Nigeria – the sixth largest producer of cashew nuts globally – exports greater than 80% of its uncooked cashews primarily to Vietnam and India the place they’re processed into varied shopper merchandise similar to butter, meals and beauty substances.
But Africa’s most populous nation can extract extra financial worth out of cashews through the use of their wastes to supply citric acid.
Cashew is a tropical tree cultivated for its fruit (cashew nut) and pseudofruit (cashew apple). The nut is the major reason for planting cashew – it is vitally nutritious. The fleshy “apple” half yields a juice which is excessive in nutritional vitamins and minerals.
But the juice is excessive in anti-nutrients too. These are compounds that stop the physique from absorbing vitamins. They additionally make the juice less palatable. Because of this, cashew apples are principally discarded.
The apple pulp, shell and liquid from the shell are all wasted or underutilised. Yet, these are valuable supplies and so they can be improved by biotechnology.
We’ve been conducting work into the potential of manufacturing citric acid from cashew juice. It was the primary effort globally to supply citric acid from cashew juice. Citric acid is extensively used to protect blood, medicine and processed meals and drinks. Its international worth is predicted to succeed in US$4 billion in 2027.
We used cashew from Ogbomoso, south west Nigeria, an space that produces a number of the finest cashew nuts in Nigeria.
Cashews in Nigeria
Nigeria presently harvests 200,000 to 240,000 metric tons of uncooked cashew nuts annually, with about 85% of this exported. Nigeria’s no totally different to different African international locations that export the majority of their manufacturing as uncooked cashew nuts.
Africa, with manufacturing of two,334,405 tons, is the world’s largest producer and exporter of raw cashew nuts, accounting for greater than 50% of manufacturing. Between 2000 and 2018, world commerce in uncooked cashew nuts more than doubled to 2.1 million tons, and African producers – led by Côte d’Ivoire – accounted for nearly two-thirds of the expansion. In 2020, trade in cashew nuts was worth US$6.87 billion.
Cashew farming contributes about N24 billion (about US$58 million) to the Nigerian economic system yearly. It employs greater than 600,000 people.
The sector might do extra. Our work reveals that citric acid can be produced from cashew apple juice, which is considerable in Nigeria. Domestic manufacturing would save Nigeria US$31 million a yr in overseas change, primarily based on citric acid imports for 2020.
Nigeria can produce citric acid from cashew apple juice through the use of biotechnology – the science of utilizing organic processes to supply valuable supplies and providers. For occasion, man makes use of some micro organism to transform milk to yoghurt. Yeast is utilized in producing bread by way of biotechnology. Biotechnological merchandise had been valued at US$752.88 billion in 2020 with projected progress of 15.83% for 2021-2028.
Cashew wastes, too, can be turned to wealth by creating new merchandise. For occasion, cashew nut shell liquid produces chemical substances that can be used within the making of paints, varnishes, agrochemicals and medicines. Shell and pulp are used by means of biotechnology to supply animal feeds and bioethanol. Biotechnology can additionally turn the juice into drinks and ethanol.
Citric acid from cashew
In our efforts so as to add worth to cashew, we centered on the underutilised cashew apple juice and aimed to check the potential for producing citric acid from the juice.
The demand for citric acid is rising due to its usefulness in meals, pharmaceutical and beauty industries. New sources of vitamins are needed to develop microorganisms that produce citric acid.
Nutrients within the cashew juice and pulp support the growth of microorganisms.
We used cashew apple juice to develop black mould to supply citric acid for the primary time globally. Black mould is a fungus that’s extensively distributed within the surroundings. It produces black spores when it grows. It is scientifically often known as Aspergillus niger.
The mould grows on easy and low-cost supplies. It has been used to produce citric acid since 1919. It is used to supply totally different merchandise, together with enzymes, proteins and animal feeds. It is celebrated as a microorganism that has made huge contributions to biotechnology for 100 years.
The finest regionally sourced black mould consumed the juice to supply citric acid in massive portions. It produced 92.8g of citric acid per litre of juice after 10 days of progress. The yield is taken into account very excessive in contrast to people who had been earlier reported.
We used the citric acid to coagulate soy milk to make cheese. Citric acid is used as coagulant in producing cheese. We requested a panel to check the standard of the cheese. They discovered the soy cheese to have higher traits than these produced regionally utilizing fermented liquor of corn. These embody higher color, texture, flavour and firmness.
We then used scientific techniques to extend the citric acid manufacturing. We manipulated progress situations of the mould and utilized nanomaterials in its vitamin on this regard. It was the primary report globally to extend citric acid manufacturing by making use of nanotechnology.
At varied occasions, we used 4 methods to enhance functionality of the mould. These embody acquiring high-yielding mould by publicity to radiation. Then, we added sugar to the juice to check its impact on yield of citric acid. We evaluated the addition of zinc oxide nanoparticles on citric acid manufacturing. Finally, we decided the perfect progress situations to help citric acid manufacturing by our mould.
These efforts elevated citric acid manufacturing by the mould in cashew juice by about 2.38 to 11.98 occasions of the unique manufacturing. For occasion, addition of zinc oxide nanoparticles gave yield of 34.62% citric acid per day. The finest progress situations turned in 92.61% citric acid per day. These outcomes confirmed that we can enhance productiveness of the mould to reinforce industrial manufacturing of citric acid.
Moving ahead
Large scale manufacturing of citric acid utilizing cashew apple juice might obtain a number of advantages. It might:
- add worth to cashew farming and enhance revenue from planting the crop
- cut back the environmental nuisance of disposal of cashew apple
- improve Nigeria’s potential to supply citric acid regionally
- enhance the economic system and save overseas change reserves.
Agbaje Lateef, Professor of Microbiology, Ladoke Akintola University of Technology, Ogbomoso and Adekunle O. Adeoye (PhD), Lecturer in Food Science, Ladoke Akintola University of Technology, Ogbomoso
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