In these days of Christmas vacations, we were intensively submitted to a deep gastronomic show due to the rich meals with family, relatives and friends. All of us know how important is to have a right diet expecially to prevent different types of diseases like as coronary heart or neurodegenerative diseases. For these reasons but not only for these ones, of course, we need to program a correct diet that doesnt forget about fruits or vegetables, that are really rich in substances, known as antioxidants. What are antioxidants? Antioxidants are molecules capable of slowing or preventing the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Antioxidants are often reducing agents such as thiols, ascorbic acid or polyphenols. Measurements of the antioxidant activity or the oxigen radical absorbance capacity (ORAC) are not easy to process. There are different tests like as for example the DPPH test. The DPPH test, which utilises a redox reaction with the 2,2-Diphenyl-1-picrylhydrazyl radical, can be used to determine the antioxidant activity of plant or fruits extracts. The radical has a violet colour due to the unpaired nitrogen electron and after reaction with a radical scavenger the reduced DPPH-H (2,2-Diphenyl-1-picrylhydrazin) is formed which is yellow. The colour change can be followed spectrophotometrically at 515 nm and in this way the antioxidant activity of a substance or a plant extract can be determined. Anyway, despite the amount of antioxidants levels in fruits or vegetables, their consumption have to be done in a proper way for a good and healthy life.
The role of chemistry in projecting new buildings is imporatant, because new materials with better thermal properties for example have to be used. One of the problems of an efficient house is its capacity to be insulated to avoid dispersion of energy in the external environment and to minimize the use of energy. We need to use less energy and to use it in a more efficient way. New materials that are able to do a thermal insulation and that are made by recycled materials are a good options to build up green houses. In the last years, in the market there are materials made with around 85% of cellulose fibers from recycled newspapers, around 15% of boric acid, used as flame retardant. These materials are used for insulations of walls. There is a big work to do in finding new materials, may be with better thermal properties. You can find several informations about this concept by visiting this website on cellulose materials for building or this italian website about ecomaterials.
Houses and buildings are responsible of a big consumption of electricity and emission of carbon dioxide all over the world. In the USA buildings and houses use around 70% of the electricity produced. Buildings require 40% of resources of our planet and they are planned to be not really efficient. In the last years a new idea of projecting houses, industries and commercial buildings grew up, based on sustainable priciples. Green buildings are constructed by using recycled materials, by avoiding dissipation of energy and with the possibility to become center of renewable energy production (through solar cells or photovoltaic plants). Reuse of water and ecological water treatment aid to preserve water resources and to plan a better future. In this scenario, the role of the materials scientist is really important, expecially in the study and choice of the materials to be used in the green buildings. There are all over the world agencies that work to give energetic certificates for green building like Casa Clima in Italy and USGBC in USA. The request of energetic certificates grew up in the last years all over the world and this helps us in reducing the emission of carbon dioxide and in managing in a better way our planet resources.
I attach here a new video about supersaturated solutions to enhance the fact on how powerful is to show this funny aspect of chemistry as a great educational tool. Supersaturated solutions are in a metastable state so that any "disturbator" (crystal seeds or impurities for example) can easily makes the system fall down into a lower energy state as it happens in these experiments.
Since I love to discover funny experiments, I have been searching for something interesting and found the famous Diet Coke and Mentos eruption experiment. This experiment became really famous all over the world cause of you tube videos diffusion. Recently there was a study made by Tonya Coffey, a physicist at Appalachian State University in Boone, North Carolina, that explained the chemistry and physics behind this experiment. The group of Tonya Coffey summerized the results, concluding that the vigour of the jets depends on various factors that affect the growth rate of carbon dioxide bubbles and particularly the rough, dimply surfaces of Mentos that encourage bubble growth, efficiently disrupt the polar attractions between water molecules, creating bubble growth sites. Diet Coke, like also other carbonated beverages, is a supersaturated solution of carbon dioxide in water. At atmospheric pressure, the carbon dioxide gas escapes very slowly from the supersaturated liquid. This process may be accelerated by the presence of nucleation sites within the solution, such as small bubbles, caused by shaking the bottle, or another solute, such as sugar powder. If you are interested you can find more informations at the American Journal of Physics. Supersaturation happens when the solution contains more of the dissolved material than could be dissolved by the solvent under normal circumstances. For example, we can obtain supersaturated solutions by melting some salts like sodium thiosulfate pentahydrate and cooling slowly the solution obtained. By adding some crystals of the salt, that act as seeds, we provide a rapid crystallization of the system. Supersaturation experiments are really funny and could be an easy tool to attract young students to chemistry!
In last years, there was a big interest in developing new technologies to produce energy in a more efficient way and furthermore from renewable sources. The growth of population and the the consequent growth of energy request as well as the use and consumption of oils and C-based fuels and the produce of carbon dioxide raised up the research for new sources of energy based on renewables. One of the most interesting renewable source is the algae biomass. Actually there are some experimental plants that use microalgae to convert carbon dioxide or other types of feeding substances like waste water and sun light to biodiesel. These plants are called photobioreactors. The lipid content depends on the type of microalgae and could be really high up to 70 % in dry weight. This is a promising renewable sources since some types of algae can grow also in saline system and there will be the possibility to couple water remediation with the production of biodiesel and energy.
In the last years, the problem of energy policies was one of the most discussed in the majority of western countries. We need energy and need to plan the supply of energy for the future generation in a sustainable way. In Italy the government wants to consider again the nuclear energy as an alternative way to produce energy for the country. But there are always problems that we have to take into considerations like: High costs Uranium supplies limited Production of nuclear wastes Security problems Accidents problems of the plants There are several facts about these problems that everybody can analyze in a better way, but the conclusion is that we need to reduce our needs of energy by starting to live in a more sustainable way!
Absinthe is a distilled, highly alcoholic (45%–74% ABV) beverage with a flavor of anise. It derives from herbs, including the flowers and leaves of the herb Artemisia absinthium, commonly referred to as "grande wormwood". The color of Absinthe traditionally ranges from a light yellow to a natural green color but it can also be colorless. It is commonly referred to in historical literature as "la fée verte" (the Green Fairy). Absinthe is not bottled with added sugar and is therefore classified as a spirit. Absinthe is unusual among spirits in that it is bottled at a very high proof but is normally diluted with water when consumed. Absinthe originated in the canton of Neuchâtel in Switzerland. It got a great popularity in late 19th- and early 20th-century in France, particularly among Parisian artists and writers. Due partly to its association with bohemian culture, Absinthe was opposed by social conservatives and prohibitionists. One of the opposition to the consume of Absinthe was the presence of high levels of thujone, a monoterpene, with a menthol odor, found in the leaves of Artemisia absinthium. Recently chemical analysis with GC-MS, even about old samples of Absinthe, found contents of thujone between 2 and 20 mg/kg, under the limits of 35 mg/kg of the recent EU regulations. This is due to the fact the thujone is extremely volatile compound and that it looses during the dry of the Artemisia absinthium leaves and of course by cutting the head of the distillation of the mix of herbs during the preparation of this beverage. No worries when you drink a good Absinthe, but be worried because it is not easy to find a good one on the market. There are some rules to follow, the famous 5 rules: It has to be a spirit distilled from a specific mix of herbs (Artemisia absinthium, anise, melissa, coriander and others) It has to be highly alcoholic (45%–74% ABV) It has to become opalescent when cold water is added It has to contain green anise instead of star anise It has to be balanced in the global aroma Here a video with a method of preparation of the Absinthe! Cheers mate!!
Since I discovered foodpairing, I started reading a lot of recipes with amazing combinations. A few days ago, in the blog of Martin Lersch, Blog.khymos, I read there was a round of TGRWT that means "they go really well together" and the challenge was to make a dessert with plums and blue cheese. I got excited about this idea, so today I bought gorgonzola cheese and other ingredients, I got the plums from the garden of one of my friends, organic yellow-green sicilian plums and went back home to make a dessert for lunch. The result was amazing, a great combination, a great dessert, I attach here pictures and recipe:
Plums and gorgonzola chip cookies in a sandwich shape
Ingredients A) For chip cookies (My version) 140 grams of flour (type OO) 60 grams of unsalted butter 30 grams of water 1 egg B) For Gorgonzola cream 100 grams of Gorgonzola cheese (italian sweet type) 4 spoons of milk C) For plums marmalade 5 plums (yellow-green ones) 70 grams of white sugar
Directions A) For chip cookies (My version) Mix all the ingredients A until they are well mixed and keep storing for 1 hour. Then make with hands chip cookies and put them in a oven at 180 °C for 25 minutes around. B) For Gorgonzola cream Cut Gorgonzola cheese in little pieces and put them in a bowl, then add 4 spoons of milk and mix until you have a smooth cream. C) For plums marmalade Cut plums in little pieces and put them in a pan, add sugar, mix and heat up slowly for 20 minutes around or until they appear soft and gelee. D) Final composition Put Plums marmalade and Gorgonzola cream between two chip cookies and put all in the oven at 180 °C for 10 minutes. Then...This is what you will eat...
Last saturday I joined a group of friends in a place in which there was a show in which you had to answer to some questions about several topics, from literature to science. During the game there was this question: how does it taste an high concentrated solution of saccharin? First of all, remembering saccharin is an artificial sweetener, the answer came out of my mind was "exteremely sweet", but the right one was: bitter. By searching how this molecule could work and give different senses by changing only concentration of it, I found the mechanism is not yet really well explained. Anyway, reading and reading, searching and searching about chemistry of senses, I arrived under the foodpairing tree and it was a great emotion! Foodpairing bases on the fact the food combine well when they have most of the flavor compounds in common. There is a website in which it is possible to find these foodpairing trees in which are amazing combinations between really different or distant food. A food product has a distinctive flavor because of a specific combination of different flavor compounds. In this way it is possible to build up the flavor of any food, by combining different food. You can have a look at this website to find beautiful combinations: Foodpairing Happy food to everyone!
Yesterday I read in one of the italian newspaper that groups of chinese people along the italian coasts from Tuscany to Sicily rent pedalò early in the morning to go fishing jellyfish they use to cook fried or to make a salad. It is interesting to see how one of the cultural differences between asian and mediterranean food could be used to write an article for a national newspaper, by the way, it is interesting to investigate at the same time how to cook jellyfish and if it is safe! Generally jellyfish are considered dangerous marine creatures and there are some of these jellyfish like the so called "box jellyfish" living out of the australian coasts that can kill humans within minutes! This is why only a few species are good to be cooked. Generally some of the species we have in the mediterranean sea are good to be cooked. Jellyfish are amongst the most fragile and simple creatures in the oceans. Only 5% of their body mass is made up of solid organic matter. They do not have any specialized systems for digestion, reproduction or defense. The survival of the jellyfish depends upon their venom apparatus. It helps them procure their food and keeps large predators at bay. The venom apparatus of the jellyfish consists of numerous nematocysts along their tentacles and oral arms. These nematocysts are hollow and capsule like. Inside these hollow capsules is a thread which is tightly coiled. The venom of the jellyfish is trapped within this thread. Depending upon the species of the jellyfish, the number of nematocysts, their location and the toxicity of the venom will vary. The jellyfish does not have a brain to control this venom apparatus. The nerve receptacles of a rudimentary nervous system are equipped to sense as well as react to external stimuli. They can sense changes in light, odor, pressure, etc. When the tentacle of the jellyfish comes in contact with any hard surface, the nervous system immediately triggers the venom apparatus. The nematocysts burst open and the thread within begin to uncoil. They are then shot forward and they lodge themselves in the flesh of their victim or prey and inject the venom into them. This is how a jellyfish stings. Jellyfish use their sting to paralyze or kill small creatures that they can eat as food. On the other hand, when faced by an attack by a large predator, they use their sting to paralyze them to get enough time to escape. When humans enter the same waters as the jellyfish, the jellyfish just reacts to the human presence in the same way as it would react to the presence of a predator. So How to cook them?? The venom of the jellyfish is a protein type toxin and it could be inactivated by common processes that we use for the "denaturation of proteins", that is the desctruction of any secondary or tertiary structure of the protein itself and that is responsible for its biological activity. Hence, temperature, pH, presence of some metal cations can do this work. You can soak jellyfish in hot water and change it several times, or treat it with salt and alum, or soak a with vinegar solution. Then you can cut it in small pieces and prepare a salad or prepare it to fry! Here a nice thai recipe for a jellyfish salad:
YAM MAENG KAPHRUN INGREDIENTS 2 cups jellyfish, cleaned and cut bite-sized 1/2 thinly sliced onion 2 thinly sliced shallots 8-10 crushed hot chillies 1 tsp. thinly sliced red spur chillies 1 1/2 tbsp. fish sauce 2 tbsp. lime juice
PREPARATION 1. Immerse the jellyfish in boiling water then remove and immediately plunge into cold water for a few moment. After removing from the water, drain. Thia will give the jellyfish the right munchy texture. 2. Toss the jellyfish with the onion, shallot, and chillies, seasoning to taste with fish sauce and lime juice. Put onto a plate on which lettuce has been arranged and decorate with slices of red spur chilli.
Here a video with an example how the same metal can form complexes with different colors depending on the ligands and coordination number! The same heart, but different colors! Life is always on!
One of the most important tools chemists have to explain chemistry is the experiment. Generally, teaching to young students is really hard, so funny experiments are important to attract them to our science. It is great to have the possibility to find a lot of funny experiments on Internet. By chance I found this beautiful experiment explains the decomposition of hydrogen peroxide, the role of catalysts in chemical reactions. Here there is a simple and safe recipe. Materials: • 125ml 6% Hydrogen Peroxide (also labelled 20Vol) • 1 Sachet Dry Yeast (powder) + 4 tablespoons of warm water • Detergent • Food colours – optional (not cochineal) • Empty bottle • Funnel • Plastic tray or tub • Dishwashing gloves • Safety goggles * 6% Hydrogen peroxide (20Vol) is available in 400ml bottles from most retail chemists and cosmetics suppliers and some supermarket Instructions: 1) Put the dry yeast in a cup, add 4 tablespoons of warm water and stir untill is well mixed 2) Put hydrogen peroxide (use the funnel), the detergent and some food colours into the empty bottle 3) Pour the yeast solution into the bottle, you will start seeing the production of foam quickly! The excess of the foam will pour out of the bottle!!!
In the previous post I talked about chilli peppers and how to make a good chilli peppers extra virgin olive oil. One of the most important steps is to dry the chilli peppers under the sun and to do it as quick as possible. One problem could be the growth of some fungi that can produce as secondary metabolites toxins, called mycotoxins. Most fungi are aerobic (use oxygen) and are found almost everywhere in extremely small quantities due to the minute size of their spores. They consume organic matter wherever humidity and temperature are sufficient. One mold species may produce many different mycotoxins and/or the same mycotoxin as another species. Major groups of these mycotoxins include aflatoxins, ochratoxin, patulin, fusarium toxins. Most official control methods all over the world are based on high performance liquid chromatography (HPLC) and it explains the important role of the chemist. There are several methods to prevention of the growth of these fungi and/or the decontamination of mycotoxins from food. How to prevent growth and invasion of pathogenic fungi in agricultural commodities is very important in preventing mycotoxin contamination. The inhibition of fungal growth as well as the decontamination of mycotoxins can be achieved by physical, chemical and biological treatments. Chemical treatment has been used as the most effective means for the removal of mycotoxins from contaminated commodities. The method should be sure that the detoxification system is capable of converting the toxin to a nontoxic derivative (s) without deleterious change in the raw product. Many common chemicals have been brought to test the effectiveness in detoxification of aflatoxin. These chemicals include the followings:
* acetic acid * ammonia gas or ammonia solutions or ammonium salts, 3-5% * calcium hydroxide * hydrogen peroxide * ozone gas * phosphoric acid * sodium bicarbonate * sodium bisulfite * sodium hydroxide * sodium hypochlorite
The chemical reactions of detoxification of aflatoxin are primary addition of the double bond of the furan ring and oxidation involving phenol formation and opening of the lactone ring. Of course among the chemical treatments, a good recipe could be to wash the fruits or vegetables, firstly with water/acetic acid from vinegar, then with a solution of sodium bicarbonate and at the end with a water solution containing some active substances that produce chlorine, like Amuchina solutions. In any case we have to remember the prevention starts during the growth of crops, then in pre-harvest and harvest time!
I am relaxing in these summer days and reading a lot. Yesterday I read an article on a recent congress about chemistry in food. It is interesting how amazing is the contribute of chemistry and chemists to the safety but also the creativity of any food. Today I would like to talk about capsaicinoids, and particularly about capsaicin, the molecule that is the cause of burning sensation in chilli peppers. Of all the capsaicinoids, only two compounds are responsible for 80-90% content of pepper, these are capsaicin and dihydrocapsaicin. Different concentrations of capsaicinoids give different pungencies and this therefore is the reason why some peppers are hotter than others. Capsaicinoids come from a larger family of chemicals called the vanilloids. The only difference between capsaicin and dihydrocapsaicin is the presence of a carbon-carbon double bond. The amount of these capsaicinoids depends on the harvest time and the variety of peppers. Wilbur Scoville developed a tool of measuring pepper ‘hotness’. He found some ‘mad’ volunteers to taste chilli powders on their own. The powders were then diluted down using sugar and water until they no longer burned the taster’s mouths. The more sugar that had to be added, the hotter the pepper. For example bell peppers were measured to be about 100 Scoville units, whilst the hottest known pepper was 577,000. Pure capsaicin has a value of 16 million Sc.units. Capsaicin is soluble in fats and oils but not in water. Therefore milk, ice cream and peanut butter can calm the pepper whilst water will spread the flames! In Italy it is used the well known "olio piccante", which is extra virgin olive oil in which it was infused crunched chilli pepper. To make it, observe these points: 1) Dry chilli peppers under the sun, by checking them often (it is better to do it during the summer when it is hot and they can be dried in a few days). 2) Crunch them in little pieces. 3) Put a cup at the bottom of a cleaned glass bottle. 4) Fill up with pure extra virgin olive oil. 5) Filter after 2 weeks. Chill out now!!
One of the most recent spots in which chemistry is involved and gets a new fascinating aspect in the molecular gastronomy. When we make any meal, we mix ingredients, we cook, we dry, basically we do chemical reactions and by control them it is possible to set up the right and balanced taste. I have been looking for some recipes about ginger ale drink, since I was curious to try to make it at home and now it is hot and I really like to drink something refreshing. I found different recipes, also a few involved fermentation processes, but I like simple recipes in which there is no fermentation. I add this recipes that also you can find with pictures of the process at Homemade Ginger Ale: Homemade Ginger Ale recipe by Jean-Georges Vongerichten from "Cooking at Home with a Four-Star Chef"
Ingredients:
1 pound fresh ginger, unpeeled and cut into small dice 2 stalks lemongrass, trimmed and roughly chopped 2 small fresh chiles, stems removed 1 1/2 cups sugar Soda water Lime wedges
1. Combine the ginger, lemongrass and chiles in food processor and process until minced, stopping the machine periodically and scraping down the sides.
2. Place the puree in a saucepan with the sugar and 1 quart water (that's four cups). Bring to a boil over high heat, then reduce to medium and simmer for 15 minutes. Turn off the heat. Cool, then strain and chill.
3. To serve, place 1/4 cup of the syrup in a glass full of ice. Fill with soda water, taste and add more syrup if you like. Garnish with a lime wedge, then serve. Basically I love the process as you heat this ginger puree and promote a retro aldol reaction that brings from gingerol to zingerone, that is responsible for the spicy aroma of the drink! There is always chemistry in every you drink, mate!
Somebody told me if sugar has an expiration date. In this post I wanna talk about the importance of some parameters in food safety and particularly about water activity. In food safety the main parameters we use to project any food and to see if they are shelf stable are: water activity, temperature, pH. Water activity is defined as the vapor pressure of water above a system divided by that of pure water at the same temperature. Distilled water has a water activity value of 1 and a pure fat system of zero. Simply speaking the water activity is a measure of "free" or "available" water in a system, since the presence of dissolved species makes an interaction between them and the water through hydrogen bonding, dipole-dipole attraction or ionic bonds. A measure of water activity will help us in predicting if the growth of mold or a microbiological contamination can happen. Therefore, taking into consideration that the water amount in the sugar we can have at home is less than 0,3 % and that chemically speaking sugar has a cristalline structure, it is hard can be contaminated if it is well stored. In fact it is used in food industry as preservative in several food formulations. If you keep it in a closed can, at room temperature, the sugar can be kept indefinitely. Dont worry about it...sugar sugar...honey...honey!!
During these summer days, it is nice to go out for a walk, a drink and may be to listen some good life music. Music is a form of art, particularly is the art of generating, manipulating and making new combinations of sounds. We always know how close is chemistry, among all the other sciences, to art and any artistic form of expression. In our science, there is a formal code to communicate chemistry and the results of any experiment. To write in any international journal, every scientist has to follow some rules and the language is strictly formal. It was really surprising for me to discover on Internet there are a lot of videos in which some scientific concepts like chemical reactions, or the enthalpy variation, are explained in a song form. I am really convinced that this new way of teaching can affect the learning of science and also stimulate students in their studies.
Generally, when I talk about extra-virgin olive oil and its amazing properties, I get several questions. The first one is about the adjective "extra virgin", whay is this "extra virgin? What does it mean? I explain that virgin and extra-virgin olive oils are those ones obtained exclusively by mechanical processes of the fresh fruits, the olives and that the difference between extra-virgin and virgin are in some chemical parameters of the oil. Here the chemical aspect! The Reg. CE 2568/91 and the Reg. CE 1989/03 contains the limits of these parameters. The first one is the acidity. Of course, when you are having a dinner with friends, it is not easy to get into chemistry for several time, so the conversation ends after replying to this and last question: what is the acidity of olive oil? I say that by our law the extra-virgin olive oil needs to have an acidity lower than 0.8% in oleic acid. Here the most difficult part, to explain this concept to people never studied it. Olive oil and vegetable oils contains mainly triglycerides that are esters of glycerol and fatty acids. The acidity is the content of the main representative free fatty acid in the oil, so more the free fatty acid, more the acidity, less pure in triglycerides the oil. That's why we call EXTRA-VIRGIN an olive oil with a really low content of free fatty acid, no more that 0.8% by weight. At the end of the conversation probably my friends know something more about chemistry appreciating in any case the beautiful scent of a pure sicilian extra-virgin olive oil in their meals!
Dopo avere visionato molti blogs di autori chimici, mi è venuta la voglia di iniziare questa avventura, perchè credo molto nelle potenzialità della rete e che in futuro il blog avrà un peso sempre maggiore nella diffusione delle informazioni e della cultura in genere. Proprio per questo ho deciso di mettere a disposizione di tutti le mie competenze e le mie conoscenze della chimica. Mi presento, mi chiamo Alessandro, ho 31 anni e faccio il chimico. Da circa quattro anni lavoro come libero professionista e mi occupo di analisi ambientali e alimentari e di consulenze nel settore della chimica ambientale, alimentare e forense. Inoltre ho maturato anche quattro anni di esperienza nella scuola pubblica avendo fatto alcune supplenze di chimica e tecnologia in un Istituto superiore. Voglio scrivere questo blog sia in italiano che in inglese per dare una maggiore visibilità. Gli argomenti di cui mi occuperò, saranno argomenti di attualità del mondo della chimica e della ricerca scientifica per cercare di darne una visione corretta, indipendente e scientifica. Mi piacerebbe potere pensare che fosse un chimico a commentare le notizie di chimica con un linguaggio che possa essere compreso da una ampia utenza, in modo tale da creare una coscienza critica nei lettori e una rinnovata immagine della chimica, materia che studio da molto tempo e che ogni giorno non smette mai di affascinarmi. English version: Today, after reading several blogs about chemistry and science, I decided to create my blog and to call it: the independent chemist! Why "The independent chemist"? The idea is to comment scientific news from the newspapers or from Internet and to offer the point of view of a scientist, in order to let the readers make a critical and scientific consciousness about chemistry and science. Some informations about me: my name is Alessandro, I am 31 years old, works as a chemist, in the field of environmental and food analysis as well as consultant in environmental, food and forensic chemistry. I have been teaching chemistry for four years in a high school. With this blog I would like to create a big network with all the people interested in discussing about science and chemistry particularly. Be ready, let's start up this brilliant journey! Everybody is welcome!
In these days of Christmas vacations, we were intensively submitted to a deep gastronomic show due to the rich meals with family, relatives and friends. All of us know how important is to have a right diet expecially to prevent different types of diseases like as coronary heart or neurodegenerative diseases. For these reasons but not only for these ones, of course, we need to program a correct diet that doesnt forget about fruits or vegetables, that are really rich in substances, known as antioxidants. What are antioxidants? Antioxidants are molecules capable of slowing or preventing the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Antioxidants are often reducing agents such as thiols, ascorbic acid or polyphenols. Measurements of the antioxidant activity or the oxigen radical absorbance capacity (ORAC) are not easy to process. There are different tests like as for example the DPPH test. The DPPH test, which utilises a redox reaction with the 2,2-Diphenyl-1-picrylhydrazyl radical, can be used to determine the antioxidant activity of plant or fruits extracts. The radical has a violet colour due to the unpaired nitrogen electron and after reaction with a radical scavenger the reduced DPPH-H (2,2-Diphenyl-1-picrylhydrazin) is formed which is yellow. The colour change can be followed spectrophotometrically at 515 nm and in this way the antioxidant activity of a substance or a plant extract can be determined. Anyway, despite the amount of antioxidants levels in fruits or vegetables, their consumption have to be done in a proper way for a good and healthy life.
