Vegetable products and Tomato area

The tomato is native to South America, from the tropical and sub-tropical regions of Peru and Ecuador, where it is still possible to find wild species with small fruits, similar, among the varieties currently cultivated, to “cherry tomato” type. According to some scholars, the English name “tomato” derives from the Aztec “xitomate” or “zitomate”, while according to others, derives from “tomati”, a name by which some indigenous peoples of Mexico used to call the fruits of the tomato plant they ate. The Italian term “pomodoro”, instead, can be associated with the yellow color of the first fruits that appeared in Europe at the end of the sixteenth century, replaced shortly after by red-fruit varieties, also present in South America; from Mexico, where it was cultivated in the midst of corn, the tomato arrived in Spain. Through the Spanish possession of Naples the tomato, initially considered a medicinal plant, entered the Italian kitchen as “golden apple” (pomo d’oro) and through Genoa and Nice it arrived in Provence, where it was mainly used to embellish balconies. From Spain, following the Arab domination, tomato also arrived in Sicily, where can be found the oldest Italian tomato-based recipes, especially sauces to dress pasta, as an alternative to the seasonings based on butter, cheese and spices. In Parma, where tomato is destined to become one of the most cultivated horticultural species, it does not enter the food habits of the rural world until late ‘800. The man who more than any other tried to spread its cultivation was the agronomist Carlo Rognoni.
A little later, in those lands, also thanks to the contribution of the Royal Experimental Station for the Food Preserving Industry, the advent was witnessed of the tomato processing industry, which still represents one of the most important realities of the Italian economy.

The tomato plant (Lycopersicum esculentum) is a solanacea, family of dicotyledonous plants, which also includes potato, pepper and aubergine. It is a perennial plant although, due to its scarce resistance to low temperatures, it is cultivated as an annual plant. It has a taproot and a stem that can reach, in the case of indeterminate plants, two meters and on which are arranged the large alternate leaves composed of numerous leaflets. The flowers are cluster-like and the ripe fruit is a berry of different shapes and sizes: globular, round, elongated or flattened. The epicarp or peel is the outermost part consisting of a film, generally yellow, which covers the mesocarp or pulp, consisting of cellulose, hemicellulose and pectin, and whose juicy content includes colouring substances (lycopene and other carotenoids) along with savory and aromatic components; finally, the endocarp, divided into two or more loculi, contains the placental tissue in which the seeds are immersed. The chemical composition of the tomato is influenced by numerous factors: variety, pedoclimatic conditions, degree and time of ripening, etc. When fully ripe, the tomato is bright red, with an edible part greater than 96%. On average, 100 g of fresh tomatoes consist of: 93-95% water, 2.5 – 3.2% reducing sugars, 0.2-0.4% fat, 0.6-1% nitrogenous substances and 1.8% polysaccharides and fibres; energy value about 100 kJ (20 kcal).

Sugars are mainly represented by glucose and fructose, which make up 40-60% of the total solids content. The most present acids are: citric acid, which represents 90% of total acids, and malic acid. The degree of acidity of the juice, expressed as pH, refers to citric acid: in cases where the pH of tomato does not exceed the value of 4.3, sterilizing thermal treatments below 100°C are sufficient, in the other cases the issue can be overcome by adding, during processing, citric acid in a quantity sufficient to adjust the pH of the tomato with no need of preserving agents; the preservation of tomato products, in fact, takes place only through heat treatments. The insoluble substances are mainly represented by polysaccharides, or complex sugars, such as: pectins, cellulose, hemicellulose and lignin. Particularly important are pectins which, combined with other polysaccharides, give rise to protopectins, responsible for the compactness and consistency of the fruit which is reflected on the viscosity and consistency of industrial products. Tomato amino acids include all the ones which are considered essential for nutrition: glutamic acid, aspartic acid, threonine and asparagine.

The main products obtained from tomato processing are: peeled, paste and strained; various pulps and crushed tomatoes and other types of preserved tomatoes. Tomato pastes are divided into: semi-concentrated, with a net total solids content above 12%; concentrated tomatoes: with a net total solids content above 18%; double concentrate: with a net total solids content above 28%; triple concentrate: with a net total solids content above 36%; sextuple concentrate: with a net total solids content above 55%. Crushed tomatoes are obtained by crushing previously peeled or coarsely strained tomatoes, with partial elimination of seeds. Tomato paste is a product intended for the direct preparation of seasonings, obtained from tomato juice not subjected to strong refining and partially concentrated, with a soluble solids content between 5 and 12°Brix, with a tolerance of 3%, net of added salt. Tomato juice, on the other hand, is a pulpy liquid, separated from the skins and seeds, obtained by crushing and sieving fresh tomato fruits, consumed directly as a drink or in cocktail-like mixtures. Tomato powder is obtained by dehydrating the concentrate up to a moisture content of 3-4% and is mainly used for the preparation of dehydrated mixtures such as vegetable soups, juices, sauces, baby foods and soups.

What are the normative references for the quality of diced tomatoes as regards the incidence of defects due to the presence of skins and of units with uneven color or with necrotic stains?

Diced tomatoes fall into the category of non-whole peeled tomatoes. The Decree of the Italian Ministry of Agriculture and Forests of 4 September 1985 “Aid for the production of tomato paste, whole and non-whole peeled tomatoes and other fruit and vegetable products, provided for by EEC Regulation No. 516/77. Terms and conditions of payment of the minimum price “(Suppl. G.U. 210 of 6 September 1985, page 5), in Article 38 of Annex 5 reports: “Non-whole peeled tomatoes must meet the following requirements:

– drained weight not less than 60% of actual net weight;

– minimum soluble solids content 4% net of added salt;

– be free of larvae, parasites and alterations of a parasitic nature consisting of necrotic spots of any size affecting the pulp and not significantly exhibiting speckling, of another nature (depigmented parts, residual mechanical lesions or growth scars) affecting the superficial part of the fruit; the occasional presence of peduncles is tolerated”.

The Commission Regulation (EEC) No. 1764/86 of 27 May 1986 concerning the minimum quality requirements that tomato-based products must have to benefit from production aid pursuant to Article 6 of the GUCE 7.6.86, in Article 6 defines the following tolerances:

– defects (areas that have deep lesions, whose color or structure contrasts sharply with the normal tomato tissue, and which should have been removed during processing): 35 cm2 of total surface;

– skins (both the peel adhering to the tomato pulp, and the peel found loose in the container): 1250 cm2of total surface;

Tolerances refer to 10 kg net weight.

At the time of presentation to the consumer, as the company that prepares preserved foods, the packer or the distributor take responsibility for the marketing, with reference to the labelling, when placing their products on the market, such as reported in paragraph 3 of article 3 of Legislative Decree 27.1.92 n. 109 “Implementation of Dir. 89/395/CEE and 89/396/CEE concerning the labelling, presentation and advertising of food products”.
It is one of the many simplifications that have been proposed to make it easier to control product batches in inter-company exchanges (others are the desire to give a soluble solids value by measuring it refractometrically, or to give a soluble solids value to a triple concentrate with high concentration or a to a super hot break product). In fact, Blotter testis not applicable to diluted concentrates since dilution (addition of water) is not able to represent the original product (the water is not reabsorbed at the level of intact cells and is therefore released during measurement). On an undiluted concentrate it is believed that a well-made HB does not have a spread over 6-8 mm. A CB spreads over 15 mm, a “normal” HB has intermediate values.

In the USA, FDA has established that when the natural pH of a food is lowered below 4.6 by the addition of acids, the acidification treatment is critical for the purposes of hygienic safety and its correct performance must be documented. In Europe and in Italy this obligation is not explicit, but derives from the correct fulfilment of the hygienic risk prevention obligations established by Directive 93/43 (EEC). However, in order to also guarantee commercial safety, it is important that at the time of filling the containers, the pH (in the slowest heating point, especially for particulate products) is not higher than the value of 4.2 pH units, in order to reduce the incidence of spoilage by butyric clostridia.

Acidification is an important phase in the preparation of preserved vegetable products (preserved food in oil, in vinegar, ready-to-use sauces, “condipasta”, “condiriso” etc.) which are stabilized with a thermal pasteurization process (temperatures <100°C) to guarantee health and commercial safety.

The most widely used acidifier is citric acid, both as it is and in concentrated solution (50%). The acidification methods for products containing a solid phase and a liquid phase such as sauces are essentially of two types:

– addition of acid as it is in the liquid phase of the processing batch;

– addition of a concentrated solution.

The use of the first method has the advantage of not significantly influencing the residue of the sauce, but some time is necessary for the acid in the feed tank to dissolve uniformly in the liquid phase. The second method involves immediate solubilisation and a very small effect on the residue of the sauce. The relation that links the quantity of acid to be added to the sauce to obtain a certain pH is given by the buffering potential of the sauce, which by definition is given by:

where dCa and dCb represent the increase in concentration of a strong acid or a strong base to obtain a decrease or increase (dpH) of the pH.
In practice the buffering potential represents the increase in concentration of a strong acid or a strong base to obtain a decrease or increase in the pH of the unit. In general it is not possible to know in advance the buffering potential of the product at the pH it has; this information is obtained through a series of preliminary acidification tests on relatively small quantities. Finally, the quantity of acid necessary for the processing batch under examination is obtained by a simple proportion; the necessary acid dose is added and, after homogenization of the sauce, the pH is the desired one.

Lycopene is a powerful antioxidant and is responsible for the red color of tomatoes. It is soluble in oil and insoluble in water. Lycopene is easily assimilated by the human body and is naturally present in human plasma and in tissues at higher concentrations than other carotenoids.

In our diet, 95% of the assimilated lycopene comes from tomatoes and its industrial products. It is also found in watermelon, pink grapefruit, papaya and rosehip.

The technological treatments for the industrial processing of tomato-based products make lycopene and other antioxidant components more bio-available by breaking the cell walls of the tomato matrix. Furthermore, as with all oil-soluble substances, lycopene is more readily bio-available when oil is added to the product; It has also been shown that lycopene metabolized by the concentrate is 2.5 times higher than from fresh tomatoes.

The number of scientific papers and the consistency of the results obtained justify the statement that eating tomatoes and its products daily helps to reduce the risk of cancerous formations of the gastro-digestive and respiratory tract, of the stomach and of the lungs. It has also been shown that the consumption of tomato products lowers the risk of prostate cancer. Further studies show that lycopene performs an effective protective action, in synergy with the other constituents of the tomato, against all possible cardio-vascular, pulmonary, visual disorders, as well as for the fight against aging.

Antioxidants are molecules that protect cells from possible damage caused by oxidation, especially those caused by free radicals deriving from oxygen. The antioxidants found in food products are molecules that allow living organisms to effectively resist oxidative stresses.

Free radicals are normally held to be responsible for infections and oxidation in the human body. At high concentrations, free radicals can severely damage cell walls, causing DNA alterations. Antioxidants release electrons from their chemical structure, to reduce and neutralize the oxygen molecules containing free radicals; consequently, the damage to the cells and the alteration of their DNA is reduced, which may lead to the formation of cancerous masses and degenerative diseases. The majority of the assimilated antioxidant substances are metabolized by the diet but are not qualitatively and quantitatively sufficient.

Tomatoes contain different antioxidants: the two main carotenoids, lycopene and beta carotene, vitamin C and E and polyphenols such as kaempferol, rutin, quercetin, etc.

Natural Total Soluble Solids (NTSS) represent the percentage of soluble substances present in tomatoes.

Natural Total Solids (NTS) represent the percentage of total solids naturally present in tomatoes (soluble substances + insoluble substances); it can normally vary in “ordinary” processing tomatoes from 5 to 7% and from 6.5 to 9.5% in “Cherry” or cluster tomatoes.