{"id":4536,"date":"2022-07-28T22:00:00","date_gmt":"2022-07-28T22:00:00","guid":{"rendered":"https:\/\/modernsciences.org\/staging\/4414\/?p=4536"},"modified":"2022-07-14T04:38:12","modified_gmt":"2022-07-14T04:38:12","slug":"how-nigeria-can-turn-its-huge-cashew-waste-into-valuable-citric-acid","status":"publish","type":"post","link":"https:\/\/modernsciences.org\/staging\/4414\/how-nigeria-can-turn-its-huge-cashew-waste-into-valuable-citric-acid\/","title":{"rendered":"How Nigeria can turn its huge cashew waste into valuable citric acid"},"content":{"rendered":"\n
\n \n
\n Cashew apples.\n VW Pics via Getty Images <\/a><\/span>\n <\/figcaption>\n <\/figure>\n\nAgbaje Lateef<\/a>, Ladoke Akintola University of Technology, Ogbomoso <\/a><\/em> and Adekunle O. Adeoye (PhD)<\/a>, Ladoke Akintola University of Technology, Ogbomoso <\/a><\/em><\/span>\n\n

Nigeria \u2013 the sixth largest producer of cashew nuts globally<\/a> \u2013 exports more than 80% of its raw cashews primarily to Vietnam and India<\/a> where they are processed into various consumer products such as butter, food and cosmetic ingredients.<\/p>\n\n

But Africa\u2019s most populous nation can extract more economic value out of cashews by using their wastes to produce citric acid.<\/p>\n\n

Cashew is a tropical tree<\/a> cultivated for its fruit (cashew nut) and pseudofruit (cashew apple). The nut is the major reason for planting cashew<\/a> \u2013 it is very nutritious. The fleshy \u201capple\u201d part yields a juice which is high in vitamins and minerals. <\/p>\n\n

But the juice is high in anti-nutrients too. These are compounds that prevent the body from absorbing nutrients. They also make the juice less palatable<\/a>. Because of this, cashew apples are mostly discarded.<\/p>\n\n

The apple pulp, shell and liquid from the shell are all wasted<\/a> or underutilised. Yet, these are valuable materials and they can be improved by biotechnology. <\/p>\n\n

We\u2019ve been conducting work<\/a> into the potential<\/a> of producing citric acid from cashew juice. It was the first effort globally to produce citric acid from cashew juice. Citric acid is widely used to preserve blood, drugs and processed foods and drinks. Its global value is expected to reach US$4 billion in 2027<\/a>. <\/p>\n\n

We used cashew from Ogbomoso<\/a>, south west Nigeria, an area that produces some of the best cashew nuts in Nigeria. <\/p>\n\n

Cashews in Nigeria<\/h2>\n\n

Nigeria currently harvests 200,000 to 240,000 metric tons <\/a>of raw cashew nuts each year, with about 85% of this exported. Nigeria\u2019s no different to other African countries that export the bulk of their production as raw cashew nuts.<\/p>\n\n

Africa, with production of 2,334,405 tons, is the world\u2019s largest producer and exporter of raw cashew nuts<\/a>, accounting for more than 50% of production. Between 2000 and 2018, world trade in raw cashew nuts more than doubled to 2.1 million tons<\/a>, and African producers \u2013 led by C\u00f4te d\u2019Ivoire \u2013 accounted for almost two-thirds of the growth. In 2020, trade in cashew nuts was worth US$6.87 billion<\/a>.<\/p>\n\n

Cashew farming contributes<\/a> about N24 billion (about US$58 million) to the Nigerian economy annually. It employs more than 600,000 people<\/a>.<\/p>\n\n

The sector could do more. Our work shows that citric acid can be produced from cashew apple juice, which is abundant in Nigeria. Domestic production would save Nigeria US$31 million<\/a> a year in foreign exchange, based on citric acid imports for 2020.<\/p>\n\n

Nigeria can produce citric acid from cashew apple juice by using biotechnology<\/a> – the science of using biological processes to produce valuable materials and services. For instance, man makes use of some bacteria to convert milk to yoghurt. Yeast is used in producing bread via biotechnology. Biotechnological products were valued<\/a> at US$752.88 billion in 2020 with projected growth of 15.83% for 2021-2028.<\/p>\n\n

Cashew wastes, too, can be turned to wealth<\/a> by creating new products. For instance, cashew nut shell liquid produces<\/a> chemicals that can be used in the making of paints, varnishes, agrochemicals and medicines. Shell and pulp are used<\/a> through biotechnology to produce animal feeds and bioethanol. Biotechnology can also turn the juice into drinks and ethanol<\/a>.<\/p>\n\n

Citric acid from cashew<\/h2>\n\n

In our efforts to add value to cashew, we focused on the underutilised cashew apple juice and aimed to test the possibility of producing citric acid from the juice. <\/p>\n\n

The demand for citric acid is growing because of its usefulness<\/a> in food, pharmaceutical and cosmetic industries. New sources of nutrients are needed<\/a> to grow microorganisms<\/a> that produce citric acid.<\/p>\n\n

Nutrients in the cashew juice and pulp support the growth<\/a> of microorganisms. <\/p>\n\n

We used cashew apple juice<\/a> to grow black mould to produce citric acid for the first time globally. Black mould is a fungus that is widely distributed in the environment. It produces black spores when it grows. It is scientifically known as Aspergillus<\/em> niger<\/em>.<\/p>\n\n

The mould grows on simple and cheap materials. It has been used to produce citric acid<\/a> since 1919. It is used to produce different products, including enzymes, proteins and animal feeds. It is celebrated<\/a> as a microorganism that has made huge contributions to biotechnology for 100 years. <\/p>\n\n

The best locally sourced black mould consumed the juice to produce citric acid in large quantities. It produced 92.8g of citric acid per litre of juice after 10 days of growth. The yield is considered very high compared to those that were earlier reported<\/a>.<\/p>\n\n

We used the citric acid to coagulate soy milk to make cheese. Citric acid<\/a> is used as coagulant in producing cheese. We asked a panel to test the quality of the cheese. They found the soy cheese to have better characteristics than those produced locally using fermented liquor of corn. These include better colour, texture, flavour and firmness.<\/p>\n\n

We then used scientific techniques<\/a> to increase the citric acid production. We manipulated growth conditions of the mould and applied nanomaterials in its nutrition in this regard. It was the first report globally to increase citric acid production by applying nanotechnology.<\/p>\n\n

At various times, we used four techniques to improve capability of the mould. These include obtaining high-yielding mould by exposure to radiation. Then, we added sugar to the juice to study its effect on yield of citric acid. We evaluated the addition of zinc oxide nanoparticles on citric acid production. Finally, we determined the best growth conditions to support citric acid production by our mould.<\/p>\n\n

These efforts increased citric acid production by the mould in cashew juice by about 2.38 to 11.98 times of the original production. For instance, addition of zinc oxide nanoparticles gave yield of 34.62% citric acid per day. The best growth conditions turned in 92.61% citric acid per day. These results showed that we can improve productivity of the mould to enhance commercial production of citric acid.<\/p>\n\n

Moving forward<\/h2>\n\n

Large scale production of citric acid using cashew apple juice could achieve several benefits. It could:<\/p>\n\n