Fruit means a group of sweet foods of vegetable origin. The fruit can be fresh or preserved and its function in the diet is to provide vitamins, mineral salts, fibers and a variable energy intake resulting from fructose (simple sugar).
Below we will focus in particular on the differences between the consumption of fresh fruit with and without peel, excluding candied citrus peel and leaving aside other nutritional aspects (for example the differences between fresh and preserved fruit), which are already extensively described at inside of other articles available in the site archive: Frutta.
Fruit peel
The fruit peel is not the same. This depends essentially on the biological differences between the various botanical typologies and on the equally different organization of the fruit itself (which can be true fruit, false fruit; simple fruit, aggregate or compound fruit, infructescence; drupes, berries, esperidi, pomi, etc.) .
The skin, more correctly defined as epicarp, constitutes (and externally delimits) the pericarp; the latter represents the fleshy portion that nourishes the seed and protects it from parasites while preserving their integrity. It is therefore logical to deduce that the external one must be the most resistant part of the whole fruit and that its chemical composition makes use of certain useful features for the purpose.
Composition of fruit peel
The fruit peel is essentially made up of molecules that are hardly degradable and physically resistant; among these, the most important are certain dietary fibers, especially NOT soluble (such as cellulose and lignin) and prina (vegetable wax). There are traces of lipids (including phytosterols), available sugars, proteins and water.
As for the bloom, it has a very important action in contrasting mycosis (just think that it is a very important constituent of the skin of Nebbiolo grapes, typical of the most humid regions of Northern Italy where certain molds are particularly aggressive).
The fibers, on the other hand, in addition to a shielding role, also have a structural function useful for preserving the hydration and maturation of the endocarp (the first nutritional substrate of the seed).
At this point, many readers will ask themselves:
" Is fruit peel an edible and / or useful food component for humans?"
To respond comprehensively, it is necessary to take a small step back and understand, from a chemical point of view, what fibers and bloom are made of.
Importance of fruit peel for humans
First of all, remember that NOT the whole peel of the fruit is edible; this does not necessarily mean that it should harm health, for example it may simply be unpleasant or compromise chewing or digestion. Some inedible peels are medlar, banana (large), coconut, pineapple, prickly pear, kiwi, watermelon, melon, etc. The peel of citrus fruits (those not treated with waxes) is edible but, if not deprived of the mesocarp, it has such a bitter taste that it cannot be eaten.
In percentage terms, the peel of the fruit is composed mainly of fibers and much less of pruina.
The fibers contained in the peel of the fruit, which we call "dietary fiber" (as they represent a very important nutritional element, although not a real nutrient - a subtle but substantial difference), are typically NOT soluble. While some animals and microorganisms are able to digest and obtain energy from them, the human being does not possess the salivary, pancreatic and intestinal enzymes responsible for this purpose. Some of them (such as cellulose), applying a chemical hydrolysis, are composed of simple carbohydrates which, at that point, could be absorbed and oxidized; others (such as lignin, formed from phenolic compounds), are polymers of monomers that are completely foreign to the energetic physiology of the human organism. On the other hand, it hardly matters to us to digest the dietary fiber contained in the fruit peel, since their nutritional function is anything but energetic.
| Food fiber functions | Benefits |
| Increases the volume of food without increasing the caloric content, requires a slower chewing, has a high satiating power | May reduce appetite |
| It attracts water and forms a viscous gel during digestion, increases the emptying times of the stomach and small intestine, sequestering carbohydrates from digestive enzymes and delaying the absorption of glucose | Reduces glycemic peaks, reduces excessive fluctuations in blood sugar levels |
| Lowers LDL cholesterol levels and total | Reduces the risk of cardiovascular disease |
| Regulates blood sugar | It can reduce the level of glucose and insulin in diabetic patients and can reduce the risk of developing diabetes |
| Increases intestinal transit speed | Promotes bowel regularity |
| Gives mass to the stool | Relieves constipation |
| Balances intestinal pH and promotes bacterial fermentation with short chain fatty acid production | May reduce the risk of colorectal cancer |
Insoluble fibers (but also SOLUBLES), while they pass inside the lower digestive tract, represent the equivalent of a "street sweeper". Fermenting by the physiological bacteria of the colon, they promote peristaltic contractions of the intestine, facilitating evacuation and preventing both constipation and the stagnation of toxic molecules responsible for the increased risk of tumors of the large intestine (and not only). During this fermentation process, our PRObiotic microorganisms release several useful molecules, a characteristic that makes the peel an excellent PREbiotic food.
The pruina, while representing an element of wine distinction and an immune defense of the plant to say the least irreplaceable, has no nutritional function relevant to humans.
Negative aspects and contraindications
That being said, it is necessary to remember that fruit peel can be a vehicle for impurities and contaminants. Most of these are deposited on the surface and very few are absorbed and then metabolized (and rendered harmless) by the plant itself. More specifically, among the undesirable elements that could be eaten by eating the skin of "dirty" fruit we recall: microorganisms (especially bacteria and molds), pollutants (such as, for example, the atmospheric content or that of irrigation water) and pesticides.
Although the third category is technically less worrying, it is instead constantly the focus of Italians. Pesticides (understood as anti-fungal, antiparasitic, herbicides etc.) are a category of synthetic based products useful to guarantee a certain yield in traditional agriculture. Of course, no one likes the idea that certain things end up on their food; however, most of the time, these are products rendered harmless that safeguard the food availability of fruit and vegetables. At the same time, a new disciplinary arose that was almost entirely dependent on the use of these synthetic pesticides: organic agriculture. By definition, this system significantly restricts the use of the treatments in question which, logically, should be totally absent in the final product. Let's just say ... it's not like that!
Indeed, we specify that in Italy the use of pesticides is strictly regulated. Even in traditional agricultural products, the possible presence of treatments is (or at least should be included) always within the safety limits imposed by law, indicating compliance with the correct choice, quantity and time of use. At the same time (as many have been able to verify) if it is true that organic agriculture denies the use of treatments, it does not guarantee that the food DOES NOT TRACK IT. The reasons why similar contaminations must occur are many and often inevitable; on the other hand, what matters is that these traces do not represent a threat to health.
Certainly there will be less honest, or just more desperate, farmers who will not risk the entire production and use pesticides less correctly; however, the checks carried out on the stored goods are always very pressing and represent an incontrovertible protection for buyers at the end of the supply chain. There are also some small exceptions. Certain types of fruit, such as citrus fruits, may undergo some surface treatments to increase their luster and shelf life (eg treatment with the imazalil fungicide). Fortunately, in our country, this occurrence is strictly tied to the obligation of a label on the label: " inedible skin " or " inedible skin ". Attention, therefore, in case you want to use the orange or lemon peel for some recipe, it is good to always read the label to make sure you use an untreated citrus.
Video Recipes based on untreated lemons
Unfortunately, currently (November 2013), European legislation (or worse than that of other non-European countries) does not require specifying what and even allows the use of certain pesticides prohibited in Italy for many years. As a result, packers from other countries can use fungicidal products that are not authorized in Italy, and we export packaged and processed fruits with these products. Obviously, the control of imported goods is one of the most effective security measures that can be had and, fortunately, Italy does not disappoint. However, with regard to exotic fruits, certainly for foreign consumption (but, you never know, even for the national one), it is certainly advisable to reduce their frequency to sporadic and certainly not frequent levels; ultimately, yellow card to: pineapple, avocado, banana, papaya, mango etc.
In conclusion, eating fruit with the skin is an excellent food habit with regard to the presence of dietary fiber (and not only), provided that certain small tricks are respected such as:
- Consult the labels and prefer foods of national origin
- Always wash the fruit carefully, preferably with the supplementary use of amuchina or bicarbonate of soda.
PLEASE NOTE: some conditions may require the consumption of strictly fruit without the skin; this is the case of low-residue diets, for example endoscopic diagnostic investigations of the intestinal tract (eg colonoscopy), in the presence of intolerance to dietary fiber (irritable bowel syndrome) or inflammatory colonic diseases (diverticulitis, colitis, Crohn's disease...).
The fruit should preferably be consumed without peel even when you are not sure of the microbiological safety of the food or the water used to wash it (eg travel in developing countries
