Browsing by Author "Santos, Tania"
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- Amylose content of rice marketed in PortugalPublication . Correia, Paula; Santos, Tania; Lemos, Diogo; Brites, Carla; Guiné, RaquelAmylose content is considered to be the most important parameter of cooking quality in rice. Presently, rice cultivars are categorized according to amylose content into three groups: low, medium and high amylose content cultivars. The specific objective of this work is to evaluate the grain amylose content of 77 cultivars, which cover Índica and Japónica subspecies, and different types of commercial rice like, aromatic (basmati and thay), wild rice, medium rice (carlose and risotto), glutinous (waxy) and parboiled rice. Generally, these types of rice are the ones commercialized in Portugal The encountered results showed that in the same group the amylose contents were consistent, and could present great variance, as it is the case of Indica subspecies, which vary between 12.0% to 29.5%, and presenting the high amylose percentages. Thus, these intermediate amylose rices could give moist and tender upon cooking. It is also important to mention that amylose consists of linearly linked glucose molecules and is relatively resistant to digestion, hence the term “resistant starch”. This means that these rice cultivars with a greater proportion of starch in the form of amylose tend to have a lower glycemic index, and could be recommended for special diets. The low values were presented for glutinous rice (1.9% and 3.3%), which means that these type of rice do not expand in volume, are glossy and sticky, and remain firm when cooked. Intermediate values were found for parboiled rice. The majority of rice types presented low amylose content, range from 9% to 19%.
- Contribution for the characterisation of Carolino rice cultivarsPublication . Santos, Tania; Lemos, Diogo; Brites, Carla; Guiné, Raquel; Correia, PaulaRice is consumed mainly as whole grain, and quality considerations are much more important than for any other food crop. Rice grain quality preference varies from country to country and among regions. Most of the rice produced in Portugal is of the Carolino type, botanically classified as Oryza sativa ssp. Japonica. Nowadays, this rice is playing a vital role in Portuguese rice trading. Thirteen types of Carolino rice were collected and analysed for biometry characteristics, amylose content and gelatinization properties. The Carolino rices are commercially classified as long grains type-A, because they present a length higher than 6 mm and the ratio length/width lower than 3 mm), and there was observed a high variability in biometric measurements. This type of rice showed a high level of plastered area, meaning low vitrea aspect. The amylose content varied from 9.4% and 15.2%, with an average of 12.4%, meaning that Carolino rice presented low value, i.e. that the rice with low amylose content is dry, less tender and hard after cooking, also showing volume expansion and a high degree of flakiness. Carolino rice flours showed significant differences of RVA viscosity profiles. Generally they presented significant differences in the pasting temperature, but similar pasting peak temperature, 95ºC. It was also observed that the different types of Carolino rice flours showed high viscosities (minimum of 2872 cP and maximum 3797 cP), as well as great differences in breakdown and setback values.
- Contribution for the characterization of carolino rice cultivarsPublication . Santos, Tania; Lemos, Diogo; Guiné, Raquel; Correia, PaulaThe objective of this work was to evaluate the grain biometric characteristics of 62 rice cultivars, which cover Indica and Japonica subspecies, and different types of commercial rice like, Agulha (Indica rice cultivars), Carolino (Japonica cultivars), aromatic (basmati and thai), integral rice, risotto, glutinous (waxy), wild and parboiled rice. It was noticed that for the same group type of rice there are a great variance. Generally, the Agulha, Aromatic and Integral rices commercialized in Portuguese trade are long (length high than 6 mm and length/width ratio higher than 3) and risotto cultivars are medium size. The two studied glutinous rice cultivars presented one cultivar long and other cultivar round (length lower than 5 mm and length/width ratio lower than 1.9). All rice cultivars presented high values of white vitreous, total whiteness, and low percentage of chalky area, presenting a crystalline and translucent aspect, but there is an exception to integral rice cultivars due to absence of polish operation during the milling process and for parboiled rice cultivars due to the effects of parboiled treatment. Moreover the vitreous percentage was also high. There was a strong correlation between the white vitreous values and total whiteness.