AAU researchers develop breakthrough technology to preserve lemon juice without bitterness

Guwahati, Dec 29: In a development that can revolutionise the citrus juice industry, a team of researchers of Assam Agriculture University (AAU) has pioneered a technology for the preservation of fresh lemon juice for nearly two years without any detectable bitter aftertaste and that too without using any preservative.

Assam lemon, commonly known as kazi nemu, is a distinctive citrus fruit of Northeast India and is characterized by its unique flavour and alluring fragrance. It also made a significant impact on global markets.

It is a nutritional powerhouse with an ample amount of vitamin C (90-70 mg/100ml) and antioxidants, which makes it an ideal commodity to enhance immunity, maintain skin health, and promote overall well-being. Despite its merits, roughly one-fourth of its yield is lost due to poor post- harvest infrastructure and majority of the produce is sold as fresh fruit, because cold-stored Assam lemon and its preserved juices develop an unpleasant bitter taste, which has been a growing concern among the stakeholders.

"The lemon juice develops bitter taste after it is squeezed out due to a chemical reaction, which causes formation of limonin. During our research that spanned over three years, we used a chemical-free physical processing method to preserve the original taste. The juice has not turned bitter even after two years. More importantly, the vitamin C content degraded by only around 20-22 percent," one of the researchers of the biotechnology department said, adding that all FSSAI guidelines were followed in the process.

The lemon juice normally available in the market has preservatives and vitamin C content either nil or extremely low. The physical processing method used by the AAU researchers to preserve the lemon juice is called ultrasonication.

The juice can be preserved in glass bottles at 4 degrees Celsius.

The seedless variety of kazi nemu, cultivated over 0.13 lakh hectares in Assam, has achieved an output of 1.04 lakh metric tons. In 2019, Assam lemon was awarded the Geographical Indication tag.

Significant achievements in export include deliveries to London and Dubai.

"A concern for the citrus juice industry has been the preservation of thick pectin cloud in the processed juices and beverage. While solutions exist to eliminate these concerns using chemical additives and expensive enzymes and adsorbents, their industrial applicability remains limited or confined to R&D labs. Emerging technologies such as ultrasonication have shown potential that is a non-thermal, sustainable, and cost-effective approach. It can revolutionize the citrus juice industry by lowering bitterness while keeping the juice's bioactive components and attractive pectin cloud intact. So far, no systematic study has addressed these concerns of Assam lemon in a cohort manner. By developing a practical and effective debittering technique, we can ensure that Assam Lemon juice can be kept under refrigerated storage, without affecting much of its nutritional integrity and its shelf-life can be prolonged up to two years without any detectable bitter aftertaste," an AAU researcher said.

AAU is now looking to transfer the technology for its commercialization.

By Rituraj Borthakur