TOMATO INDUSTRIAL WASTE AS POTENTIAL SOURCE OF NUTRIENTS

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1 TOMATO INDUSTRIAL WASTE AS POTENTIAL SOURCE OF NUTRIENTS Y. P. A. Silva 1, B. C. Borba 2, M. G. Reis 3, M. Caliari 4, T. A. P. C. Ferreira College of Nutrition, Federal University of Goiás Rua 227, qd. 68, Setor Leste Universitário Zip Code: Goiânia, GO, Brasil yasminiportes@gmail.com 2 - College of Nutrition, Federal University of Goiás Rua 227, qd. 68, Setor Leste Universitário Zip Code: Goiânia, GO, Brasil barbaracb93@hotmail.com 3 - College of Nutrition, Federal University of Goiás Rua 227, qd. 68, Setor Leste Universitário Zip Code: Goiânia, GO, Brasil nutricao.marcela@gmail.com 4 - School of Agronomy, Food Engineering and Forestry Engineering, Federal University of Goiás Avenida Esperança, Campus Samambaia Zip Code: Goiânia, GO, Brasil, macaliari@ig.com.br 5 - College of Nutrition, Federal University of Goiás Rua 227, qd. 68, Setor Leste Universitário Zip Code: Goiânia, GO, Brasil, Phone: (55-62) taniaferreira@ufg.br RESUMO Pomace de tomate é um resíduo gerado durante o processamento de tomate, composto de casca, polpa e semente de tomate. Este trabalho avaliou a proporção de cascas e sementes e a composição centesimal de pomace de tomate obtido em uma indústria processadora de tomate de Goiânia, Goiás, Brasil. Amostras foram coletadas da indústria em 6 dias úteis consecutivos. Pomace era composto de 61,5% de casca+polpa e 38,5% de sementes. O teor de umidade médio dos 6 lotes era 66,58 ± 0,45 g.100g -1 (base úmida). A composição centesimal média dos 6 lotes (base seca) era: 50,74 ± 1,30 g.100g -1 fibra alimentar, 6,73 g.100g -1 carboidratos disponíveis, 20,91 ± 0,96 g.100g -1 proteínas, 14,14 ± 1,22 g.100g -1 lipídeos, e 3,60 ± 0,05 g.100g -1 cinzas. Pomace de tomate apresenta potencial pra ser usado como fonte importante de nutrientes, principalmente fibra alimentar. ABSTRACT Tomato pomace is a residue generated during tomato processing, composed of tomato skin, pulp and seeds. This paper evaluated the proportion of skin and seeds and the proximate composition of tomato pomace from a tomato processing plant located in Goiânia, Goiás, Brazil. Samples were collected from a processing plant in 6 consecutive work days. Pomace was composed of 61.5% skin+pulp and 38.5% seeds. Average moisture content of 6 batches was ± 0.45 g.100g -1 (wet basis). Average proximate composition of the 6 batches (dry basis) was: ± 1.30 g.100g -1 dietary fiber, 6.73 g.100g -1 digestable carbohydrates, ± 0.96 g.100g -1 protein, ± 1.22 g.100g -1 fat, and 3.60 ± 0.05 g.100g -1 ash. Tomato pomace shows potential for being used as source of important nutrients, especially dietary fiber. PALAVRAS-CHAVE: pomace, subproduto, reutilização, Bligh-Dyer, fibra alimentar. KEYWORDS: pomace, byproduct, reutilization, Bligh-Dyer, dietary fiber. 1. INTRODUCTION Tomato (Solanum lycopersium) is one of the vegetable crops most widely produced in the world (Rossini et al., 2013), both for direct consumption (fresh tomato) and for production of tomato products (processing tomato). According to the Food and Agriculture Organization of the United

2 Nations (FAO), worldwide production of fresh and processing tomato combined has been steadily increasing, with total annual production growing from 129 million tonnes in 2005 to 163 million tonnes in 2013 (latest data available) (FAO, 2016). The world production of processing tomato has increased from 33 million tonnes in 2005 to 41 million tonnes in 2015 according to estimates of the World Processing Tomato Council (WPTC, 2016), representing, on average, 24.25% of the total tomato production over this period. Brazil is the world s 9 th largest tomato producer (FAO, 2016), and the state of Goiás is its biggest producer, responsible for 20% of the national production (IBGE, 2016). From 2001 to 2012, the worldwide growth of the production of processing tomato has been caused by a combination of demographic growth (which accounts for 40% of the growth) and an increase in per capita consumption of tomato products such as paste, juice, puree, sauce, soup, catsup, whole dried tomatoes and tomato powder (60% growth) (TIS, 2014). Therefore, the processing of tomatoes to obtain tomato products is an industrial activity with growing importance on a worldwide scale. In this scenario, the matter of the management of waste generated by the industrial activities must be carefully considered. During the processing of tomatoes, the main residue generated is the tomato pomace, a mix of tomato skin, seeds and a small fraction of pulp, produced in amounts between 1.5% (personal communication) to 5% (Del Valle et al., 2006; Knoblich et al., 2005) of the initial weight of tomatoes. Considering the worldwide annual production of 41 million tonnes of processing tomato in 2015 (WPTC, 2016), this represents from 615 thousand to 2 million tonnes of pomace produced annually. Both the amount of pomace produced and its constitution in terms of proportion of skin, seeds and pulp depend on raw material characteristics and processing conditions, varying from one processing plant to the other. This residue is mainly destined to animal feed or dumped in landfills (Ruiz Celma et al., 2012), thus representing costs and environmental concern for the tomato processing industry. Considering the worldwide presence of the tomato processing industry and the matter of disposal of tomato processing waste, this work evaluated tomato pomace composition in terms of proportion of skin, pulp and seeds and its proximate nutritional composition (moisture, carbohydrates, dietary fiber, protein, fat and ash), to assess the potential of reusing this residue as source of nutrients. 2. MATERIAL AND METHODS 2.1 Sample Tomato pomace samples were obtained from an industrial plant located in the municipality of Goiânia, Goiás (Brazil). Samples were collected in 6 consecutive work days, totaling 6 batches of tomato pomace, all originated from the same tomato variety. Each day, approximately 25 kg of pomace were collected in plastic containers immediately after being produced, transported to the laboratory, vacuum packed in plastic bags containing approximately 1 kg of sample, wrapped in aluminum foil and frozen at -40 C in biofreezer (FV500, Liotop, São Carlos, Brazil) until further use. 2.2 Composition in skin and seed fractions For the determination of the percentage of skin, seeds and pulp in fresh samples, approximately 3 g of sample were taken and manually separated, using stainless steel forceps, in two fractions: skin + pulp combined, and seeds. Each fraction was then weighted and expressed as percentage weight. Separation was performed in triplicate.

3 2.3 Proximate nutritional composition Fresh samples were grounded in benchtop mill (A11, IKA, Staufen, Germany) for homogenization before analysis. The proximate composition (moisture, dietary fiber, protein, total fat, ash and available carbohydrates content) of samples was then determined in triplicate. Moisture was determined by drying in air oven at 105 C until constant weight; dietary fiber was determined by enzymatic digestion of dried and defatted sample (AOAC, 2005). Total nitrogen content was determined by the micro-kjeldhal method, and protein content was then calculated using a conversion factor of 6.25 (AOAC, 2005). Total fat content was determined according to the method described by Bligh and Dyer (1959). Ash content was determined by incineration in muffle furnace at 550 C for 8 hours (AOAC, 2005). Finally, available carbohydrates content was determined by difference, using the average values of moisture, dietary fiber, protein, fat and ash contents (AOAC, 2005). 2.4 Statistical analysis Results are expressed as average of replicate ± standard deviation. One-way analysis of variance (ANOVA) and Tukey test were performed at a 5% confidence level (p < 0.05). Correlation between fraction of skin and nutrients was evaluated (significant correlation when Pearson correlation coefficient > 0.7). Statistical tests were performed in R software v (R Core Team, 2015). 3. RESULTS AND DISCUSSION 3.1 Composition in skin and seed fractions Whole pomace, and skin + pulp and seed fractions after separation are shown in Figure 1. The skin + pulp fraction was composed mainly of skin, with very little pulp found. Therefore from now on this fraction will be referred to on this work as skin only. Figure 1 Whole pomace (a), and skin (b) and seed (c) fractions of tomato pomace after separation. (a) (b) (c) The percentage of weight of skin and seeds of tomato pomace is shown on Table 1. Average composition of the 6 batches was of 61.5% skin and 38.5% seeds, and no pulp could be identified. Sogi and Bawa (1998) reported values of 40% pulp, 27% skin and 33% seeds. The pulp usually is the fraction of greatest interest for the industry, from which juice is extracted for the production of tomato paste, the base from which other tomato derived products are manufactured. This small amount of pulp on the residue indicates that the processing conditions applied by the industrial plant that produced the material used in this study are very effective in extracting the pulp, which contributes to the smaller amount of pomace generated (1.5% of the weight of raw tomatoes) than the reported by other studies, of up to 5% (Del Valle et al., 2006; Knoblich et al., 2005).

4 Table 1 Composition in skin and seeds (% of weight) of 6 batches of tomato pomace. Fraction Batch (% weight) Skin 65.3 ± 1.9 a 59.4 ± 2.5 bc 63.2 ± 1.4 ab 63.6 ± 1.1 ab 57.5 ± 1.7 c 61.1 ± 1.9 abc Seeds 34.7 ± 1.9 c 40.6 ± 2.5 ab 36.8 ± 1.4 bc 36.4 ± 1.1 bc 42.5 ± 1.7 a 38.9 ± 1.9 abc 3.2 Proximate nutritional composition Proximate composition of tomato pomace is shown in Table 2. Significant differences on components were observed among batches, as shown by the Tukey test. These differences were probably caused by differences in the raw tomato characteristics processed by the industrial plant. Although the 6 batches of pomace were produced from the same tomato variety, each one came from a different producer, and the differences among batches could be due to different farming conditions during the plant development. Considering these differences were observed over a 6 days period, larger variations can be expected throughout the entire harvesting season due to climate conditions. Table 2 Moisture (g.100g -1 wet basis w.b.) and proximate nutritional composition (g.100g -1 dry basis d.b.) of six batches of fresh tomato pomace (*). Batch Dry component (g.100g -1 d.b.) Moisture (g.100g -1 Available w.b.) Dietary fiber Proteins Fat Ash Carbohydrates ± 0.23 b ± 1.01 a ± 0.49 c ± 0.92 abc 3.53 ± 0.04 c ± 0.30 c ± 0.77 b ± 1.11 bc ± 1.91 abc 3.33 ± 0.02 d ± 0.42 c ± 1.96 b ± 1.14 ab ± 0.90 ab 3.57 ± 0.04 bc ± 0.37 a ± 0.69 b ± 1.26 a ± 0.79 bc 4.02 ± 0.05 a ± 0.85 a ± 1.62 b ± 1.21 a ± 2.32 c 3.69 ± 0.10 b ± 0.54 d ± 1.30 b ± 0.53 a ± 0.51 a 3.47 ± 0.02 cd (*) On the same column, averages followed by the same letter do not statistically differ at a 5% confidence level (p<0.05) Samples presented a very high moisture content, ranging from ± 0.54 to ± 0.37 g.100g -1 (wet basis - w.b.). Similar or even higher values for moisture contents are reported by other studies. Kalogeropoulos et al. (2012) found moisture content of ± 0.24 g.100g -1 (w.b.) for whole pomace, and Del Valle et al. (2006) reported values ranging from to g.100g -1 (w.b.). Knoblich et al. (2005) found 90.0 g.100g -1 (w.b.) for skin and 91.2 g.100g -1 (w.b.) for seeds; and Lavelli and Torresani (2011) found values between 90.0 ± 0.2 and 92.7 ± 0.1 g.100g -1 (w.b.). Del Valle et al. (2006) suggest that differences in moisture content among pomace samples from different processing plants can be caused by the processing conditions such as the use or not of water to transport the residue for final disposal. This high moisture content makes tomato pomace a product prone to physico-chemical and microbiological degradation. Therefore, a drying step is required to avoid deterioration and to allow storage before its utilization. This adds costs that should be considered when evaluating potential applications of tomato pomace. Regarding other nutrients evaluated, the highest content found was of dietary fiber, ranging from to g.100g -1 in dry basis (d.b.) (Table 2). This result suggests a potential of use of tomato pomace as source of dietary fiber. Further studies should be conducted to evaluate the constitution of these fibers in terms of soluble and insoluble fibers. Considerable amounts of protein (16.82 to g.100g -1 d.b.) and fat (11.18 to g.100g -1 d.b.) were also found. Different values for proximate composition of tomato pomace and its fractions are reported on the literature. Some of these results, along with the average results of the 6 batches of the present

5 work, are shown on Table 3. Del Valle et al. (2006) evaluated the proximate composition of tomato processing residues collected at 21 points along the processing line of an industrial plant in Spain. The average values of fiber (59.03 g.100g -1 d.b.), proteins (19.27 g.100g -1 d.b.) and ash (3.92 g.100g -1 d.b.) of the different residues are similar to the present study, but fat is significantly lower (5.85 g.100g -1 d.b.). Rossini et al. (2013) found similar values of ash in whole fresh pomace (3.3 g.100g -1 d.b.) from Italian processing plants. Kalogeropoulos et al. (2012) found significantly lower results for fat content (6.88 g.100g -1 d.b) in pomace collected at a Greek processing plant. Knoblich et al. (2005) evaluated skin and seed fractions of tomato pomace separately. Proteins values were similar to the ones on the present work, g.100g -1 (d.b.) for the skin fraction and g.100g -1 (d.b.) for the seed fraction. However total fat values were significantly lower (3.22 g.100g -1 d.b. for skin and 6.37 g.100g -1 d.b. for seeds) and ash was higher (25.64 g.100g -1 d.b. for skin and 5.18 g.100g -1 d.b. for seeds) than the present study. Table 3 Proximate composition (g.100g -1 dry basis) of tomato pomace according to several authors. Component (g.100g -1 dry basis) Product Dietary Available Reference Protein Fat Ash Fiber Carbohydrates Whole pomace (a) Present work Whole pomace (b) (c) n.r Del Valle et al. (2006) Whole pomace n.r. n.r. n.r n.r. Kalogeropoulos et al. (2012) Skin byproduct (d) n.r Knoblich et al. (2005) Seed byproduct (d) n.r Knoblich et al. (2005) Whole pomace n.r. n.r. n.r. n.r. 3.3 Rossini et al.(2013) n.r. = Results not reported (a) Average of results of the 6 batches evaluated (b) Average of results of residues collected at 4 different processing steps in 10 different plants (c) Neutral detergent fiber (d) Acid detergent fiber As reported by other studies (Del Valle et al., 2006; Knoblich et al., 2005), most of the fibers and proteins of tomato pomace is found on the skin fraction, and most of the fat and ash is found on the seed fraction. Therefore, it could be expected that different results of proximate composition observed among studies could be explained by the proportions of skin and seeds in the pomace. However, in this study no direct correlation between fraction of skin and different components was found (Pearson s coefficient < 0.3) for any of the components. Therefore, it can be assumed that differences among studies are more due to the processing conditions and the raw tomatoes characteristics, than to the proportion of skin and seeds on the residue. Given the lowest estimate of 615,000 tonnes of tomato pomace produced annually worldwide (see item 1), and the average proximate composition of the 6 batches evaluated in the present study, an average of 312,000 tonnes of dietary fiber, 43,000 tonnes of proteins, 29,000 tonnes of fat and 7,000 tonnes of minerals are estimated to be lost with tomato pomace. These amounts are not insignificant, and could be used for nutrient recovery for human health instead of being disposed or used as animal feed. 4. CONCLUSIONS No correlation was found between the proportion of skin and seeds in tomato pomace and its proximate composition, indicating that variations among studies are due to differences in raw material

6 composition and processing conditions. Tomato pomace has very high moisture content, thus its reutilization should take into account a drying step to allow storage and avoid degradation. Among the nutrients studied, the highest content found was of dietary fiber, and also a considerable amount of protein and fat. Further studies, such as soluble and insoluble fibers content, protein digestibility and amino acids score, and fatty acids profile, should be conducted to evaluate the quality of these nutrients in order to provide the best uses of the residue. Considering that tomato pomace is a waste for the food industry, being at most used as animal feed, there is a great potential of better use for this product, as source of ingredients of high nutritional value. 5. REFERENCES AOAC Association of Official Analytical Chemists. (2005). Official methods of analysis of the AOAC International. (18 th ed.). Gaithersburg (USA): AOAC International. Bligh, E. G., & Dyer, W. J. (1959). A rapid method of total lipid extraction and purification. Canadian Journal of Biochemistry and Physiology, 37(8), Del Valle, M., Câmara, M. M., & Torija, M. E. (2006). Chemical characterization of tomato pomace. Journal of the Science of Food and Agriculture, 86, FAO Food and Agriculture Organization of the United Nations. (2016). World Crops Production. Available at IBGE Instituto Brasileiro de Geografia e Estatística. (2016). LSPA Levantamento Sistemático da Produção Agrícola (v. 29). Rio de Janeiro: IBGE. Kalogeropoulos, N., Chiou, A., Pyriochou, V., Peristeraki, A., & Karathanos, V. T. (2012). Bioactive phytochemicals in industrial tomatoes and their processing byproducts. LWT Food Science and Technology, 49, Knoblich, M., Anderson, B., & Latshaw, D. (2005). Analyses of tomato peel and seed byproducts and their use as a source of carotenoids. Journal of the Science of Food and Agriculture, 85, Lavelli, V., & Torresani, M. C. (2011). Modelling the stability of lycopene-rich by-products of tomato products. Food Chemistry, 125, R Core Team. (2015). R: A Language and Environment for Statistical Computing. Vienna: The R Foundation for Statistical Computing. Rossini, G., Toscano, G., Duca, D., Corinaldesi, F., Pedretti, E. F., & Riva, G. (2013). Analysis of the characteristics of the tomato manufacturing residues finalized to the energy recovery. Biomass and Bioenergy, 51, Ruiz-Celma, A., Cuadros, F., & López-Rodríguez, F. (2012). Characterization of pellets from industrial tomato residues. Food and Bioproducts Processing, 90, Sogi, D. S., & Bawa, A. S. (1998). Studies on dehydration of tomato processing waste. Indian Food Packer, 52 (2), Sogi, D. S., Bawa, A. S., & Garg, S. K. (2000). Sedimentation system for seed separation from tomato processing waste. Journal of Food Science and Technology, 37(5), TIS Tomatoland Information Service. (2014). Tomato News Global consumption survey 2012/2013. Suresnes (France): Tomatoland Information Service. WPTC World Processing Tomato Council. (2016). World production estimate. Available at: