stage are preferred since they are considered the sweetest and softest. Although tamar dates have the highest sugar content, owing to moisture loss, rutab dates may be preferred not necessarily for their grea t sweetness and soft texture, but rather for their lack of astringency. (C) 2000 Society of Chemical Industry.