the thickening effect of elephant foot yam in milk systems

137 Pages·2011·8.83 MB·English

THE THICKENING EFFECT OF ELEPHANT FOOT YAM IN
MILK SYSTEMS

THESIS SUBMITTED TO THE
NATIONAL DAIRY RESEARCH INSTITUTE, KARNAL
(DEEMED UNIVERSITY)
IN THE PARTIAL FULFILLMENT OF THE REQUIREMENT
FOR THE AWARD OF THE DEGREE OF

MASTER OF TECHNOLOGY
IN
DAIRYING
(DAIRY TECHNOLOGY)

BY
POLA RAMAKUMAR
B.Tech (Dairying)

DIVISION OF DAIRY TECHNOLOGY
NATIONAL DAIRY RESEARCH INSTITUTE
(I.C.A.R.)
Karnal – 132001 (Haryana), India
2011

Regn. No. 2030904

ABSTRACT

Elephant foot yam [Amorphophallus paeoniifolius (Dennst.) Nicolson] is a staple food
crop which is widely grown in tropical and subtropical zones. It is commonly known
as Jimmikand/ Ol/ Suran and used as vegetable, chutney, pickle, etc. in
different parts of India. It is a good source of starch (approx 20%). As starches
act as thickeners, the thickening effect of processed-yam powder in milk was
studied. Effects of time of cooking in excess water and drying temperature for
the preparation of yam powder on properties including pasting behaviour of
the powder were investigated. Darkening of yam powder increased with
increasing cooking time and drying temperature. The pasting properties as
determined by a visco-amylograph (Rapid Visco-Analyser, RVA) revealed that
the un-cooked yam powder prepared by tray-drying at 70°C had the highest
final viscosity (3313 mPa.s), setback (952 mPa.s) and pasting temperature
(88.8°C) but exhibited low sensory scores, when added to milk. The powder
prepared by 30 min cooking and 60°C drying having medium final viscosity
(2862 mPa.s) and low breakdown viscosity (38 mPa.s) was selected on the
basis of sensory evaluation (2.5% powder admixed with milk and heated to
75°C/5 min). In order to quantify the role of yam solids and milk solids in the
physico-chemical characteristics of the yam-milk mixture, the two variables
were investigated employing Central Composite Rotatable Design of
response surface methodology (RSM). The yam-milk mixture was analyzed
for apparent viscosity, Hunter lab colour parameters, heat stability in terms of
heat coagulation time (HCT) at 130°C, as also sensory attributes. With the
increasing level of yam powder, the sensory scores and HCT of the mix
decreased, and the dispersion tended to be less white. The combination of
yam solids (0.5%) and total milk solids (14%) aimed at having maximum
values for the desirable sensory attributes in the yam-milk mix resulted in a
moderate viscosity, reasonable HCT and good sensory status.

CONTENTS
Page
Chapter Title
No.
1. Introduction 1-3
2. Review of Literature 4-31
2.1 Root and tuber crops 4
2.2 Elephant foot yam 4
2.2.1 Production 5
2.2.2 Botanical description 5
2.2.3 Nutritive value of elephant foot yam 5
2.2.4 Anti-nutritional/toxic factors 7
2.2.5 Non-acrid-varieties 8
2.2.6 Processing of yam 8
2.2.6.1 Traditional methods 8
2.2.6.2 Boiling 8
2.2.6.3 Fermentation 9
2.2.6.4 Drying and Baking 9
2.2.7 Food Uses of EFY 10
2.3 Drying of yam 11
2.3.1 Effect of drying on colour 12
2.3.2 Effect of drying on pasting properties 13
2.4 Starch and its properties 14
2.4.1 Properties of starch 15
2.4.1.1 Swelling and solubility 15
2.4.1.2 Gelatinization and pasting 16
2.4.2 Elephant foot yam starch 19
2.4.3 Starch functionality 20
2.4.4 Starch behaviour in milk 23
2.4.5 Starch and heat stability of milk 30
3. Materials and Methods 32-46
3.1 Materials 32
3.1.1 Buffalo Milk 32
3.1.2 Elephant foot yam 32
3.1.3 Chemicals 32
3.2 Equipment 32
3.2.1 Cheese grinder 32
3.2.2 Tray dryer 32
3.2.3 Colloid mill 33
3.2.4 Homogenizer 33
3.2.5 BOD incubator 33
3.2.6 Texture Analyzer 33
3.3 Methodology 34
3.3.1 Elephant foot yam processing 34
3.3.1.1 Washing and peeling 34
3.3.1.2 Slicing / Cutting 34
3.3.1.3 Selection of cooking conditions 34
3.3.1.4 Mashing 34
3.3.1.5 Tray loading 35
3.3.1.6 Tray drying 35