*2.3.1 Drying of foods*

Drying is a food preservation method that involves the removal of moisture from food to a safe moisture level that inactivates microorganisms. Sun drying is only possible when the sun is available for a longer time [52]. Freeze-drying involves sublimation by converting food into ice without allowing water but through vacuum and heat applied in the drying chamber. The produce is frozen, and then water is removed by vacuum and application of heat. This coincides in the same chamber binding the moisture in food. High sugar concentration can also bind up the moisture and give the food a certain level of humidity at which micro-organisms cannot grow. Salt with high concentration can be used, resulting in high osmotic pressure that ties up the moisture and consequently inhibiting the growth of micro-organisms. It dehydrates the food by drying out and tying up moisture as it drains the microorganism's cells [58]. Pepper fruits parboiled at 75°C for 3 minutes before sun-drying had the highest nutrient composition with respect to fat, protein and capsaicin contents among various treatments evaluated. The efficient conservation of nutrients could be attributed to the inactivation of the enzyme system and retardation of physiological processes by parboiling which consequently prevents deterioration and nutrient losses. Parboiling has been found to reduce the period of drying and the maintenance of the red color of fresh pepper [59]. During drying, two processes occur – heat application and moisture evaporation from the sample. Nutrient losses were due to a more application of heat than the removal of moisture, which increased the concentration of nutrients in the fruit.

Using oven and dry parboiled, pepper fruits accelerated the moisture removal but resulted in lower nutritional composition than sun drying. Pepper fruits subjected to heat sterilization had high crude fibre, ash content and moisture content and had the lowest crude protein, fat, carbohydrate, capsaicin and oleoresin content. The ash content was highest in sun-dried pepper fruit. This agreed with the findings of

Mepba, who observed that the ash content of sun-dried vegetables was higher than the blanched samples. The parboiled pepper fruits had higher oleoresin and capsaicin content [52]. The crude fiber content of pepper fruits parboiled before oven drying or sun drying was significantly higher than those of the respective ones dried without parboiling. Oleoresin was positively correlated with all proximate content of pepper fruits except crude protein and fat content.

Furthermore, carbohydrate was correlated with protein, fat and fiber, while crude fiber was also linked to ash content. Fat content was also associated with moisture content and crude protein. In this study, mineral element content varied among treatments; Pepper parboiled before sun-drying or oven-drying had maximum values for all the mineral elements viz.: phosphorus, zinc, iron, potassium, calcium and sodium content. The mineral elements and vitamin C composition of pepper parboiled before sun-drying were significantly higher than those of the corresponding treatments. Heat-sterilized samples had the lowest phosphorus, calcium and vitamin C content than those subjected to various drying methods. Solanke and Awonorin (2002) have also reported losses of 62 to 93% of vitamin C in cooked vegetables [60]. The high solubility of vitamin C in water and the relative ease with which it is oxidized renders it susceptible to deterioration during processing. The route and rate of oxidation of vitamin C are influenced by several factors such as pH, presence of trace metals, enzymes, oxygen availability, time and temperature. The relationship of each nutrient element evaluated indicated a strong correlation among the treatments. Phosphorus content was highly correlated with calcium, zinc, iron, potassium, and sodium. Calcium was highly correlated with zinc, iron, potassium and sodium, while magnesium was moderately correlated with zinc and iron. Vitamin C was highly associated with potassium. The relationship between nutrients and vitamin C was all positive. Zinc was also highly correlated with iron, potassium and sodium, while potassium was moderately related to sodium.
