Jabuticaba peel improves nutritional characteristics of bread

Researchers at the State University of Campinas (UNICAMP) in São Paulo state, Brazil, have developed a sourdough bread formulation enriched with jabuticaba peel that could be an alternative for people with diabetes and others who need to control blood sugar. An article describing their research and test results is published in the journal Foods.

As noted in the article, the high carbohydrate content of bread can sharply raise blood sugar levels, risking hyperglycemia. Given the high demand for healthier bread, which is widely consumed, artisanal bakers seek to diversify their products with formulations that add nutritional value while involving fermentation methods that favor a less intense glycemic response. 

According to data in the article, the addition of jabuticaba peel flour increased the bread’s fiber content by more than 50% and raised its antioxidant capacity by between 1.35 times and 3.53 times depending on the proportion of jabuticaba peel flour added to the formulation. This supplementation increased the bioavailability of nutrients and enhanced the nutritional composition of the final product.

The researchers conducted a crossover trial to assess the glycemic peak (the highest blood sugar level reached) after consumption of normal bread made by the long fermentation method (which tends to induce a lower glycemic peak) and consumption a week later of bread containing jabuticaba peel flour. Blood sugar peaked 30 minutes after ingestion of the normal bread without jabuticaba peel flour, remaining high for another 15 minutes and then trending down. In the case of the bread supplemented with jabuticaba peel flour, the peak was lower, occurring 45 minutes after ingestion, and blood sugar fell slowly for two and a quarter hours.

Metabolism

Blood sugar rises after ingestion of bread and other carbohydrate-rich foods. Digestion releases glucose, telling the pancreas to secrete insulin, which induces a return to prior blood sugar levels. Flaws in this process lead to health problems, and it is important to observe the extent to which blood sugar spikes in response to eating.

“If we have lower post-prandial spikes in sugar and insulin levels, we’ll be less likely to develop diabetes and metabolic syndrome. For people who already have hyperglycemia, controlling sugar spikes after meals can reduce the risk of heart disease. Also, we can extend the lives of insulin-producing cells,” said Bruno Geloneze, penultimate author of the article. Geloneze is a professor at UNICAMP’s School of Medical Sciences (FCM) and a member of the Obesity and Comorbidities Research Center (OCRC), a Research, Innovation and Dissemination Center (RIDC) funded by FAPESP.

For last author Cinthia Cazarin, a professor at the School of Food Engineering (FEA-UNICAMP) and supervisor of the thesis that served as a basis for the article, the main challenge in producing bread for the trials was deploying the technology while maintaining nutritional and functional value. 

“Jabuticaba peel flour has highly specific sensory characteristics, and its inclusion had to be evaluated with regard to both the technological characteristics of breadmaking and the processing and conservation of the bioactive compounds involved,” she said.

Conservation is relevant because the improvement in blood sugar control and insulin response is associated above all with the phenolic compounds present in jabuticaba peel, such as anthocyanins, which account for the fruit’s dark purple color, and avoidance of their “loss” during processing is therefore essential.

Another important finding relates to satiety. The participants felt fuller 60 minutes after eating the bread with jabuticaba peel flour than after they ate the control bread. The authors of the article note that satiety is generally found to improve when blood sugar returns to baseline more slowly, as it does with foods that have a low glycemic index.

Antioxidant capacity was monitored for three hours after ingestion of the bread. Neutralization of free radicals increased significantly and lasted longer after consumption of the bread with jabuticaba peel flour. 

“This improvement in antioxidant capacity is important because the development of metabolic disorders, cardiovascular disease and cancer, as well as the aging process, involve protein oxidation mechanisms in the body.  The antioxidant capacity of a food can be beneficial in all these mechanisms,” Geloneze said.

Another significant finding was extension of shelf life to seven days, which according to the researchers showed that the bacteria in jabuticaba peel and metabolites formed during the fermentation process can act as natural preservatives in long-fermentation products, inhibiting the growth of pathogenic microorganisms.

Jabuticaba

Researchers have focused in recent years on the inclusion of ingredients with high biological value in food products, especially agroindustrial byproducts, given the large quantities produced, their nutraceutical potential, and the environmental impact associated with their disposal, the article notes.

For example, Mário Maróstica, full professor at FEA-UNICAMP and a co-author of the article supported by FAPESP, has led many studies on the characterization of bioactive compounds in native Brazilian fruits (read more at: agencia.fapesp.br/51723). 

Consumption of jabuticaba (Plinia jaboticaba) and other red and purple berries is known to help prevent or delay the emergence of non-transmissible chronic diseases. “Jabuticaba peel contains phenolic compounds and fibers that have been shown in several studies to contribute to the control of blood sugar and cholesterol,” Maróstica said.

The juice of this berry has also been shown to reduce insulin resistance and increase the production of GLP-1, a hormone that helps regulate digestion, satiety and glycemia (as emulated by medications such as semaglutide and liraglutide).

The results of all this research are promising, and the group comprising scientists from UNICAMP’s medical and food engineering schools continue to investigate the fruit’s bioactive compounds. They are now conducting in vivo trials with animal models to find out whether and how these compounds can combat depression and help prevent colorectal cancer.

About FAPESP

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the state of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration.