Researchers obtain chocolate aroma from jackfruit seeds

Study shows compounds found in jackfruit seeds produce many of the aromas extracted from cocoa beans and can be used in the manufacturing of food products and cosmetics.

By Elton Alisson  |  Agência FAPESP – The seeds of the hard jackfruit (Artocarpus heterophyllus Lam.) can be substituted for cocoa in the formulation of products with chocolate aroma but without chocolate flavor.

A group of researchers at the University of São Paulo’s Luiz de Queiroz College of Agriculture (ESALQ-USP), in collaboration with colleagues at the Technology College (FATEC) in Piracicaba and Piracicaba Methodist University (UNIMEP) in Brazil and the University of Reading in the UK, have discovered that volatile compounds found in jackfruit seeds produce many of the aromas obtained from cocoa beans. As a result, these seeds, which are cheaper and more abundant, are potential substitutes for cocoa in products with chocolate aroma, such as cosmetics, foods and beverages.

The study, which resulted from projects supported by FAPESP, was described in an article published in the American Chemical Society’s Journal of Agricultural and Food Chemistry.

“We found that jackfruit seeds contain large amounts of pyrazines, the main compounds that determine chocolate aromas,” said Solange Guidolin Canniatti Brazaca, a professor at ESALQ-USP and principal investigator for the project.

The discovery was accidental, Brazaca told Agência FAPESP: it happened during a nutrition student’s scientific initiation project at UNIMEP. 

The aim of the project was to use jackfruit seed flour to make cakes, biscuits and bread because jackfruit seeds contain high proportions of starch and proteins. When they roasted the seeds as a first step to make flour, the researchers noticed that the seeds released an aroma very similar to that of chocolate.

The discovery inspired them to start a research project with the goal of identifying the volatile compounds in jackfruit pulp and seeds in 2011.

They studied both the hard and the soft varieties of jackfruit. The hard variety has larger fruit and firmer, crisper flesh. The results showed that hard jackfruit seeds had a more intense chocolate aroma.

To find the best method of obtaining flour with an aroma similar to that of chocolate from roasted seeds of the hard jackfruit, food scientist Fernanda Papa Spada undertook a PhD project with a scholarship from FAPESP, supervision by Brazaca, and collaboration with researchers at the University of Reading.

During the project, the researchers produced flour from jackfruit seeds that had been roasted and acidified or fermented before drying. The different batches of flour were roasted for different lengths of time and at different temperatures, using similar roasting and fermenting procedures to those used to obtain compounds with chocolate aroma from cocoa beans.

Analysis showed that fermentation was the best method to obtain flour with an aroma similar to chocolate from jackfruit seeds. However, the researchers observed that when seeds were only dried and roasted, without being fermented or acidified, they also contained a large number of compounds, and their high amino acid and sugar contents reacted during roasting to produce odors characteristic of chocolate.

“We tried acidifying roasted jackfruit seeds to release more pyrazine, but some undesirable residual odors resulted from acidification,” Brazaca said. “So we left aside acidification and opted instead for natural fermentation followed by drying.”

Using gas chromatography coupled with mass spectrometry (a technique employed to separate and analyze mixtures of volatile substances), the researchers also identified several compounds associated with chocolate aroma in the jackfruit seed flour, including 3-methylbutanal, 2,3-diethyl-5-methyl-pyrazine and 2-phenylethyl acetate.

They then used olfactometry to analyze each of these volatile compounds and asked a panel of trained experts to describe the intensity and other characteristics of the compounds’ aromas.

The panel’s descriptions associated fermented jackfruit flour with more caramel, hazelnut and fruity aromas than for acidified flour.

“Cocoa beans were found to contain more pyrazine compounds than cocoa, and fermented seeds had a more intense chocolate aroma owing to the formation of aldehydes and esters, which are characteristic of cocoa,” Spada said. 

Formulations

The researchers then added jackfruit seed flour to a cappuccino mixture to find out whether it could be used as a substitute for chocolate aroma extracted from cocoa.

The results of the test showed that jackfruit seed flour could be used as a substitute for chocolate aroma from cocoa without interfering with the drink’s coffee flavor.

“The tasters found no difference between the chocolate aroma obtained from jackfruit seeds and the chocolate aroma produced by cocoa beans,” Brazaca said.

As part of a master’s research project also supported by a scholarship from FAPESP, the researchers now plan to evaluate the use of two microorganisms currently used to ferment cocoa – Kluyveromyces marxianus and Saccharomyces cerevisiae – in fermenting seeds of the hard jackfruit and to estimate the microorganisms’ effect on the production of the chocolate aroma.

“Our initial idea was to promote more complete use of the jackfruit,” Brazaca said. “In Brazil, only the pulp is used, corresponding to 30% of its weight, and the remaining 70%, consisting of the rind, central portion and seeds, is discarded.”

Boiled jackfruit seeds are consumed in Asia, whereas in Brazil, which produces more jackfruit than any other country in the Americas, jackfruit seeds are considered waste, Brazaca noted.

The article “Optimization of postharvest conditions to produce chocolate aroma from jackfruit seeds” (doi: 10.1021/acs.jafc.6b04836), by Spada et al., can be read by subscribers to the Journal of Agricultural and Food Chemistry at pubs.acs.org/doi/abs/10.1021/acs.jafc.6b04836.