Chinese consumers embrace fruit peel delights, scientists examine nutritional value and pesticide concerns

A survey was conducted by a group of scientists in China to investigate the inclination of Chinese consumers toward consuming fruit peels.

In the research published in the journal Food Research International, the scientists provided reasonable dietary recommendations for consuming fruit peels and discussed the methods of detecting and removing pesticides from fruit peels.

Review: Eating with peel or not: Investigation of the peel consumption situation and its nutrition, risk analysis, and dietary advice in China. Image Credit: Oxs Fraim / Shutterstock

Background

Fruits are essential to a healthy diet as they contain high amounts of minerals, vitamins, dietary fibers, and other phytochemicals with health benefits. Regular consumption of fruits is known to reduce the risk of cardiovascular diseases, dementia, age-related diseases, and cancer.

Studies analyzing fruit nutrients have pointed out fruit peels can often have more nutritional value than fruit pulp. However, the suitability of fruit peel consumption depends on various factors, including nutrient content, amount of pesticide, microbial contamination, ease of peeling, and fruit texture.

The survey explored fruit peel consumption preferences of consumers across 28 provinces in China. The age range of the survey population was 15 – 70 years, with the majority of participants aged 18-25 years. The survey included three basic questions: preference for consuming fruits with peel, reasons for consuming peels, and factors influencing peel consumption.

The survey findings concluded that nutrient content and the presence of pesticides are the two major concerns of Chinese consumers who prefer to consume fruits with peel.

Presence of pesticides

Pesticides are widely used in the food industry to improve the production and quality of fruits, vegetables, and other food products. However, direct or indirect consumption of pesticides can have detrimental effects on human health.  

In the survey, scientists primarily focused on eight kinds of fruits, including apple, grape, pear, peach, kumquat, lemon, melon, and persimmon. According to the observations made by the scientists, the production of apples, pears, and grapes needs higher amounts of pesticides compared to other fruits tested. However, based on the Chinese national standard, the amount of pesticide used for production does not exceed the maximum residue limits for these fruits. In other words, the amount of pesticide residues present in the pulp and peels of these fruits is well within the safety limits.

The amount of pesticide residues in fruit peels was found to be higher than that in the pulp. However, in some fruits, including grapes, higher amounts of pesticide residues were found in pulps than in peels.

Given these findings, scientists recommend that country-specific food-quality inspection standards be considered while analyzing the risk of fruit peel consumption based on pesticide content.

Consumption of pesticides can have both short-term (headache and nausea) and long-term (reproductive problems, endocrine disorders, and cancer) health effects. Studies have found that certain fungicides (prochloraz, pyraclostrobin, and tebuconazole) found in pear peel can disrupt endocrine functions, mitochondrial respiration, and steroid biosynthesis. Organophosphate pesticides are known to affect human metabolism and increase obesity risk. DDT is another insecticide already banned in many countries because of carcinogenic activities.

Detection of pesticides

Liquid and gas chromatography are the two most commonly used methods to detect pesticides in fruit peels.

High-performance liquid chromatography (HPLC) in combination with tandem mass spectrometry has been found to simultaneously detect 22 chiral pesticides and their enantiomeric compositions in fruits and vegetables. Nanoparticles can be introduced in this kind of method as matrix solid-phase dispersive extraction sorbents to rapidly detect multiple pesticides in food products with high specificity, sensitivity, and accuracy.  

Gel permeation chromatography Gas chromatography-mass spectrometry (GPC–GC/MS) is another widely used method to rapidly detect pesticides in fruits. This method includes simple sample preparation procedures, efficiently eliminating matrix interference.

Gas chromatography, in combination with an electron capture detector, is another widely used method to detect organochlorine and pyrethroid pesticides in fruits and vegetables. However, one disadvantage of this method is the production of false-positive results.

Removal of pesticides

Washing fruits and vegetables with clean water is the most commonly used method to remove pesticides in daily life. Washing food items with tap water has been found to reduce pesticide content by 35-38% on average.

While washing with tap water has been found to reduce pesticide content by 70% from grapes, the same method has been found to reduce only toluofluoroaniline and no other pesticides from apples. This indicates that water-insoluble wax on the peel may hinder the removal of some pesticides.     

Compared to cold water, hot water, saline water, and rice water are considered better options for pesticide removal. Some chemicals that can be used with water for better cleaning fruits and vegetables include sodium bicarbonate, ethanol solution, and alcohol solution.  

Some household cleaning machines, including ozone cleaning machines, ultrasonic cleaning machines, and low-temperature plasma cleaning machines, are gaining popularity for pesticide removal from fruits and vegetables.

Nutritional value of fruit peels

Apple peel is a rich source of flavonoids and phenolic acids. Compared to apple pulp, apple peel contains higher amounts of dietary fibers, minerals, flavonoids and triterpenoids, and other phytochemicals with antioxidant and anticancer properties. 

Pear peel contains high amounts of glucose, sucrose, citric acid, malic acid, quinic acid, caffeic acid, arbutin, flavanols, and phenolic acids. These compounds are known to have antioxidant, anti-inflammatory, anti-diabetic, and lipid-lowering properties.  

Peach peel contains high amounts of organic acids, vitamins, minerals, dietary fibers, phenolic acids, and flavonoids with high antioxidant and anti-inflammatory properties.

Grape peel contains high amounts of anthocyanins, tannins, terpenes, nitrogen-containing substances, and fatty acid substances. These compounds have potent antioxidant, anti-inflammatory, and anticancer properties.

Melon peel is a rich source of vitamins, dietary fibers, unsaturated fatty acids and their esters, cyclic ketones, aldehydes, anthocyanin derivatives, potassium, calcium, magnesium, and other mineral salts and phenolic compounds. These compounds have antibiotic and anticancer properties.

Lemons and kumquats are citrus fruits and rich sources of vitamin C and dietary pectin. Lemon peel extract containing at least 70 kinds of volatile compounds has been found to have a strong antibacterial effect against Gram-negative bacteria. Kumquat peel is also a natural source of many bioactive compounds with antioxidant and lipid-lowering properties.  

Persimmon peel contains high amounts of vitamins, polyphenols, and tannins. Persimmon peel extract is known to reduce the risk of high blood pressure, coronary heart disease, and type 2 diabetes.

Certain molecules found on fruit peels, including pathogenesis-related 10 (PR-10) proteins and lipid transfer proteins, can induce allergic reactions in some individuals. Peach peel can induce severe, life-threatening allergic reactions in allergic individuals, and immature persimmon can induce abdominal pain.