If fresh fish is already a rich source of protein (17-19%) depending on the fish variety, dry fish with up to 70% protein is a far superior source of protein. Besides high protein content, dry fish is also a rich source of omega-3 fatty acid, calcium and iron. Since the protein content is high, a substantial amount of protein requirement can be met by consuming just 5 grams of dry fish. Epipelagic fish such as mackerel, sardine, anchovy, and ribbon fish are chosen for fish drying.
“Dry fish is a great source of protein. It can be a good supplement for Anganwadi and midday meals, especially in coastal fish-eating communities,” says Dr. Soumya Swaminathan, Chairperson of MSSRF.
One of the major drawbacks of traditional drying of fish is the high salt content of over 30%, far exceeding the FSSAI limit of 15%. Together with high salt content, traditionally dried fish is often unhygienic by virtue of being dried in the open, and has a short shelf life of about two months. Researchers at M.S. Swaminathan Research Foundation (MSSRF), Chennai and Fish for all Research and Training Centre at Poompuhar, Tamil Nadu, which is a MSSRF hub of innovation, have turned to solar drying to successfully address these pain points.
Cutting down salt content
“The salt content of solar-dried fish is about 12%. FSSAI has set a limit of 10-15% salt content for salted dried fish,” says Ms. N.A. Anbu Vahini, Lead, Training and Development at MMSRF, Chennai. “Only about 3% salt is added to fresh fish, which becomes 12% when the fish gets dried. Traditionally dried fish has over 30% salt content.”
Fresh anchovies from the sea naturally contain around 1-2% salt. After drying, even when no salt is added, the natural salt concentration in the fish increases to around 5-7% due to moisture loss. “We have also studied the shelf life of unsalted fish dried under hygienic conditions and packed in aluminium foil. This method has provided a shelf life of up to nine months. However, according to FSSAI and CODEX standards, dried fish must have a minimum salt content of 12% to meet compliance requirements,” she says.
Doubling the protein content
If the protein content in traditionally dried fish is about 35-40%, it goes up to 70% in solar dried fish. “The low protein content in traditionally dried fish is because of high moisture content,” Ms. Vahini says. The main reason why the moisture content is high in traditionally dried fish is because the fish is not dried fully to reduce the moisture content below 16% as specified by FSSAI. The moisture content is reduced from about 70% to about 35-40% during summer and over 45% in winter in traditionally dried fish. In contrast, moisture content in solar dried fish is 5-15% to achieve higher shelf life. But up to 16% moisture is permissible.
“When the moisture content is high the shelf life is short. This is the reason why traditionally dried fish has a short shelf life of about two months,” Ms. Vahini says. “The solar dried fish has a shelf life of nine to 12 months when moisture content is 5-7, and nine months when the moisture content is about 10-15%.”
Even during peak summer, it takes about 22 hours to dry anchovy fish with 18% moisture using open sun drying, whereas solar drying takes only nine hours and reduces the moisture to just 6%. The open sun-drying method relies on ambient conditions of 34 degree C and a relative humidity of 54%, whereas solar drying increases the temperature to 55-60 degree C and reduces the humidity to about 17%. This quickens the drying process, she says. In winter, it takes about a day to dry using a solar drier, achieving 23% moisture content, compared to three days with 39% moisture content in the case of traditional open sun drying. “The solar drying method is 1.2 to 2.4 times faster compared with traditional sun drying, depending on the weather conditions,” Ms. Vahini says.
Importance of packaging
Shelf life depends not only on the moisture content but also on how the dry fish is stored post-drying. While no packaging material is used to store dried fish in the traditional method, people using solar driers use aluminium foil pouches or HDPE tray boxes to pack the dry fish. “Solar dried fish is stored in the containers and then packed using aluminium foil pouches. Vacuum packaging will make it airtight but then we don’t recommend it because it’s costly for small-scale fishers. Aluminium foil solves the problem when it is properly sealed. When correctly packed, the moisture content is about 5-7% and we have achieved 12 months of shelf life,” Ms. Vahini says. Proper selection of fresh fish, thorough cleaning using potable water, solar drying, and packaging using aluminium foil ensure that the dried fish is hygienic
Another key reason traditional open sun drying results in inferior dried fish is the use of leftover or unsold fresh fish, rather than fish specifically selected for drying. In some cases, even poor quality or spoiled fish is used. Fisherwomen have now been trained on all aspects of the process, including the importance of using fresh, high-quality fish for drying, she says.
Dry fish has a stronger smell than even fresh fish but can be reduced if care is taken at every step of the drying and packaging process. “The smell is greatly reduced when fish is washed properly prior to drying, following the correct salting process, maintaining hygienic conditions during the drying process, by increasing the rate of drying, reducing the amount of moisture in the dried fish, and proper packaging post-drying,” Ms. Vahini says. “Smell can be further reduced if the dry fish is powdered.”
Solar drying not only accelerates the drying process but also ensures superior product quality, lower moisture content, reduced microbial contamination, and enhanced nutritional retention.
Higher profits
According to Dr. S. Velvizhi from Fish for All Research and Training Centre, MSSRF, Poompuhar, traditionally dried anchovy sells at Rs.200-250 per kg, while solar dried anchovy sells for Rs.450-600 per kg. If the traditionally dried anchovy fish is bigger in size, it sells for Rs.300-400 per kg, while solar dried fish sells for Rs.750-800 per kg.
MSSRF has trained the fishing community in Tamil Nadu around the Poompuhar region, Nagapattinam, Cuddalore, and Rameshwaram on every aspect of fish drying starting with selecting fish for drying to packaging. Besides housing a large solar drier at its centre in Poompuhar, MSSRF has also supplied 50 mini, portable solar dryers with a capacity of 25-30 kg per day to women in Mudasalodai in Cuddalore district so they can dry fish in their own place instead of coming to the centre. Dr. Velvizhi says the Tamil Nadu government wants MSSRF to replicate the project in some fishing villages in the State.
Published – July 29, 2025 02:00 am IST
