Lycopersicon esculentum Mill.
History and Origins
The Aztec name was tomatl (or tumate), from which the English tomato and the French tomate derive.
It was known to the Mexicans at the time of the Spanish conquest in the XVI century and introduced into Spain first, and then into the rest of the Mediterranean countries and the world. There are no names for this plant in ancient Asiatic or modern Indian languages; ancient Japanese and Chinese authors did not know of it either.
In 1544 Mattioli announced the presence of edible berries in Italy; they were basically flat and green, and became yellow when ripe. The yellow coloring of the first varieties is probably the reason why the berry was called pomo d’oro, i.e. “gold apple” in Italian.
At first, the tomato was considered a kind of aubergine (eggplant); it was cultivated only in botanical gardens, mainly as a decorative species as its fruits were deemed toxic. It was classified among aphrodisiac plants under the name “pomo d’amore”, love apple (this common name is still used, though rarely, in a few countries: e.g. love apple in England and liebesapfel in Germany).
Only in the XVIII century was it considered an edible plant.
In the Vilmorin seed catalogue (one of the oldest and most famous seed companies in Europe), it was still among the decorative plants in 1760 and appeared as an edible plant only in the 1778 catalogue. Goethe, in his Italian Journey (about 1780), notes that maccheroni was seasoned with cheese and pepper (cacio e pepe), and he does not mention tomato sauce at all.
As far as the USA is concerned, we know of a first cultivation in Virginia in 1782; the product, however, continued to puzzle people so much so that in 1820 a certain Gibson Johnson had to eat tomatoes in public on the steps of the courthouse in Salem, New York to persuade his fellow citizens of the nutritional value of those berries.
Extensive cultivation for consumption was reported around 1812 in Sicily; from there, the product was brought to the marketplaces in Naples and Rome. Tomato was only eaten fresh until the first half of the XIX century. It seems certain that the processing of tomato sauce dates back to the first years of the 1800s and that it started in Campania thanks to the pioneering work of Francesco Cirio. The tomato and its different uses then spread to the rest of Italy with Garibaldi’s “Thousand”.
Proteins do not exceed 1% and fats are almost completely absent (0.2%). Carbohydrates (mainly fructose and glucose) content is about 3%: the rate between high water content and low sugar content means that tomatoes provide little energy, but that it is of immediate use.
The characteristic taste of tomato is due to the presence of citric and malic acids that help digestion, increase salivation, whet the appetite and, combined with minerals, determine its alkalizing properties.
Tomatoes also contain about 2% of fiber, such as cellulose and hemicellulose, mostly in the peel and seeds.
Nowadays tomato is arousing more and more attention as a nutraceutical food for its high lycopene content; lycopene is a carotenoid pigment that gives tomato its bright red color and has high antioxidant activity with immune system strengthening, protection from sun rays, antiradical activity and protection from some tumors. Lycopene concentration is about 2 mg/100 g in fresh ripe tomatoes and canned peeled tomatos, 14 mg/100 g in juice, 40 mg/100 g in concentrates and dried tomatoes. Epidemiological studies confirm that in order to maintain an elevated antioxidant capacity and to prevent cancer and cardiovascular diseases, at least 4 mg of lycopene a day are necessary. Its absorption by our organism increases when tomatoes are cooked: cooking breaks down protein-carotenoid complexes in cell walls and increases their availability. Lycopene is a liposoluble compound, so absorption and transport are easier if fats are taken as well: combining it with extra virgin olive oil, as in the Mediterranean diet, is therefore excellent from a nutritional point of view. Different varieties of tomatoes have different lycopene contents, so vegetable improvement aims at selecting tomatoes with high lycopene content. Cultivation conditions affect lycopene content: with a moderate salinity stress, e.g. lycopene concentration increases (up to about 10 mg/100 g).
Other phytoactive antioxidant compounds in tomatoes are among carotenoids, phytoene, phytofluene and beta-carotene; while among phenolic compounds (with anti-inflammatory, antibacterial and antiviral properties), 98% of which are in the peel, we find quercetin, kaempferol and naringenin.
Diffusion and importance
The main producers are China (about 1 million ha), India (880,000 ha), the USA (150,000 ha), Turkey (300,000 ha) and Egypt (210,000 ha).
Italy is the first European producer (about 40% of the 27-member European Union) with around 5 million tons on about 100,000 hectares (80,000 hectares of tomatoes for industrial processing and 20,000 hectares of table tomatoes of which about 7,000 are cultivated in greenhouses).
Household consumption in Italy is about 300,000 tons of table tomatoes (16% of all fresh vegetable consumption); 90% of Italians eat fresh tomatoes. As for canned tomatoes, consumption is about 400,000 tons equal to 68% of all canned vegetables (40% from an economic point of view); 85% of Italians eat canned tomatoes.
In Italy, industrial tomato production is mainly in Apulia and Emilia-Romagna, followed at a distance by Sicily, Campania and Lombardy; table tomatoes are mainly cultivated in the open field (about 50% of the total amount) in Sicily and Calabria, while more than 60% of greenhouse production is in Sicily.
Growth habit: can be determinate or indeterminate.
Tomato cultivars for the processing industry have determinate development (growth is stopped by the differentiation of an apical inflorescence) and a bushy structure; they blossom and ripen over a short period of time.
Table tomato cultivars generally have indeterminate development, i.e., terminate with a vegetative apex and grow indefinitely, and therefore must be grown with supports (poles, canes, stakes and strings…) to climb on and be tied to; blossom and ripening are very gradual; there are, however, table varieties with determinate development (for so-called “flat cultivations”).
Stem: pubescent, erect then prostrate, semi-ligneous, ramified.
Leaves: alternate, pinnatisect, consist of 7-11 simple leaflets, with glandular hair (like all the green parts of the plant) exuding a substance with a typical pungent smell; at the axil of every leaf there is a bud that will evolve into a branch that, in turn, will develop leaves and inflorescences.
Flowers: yellow, assembled in inflorescences (racemes) every 2-4 leaves. Blossoming is gradual; fecundation is autogamous with 0.5-4% allogamy.
Fruit: a berry; its shape (oblong, oval, round) and size (15 to 300 g) varies according to type and destination. About 40 days elapse between setting and ripening. The berry consists of about 93-96% water (dry matter is 4-7%).
This is, on average, the dry matter composition:
sugars (40-60% dry matter): mainly glucose and fructose;
organic acids (4-10%): mainly citric acid (50% of total acids), malic acid and slight amounts of other organic acids (tartaric, succinic…);
proteins and amino acids (15-20%): among free amino acids, there are glutamic and aspartic acids, threonine, asparagine;
minerals: mainly K, slight amounts of Cl, Mg, P, Ca, Na;
vitamins and pigments: vitamins C and A; lycopene (red color) and carotene (yellow color). Lycopene synthesis is much reduced with temperatures < 16-21o C and > 30-32o C;
insoluble substances: (15-20%): cellulose, hemicellulose, pectins.
Climate and soil requirements
Suitable for temperate-hot climates. Thermal requirements are shown in the table below.
To meet these thermal requirements, the typical cultivation cycle is in spring-summer in Mediterranean environments, though temperatures higher than 30-35o C cause flowers to fall and lead to color flaws in the berries (insufficient synthesis of lycopene).
Photoperiodic needs: the tomato is a day-neutral plant.
Water availability is another essential productive factor: in hot-dry conditions during spring-summer, irrigation is fundamental.
The tomato plant can adapt to different types of terrain, but the best productions are in soil with medium texture, and is deep, cool, fertile, rich in organic matter, with no stagnant water, with a pH of 6-7.5. Extremely sensitive to salinity.
It is not advisable to plant tomatoes again in the same soil in short intervals or rotate them with other species of the Solanaceae family (sweet pepper, aubergine, potato…) as they would be prone to attacks from fungal parasites (Verticillium, Fusarium), nematodes, insects and increased weed infestation.
Varieties and commercial types
First, a distinction must be made between tomatoes to be processed into preserves (e.g. concentrates, purees, crushed tomatoes, peeled tomatoes…) and those for fresh consumption. The first kind is commonly called processing tomato and the second, table tomato.Processing tomato is cultivated in open fields (generally large areas); cultivars (mainly hybrids) have plants of determinate development (indeterminate types, e.g. San Marzano, are used only in kitchen gardens), are bushy in appearance and have prostrate bearing.
Cultivars with oblong berries are preferred for tinned peeled tomatoes while cultivars with roundish berries are adopted for the production of concentrates, purees, crushed tomatoes, chopped tomatoes and juices.
Following are the main industrially processed products:
Concentrates. Are extracted from tomato juice (after removing the peel and seeds) by the elimination of a part of the water through the application of heat (concentration). They are classified, based on the minimum amount of dry matter (without salt) as: semi-concentrate (12% dry matter), concentrate (18%), double concentrate (28%), triple concentrate (36%) and sixfold concentrate (55%).
Peeled tomatoes. Oblong, whole, peeled tomatoes. They may be: with juice (if simple juice and/or concentrate is added), with sauce (if tomato sauce is added) and natural (if nothing is added).
Pureed tomatoes. Preserves made with chopped, strained, peeled, without seeds, partially concentrated tomatoes.
Juices. From peeled pulp; suitably homogenized and flavored to produce drinks.
Ground tomatoes and pulps. Peeled tomatoes, with no seeds, more or less roughly ground (pulp pieces are larger than ground tomato pieces).
Chopped tomatoes. Preserves from peeled tomatoes chopped in different ways: diced, slivers, slices.
Dehydrated tomatoes. From fresh tomatoes that are chopped, peels and seeds removed, then dehydrated until dry matter is > 93%. Main use: flakes for dehydrated soups.
Sauces. Diluted juices or concentrates with herbs, vinegar, spices.
A good cultivar of processing tomatoes must have the following qualitative features: uniform red color (inside and out), compact pulp, high consistency (high percentage of dry matter), high sugar content (high refractive index), high juice acidity (which supports preservation).
The San Marzano dell’Agro Sarnese-Nocerino is the only processing tomato which has acquired the PDO (Protected Designation of Origin, or “DOP”) certification (www.consorziosanmarzano.it) and is among the presidi Slow Food (www.presidislowfood.it).
Table tomatoes are cultivated in open fields in spring-summer or under shelter for out of season production. The table tomato cultivars generally have indeterminate development, i.e. finish off with a vegetative apex and grow indefinitely, so they must have supports (poles, canes, stakes and strings…) to climb on and be tied to; blossoming and ripening are very gradual; there are, however, table varieties with determinate development (for so-called “flat” cultivations).
In Italy, an enormous number of types and varieties, differing mainly in the shape and size of the fruit, is cultivated and marketed.
These are the main types:
Green, for salad: it is a large and spherical fruit, deep green, harvested when the color begins to change (it becomes rosy near the stalk); this variety is cultivated in Italy on about 5,000 ha (3500 of which in greenhouses). Main production areas are Sicily (Ragusa, Vittoria, Palermo), Calabria (Lamezia Terme), Basilicata (Metapontino), Campania (Piana del Sele and Agro Nocerino), Latium (Fondi and Latina), Tuscany (Versilia), Liguria (Sarzana, Albenga), Veneto (coastal area of Cavallino), Emilia-Romagna (in the provinces of Forlì, Rimini, Bologna), Piedmont (in the provinces of Turin and Asti) and Marche (mainly with open field cultivations).
Red cluster: a spherical fruit harvested in bunches and marketed when it is completely red, appeared on the Italian market during the ’80s. Tomatoes in this category must have the following features: very good consistency; average weight 80 to 160 g; homogeneous size; resistance to detachment of the berry from the stalk; intense, uniform red color; simultaneous ripening of all the berries in the same bunch; herringbone setting of the berries. In Italy, it is cultivated in approximately the same areas as the green tomato for salad.
Plum type: a tomato with egg-shaped berries, of medium or medium-small size (120-150 g), harvested in bunches, bright red. The type is also known as “Cencara“.
Green, type Camone: small spherical tomato, weighing up to 60-80 g, with a typical red-orange color except on the upper part, which is bright green. It is mainly produced in Sardinia between December and June; the salty soil gives it its special flavor.
Cherry: a variety that appeared in the markets at the beginning of the ’90s. Characterized by small berries (diameter 15 to 25 mm, average weight 10 to 30 g) harvested ripe and red, mostly in bunches or as single berries and marketed in small, transparent, closed containers. Organoleptical properties are exalted by soils with high salinity and by climates with high light intensity. The main areas of production in Italy are the province of Ragusa (almost all of the cherry tomatoes produced in Italy are ciliegino di Pachino), Latium (Fondi and Latina), Veneto (Cavallino), Sardinia (Cagliari area).
Other bunch types: in this category there are different types such as the Cocktail tomato (45-70 g), e.g. Datterino, Perino, mini-Perino and several ecotypes from Apulia (Pizzetto: elongated-ovaloid, 50 g, eaten before full ripening; Francesino: elongated-ovaloid, 60-70 g, red, eaten when fully ripe; Olandese: spherical, smooth, 80-90 g; Regina di Brindisi: round, flattened, 40-50 g, harvested in bunches to keep for winter) and from Campania (pomodorino di Corbara: elongated/pear-shaped, in bunches of 5-7 berries, average weight 15-20 g; Vesuviano: small tomato with a slight bottleneck near the stalk, eaten fresh or kept in interwoven bunches).
Elongated: tomato with an elongated bulb shape, cultivated on about 2500 ha, 60% of which in open fields; the main Italian production areas are in Sicily, Latium, Campania, Veneto and the Adriatic coast; it is harvested both in the veraison phase and when fully ripe; mostly marketed in Italy.
Ribbed for salad: plant with medium-large sized (200 g to more than 500 g) berries, ribbed and of excellent quality. It is known as “Marmande” as well, after the name of an old historical variety. Marketed at the varaison phase (when the color goes from green to rosy). Mostly cultivated in greenhouses between November and June. The main Italian production areas (total 700-800 ha) are Sicily (provinces of Ragusa and Trapani), Liguria (Albenga area), Latium. The tomatoes Cuore di Bue (beef or beefsteak tomato), Pachino costoluto and Casalino are in this category.
All four types of “pomodoro di Pachino” (round and smooth, red clusters, cherry and ribbed) (www.igppachino.it) have the GPI (Protected Geographic Indication) qualification.
The “pomodorino del Piennolo del Vesuvio” and the “fiaschetto di Torre Guaceto (Puglia)” tomatoes are among the presidi Slow Food (www.presidislowfood.it).
Despite the large number of types on the market, European quality standards recognize only three: 1) “globe” tomatoes, roughly spherical, cherry tomatoes included; 2) “ribbed” tomatoes; 3) “elongated” or “oblong” tomatoes.
Qualitative characteristics of table tomatoes are generally connected to their morphological features (shape and size, color intensity and uniformity), structural features (peel and pulp thickness, amount of seeds), nutraceutical features (sugar, acid, mineral, vitamin and lycopene content), organoleptic features (flavor intensity, consistency, digestibility) and shelf life.
In recent years, there has been the development of cultivars called L.S.L. (Long Shelf Life), with highly consistent berries, very appreciated by markets but, sometimes, excessively fibrous and difficult to digest if harvested when still unripe.
In all the categories for quality, tomatoes must be: whole; fresh looking; healthy; clean (above all, with no residual pesticides); no abnormal external humidity; no extraneous smells and/or flavors.
Table tomatoes have the following quality categories: Extra, I and II (category III is only assigned with specific authorization by the EEC). Calibration (which does not apply to cherry tomatoes) is determined by the maximum diameter of the equatorial section at the berry axis: minimum size is 35 mm for “globe” and “ribbed” types, and 30 mm for “elongated” types.
Fundamentals of cultivation practices
Tomato for the processing industry can be sown directly into open fields (in March in Italy,) but it is usually transplanted (in Italy, between April and the beginning of June).
Table tomatoes are transplanted to open fields from April to mid-June and under shelter in the other months. For greenhouse production or even outdoor vegetable gardens, grafted seedlings can be used (on special hybrids), as they are more resistant to disease and have more vigor.
Planting is done in single rows (80-120 cm apart) or in binate rows (40-50 cm between the two twin rows, 100-120 cm between every pair of twin rows) with a density of about 3 plants/m2 (1-1.2 plants/m2 for flat table tomatoes).
Mulching with organic matter (e.g. straw), plastic non-biodegradable film or biodegradable film is generally aimed at accelerating the culture growth and controlling weeds (with black films that do not permit light to penetrate).
For processing tomatoes, mulching (with plastic films or biodegradable black films) is useful only in the case of manual harvesting; in case of mechanical harvesting, mulching is not recommended as the film would interfere with the harvesting machines.
Table tomatoes are often mulched both in fields and in greenhouses.
During the tomato cultivation cycle, mechanical hoeing between the rows can be useful in crusty soil and when removing weeds.
Processing tomatoes are left to grow in their natural shape, bushy and prostrate. The same happens with table “flat” tomatoes.
The table tomato with indeterminate development, though, is traditionally cultivated vertically, on supports to which it must be tied early on.
Table tomatoes are generally pruned out and lopped. Pruning out is the removal of side shoots (“suckers”) from the leave axils to leave 1 stem (only the main stem) or 2 stems (the main stem + a side shoot that has been allowed to grow).
Lopping means cutting the stem apex to stop terminal growth, leaving 5-6 fruit-bearing branches in ribbed cultivars, or 7-8 branches in other varieties.
Pruning out and lopping allow for a more balanced development; berries will be fewer but larger and foliage will protect them better from sunburn and fissures.
The table tomato with determinate development, grown vertically, is pruned out and not lopped.
Tomato has to be mucked and irrigated regularly.
Mucking must be done to ensure an adequate supply of nitrogen, taking care to avoid excesses that worsen fruit quality and increase environmental damage; potassium is essential for fruit growth and quality.
Irrigation is essential: water imbalance favors apex rot in berries. Too much water near harvesting lowers the quality of, and favors fruit fissures in, table tomatoes.
Table tomato is harvested manually. Globe tomato: in some medium-large sized cultivars, single berries are harvested during the veraison phase; in other medium-small sized cultivars, whole bunches with completely ripe and red berries are harvested. Ribbed cultivars are harvested during the veraison phase; cultivars with elongated fruit are harvested both in the veraison phase and when totally ripe, depending on the varieties and market demands.