By Roseanne Mwangi
BLACK SOLDIER FLY larvae farming aims at producing protein rich larvae that is very well suited as feed ingredient first for poultry, fish, pigs and pets, and then for other livestock. The protein content of BSF larvae ranges from 40% to 60%, depending on the feeding regime/ waste stream substrate that the larvae has been fed on. BSF is also an excellent source of fat, which can be extracted and used in various applications, such as feed additive, biofuels and cosmetics. BSF’s products are unique in that there is no waste at all from the process of farming the BSF Larvae. The two main line of products come from the waste/substrate that the larvae feed on, and the larvae themselves.
As a biofertilizer the frass or excreta of BSF larvae is rich in nutrients and can be used as organic fertilizer for plants.
The BSF Larvae itself is the base product of high-quality insect protein of sufficient digestibility that is presented in the biomass of the larvae. This protein has a good amino acid profile that is sufficient for the nutritional needs of most livestock and animals and is also rich in fats.
From the larvae we get the following products:
- Whole wet larvae
- Whole dried larvae
- BSF meal
- BSF oil
After harvesting, the product achieved is whole wet larvae, also referred to as live larvae. This is washed and blanched in hot water for 50 seconds to kill the larvae and arrest their development at the 5th instar, which is the stage at which they have the highest levels of protein and nutrients. The larvae can be used as wet larvae, and can also be taken for further processing by drying them. The best method of drying them is through hot air drying.
Efficient drying services are required because once a farmer collects his/her BSF larvae, they must decide how best to dry
them so that they can store them potentially long-term (outside of freezing). The larvae enter the drying phase of the process coming from a wash to remove residual feed needs to be adequately and well dried before packaging and storage.
Freshly harvested BSF larvae contain ±70% water and ± 30% dry matter and have a high-water activity of 0.9. Water activity is a measure for the free water in the product, which is available for microorganisms, whereas a water activity lower than 0.6 inhibits growth of any bacteria and yeasts. The high-water activity makes the fresh larvae highly susceptible to lipid oxidation, enzymatic degradation, and microbiological spoilage.
Removal of water and thereby reducing water activity inhibits microbial and enzymatic activity and thus, makes the product storable. By evaporation of water, the remaining nutrients in the product become more concentrated, which means dried larvae have a higher protein content compared to fresh larvae. This necessitates acquisition and utilization of an efficient mechanical dryer to ensure best results.
A hot air drier works on the principle of hot air being blown on the product, after the product is washed and blanched at a
temperature of 90 degrees, to kill the larvae to arrest the growth of the larvae at the point where they have the highest protein content. This clean wet dead larvae then needs to be dried at once in order to preserve the nutrition quality as well as arrest the decay that is caused by wetness and a moist environment.
The hot air drier works to do these two functions effectively by drying the larvae as individual pieces, and drying the entire
quantity at once, without interruption as is sometimes seen when using other forms of drying like solar drier. Uniform drying is critical in order to preserve the freshness of the dried larvae. As it dries, it concentrates the protein and fats while removing the moisture. The fats have the characteristic of making the product go rancid if its not handled well, and this would spoil the entire production.
Dried larvae lose 70 per cent of the body weight of live larvae, and get a concentration level of up to 3 times that of the protein in the live larvae. As such, drying is mainly done in order to ensure transportation and storage. In order to best mix the larvae as feed in feed formulations a further step of defatting is sometimes necessary. This is because when milled without defatting, a substantial quantity of the BSF protein is left in the machine due to the oily nature of the dried larvae.
Defatting is still quite new in Kenya, and so to navigate this hurdle, the BSF is milled with a grain e.g. maize, in order for
the oil and protein to be soaked up by the dry part of the grain. Some applications are also being adapted for use with the larvae, where the wet, cleaned and arrested larvae is mixed with a drying agent such as bran and passed through an extruder to get it to dry to the desired levels. Through the generous support of friends and associates of BSF, the Association of Insect Farming and its Products (AIFP) is looking to develop a model where hot air drying can be made available to insect farmers who would want the service, in a way that would keep the quality of the product optimal,
in order to attract and maintain the interest the insects are generating in the marketplace
There are various reasons for drying the larvae. Freshly harvested BSF contains 70% water and 30% dry matter. Drying enables longer storage, transportation, and selling of the BSF larvae as the process of drying reduces water activity. Removing water by drying, leaves larvae with a higher concentration of protein, compared to fresh larvae.
To ensure that enough drying has been done, one should calculate the difference in mass between the dried larvae, against the fresh larvae. If the mass of the dried larvae, divided by the mass of the wet larvae is 25-35%, then that means the larvae is dry, it has lost about 70% of water.
Defatting BSF
The whole dried larvae can then be pressed to remove the fats, this process is called defatting. It results in defatted BSF larvae that is in powder form- BSF larvae meal- leaving behind the BSF oil. BSF oil adds to the energy requirements of growing livestock and provides the much-needed oil and sheen for their glow of health.
Then there is chitin which is extracted from the pupae shells of emerged flies and is proving to have very interesting applications in industries, including agriculture, medicine, and biotechnology. Uses include making of biodegradable plastics, and water purification systems. Also, since it has been shown to have antimicrobial properties, it is being applied in the making of wound dressings and medical implants.