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The Impact of Blanching, Sweating, and Drying Operations on Pasting of Yam (PDF)

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The Impact of Blanching, Sweating, and Drying Operations on Pasting of Yam


The effect of blanching and sweating pretreatment on pasting properties of white yam (Dioscorea rotundata) was investigated. Blanching was done at 600c. sweating was done using butter at 350c.

After drying and grinding, the flour pasting properties were determined using the RVA. The blanched sample gave the most preferred values for pasting properties as compared to the sweated one, and the one that didn’t undergo any pretreatment.

Moreso the impact of blanching time and temperature on the drying kinetic of white yam was investigated.

Yam was blanched at 600c and 900c for 5 and 15 minutes; and then dried. The optimum pretreatment was a blanching time and temperature of 15min and 900c. Results from the drying profile were fit into some model.

The best fit was gotten from Page, and Anderson and Pabis models. The study shows that blanching pretreatment is efficient in the yam flour processing plant.


CONTENTS                                                                                                 PAGES

Certification ————————————————————————————– i

Dedication —————————————————————————————-ii

Acknowledgement ——————————————————————————iii

Table of content ———————————————————————————iv

Abstract ——————————————————————————————-vi


1.0 Background information ——————————————————————-1

1.1 Statement of the problem ——————————————————————-2

1.2 Aim and objectives of the study ———————————————————–2

1.3 significance of the study ——————————————————————–3

1.4 Scope and Limitation————————————————————————3


2.1 Yam ——————————————————————————————-4

2.2 Blanching ————————————————————————————-5

2.3 Sweating ————————————————————————————–6

2.4 Drying —————————————————————————————–6

2.5 Pasting properties —————————————————————————7


3.1 Materials ————————————————————————————–8

3.2 Methods —————————————————————————————8

3.3 Determination of functional properties —————————————————9

3.4 Procedure for obtaining Drying Kinetics ———————————————–10

 CHAPTER FOUR: Results and discussion ———————————————–12

 CHAPTER FIVE: Conclusion and recommendation ————————————18

REFERENCES ——————————————————————————–19


Yam (Dioscorea sp.) is an important source of carbohydrate for many people of the sub-Saharan Africa, especially in the yam zone of West Africa (Akissoe et al. 2003).

It is one of the important crops in the farming systems of Nigeria with more than 2.8 million hectares of land under cultivation annually (IITA, 2002).

It contributes significantly to dietary calories per capita daily and serves as important source of income to the people (Olaoye and Oyewole 2012).

There are many varieties of yam species widespread throughout the humid tropics, but the edible yams are derived mainly from about 10.

The most economically important species are white yam (Dioscorea rotundata), yellow yam (Dioscorea cayenesis), water yam (Dioscorea alata), and bitter yam ((Dioscorea dumetorum) (Key 1987).

Fresh yams are difficult to store and are subject to deterioration during storage (Afoakwa and Sefa-Dedeh 2001). Olayemi et al. (2012) reported postharvest losses of yam in Nigeria to be about 37% which underscores the need for processing this staple food crop into product(s) of longer shelf life such as flour.

Yam tubers have been used as a traditional food in home with little industrial use; however the traditional uses are diverse and the crop has more utilization potentials.

The main shelf-stable product of yam is the traditional yam flour (elubo) with little or no industrial applications. High-quality yam flour is a novel product of yam which is produced from wholesome fresh tubers.

It is odorless, crystal white, and free from foreign or extraneous material. It could find wide applications in the baking and confectionery industries.

The HQYF (High-quality yam flour) can be easily stored for a longer period (12-18 months) if the flour has low moisture.

The slow progress in upgrading the traditional food processing and preservation techniques in West Africa contributes to food and nutrition insecurity in the sub-region (Aworh 2008).

In recent years, much attention has been drawn to the quality of dehydrated food products.

Different drying methods have effects on the biochemical and functional properties of dehydrated products (Ogunlakin et al. 2012).

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