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Functionality of Acetylated Distarch Phosphate in tomato ketchup processing
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Sunday, 01 May, 2011, 08 : 00 AM [IST]
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Mahesh B Zamre & Harish K Tekchandani
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Introduction
Starch is one of the important food ingredients in terms of sheer versatility of applications in the food industry. The native and modified starches from different sources like corn, tapioca, wheat, rice and potato are extensively used in many processed foods. The native starches may not possess the functionalities required for many processed food systems. They do not offer freeze-thaw stability and stable viscosity under various process conditions. In addition, syneresis occurs in starchy foods as a result of starch retrogradation. Chemical and physical modifications to native starches can help in enhancing required functionalities. The modified starches have been tailored to create competitive advantage in a food product to enhance product aesthetics, reduce production costs, ensure product consistency and extend shelf life.
Starch can be modified by physical, chemical methods and combination of both treatments. Physical treatment improves water solubility and chemical modifications add functional properties. The most common chemical methods involved in starch modification include acid treatment, cross linking, oxidation, substitution and combinations of two or more of these treatments. The emergence of biotechnology has helped in starch modification during the growth phase of the plant. Different amylose levels, amylopectin structure can be produced with the help of biotechnology.
Application of modified starches
The general applications of modified starches in food industry are summarised in the following table:
Modified starches for ketchup
Tomato, botanically a fruit, is generally considered a vegetable for culinary purposes. Tomatoes are widely grown in all parts of the world and it is important to process them as preserved food products. Tomato products such as puree, juice and ketchup are commonly used commodities in households, hotels and restaurants. Due to increasing standards of living in the cities and the rapid urbanisation taking place in the rural areas, consumption of tomato based products is increasing rapidly. These items are used to enhance the taste of different food products. Ketchup is a descriptive term for a number of different products, which consist of various pulps, strained and seasoned fruits; the variety made from tomatoes being the most popular condiment. Besides the boom in the food service sector including fast food chain has widened the demand potential for tomato ketchup and other tomato products.
Tomato ketchup / sauce is prepared by blending tomato juice / puree / paste of appropriate concentration with nutritive sweeteners, salt, vinegar, spices and condiments and heating to the required consistency. It also contains permitted stabilisers and thickeners like modified food starches (0.5% by weight as per Indian regulations). Both sauce and ketchup are consumed with food and snacks.
Cross-linked and stabilised starches (such as acetylated distarch phosphate) are the most suited starches for use in ketchup because of the functional attributes they provide. Owing to their beneficial functional properties like excellent freeze-thaw stability and resistance to breakdown under harsh processing conditions, they are especially suitable for use in ketchup processing. It contributes in extending the shelf life of the ketchup by preventing syneresis during cold storage and repeated freeze-thaw cycles. It also provides uniform and homogenous appearance to the ketchup. Their lower cost relative to other thickeners such as natural gums and other hydrocolloids, may provide a significant economic advantage.
Cross-linking with phosphates or adipates provides following benefits:
● Better resistance to adverse processing conditions like high temperature, low pH and high shear
● Improves the textural attributes provided by cooked starch pastes
Stabilisation by esterification or etherification imparts following benefits.
● Reduces the gelatinisation point of starch
● Improves freeze / thaw stability, low temperature storage stability and minimises syneresis
● Improves the paste clarity
Materials & Methods
The tomato paste required for the trials was purchased from market with minimum solids content of 30%. The modified starch Ultraflo 2.5T10 (acetylated distarch phosphate) used for the trials was manufactured by Anil Limited, Ahmedabad. Other ingredients were purchased from the local market. The ketchup samples were prepared at Anil Limited R&D, Ahmedabad.
The ketchup was prepared as per the process outlined given in Flow chart 1. The viscosity of ketchup was measured with Brookfield viscometer.
Benefits of modified starches in ketchup - Thickener and texture stabiliser
Texture is one of the most important factors to be considered in determining the quality and overall acceptability of many food products including tomato ketchup. A good quality tomato ketchup is expected to possess pseudoplastic behaviour i.e. it should spread and flow easily under a small external force but should hold its shape when not subjected to any such force. Ketchup consists of two parts, a thick syrup and tomato fibre. The proportion of these two components and the characteristics of the syrup are the principle factors that determine the consistency of ketchup. The thickness or body of ketchup is largely determined by the viscosity of the liquid and the proportion of insoluble tomato fibre present. Viscosity has economic implications for tomato ketchup processors because it largely determines processing yields and product quality. For this reason, different thickeners like modified starches and gums are used to increase the viscosity of the syrup, yielding more consistent products and minimising the phenomenon of syneresis.
The modified starch acetylated distarch phosphate imparts great thickening properties to the ketchup samples at low concentrations and also acts as a texture stabiliser during processing and storage.
Provides freeze-thaw, low temperature storage stability & prevents syneresis
The household consumption of ketchup involves many freeze-thaw cycles. The ketchup should withstand these temperature changes and should not show noticeable evidence of syneresis. The added stabilisers like modified starches help in giving freeze-thaw stability to the product. Repeated freeze-thaw cycles produce marginal effects on the viscosity profile of the ketchup prepared using modified starches. Acetylated distarch phosphate provides very good cold temperature storage stability thereby extending the shelf life of ketchup.
Tolerates high processing temperatures
The ketchups are generally produced commercially under high temperature processing conditions. The added thickeners and stabilisers should be resistant to breakdown under these conditions. The viscosity profile of acetylated distarch phosphate and the ketchup made with acetylated distarch phosphate is little influenced by the high temperature processing conditions and it almost remains constant over prolonged exposure to high temperatures providing excellent resistance to breakdown under these conditions.
Improves low pH stability
The pH of commercial ketchup preparations falls in the range of 3.5 to 4. The ketchup should be uniform and homogenous throughout the storage under acidic pH. The added acetylated distarch phosphate provides stable viscosity against low pH.
Stable against high shear enc
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