What is passion fruit

The passion fruit is the fruit of a number of plants in the Passiflora family. There are more than 520 varieties, about 30 of which are edible ¹⁾. The vast majority of Passiflora species (approximately 96%) are distributed throughout the Americas and Brazil and Colombia are prominent centers of diversity for this genus, as approximately 30% of Passiflora species (~150 species in Brazil and ~170 species in Colombia) are found in these regions, with 89 species being endemic to Brazil ²⁾. Brazil is the largest producer and consumer of passion fruit ³⁾) and production was estimated at 676,000 tons annually for the last 10 years, with approximately 776,000 tons in 2012 alone, totaling approximately 70% of the global supply ⁴⁾). Currently, the average Brazilian productivity is estimated at 14 ton per ha per year ⁵⁾), with the potential to increase up to 50 ton per ha per year.

Edible passion fruits can be divided into three main types ⁶⁾:

• Purple ones (fruits of Passiflora edulis Sims),
• Yellow ones (Passiflora edulis f. flavicarpa Deg.), and
• Giant granadilla (Passiflora quadrangularis L.).

Shaped like an egg, the passion fruit ranges from 2 to 8 inches long. The yellow pulp has a jelly-like consistency and contains many edible graped-size, flesh-covered black seeds that are somewhat like those of a pomegranate.

The purple varieties bear dark purple to black fruits that are about 2 inches long. The yellow varieties bear slightly longer (2.5 inches) deep-yellow fruits. Less commonly found are the giant granadilla varieties, which can reach 8 inches in length.

Being a tropical to subtropical fruit, the passion fruit is best grown in the frost-free climates. In addition to South America, United States, Malaysia, Africa, the West Indies and New Zealand also grow passion fruit. California and Florida account for the majority of domestic production of the purple passion fruits, whereas Hawaii produces mainly the yellow varieties.

Passion fruit is more commonly used as an ingredient in commercial food and drink products.

The passion fruit plant is a vigorous climbing vine that can grow 15 to 20 feet a year once established. Each fruit develops from a small fragrant flower that is 2 to 3 inches wide with green and white petals. The passion fruits quickly turn from green to purple (or yellow) when ripe and fall to the ground within a few days. They can be picked from the vine or harvested off the ground.

Figure 1. Passion fruit (purple – Passiflora edulis)

Figure 2. Passion fruit (yellow)

Figure 3. Passion fruit (giant granadilla)

Figure 4. Passion fruit plant

Passion fruit nutrition facts

Passion fruit is high in vitamin C and dietary fiber if the seeds are consumed along with the pulp. In addition, passion fruit is a good source of vitamin A (beta-carotene). The passion fruit seeds contains between 30-40% of your daily dietary fiber requirement. The World Health Organization recommends a diet fiber consumption of 25 – 35 g/day, 35% of which shall consist of 65% soluble and insoluble fiber.

Table 1. Passion fruit (granadilla), purple raw nutrition facts

[Source: United States Department of Agriculture Agricultural Research Service ⁷⁾]

Table 2. Passion fruit juice (purple, raw) nutrition facts

[Source: United States Department of Agriculture Agricultural Research Service ⁸⁾]

Table 3. Passion fruit juice (yellow, raw) nutrition facts

[Source: United States Department of Agriculture Agricultural Research Service ⁹⁾]

What does passion fruit taste like ?

The passion fruit pulp’s flavor is sweet-tart and lemony and it is high fragrant.

How to eat a passion fruit

Passion fruit’s pulp can be eaten plain or spooned over ice cream, cakes and other desserts. Passion fruit also makes delicious jams and jellies, to which the seeds add a crunchy texture.

The fruit also can be pressed to extract the highly fragrant juice that adds a pleasant flavor to beverages such as iced tea, punch and cocktails.

Passion fruit benefits

Passion fruit species are used as a natural resource for the pharmaceutical ¹⁰⁾, cosmetic ¹¹⁾ and juice industries ¹²⁾); they are also used as ornamental plants ¹³⁾) and consumed as a fresh food item ¹⁴⁾).

A study by Córdova and colleagues ¹⁵⁾ reported the functional properties of passion fruit peel, especially those related to the content and type of fiber.  Several studies have reported that the genus passion fruit has been used as an aid in the treatment (or control) of diabetes, mainly due to the presence of soluble fibers such as pectin ¹⁶⁾, ¹⁷⁾. According to Pereira ¹⁸⁾, soluble fibers tend to delay gastric emptying and the passage of food through the intestines. Therefore, promoting lower glucose absorption, increased insulin sensitivity, reduction in plasma cholesterol and blood pressure, and also helping in weight control. These actions are due to the property of soluble fibers to bind water molecules and forming a gel-like substance. This reduces the absorption of fat and sugars and promotes lubrication of the stomach and intestinal wall, thus contributing to the proper functioning of the intestinal transit ¹⁹⁾. As for the insoluble fiber, it has been found to accelerate intestinal transit, increasing fecal bulk and slowing the hydrolysis of glucose ²⁰⁾. Thus, a high fiber diet tends to lower the risk of obesity and cardiovascular and gastrointestinal diseases ²¹⁾. There is no doubt of the great benefits of dietary fiber as a constituent of food.

The action of pectin as a hypocholesterolemic agent in animals has also been demonstrated ²²⁾. Moreover, pectin showed a hypoglycemic and plasma insulin secretion-inducing effects in rodents ²³⁾. These characteristics and functional properties make the passion fruit peel a potential ingredient for the development of new products such as foodstuffs, mainly due to the considerable amount of pectin in the fruit mesocarp ²⁴⁾.

Passion fruit seeds also contain an active phenolic compound called Piceatannol, a resveratrol metabolite ²⁵⁾. Previous reports showed that piceatannol has various effects, such as improvement of hyperglycemia. Uchida-Maruki et al. demonstrated that piceatannol or a passion fruit seed extract reduced blood glucose levels in mice consuming a high-fat diet or a genetic diabetic mouse model (db/db mice) without changing body weight and visceral fat weight ²⁶⁾. Minakawa et al. also reported that piceatannol promoted glucose uptake, AMPK phosphorylation and glucose transporter4 (GLUT4) translocation in cultured L6 myotubes in the absence of insulin. Furthermore, piceatannol suppressed rises in blood glucose levels at early stages and improved impaired glucose tolerance at later stages in a genetic diabetic mouse model (db/db mice) ²⁷⁾. In addition, Zhang et al. demonstrated that dietary polyphenols, such as resveratrol and piceatannol in mice with a high-fat diet, lowered postprandial hyperglycemia, indicating that inhibition of intestinal α-glucosidase activity may be a potential mechanism contributing to their anti-diabetic properties ²⁸⁾. Therefore, piceatannol may achieve an anti-diabetic effect through multiple mechanisms in animal models. However, the effects of piceatannol in humans have never been reported.

In this piceatannol human study ²⁹⁾ involving 39 Japenese subjects, 10 non-overweight (Body mass index (BMI) < 25 kg/m2) men and 10 non- overweight women, as well as 10 overweight (BMI ≥ 25 kg/m2) men and 9 overweight women aged between 20-70 years old. Subjects were randomly assigned (1:1) to treatment for 8 weeks with capsules containing 5 mg of piceatannol, which was purified from passion fruit seed extract using gamma-cyclodextrin (Purity 81.4%) or containing dexitrin, a placebo (2 capsules of piceatannol with 5 mg/capsule, twice daily for a total of 20 mg/day or 2 capsules of placebo (dextrin) 5 mg/capsule, twice daily). During the trial period, subjects were instructed to abstain from using nutritional supplements and consuming food suspected to contain polyphenols in significant amounts. Furthermore, the importance of maintaining their normal way of life was underscored. Compliance, defined as the proportion of tablets ingested relative to the intended number, was calculated when participants returned the remaining tablets during the final examination. The researchers showed that supplementation with piceatannol for 8 weeks led to an improvement in insulin sensitivity, which was evaluated by fasting serum insulin and HOMA-IR, in overweight men. Additionally, in non-overweight women, piceatannol reduced serum glycated albumin (HbA1c) levels after 8 weeks. This data indicates that piceatannol may have anti-diabetic properties in humans ³⁰⁾. It is still unclear why piceatannol only improved insulin sensitivity in overweight men and gender difference on the effect of piceatannol is also unclear, as well ³¹⁾. However, fat weight and visceral fat area at the baseline in overweight women treated with piceatannol at baseline were significantly higher than those of overweight men treated with piceatannol. In addition, skeletal muscle weight at the baseline in overweight men treated with piceatannol was significantly heavier than that of overweight women treated with piceatannol. However, it is unclear whether the differences in body composition, including fat and skeletal muscle weights, between overweight men and women treated with piceatannol may be related to the effect of piceatannol on insulin sensitivity. Furthermore, there is a limitation to understanding the effect of piceatannol on detailed glucose metabolism because they only evaluated fasting serum insulin and blood glucose levels, and calculated HOMA-IR, HbA1c and serum glycated albumin. They could not perform a glucose tolerance test or a glucose cramp test.

In addition to the improvement in insulin sensitivity, BP (blood pressure) and HR (heart rate) were significantly reduced by piceatannol for 8 weeks in overweight men, which suggested that there is a beneficial effect of piceatannol on the vasculature ³²⁾. Previous reports have shown that piceatannol protects vascular function and exerts anti-oxidative stress and anti-inflammation ³³⁾, ³⁴⁾, ³⁵⁾, ³⁶⁾.

Endothelial dysfunction is characterized by impaired endothelium-dependent vasorelaxation and represents an early step in the pathogenesis of atherosclerosis ³⁷⁾. The known mechanisms of atherosclerosis related to endothelial dysfunction include impaired NO (nitric oxide) production from eNOS (endothelial nitric oxide synthase) and defects in its signaling pathway, increased oxidative stress, and inflammation. Piceatannol may protect vascular function through the improvement in eNOS, as well as the reduction of oxidative stress and inflammation. Kinoshita et al. demonstrated that piceatannol increased eNOS expression in cultured endothelial cells ³⁸⁾. As obesity is closely related to insulin resistance and increased sympathetic nerve activation, piceatannol may exert beneficial effects on insulin sensitivity, BP and HR in overweight men. In addition, piceatannol has been already reported to modify cardiac protein expression such as ephrin-B1, a membrane protein that contributes to maintaining cardiomyocyte architecture, in Zucker obese rats. Therefore, a direct effect of piceatannol on cardiac muscle cannot be excluded ³⁹⁾. Further studies are needed to determine the mechanism of piceatannol for glucose metabolism, BP and HR, as well as why piceatannol only showed benefits in overweight men.

Piceatannol has also been shown in test tube study using melanoma cell lines ⁴⁰⁾ as having a strong antioxidant and anticancer and chemo preventive abilities ⁴¹⁾, ⁴²⁾, ⁴³⁾. Piceatannol restrains the growth of melanoma cells in a test tube study ⁴⁴⁾.