Module 6. Tomato and tomato-based products

Lesson 23

 NOVEL TOMATO BASED PRODUCTS

23.1  Technology of Tomato-Chili Sauce

Tomato sauce is equally popular like tomato ketchup and there is lot of scope of innovation in formulation and manufacturing process to develop newer variant of it. Several such commercial preparations like Tom-chi (Tomato-Chili Sauce), Tom-Imli (Tomato & Tamarind sauce) etc; are available in Indian market. The purpose of developing such novel products is to utilize tomato, offer new products to consumer and diversify the product profile. Tomato sauce is slightly thinner in consistency than tomato ketchup and may contain certain thickening agents derived from vegetable starch (potato, cassava) or cereal (maize). It also contain higher amount of acetic acid i.e. around 1.60 percent to improve the keeping quality. The amount of sugar is usually higher (15-23 percent) to counteract harsh acidic taste and flavour. The concentration of spices is kept less as compared to ketchup.

The manufacturing technology for the tomato-chili sauce is similar to as discussed for tomato ketchup. The green chili is pureed by hot break method and seed as well as coarse fibrous portions are removed. The pureed chili is added in the formulation and ratio of sugar-acid-pungency is maintained in such a way that resultant product provide the flavour sensation of all the three in balanced way. Similarly, in tomato-imli sauce, the tamarind pulp is added along with tomato pulp and to balance more acidity slightly higher percentage of sugar is added. These novelty products are popular among all age groups and consumed with snacks. 

23.2  Dried Tomato Products

Tomatoes are quite perishable in nature and can be processed as dried product for value addition. Tomato slices can be dried by using tray or tunnel drying process or alternatively tomato pulp of juice may be spray dried to yield tomato powder of excellent quality. Drying process increases their availability round the year in convenient form.

23.2.1  Dried tomato slices

Dried tomato slices are versatile ingredient and find its application in various food formulations. Tomatoes of good quality are after through washing are blanched either in plain water or in 2.5% salt solution for 1 min.  These blanched tomatoes are dropped in cold water to quickly cool the product.  This also helps 1.5 cm thick slices, and excess juice is drained off.  Tomato slices are dipped in 2.5% gelatinized starch containing 5% potassium meta-bisulphate for 9 min.  They are spread over perforated or aluminum trays.  Drying is carried out at 65-70°C in a tray drier till the moisture reached to 4.5%.  These slices may be packed in polythene bags or grind as powder (Fig. 23.1).

Fig. 23.1 Tray drying process for tomato slices

23.2.2  Tomato powder

Tomato powder preparation is another technique for the preservation of tomato solids during off-season and offer convenience to consumers. The powder may be used in formulation of other processed products like culinary recipes or can be reconstitute in the form of juice or used as starting material for the manufacture of secondary products like sauce, ketchup and chutney. The tomato powder can be manufactured by using tray drying, foam mat drying or spray drying process. The powder obtained by different methods also varies in their properties mainly colour, nutrients and reconstitution.

For the manufacture of tomato powder whole tomatoes are cleaned, washed and surface moisture is allowed to evaporate. The juice is extracted by hot pulping methods and pulp is filtered to obtain pulp free juice which is subjected to vacuum concentration. The concentrated juice is mixed with foaming agent to form foam which is dried by using hot air. The dried powder is cooled, conditioned and ground in the form of powder.

Fig. 23.2 Spray drying process for the preparation of tomato powder

The spray drying process for the manufacture of tomato powder is outlined in Fig 23.2. The tomatoes with thick walled, bright red colour, high solids and high pectin content are the best for dehydration. The juice is extracted by hot break method and may also be subjected to enzymatic treatment to improve the recovery of juice, solids and colouring pigments. Seeds and skin pieces are removed prior to particle size reduction. The juice is concentrated in vacuum pan or double effect evaporators to desired total solid level. Maltodextrin (10 DE @ 10%) and SiO₂ (@ 1%) are added in concentrated juice to improve the colour and reconstitutional properties of the powder. The atomization speed of 25,000 rpm and inlet air temperature of 200°C is recommended for obtaining good quality tomato powder.

Colour of tomato powder depends on the lycopene content which is affected by thermal treatment. Therefore, optimization of feed rate, temperature of inlet and outlet air, additives and atomization speed determine the extent of thermal damage and quality of powder. The powder can be packaged in oxygen and moisture impermeable films. Further it can be also packed under vacuum for prolonging the shelf-life.

23.3  Whole Tomatoes in Sauce

This product is a new kind of product.  In this product whole tomatoes are preserved in their natural form, which is quite appealing to the consumers.  The tomatoes dark red in colour, firm and free from any defect, are selected, washed thoroughly in water.  The uniform elliptical shape or round shaped tomato varieties are preferred.  These tomatoes are blanched in boiling water for 230-60 seconds and quickly cooled to avoid softening.  They may be placed in 5% brine solution or 20% sugar solution or a combination of these two to remove excess moisture for 230 min.  Alternatively, they may be surface dried in a stream of hot air (45°C).  The dipping solutions may contain calcium salts to improve the firmness of the product.  The pH of the covering liquid tomato may be adjusted to below 4.5 by adding citric acid and thermally processed at 80-85°C for 20-30 min., cooled quickly.  The glass jar should be air tight.

23.4  Whey-Tomato Soup

Soups are served as appetizers before meals as they stimulate the secretion of gastric enzymes that leads to feeling of hunger. In market a large number of ready-to-make soup mixes are available to suit the palate of consumers. But certain additives in such soups mixes are considered harmful particularly to children. Moreover apparently they do not seem to provide quality nutrients and utilization of whey for soup preparation is attractive possibility.

The process for the manufacture of whey based soup involves blending of vegetables in whey and cooking of corn flour followed by heating (Fig. 23.3). The time-temperature combination of cooking of vegetables, corn flour and seasoning is important for dispersion of vegetables, gelatinization of starch and flavour perception of soup respectively. The developed product could be stored for a week under refrigeration and UHT treatment can be adopted to improve the shelf-stability. The soups can be packaged in retort pouches as well and processed in boiling water bath (85-90°C) for at least 30 min.

Cheese whey is preferred for the manufacture of vegetable soups than paneer whey, the latter being acidic. Whey based soups have been reported to be more viscous as compared to water based most probably due to gelation of whey proteins on heating. Whey based soups require less amount of salt, thickener and fat.

Fig. 23.3 Manufacturing process for whey-tomato soup