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Solar Drying: Fundamentals,Applications and Innovations - National ...

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Hii <strong>and</strong> Ong - Quality Characteristics of <strong>Solar</strong> Dried Products<br />

Plums<br />

Greenhouse<br />

dryer<br />

- Both solar <strong>and</strong> open sun drying of<br />

plums pre-treated by combination of<br />

1% potassium hydroxide <strong>and</strong> 60°C<br />

dipping temperature or by combination<br />

of 1% sodium hydroxide <strong>and</strong><br />

60°C dipping temperature resulted<br />

in relatively higher values of redness<br />

<strong>and</strong> yellowness as compared to artificial<br />

drying.<br />

- The combined effect of solar radiation<br />

<strong>and</strong> these pre-treatment combinations<br />

reduced the darkish colour<br />

of plums during solar drying <strong>and</strong><br />

open sun drying.<br />

Tarhan<br />

(2007)<br />

Indian<br />

gooseberry<br />

Forced<br />

convective<br />

solar dryer<br />

- Flaking treated sample retained<br />

maximum ascorbic acid (76.6%).<br />

- The greater retention of ascorbic<br />

acid in flaking treated sample might<br />

be due to reduced exposure of the<br />

sample in the drying air.<br />

- Loss of taste <strong>and</strong> flavour were found<br />

lower in flaking <strong>and</strong> pricking treatments.<br />

Verma <strong>and</strong><br />

Gupta (2004)<br />

Papaya<br />

latex<br />

Rock bed<br />

indirect<br />

solar dryer<br />

- <strong>Solar</strong> dried latex had a slightly<br />

higher preteolytic activity than the<br />

fresh sample because of the effect of<br />

ultraviolet radiation on the histidine<br />

residue which is essential for proteolytic<br />

activity.<br />

- This was attributed to the use of the<br />

indirect dryer since the latex was<br />

not exposed to any direct radiation.<br />

Narinesingh<br />

<strong>and</strong> Mohammed-Maraj<br />

(1989)<br />

Table 5.5. <strong>Solar</strong> dried grains/seeds/beans<br />

Product<br />

type<br />

Cocoa<br />

beans<br />

Type of solar<br />

dryer<br />

Direct solar<br />

dryer<br />

Major findings<br />

- Overall quality evaluation (flavour,<br />

acidity, fermentation index, appearance<br />

<strong>and</strong> odour) indicated that loading<br />

of 20 kg cocoa beans is recommended.<br />

- At this quantity, duration of drying was<br />

shorter <strong>and</strong> this reduces the risk of putrefactive<br />

development in the beans<br />

due to unfavourable weather condition.<br />

References<br />

Hii et al.<br />

(2006)<br />

Cocoa<br />

beans<br />

Indirect <strong>and</strong><br />

direct type<br />

- Dried sample from indirect dryer<br />

showed the highest cut test score while<br />

the direct dryer showed the lowest.<br />

Bonaparte<br />

et al. (1998)<br />

116 <strong>Drying</strong> of Foods, Vegetables <strong>and</strong> Fruits

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