Bergamot (Citrus Bergamia Risso) is a natural hybrid of bitter orange and lemon. It is grown almost exclusively in the Reggio Calabria region of Southern Italy. Annual production is around 25,000 tonnes, most of which is used for the production of essential oil from the skins.
While the essential oil is used by the pharmaceutical, cosmetics industries and food industries (its primary food use is as an aroma for confectionery, liquors and tea), the juice is considered a waste product.
Its bitter taste has precluded the juice from food industry uses in the past, and its disposal represents a big economic and environmental burden.
But Rita Pernice and colleagues from the University of Naples believe that juice could actually be used to fortify other, commonly consumed, fruit juices with additional flavonoids and to prevent the thermal degradation of ascorbic acid (vitamin C) during processing.
The first stage of the research was to identify the phenolic pattern of bergamot juice “so as to understand the potential use of this by-product as a natural additive that has healthful properties”.
Analysis by HPLC showed the presence of narirutin, naringin, isorhoifolin and rhoifolin, as well as lower amounts of rutin. Analysis by LC/MS/MS also allowed additional compounds to be identified: neoponcirin, hesperidin and neodiosmin.
Interestingly, the researchers reported that this is the first study to have reported the presence of isorhoifolin, rhoifolin and rutin.
Next, Pernice and team tested the bergamot juice in a real food system. They used a traditional industrial recipe to make fruit juice from apples and apricots on a laboratory scale. They also made variants that contained 10 and 20 per cent bergamot juice, both together with and replacing synthetic ascorbic acid and citric acid.
The juices were tested throughout the production process and after storage at 37ºC for 15 days.
“All the results obtained support the hypothesis that the addition of bergamot juice to juices preserves their ascorbic acid content from thermal degradation and contributes to enhance the antioxidant activity, ensuring a product much richer in antioxidants and ascorbic acid,” wrote Pernice.
In particular, it was noted that the bergamot had a better effect on preserving ascorbic acid after thermal treatment and storage than the synthetic additives. The reasons for this are not known, but it may be due to the bioactive compounds – the bergamot polyphenols in particular.
The final part of the study was to try out the juice enhanced with bergamot with consumers, to see if they found the product acceptable.
Colour- and visual viscosity wise, the fortified juices ranked quite highly (5.2 to 6.8 and 5.1 to 6.5 respectively, on a scale of 1 to 10). However while the 10 per cent bergamot juice had an acceptable taste (4.3 to 6.6), the 20 per cent juice was not acceptable as it was too bitter or astringent.
The researchers did not rule out using the bergamot juice at a level of 20 per cent however; they said that modifications to the recipe could reduce bitterness, as could a milder extraction procedure.
Although these responses from consumers were only preliminary, involving 60 untrained panellists who said they drank fruit juice at least twice a week, they were taken to be “encouraging”.