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Central Composite Rotatable Design (CCRD) was used to generate twenty combinations of these factors: blanching time, processing time and sodium metabisulphite concentration. The optimized conditions were then adapted for the canning process of green pepper. Blanching time ranged from 0-1 min whereas processing time and sodium metabisulphite concentration ranged from 10-30 min and 0-0.2%, respectively. The canned products were analyzed for physico-chemical qualities using standard analytical methods. Results obtained from various physico-chemical analyses showed variable trends and influences of the linear, quadratic and exponential interactions on the measured quality indices such as pH of the drained liquid, drained weight of the canned product, leached solids and colour of the canned products. The results showed significant (p.0.05) quadratic effect of sodium metabisulphite as well as linear effect of blanching time on the drained weight of the canned green pepper. Generally, the pH of the medium decreased (increased acidity) with increasing processing time, which was also positively associated with the extent or amount of leaching. Additionally, all three factors were observed to have affected (to variable extent) the colour of the canned products. Blanching and processing times also affected the degree of browning. There was a strong significant (p.0.05) influence of the quadratic factors of blanching time, processing time and sodium metabisulphite concentration on the colour properties (a-values, b-values and L-values) of the canned products. Statistical analysis showed significant (p.0.05) linear effects of blanching time and sodium salt concentration as well as the combined effect of both factors on all the colour properties. All the studied parameters had significant regression coefficients (p.0.05) suggesting the studied parameters contributed significantly to the observed changes. Colour of the canned products changed from green toward redness with increasing blanching time at all concentrations of sodium metabisulphite. Optimal processing combination of 0 min blanching time, 10 min processing time and sodium metabisulphite concentration of 0.2% produced a highly acceptable canned pepper product with preferred physico-chemical and appearance properties.
Key words: Canning, pepper, blanching, antibrowning agents