Author: Lara Román

Experiments to measure starch yield (III)

100g of each type of rice was mixed with 200g of distilled water at room temperature. The slurries were vacuum packed using a Sammic Vacuum Sealer V410 and heated for 15h at 35ºC in a water bath. Together with the rice and water one magnetic stirring bar was placed inside each vacuum sealed bag to stir the samples during 3min at 1000rpm at room temperature. Then, the sealed bags were opened and sieved during 2min more. Each water-starch solution and sample of sieved rice was weighted separately. After that, the rice grains were washed with 50g of distilled water, stirred at 1000rpm during 2min and sieved.

Experiments to measure starch yield (II)

100g of each type of rice was mixed with 200g of distilled water at room temperature. The slurries were vacuum packed using a Sammic Vacuum Sealer V410 and heated for 20 h at 35 ºC in a water bath. Together with the rice and water one magnetic stirring bar was placed inside each vacuum sealed bag to stir the samples during 3min at 1000rpm at room temperature. Then, the sealed bags were opened and sieved mixing manually during 2min more. Each water-starch solution and sieved rice was weighted separately. After that the rice grains were washed two times with 80g of distilled water and mixed manually during 2min.

First Experiments to measure starch yield

We used five types of rice: arborio, carnaroli, basmati, bomba and sushi rice. 50g of each type was mixed with 100g of distilled water at room temperature. The slurries were vacuum packed using a Sammic Vacuum Sealer V410 and heated for 2.5hat 40ºC in a water bath. Then, the samples were manually mixed during 2min and sieved during 2min more. The water-starch solutions and sieved rice were weighted separately for each genotype. After that, the rice grains were washed with 10g of distilled water and mixed during 2min more. Each of this water-starch solutions was added to the  initial solutions obtained after sieving.

Creaminess: viscosity and friction

Creaminess is the term used for the velvety coating sensation normally assessed in the tongue and palate. It is one of the most relevant textural properties of risotto. Understanding creaminess requieres a multidisciplinary effort: from physical and chemical techniques to sensory perception studies and human-food interaction knowledge. After a review of the literature, we can conclude that it is undoubtedly related to thickness and smoothness. Other factors such as flavour or surface properties may also contribute to the perceived creaminess. An attempt to quantify creaminess was proposed by Kokini and Cussler1:

Creaminess = (Thickness)a(Smoothness)b

where a = 0.54 ± 0.1, b = 0.84±0.1.

Amylose content measures

Amylose content (AC) in rice grains is a relevant parameter for predicting pasting properties of cooked rice as it is often used for  a tenderness prediction. We will perform experiments to measure the AC in different types of rice grains commonly used in risottos, such as carnalori, arborio or vialone nano. For that purpose  we will:

1. Isolate starch

A wide range of methods are available for isolation of starch from rice. They are grouped into three categories: alkali isolation, acid isolation and water isolation. The main objective of the alkali and acid methods is to separate proteins and lipids from starch.

Understanding rice gelatinisation to cook the perfect risotto (Introduction)

The process of cooking risotto is sometimes confusing and several procedures have been proposed to be the key to cook the real risotto, which requires ‘al dente’ rice grains and the adequate creamy texture.

If we want to prepare the ultimate risotto recipe we will have to answer some questions: what type of rice should we use?, should we stir while cooking the rice? , what is the cooking time?

Starch plays a vital role in achieving the desired consistency. Starch is a polysaccharide mainly composed by amylose, fundamentally linear, and amylopectin, highly branched. It presents a semi-crystalline structure.