What is retrogradation process in starch?

What is retrogradation process in starch?

Retrogradation is an ongoing process, which initially involves rapid recrystallization of amylose molecules followed by a slow re- crystallization of amylopectin molecules. Amylose retrogradation determines the initial hardness of a starch gel and the stickiness and digestibility of processed foods.

What is retrogradation and examples?

When starchy foods—rice, pasta, bread dough—are cooked in the presence of water, all those individual granules of starch absorb water and swell up. The amylose and amylopectin molecules in the granules, formerly clinging together, relax a bit and come apart, allowing water to seep in among them.

What is retrogradation and gelatinization?

The key difference between gelatinization and retrogradation is that gelatinization refers to the act of making or becoming gelatinous, whereas retrogradation refers to the motion in a retrograde manner. The terms gelatinization and retrogradation describe the properties of starch.

What is starch retrogradation in bread?

When the loaf comes out of the oven and cools to below the gelatinization temperature, the starch molecules reform and harden – starch retrogradation. The water that was absorbed during baking gets slowly expelled and eventually evaporates. Bread that was initially soft and moist becomes progressively harder and dry.

What happens retrogradation?

Retrogradation is a reaction that takes place when the amylose and amylopectin chains in cooked, gelatinized starch realign themselves as the cooked starch cools. The crystal melting temperature of amylose is much higher (about 150 ℃) than amylopectin (about 50-60 ℃).

How does retrogradation occur?

When starch is heated in the presence of water and subsequently cooled, the disrupted amylose and amylopectin chains can gradually reassociate into a different ordered structure in a process termed retrogradation.

Which portion of starch contributes to retrogradation?

Retrogradation involves the destruction of the original granular crystalline structure (gelatinization), and then reconstruction of the novel crystalline structure [8] . The retrogradation of starch mainly depends on the structure of amylose and amylopectin in starch. …

What happens when starch is cooled?

During cooling, starch molecules gradually aggregate to form a gel. Retrogradation restricts the availability for amylase hydrolysis to occur which reduces the digestibility of the starch.

What is hydrolysis in starch?

This test is used to identify bacteria that can hydrolyze starch (amylose and amylopectin) using the enzymes a-amylase and oligo-1,6-glucosidase. The iodine reacts with the starch to form a dark brown color. Thus, hydrolysis of the starch will create a clear zone around the bacterial growth.

What is the importance of retrogradation?

Amylose retrogradation determines the initial hardness of a starch gel and the stickiness and digestibility of processed foods.

What is Rice retrogradation?

Starch retrogradation is a process whereby when a gelatinized solution is cooled for a long time, it changes into a gel and rearranges itself into a crystalline structure. It is an unavoidable phenomenon affecting the texture and quality of many ready meals, including starchy rice foods [2. M.

How does retrogradation relate to food science?

Retrogradation is an ongoing process, which initially involves rapid recrystallization of amylose molecules followed by a slow recrystallization of amylopectin molecules. Amylose retrogradation determines the initial hardness of a starch gel and the stickiness and digestibility of processed foods.

When does the retrogradation of starch take place?

Starch retrogradation occurs when molecules comprising gelatinized starch begin to (re)associate into an ordered structure ( Biliaderis, 1992; Slade and Levine, 1987c) as shown in Fig. 6.14. In this initial phase, two or more starch chains may form a simple juncture point, which then may develop into more extensively ordered regions.

How is starch retrogradation achieved in amylose molecules?

This degree of starch retrogradation is achieve by amylose realigning themselves together, as amylose as linear chain molecules can start to align earlier than branched amylopectin. Starch retrogradation is also important for products like crouton.

What kind of diffraction is used to analyze retrograde starch?

Another technique that can be used for analyzing starch retrogradation is X-ray diffraction, whereby retrograded starch exhibits a V-type structural pattern. Both amylose and amylopectin can retrograde.

How does retrogradation affect the textural properties of food?

Starch retrogradation is recrystallization of amylose and amylopectin in gelatinized starch due to moisture migration, thereby affecting the textural properties of foods. Victor T. Huang, Alicia A. Perdon, in Breakfast Cereals and How They Are Made (Third Edition), 2020