INTRODUCTION :
Dehydration is a method of food preservation that removes moisture from vegetables like tomatoes and onions, extending their shelf life and reducing weight for easier storage and transport. The process involves drying the vegetables using methods such as sun drying, air drying, or mechanical drying (e.g., hot air, freeze drying).
Tomato Dehydration: Tomatoes are sliced or pureed and dried at moderate temperatures (50–70°C) to retain colour and flavour . Common products include dried tomato slices, powders, and flakes. Onion Dehydration: Onions are peeled, sliced, and dried at around 50–60°C. The final product includes onion flakes, granules, or powder, commonly used in seasonings and processed food Dehydration helps preserve the natural taste and nutrients while preventing microbial growth.
Solar dryer
Solar dryers are devices that use solar energy to remove moisture from food products. Solar dryer are protects dust, insects and avoid contamination.
The main types of solar dryers include:
1. Direct Solar Dryer : Food is exposed to sunlight inside an enclosed chamber with a transparent cover Heat builds up inside, accelerating the drying process Example: Box-type solar dryer.
2. Indirect Solar Dryer : Sunlight heats the air in a separate solar collector, and the warm air is circulated into the drying chamber. Prevents direct exposure to sunlight, preserving colour and nutrients. Example: Cabinet solar dryer.
Dome Solar Dryer
A Dome Solar Dryer is a type of solar drying system designed with a dome-shaped structure that efficiently traps solar heat, providing uniform drying conditions for various agricultural products like fruits, vegetables.
Features & Working Principle Dome-Shaped Structure: Maximizes sunlight absorption and enhances airflow. Transparent Cover: Usually made of polycarbonate or UV-stabilized plastic, allowing sunlight to penetrate while preventing heat loss. Ventilation System: Ensures proper air circulation to remove moisture efficiently. Solar Energy Utilization: Uses direct solar radiation to heat the air inside the dome, accelerating the drying process.
01/03/2025
On the first day, I received an overview of the industry from Mr. Dixit sir. He provided into the daily operations, processes, and activities that take place within the industry. Understanding the workflow helped me get a clear picture of my responsibilities during vigyan ashram.
02/03/2025
Learning About Dryers & Flat-Bed Dryer Modification
I gathered information about different types of dryers and their applications. One key task was disassembling a flat-bed dryer to replace its plywood with a polycarbonate sheet. This change aimed to improve durability and efficiency, as polycarbonate is more resistant to moisture and heat.
We calculate the dimensions of all the components of flat bed dryer.
4=6ft
2-1ft
1=0.5
2=3ft 1inch
2=2ft
03/03/2025
Discussion on Product Drying Feasibility
I had a discussion with Mr. Dixit Sir regarding the types of products that could be dried using the available dryers. We explored the pre-processing required for different materials and the feasibility of drying various agricultural products.
04/03/2025
Cleaning Solar Dome Dryer Trays
Before starting trials, I cleaned and washed the trays of the solar dome dryer to maintain hygiene and prevent contamination during the drying process.
05/03/2025
Industry Visit to AGRO Ranger Grading Startup
Visiting the AGRO Ranger Grading startup provided insights into their grading and drying processes. Observing their techniques helped me understand different approaches to handling agricultural produce efficiently.
06/03/2025
Why plywood is not used in the flat bed dryer?
1)Moisture Absorption-It easily absorbs moisture.
2)Fungal Growth-Moist conditions inside the dryer can promote fungal or mold growth on plywood.
Why polycarbonate is used?
1)High transparency-Polycarbonate allows a high amount of sunlight to pass through ,which helps in utilizing solar energy for drying.
2)Impact Resistance-It is much stronger than glass and can withstand impacts (e.g., hail).
3)UV Protection-Prevents degradation of sensitive crops or materials from direct UV rays.
4)Weather Resistance-Resistances to rain, moisture, and temperature fluctuation.
Cut the Polycarbonate Sheets for Flat-Bed Dryer
I measured and cut the polycarbonate sheets to fit the flat-bed dryer, ensuring proper installation for enhanced performance. We decided to change our priorities and kept tomato drying trial on hold.
We calculate the dimensions of all the components of flat bed dryer:
1=0.5ft
1=3ft 2inch
2=3ft2inch
1=1ft 6inch
07/03/2025
Attaching Polycarbonate Sheets to the Flat-Bed Dryer
After cutting the sheets in proper dimensions, I attached them to the dryer structure, replacing the old plywood material. This modification is expected to improve the dryer .
The bottom surface was covered with a black HDPE sheet because black colour absorbs more heat, which helps the slices dry faster.
CONCLUSION : Polycarbonate and plywood are both used in flat bed dryers for different reasons, each offering specific benefits depending on the design and application. Here’s a breakdown of why they’re considered good choices:
Polycarbonate:
Polycarbonate sheets are often used as a cover material in solar flat bed dryers because they let sunlight through while offering good insulation. Helps in greenhouse effect — trapping heat inside the drying chamber.
1.Very durable and can withstand rough weather, hail, or impacts better than glass or other plastics.
2.When UV-treated, polycarbonate resists degradation from sunlight, making it last longer outdoors.
3.Lightweight & Easy to Install:
Much lighter than glass but still strong, which makes it easier to construct and transport flat bed dryers.
08/03/2025
Installing a Data Logger in the Polyhouse
A visit to a to install a data logger, which helps in monitoring environmental parameters such as temperature and humidity.
12/03/2025
Painting and Positioning the Flat-Bed Dryer
I painted the flat-bed dryer to protect it from rust and environmental wear and then placed it on the terrace for testing.
13/03/2025
Purchasing Mesh for Solar Dome Dryer Trays
I purchased mesh for the solar dome dryer trays. This addition helps to cannot drop out the tomato slices.
Using a small-sized mesh is ideal for the dehydration process, especially when drying thinly sliced vegetables like tomatoes and onions.
Here are some benefits:
Prevents slices from falling through – The small mesh keeps even very thin slices secure and in place.
Uniform drying – The slices stay flat, allowing air to circulate evenly, resulting in proper and safe dehydration.
Stability – Once dried, the slices remain on the same mesh without breaking or shifting around.
Reusable – These mesh trays are easy to clean and can be reused multiple times.
14/03/2025
“Mesh Cutting and Tray Fitting Process”
“I purchased a polypropylene mesh, then took proper measurements of the tray. We selected a mesh such that slices would not fall through it, and the tray is 13 square feet in size, so we cut the mesh accordingly to fit those measurement, and attached it to the tray using zip ties. “Five zip ties were used to secure the mesh.”
15/03/2025
Fixing the Trays on Tray Structure of Solar Dome Dryer
mesh trays were first securely fitted and then placed into a tray framework or structure.
16/03/2025
Measuring Tomato Requirement for Drying
“I purchased tomatoes and sliced them into 4mm thick slices using a slicer machine. Then, I measured an area of 1 square foot on a steel tray and spread the tomato slices evenly over it. However, some slices turned out smaller in size, and the slices were not uniformly even. Based on this experiment, I want to determine how many kilograms of tomato slices can be spread over a 13 square feet tray.”
17/03/2025
Preparing Steel Strips for Fan Installation
I acquired steel flat strips, cut them to the required size, and bent them to fit the dryer’s fan installation system. This was essential for enhancing air circulation within the dryer.
18/03/2025
Celebrating Cultural Day
Participating in Cultural Day at the institute was a refreshing break. It provided an opportunity to interact with colleagues and understand workplace culture.
19/03/2025
Setting Up Air Circulation System & Purchasing Tomatoes
I worked on setting up an air circulation system in the solar dome dryer to improve drying efficiency. Additionally, I purchased tomatoes for conducting drying trials.
20/03/2025
Tomato Drying Procedure
- Selection & Sorting
Choose ripe, healthy tomatoes
Remove damaged or spoiled ones
- Washing & Cleaning
Wash thoroughly with clean water
Remove dirt and pesticide residues
- Cutting & Slicing
Slice tomatoes into uniform pieces (e.g., halves or thin slices)
Remove seeds if necessary
- Pre treatment (Optional)
Dip in citric acid or blanching for colour retention and microbial control
- Drying Method Selection
Sun Drying → Spread on trays under direct sunlight
Solar Drying → Use a solar dryer for better efficiency
Oven Drying → Dry at 50-60°C in an oven
Dehydrator Drying → Use a food dehydrator at 50-60°C
- Monitoring & Turning
Turn slices regularly for even drying
Ensure proper air circulation
- Final Drying Stage
Continue drying until moisture content is 10-15%
Texture should be leathery and flexible
- Cooling
Allow dried tomatoes to cool before packaging
- Packaging & Storage
Store in airtight containers or vacuum-sealed bags
Keep in a cool, dry place away from sunlight
Preparing & Placing Tomato Slices for Drying
“I used a slicer to cut tomato slices of 4 mm thickness and measured a total weight of 3 kg. The slices were then uniformly spread on trays and arranged across all domes. A data logger and fan were connected, and finally, the domes were covered with black HDPE plastic tarpaulin.”
21/03/2025
Recording & Analyzing Temperature and Humidity
Throughout the day, I monitored and recorded temperature and humidity readings. This data helped analyse drying efficiency and environmental impact
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22/03/2025
Transferring Tomatoes to Flat-Bed Dryer
To compare drying methods, I transferred the partially dried tomatoes from the solar dome dryer to the flat-bed dryer for further experimentation.
23/03/2025
We discussed with Dixit sir and Prasad sir and they interpreted following data .
Using an Electric Dryer for Final Moisture Removal
Once the tomatoes had dried significantly, I placed them in an electric dryer to remove any remaining moisture, ensuring optimal storage quality.
Final dried tomatoes.
Total initial weight of tomato = 60 kg
total loaded weight of tomato = 48 kg
total dried weight after removed from solar dome dryer = 3.828 kg
Total dried weight after removed from electric dryer = 3.299 kg .
24/03/2025
Cleaning the Solar Dome Dryer & Planning Onion Drying
After completing the tomato trial, I cleaned the solar dome dryer and discussed the next trial, which involved drying onions.
25/03/2025
Purchasing & Preparing Onions for Drying
Process followed:
Raw Onion Selection
↓
Cleaning & Peeling
↓
Slicing/Chopping
↓
Blanching (Optional)
↓
Pre-Drying Treatment (if needed)
↓
Drying Process
│
├── Hot Air Drying
├── Freeze Drying
├── Sun Drying
└── Vacuum Drying
↓
Cooling
↓
Grinding (if powder is needed)
↓
Sieving & Grading
↓
Packaging
↓
Storage & Distribution
“We went to the market to purchase 45kg onions and peeled them the night before the trial. The peeled onions were then weighed and kept ready.”
26/03/2025
Preparing Sample Meshes for Monitoring Drying
To monitor the drying process effectively, I cut 15 meshes of 20 sq. cm each for sample placement in different trays.
Surface area of one tray= 13 sq. ft.
Therefore, 13*204=2652
So we take 2500 gm for 13 sq. ft.
Therefore, for 15 trays we use 37.5 kg onions.
27/03/2025
Slicing Onions & Placing Them in the Dryer
“Using a slicer, the onions were sliced and weighed to 2.5 kg. The slices were then uniformly spread on trays.”
Total initial weight of onions =44 kg
Total loading=37.5 kg
29/03/2025
Monitoring & Analyzing Temperature and Humidity Data
I recorded temperature and humidity levels throughout the day and analysed how they affected the drying process.
30/03/2025
Discussing Onion Drying Results with Mentors
After drying the onions, I consulted with my mentors to discuss the results and determine whether any process adjustments were needed.
Further Drying Onions in Electric & Flat-Bed Dryers
To compare different drying techniques, I placed some of the dried onions in an electric dryer and others in a flat-bed dryer for additional trials.
We have completed the packaging of dry onions ,with each unit containing two packs of 100 grams each ,ready for sale.
31/03/2025
Analyzing Onion Drying Time & Temperature Requirements
I conducted an analysis to determine the optimal time and temperature for drying onions, ensuring maximum efficiency and quality.
Writing a Report on Industrial Attachment
Finally, I compiled all my findings, observations, and learnings into a comprehensive report on my industrial attachment experience.
Conclusion:
This day industrial attachment was an enriching experience. It provided hands-on exposure to various drying technologies, product trials, and data analysis techniques. I gained practical skills, problem-solving abilities, and a deeper understanding of industry operations. The knowledge I acquired during this period will undoubtedly help me in my future endeavours within the food processing and drying industry.
04/04/2025
Costing and Branding of dried Onion and Tomato flakes:
“I have created a design for the product labels of onion flakes and tomato flakes. This design includes the visual layout, branding elements, and essential product information that will appear on the packaging. The goal of the label design is to clearly communicate the contents of the product, attract customer attention, and comply with standard packaging and labelling guidelines. The labels are tailored specifically for onion flakes and tomato flakes, ensuring that each has a distinct yet cohesive look that aligns with the overall brand identity.
we have placed the tomatoes and onions in plastic bags and packed them properly, with each unit containing two packs of 100 grams each, ready for sale.
06/04/2025
We are trying to find out how much it costs to dry onions by looking at all the things that can affect the process. This includes the cost of the machines used for drying, how much electricity the machine used, how many workers are needed to run them, and how much time it takes to dry the onions. By looking at all these factors, we can better understand the total cost of drying onions.
07/04/2025
We have finished calculating all the final costs and have written down all the details here:
-Central fan
-Outer fan
-Slicer
-Onion
-Electric Dryer
-Operating cost
-Labour
-Labelling and Packaging
1) Central fan :-
Given:
-Power = 85 watts
-Conversion to kilowatts: 85/1000=0.085 kW
Operating pattern (Daytime Only):
– 2 min ON, 1 min OFF = 2/3 of each cycle ON
-Operating hours: 10AM to 6PM= 8hours/day
-Duration = 3 days
So, effective ON time:
8 hrs/day*3days*2/3=16hrs
Energy Consumption:
Units = 16hrs*0.085kW = 1.36 units
Cost (10rs/unit):
1.36*10+13.6rs.
2)Outlet Fan :-
Given:
-Power = 16 watt
-Conversion to kilowatts:16/1000=0.016kWh
Operating Pattern
-Day time: 1min ON/ 2 min OFF = 3 min cycle
8hrs*3days=24/3=8hrs (3 days total fan on).
-Night time: 5min ON/ 5min OFF = 10 min cycle
16hrs*2/2=16hrs (2 days total fan on).
-Total time on outer fan:
8+16=24hrs
Energy Consumption:
-Energy consumed by one fan in 24hrs:
24*0.016=0.0384kW/hrs
-For 16 Fans: 0.384*16=06.144kWh
if cost is 10rs per kWh:
6.144*10=61.44rs.
3)Slicer Machine :-
Given:
-1hp = 745watts.
-Usage Time = 1hr.
-Energy Used : 0.745
-Cost: 0.745*10 = 7.45rs.
4)Onion :-
-Onion quantity = 44kg
-Rate = 25rs/kg
-44*25=1100rs.
5)Electric Dryer :-
-Power 2100W = 2.1kW
-Used for 9 hrs : 9*2.1=18.9kWh
-Costing = 18.9*19=189rs.
6)Operating Cost :-
Onion + E.D + C.F + O.F + Slicer
1100+189+13.6+61.44+7.45
=1371.49rs
7)Labour cost:-
-2 labour = 500rs
-8hrs working
500*8=62.5 in 1 hr
-Total 3*62.5=187.5
And here 2 labour cost is 375rs.
8)Labelling and Packaging :-
– One label and packet cost is around 3rs.
-Total 45 packets.
3*45=135rs
9)Per Packet Cost (100gm)
9) Per Packet Cost:-
Total cost/Total packet=1881.49/45=41.81rs(~42rs).
10)profit:-
-Cost price(CP)=41.81rs
-Selling price(SP)=90rs
so here,
Profit% = (SP-CP/CP)*100
=(90-41.81/41.81)*100=115%
Per Packet Cost:
The cost to manufacture one 100g packet is ₹41.81, based on a total cost of ₹1881.49 for 45 packets.
Profit Percentage:
Selling each packet at ₹90 gives a profit of approximately 115%.
08/04/2025
“We purchased tomatoes from the local market.” and are currently in the process of cleaning and sorting them in preparation for drying tests using a dome dryer. This step is essential to evaluate the effectiveness of the drying method and assess product quality.
09/04/2025
We had arranged for a batch of tomatoes to conduct a drying trial. But Unfortunately, we couldent get a full load of tomatoes trial had to be cancelled. We plan to reschedule it for when tomatoes are available for full load.
11/04/2025
We brought 145 kg of tomatoes from the market, out of which 120 kg were fully loaded onto the solar dome dryer. From this batch, 25 kg of tomato water was removed. The tomatoes were sliced in 4mm size then spread on trays of 3 kg per tray. A data logger was attached at one on the south-facing side, one near the duct, and another on the outer fan. The dome was then covered with an HDPE sheet, “The data logger was turned on to record temperature and humidity readings.”
To determine the sample weight, 85 grams of tomato were placed on an area of 1 square foot.
“Tomatoes were sliced using the 4 mm cutter plate of the slicer, and the size of the tomato slices was measured using a vernier calliper.” but the tomato was cut with a thickness of 3.29mm it.
12/04/2025
We monitored temperature and humidity data throughout the day to examine their effect on the drying process and took the Weight of the onion sample at 10:00AM and 6:00PM.
