Drying Characteristics and Microbiological Quality Assessment of Solar-Dried Tomato

Area of Science:

• Food Science and Technology
• Agricultural Engineering
• Microbiology

Background:

• High post-harvest losses of tomatoes in Ghana due to inadequate processing facilities.
• Solar drying as a viable, low-cost method for preserving and adding value to tomatoes.
• Consumer concerns regarding the quality and safety of traditionally dried tomatoes.

Purpose of the Study:

• To adapt and evaluate a passive mixed-mode solar dryer for tomato processing.
• To investigate the dehydration characteristics and microbiological quality of solar-dried tomatoes.
• To assess the efficiency of the solar dryer in producing tomato powder.

Main Methods:

• Adaptation and utilization of a passive mixed-mode solar dryer.
• Pretreatment of 6mm Roma tomato slices with potassium metabisulfite and ascorbic acid solutions.
• Assessment of moisture content, moisture ratio, dehydration rate, and microbial counts (aerobic mesophiles).

Main Results:

• The solar dryer achieved a 24-hour efficiency of 24.2%, reducing tomato moisture to 12-14%.
• Solar-dried tomatoes pretreated with potassium metabisulfite showed lower aerobic mesophile counts (3.90 CFU/g) than sun-dried samples (4.85 CFU/g).
• Solar-dried tomato powder demonstrated improved microbiological safety compared to open sun-dried samples.

Conclusions:

• Passive mixed-mode solar drying is an effective technology for processing tomatoes into powder.
• Pretreatment with potassium metabisulfite enhances the microbiological quality of solar-dried tomatoes.
• Solar-dried tomato powder offers a safer and more stable product, mitigating post-harvest losses.