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Studies on the changes in physico-chemical properties and chemical constituents of turmeric powder during agglomeration.

Dhanalakshmi, K. (2012) Studies on the changes in physico-chemical properties and chemical constituents of turmeric powder during agglomeration. Doctoral thesis, University of Mysore.

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Abstract

Dehydrated foods in powdery form have gained increased attention in recent years due to their convenience in use, and ease during transportation, handling, processing and for product formulations. Agglomeration process modifies the physico-chemical and functional properties of the powders. Turmeric powder having diverse applications in food, pharmaceutical and cosmetic industries has been selected for agglomeration process. The present thesis deals with the agglomeration of turmeric powder with an intention of improve the physical, physico-chemical and functional properties. The present thesis has been subdivided into five chapters with each chapter focussing on different objectives. Turmeric rhizomes contain about 70% starch. X-ray diffractogram shows the starch to be of B-type. The FTIR spectrum of isolated starch shows characteristic peaks at 1020, 1080 and 1156 cm-1. Dried and cured-dried turmeric powder samples show higher water holding capacity (3.62 and 4.78 g/g, respectively) compared to isolated starch (1.07 g/g) at 30C. Non-Newtonian shear-thinning characteristics are observed with turmeric powder dispersions containing 10% (w/w) solids. A power law model can fit the shear-rate and shear-stress data (r = 0.993-0.999, p≤0.01). Apparent viscosities of isolated turmeric starch and cured-dried turmeric powder dispersions containing 10% (w/w) solids are 1.29 and 7.57 mPas, respectively. Microstructure of starch particles shows a smooth flat outer surface. The approximate length and breadth of isolated elliptical starches are 25 and 10 μm while the thickness is about 5 μm. Turmeric starch can be used in agglomerated products as they are flaky in nature and can pack well in a stack due to structural similarity. Studies on chemical composition of volatile and non-volatile components present in turmeric rhizome under different post-harvest treatments reveal that cured-dried rhizomes can release higher quantities of volatile and non-volatile components during extraction. Major components are ar-turmerone (21.0-30.3%), α-turmerone (26.5-33.5%) and -turmerone (18.9-21.1%). Trolox equivalent antioxidant capacity (TEAC) values are 38.9, 68.0 and 66.9 μm at 1 mg of oil/ml for fresh, dried and cured-dried rhizome, respectively. The IC50 values for fresh, dried and cured-dried rhizome oil to quench DPPH radicals are 4.4, 3.5 and 3.9 mg of oil/ml, respectively. The rhizome oil shows good reducing potential and is concentration dependent. Volatile oil and non-volatile extracts from cured-dried rhizomes contain higher xxiii quantities of ar-turmerone (principal flavour component) and total polyphenols as well as curcuminoids (possessing high pharmacological activities), respectively. Hence, the cured-dried rhizome powder has been selected for agglomeration process. Turmeric powder (cured-dried) samples have been subjected to agglomeration process by varying the moisture content of the feed and steaming time. Physico-chemical properties like bulk density, wetting and sinking times of the agglomerated samples decrease with an increase in moisture content of the feed. Principal chemical components like volatile and non-volatile components decrease with an increase in moisture content of the feed and steaming time. There is an increase in the ratio of oxygenated terpenoids to terpene hydrocarbon. It means that compounds responsible for aroma/flavour of turmeric powder (i.e., oxygenated terpenoids) are retained in agglomerated samples. Hence, agglomeration process improves the aroma and flavour in addition to its physico-chemical characteristics. The turmeric sample shows a good fit for kinetic based sorption isotherms such as Langmuir, Brunauer-Emmet-Teller (BET) and Guggenheim-Anderson-de Boer (GAB) models. The microstructural observation shows that the non-agglomerated sample possesses spheroids and ellipsoids of different sizes having uneven outer surfaces. The image analysis infers that the size related parameters like surface area, perimeter and equivalent diameter increase with an increase in moisture content and/or steaming time. A five-layered artificial neural network (ANN) having a structure of 2-9-10-9-6 has been developed that links the input process variables and output functions concerning the agglomeration process of turmeric powder. It is concluded that the agglomeration process improves certain physical and physico-chemical properties of products as well as effective aroma and flavour; however, there is a marginal loss in the chemical components like volatile oil and curcuminoids contents due to processing.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Agglomeration, turmeric powder, Dehydrated foods
Subjects: 600 Technology > 08 Food technology > 30 Spices/Condiments > 07 Turmeric
600 Technology > 08 Food technology > 05 Processing and Engineering
600 Technology > 08 Food technology > 06 Preservation and Storage > 02 Drying and Dehydration
Divisions: Food Engineering
Plantation Products Spices and Flavour Technology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 13 Nov 2013 05:06
Last Modified: 25 Sep 2018 06:50
URI: http://ir.cftri.com/id/eprint/11283

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