Recovery of carotenoids from tomato processing by-products – a review

Screening of Ten Tomato Varieties Processing Waste for Bioactive Components and Their Related Antioxidant and Antimicrobial Activities

Global tomato production is currently around 180 million tons, of which more than a quarter undergoes processing. The removed peels, seeds, and vascular tissues usually end up in landfills, creating environmental pollution. In order to highlight the alternative use of these vegetal wastes, our study investigated 10 tomato varieties in terms of carotenoids content, phenolic composition, and their related antioxidant and antimicrobial activities. Tomato peels extracts were screened by high performance liquid chromatography with diode-array detection (HPLC/DAD) for qualitative and quantitative analyses. The extracts were tested against six bacterial strains to determine their antimicrobial effect; the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay was applied to estimate their antioxidant capacity. Total carotenoids content was significantly higher in Ţărănești roz, a local variety (5.31 ± 0.12 mg/100 g DW), while Mirsini, a commercial hybrid, presented significantly higher total phenolic content (155 ± 2 mg/100 g DW) compared to the mean value of all analyzed samples. The methanolic extracts of tomato peels presented acceptable antimicrobial activity against Staphilococcus aureus and Bacillus subtilis, and the mean antioxidant activity was 201 ± 44 µmol Trolox/100 g DW tomato peels. Considering that tomato peels have lycopene, β-carotene, lutein, and different phenolic compounds in their composition, tomato industrial by-products could represent a source of natural bioactive molecules with applicability in nutraceuticals and food industry.

Bioactive potential of fruit and vegetable wastes

Fruits and vegetables are essential for human nutrition, delivering a substantial proportion of vitamins, minerals, and fibers in our daily diet. Unfortunately, half the fruits and vegetables produced worldwide end up as wastes, generating environmental issues caused mainly by microbial degradation. Most wastes are generated by industrial processing, the so-called by-products. These by-products still contain many bioactive compounds post-processing, such as macronutrients (proteins and carbohydrates) and phytochemicals (polyphenols and carotenoids). Recently, the recovery of these bioactive compounds from industry by-products has received significant attention, mainly due to their possible health benefits for humans. This chapter focuses on the bioactive potential of fruit and vegetable by-products with possible applications in the food industry (functional foods) and in the health sector (nutraceuticals).

Potato Peels as a Source of Novel Green Extracts Suitable as Antioxidant Additives for Fresh-Cut Fruits

Potato is a source of different bioactive compounds, and the potato transformation industry produces conspicuous quantities of potato peels as waste. In this context, the objective of this research was twofold: (i) the evaluation of the recovery of bioactive compounds from organic potato byproducts through an innovative multistep green extraction process; (ii) to evaluate the preservation during storage of the main quality-physicochemical parameters of minimally processed apples treated with two different natural extracts obtained. The potato extracts were obtained by solid CO2 cryomaceration followed by solid/liquid extraction based on water or 10% ethanol/water solutions. The efficacy of potato extracts, with or without 1% of citric acid, was tested in comparison with traditional preserving compounds in minimally processed apple preparation. All the extracts were characterized by a high antioxidant power and were rich in phenol compounds, showing a good activity in keeping the qualitative parameters of fresh-cut apple. A significant anti-browning effect as well as a slowing down of the softening of fruits during storage were observed. The obtained results suggest the suitability of the potato extracts as antioxidant additives for fresh-cut fruits, thus avoiding the use of unsafe chemicals.

OPTIMISATION OF ORGANIC SOLVENT EXTRACTION OF TOTAL CAROTENOIDS FROM BULGARIAN TOMATO PROCESSING WASTE

The quantity of tomato wastes combined with beneficial characteristics of components of the wastes justifies the great interest of researchers and manufacturers in extracting of carotenoids from this low cost material. In this study the response surface (RSM) approach and Box-Behnken design (BBD) were used to explore the possibility of modelling and optimisation the organic solvent extraction of total carotenoids from Bulgarian tomato processing waste (TPW).  Bulgarian TPW consists of tomato pomace was used in this study. Dried and ground TPW was plased in the extraction flask and stirred with acetone at various extraction conditions. The extract obtained was vacuum filtered through filter paper and was subjected to spectrophotometrically total carotenoids content determination. A three-variable, three-level BBD of RSM was employed in optimisation the extraction conditions for the highest recovery of total carotenoids from Bulgarian TPW. A response surface quadratic model was developed and statistical analysis was carried out. Data concerning model adequacy tests indicated that the values of R2 and Radj2 for quadratic model were the higest in comparison to the other models. The obtained F-value of 38.65 implies the model was significant (p < 0.05) and could be used for optimisation. The effects of extraction temperature, solvent to solid ratio and extraction time were significant in total carotenoids yield. Total carotenoids content ranged from 9.78 to 25.28 mg/100 g dried TPW. The predicted values of total carotenoids content were closed to the experimental observed values. By use of RSM the optimal extraction conditions were determined as follow: extraction time of 90 min, solvent to solid ratio of 60 mL/g and extraction temperature of 50ºC. The results obtained showed that predicted (28.40 mg/100 g dried TPW) and experimental (28.86±0.92 mg/100 g dried TPW) values of total carotenoids content were not significant different (p > 0.05).

Ascorbic Acid Effectively Improved Lutein Extraction Yield from Australian Sweet Lupin Flour

Lutein is a xanthophyll, a bioactive phytochemical that presents itself as colourful pigments in plants. Australian sweet lupin flour has been incorporated as a food ingredient in wheat bread and pasta to improve their sensory property and nutritional quality. However, the amount of lutein in lupin flour has not yet been determined. This is the first study to quantify naturally occurring lutein in Australian sweet lupin flour after the extraction efficiency was optimised. Several organic solvents (acetone, isopropyl alcohol, ethyl acetate and hexane), the use of an ultrasonic bath or a probe, the need for saponification and addition of ascorbic acid (served as antioxidant) were tested to compare the extraction yield. HPLC was employed to analyse lutein in flour. Lowest lutein (68 μg/100 g) was determined in the hexane extract. Samples extracted using an ultrasonic bath (126-132 μg/100 g) contained higher lutein than those extracted using a probe (84-109 μg/100 g). Saponified samples showed significantly less lutein (30-64 μg/100 g) than their respective non-saponified ones (122-134 μg/100 g). Without added ascorbic acid, lutein that was extracted into isopropyl alcohol was 143 μg/100 g and was higher than those released into acetone (92 μg/100 g). When ascorbic acid was added, measured lutein in the extracts of isopropyl alcohol (155 μg/100 g) and acetone (138 μg/100 g) increased by 8 and 33%, respectively. Our results suggested that the choice of extraction solvents and addition of ascorbic acid was crucial for quantitative analysis of lutein, so that the lutein content in lupin flour can be accurately reported.

Sustainable approach for lycopene extraction from tomato processing by-product using hydrophobic eutectic solvents

Lycopene, a non-polar antioxidant compound with important effects on human health and wide commercial applications, was extracted from tomato processing wastes using innovative hydrophobic eutectic mixtures (HEMs) replacing traditional organic solvents. HEMs were prepared using DL-menthol as hydrogen-bond acceptor (HBA) and lactic acid as hydrogen-bond donor (HBD), and the ultrasound-assisted extraction (UAE) was optimized using a Box-Behnken design to evaluate extraction conditions: extraction temperature (°C), molar ratio of eutectic mixture (moles HBA: mol HBD), solvent to sample ratio (volume to mass, mL/g), and extraction time (min), with lycopene extraction yield (µg/g d.w.) as the response variable. Optimization of parameters was performed using response surface methodology, and the optimized extraction conditions were determined to be 70 °C, 8:1 mol HBA/mol HBD, 120 mL/g solvent: sample, and 10 min. The experimental optimal yield was 1446.6 µg/g, in agreement with the predicted optimal yield, indicating the validity of the model. This new technique for lycopene extraction, using a HEM as extraction solvent in replacement of hazardous organic solvents, and tomato pomace as source material, represents a viable and more sustainable approach for obtaining a high value-added bioactive compound, and can contribute towards the development of greener extraction processes.

Bioactive Compounds Extracted from Tomato Processing by-Products as a Source of Valuable Nutrients

Alongside paper, plastic, metal and glass, an important segment in the recycling area is represented by the wastes of different vegetal processing industries. These by-products gained interest lately, in the context of food waste prevention and growing population number. In the tomato processing industry approximately, 8.5 million tons of wastes are generated globally, each year. The present study highlights the valuable bioactive constituents as lycopene, beta-carotene, glutamic acid or aspartic acid from the by-products of tomato processing industries, which can be revalorized as incorporated nutrients in functional foods. Tomato consumption is directly associated with the prevention of different chronic diseases and carcinogenesis, however the carotenoids bioavailability is a key factor in this process. Further, fiber content together with protein content of tomato seeds and benefits of their consumption are emphasized. Value-added food products obtained by tomato peels or seeds addition are exemplified in this review (bakery, meat products, pasta and noodles, dairy and oil products as well as jams and functional ice cream), in order to embrace next prototypes that can transform vegetal by-products in functional nutrients.

Characterization of tomato processing by-product for use as a potential functional food ingredient: nutritional composition, antioxidant activity and bioactive compounds

Tomato pomace, a by-product generated during tomato processing, was collected at a large tomato processing industry. The by-product was mainly constituted of tomato skin (61.5%), and presented high moisture content (66.58 g.100g^-1 wet basis). Among the nutrients, the highest content was of dietary fibre, followed by proteins and fat (50.74, 20.91, 14.14 g.100g^-1 d.w., respectively). The pomace has high in vitro antioxidation capacity, especially when measured with the TEAC assay (224.81 μmol Trolox equivalent 100g^-1 d.w.). This is due especially to the high amount of lycopene remaining in the by-product after processing (446.9 μg.g^-1 d.w). The waste was fractioned into skin and seed fractions by sedimentation, resulting in the increase of lycopene yield by 55%, when using skin fraction as the source material in place of the whole pomace. This by-product shows great potential for being used as a source of the ingredients of high nutritional value, especially dietary fibre and lycopene.

An updated review on use of tomato pomace and crustacean processing waste to recover commercially vital carotenoids

Globally, the amount of food processing waste has become a major concern for environmental sustainability. The valorization of these waste materials can solve the problems of its disposal. Notably, the tomato pomace and crustacean processing waste presents enormous opportunities for the extraction of commercially vital carotenoids, lycopene, and astaxanthin, which have diverse applications in the food, feed, pharmaceuticals, and cosmetic industries. Moreover, such waste can generate surplus revenue which can significantly improve the economics of food production and processing. Considering these aspects, many reports have been published on the efficient use of tomato and crustacean processing waste to recover lycopene and astaxanthin. The current review provides up-to-date information available on the chemistry of lycopene and astaxanthin, their extraction methods that use environmentally friendly green solvents to minimize the impact of toxic chemical solvents on health and environment. Future research challenges in this context are also identified.

Oxidative stability of refined olive and sunflower oils supplemented with lycopene-rich oleoresin from tomato peels industrial by-product, during accelerated shelf-life storage

Tomato peels by-product from a Tunisian industry was used for the extraction of lycopene-rich oleoresin using hexane solvent maceration. Tomato peels oleoresin, TPO, exhibited competitive free radicals scavenging activity with synthetic antioxidants. The efficacy of TPO in stabilizing refined olive (ROO) and sunflower (RSO) oils was investigated for five months, under accelerated shelf-life, compared to the synthetic antioxidant, butylated hydroxytoluene (BHT). TPO was added to ROO and RSO at four different concentrations, namely 250, 500, 1000 and 2000 µg/g and BHT standard at 200 µg/g. Lipid oxidation was tracked by measuring the peroxide value, acidity, conjugated dienes and trienes. Results suggested the highest efficiency of 250 µg/g and 2000 µg/g of TPO, referring to 5 µg/g and 40 µg/g of lycopene, for the oxidative stabilization of ROO and RSO, respectively. The protective effect of TPO against the primary oxidation of these refined oils was significantly correlated to their lycopene contents.

Side Streams of Plant Food Processing As a Source of Valuable Compounds: Selected Examples

Industrial processing of plant-derived raw materials generates enormous amounts of by-products. On one hand, these by-products constitute a serious disposal issue because they often emerge seasonally and are prone to microbial decay. On the other hand, they are an abundant source of valuable compounds, in particular secondary plant metabolites and cell wall materials, which may be recovered and used to functionalize foods and replace synthetic additives with ingredients of natural origin. This review covers 150 references and presents select studies performed between 2001 and 2016 on the recovery, characterization, and application of valuable constituents from grape pomace, apple pomace, potato peels, tomato pomace, carrot pomace, onion peels, by-products of citrus, mango, banana, and pineapple processing, side streams of olive oil production, and cereal by-products. The criteria used were economic importance, amounts generated, relevance of side streams as a source of valuable compounds, and reviews already published. Despite a plethora of studies carried out on the utilization of side streams, relatively few processes have yet found industrial application.

Production and Properties of a Thermostable, pH-Stable Exo-Polygalacturonase Using Aureobasidium pullulans Isolated from Saharan Soil of Algeria Grown on Tomato Pomace

Polygalacturonase is a valuable biocatalyst for several industrial applications. Production of polygalacturonase using the Aureobasidium pullulans stain isolated from Saharan soil of Algeria was investigated. Its capacity to produce polygalacturonase was assessed under submerged culture using tomato pomace as an abundant agro-industrial substrate. Optimization of the medium components, which enhance polygalacturonase activity of the strain Aureobasidium pullulans, was achieved with the aid of response surface methodology. The composition of the optimized medium was as follows: tomato pomace 40 g/L, lactose 1.84 g/L, CaCl₂0.09 g/L and pH 5.16. Practical validation of the optimum medium provided polygalacturonase activity of 22.05 U/mL, which was 5-fold higher than in unoptimized conditions. Batch cultivation in a 20 L bioreactor performed with the optimal nutrients and conditions resulted in a high polygalacturonase content (25.75 U/mL). The enzyme showed stability over a range of temperature (5–90 °C) with an optimum temperature of 60 °C with pH 5.0, exhibiting 100% residual activity after 1h at 60 °C. This enzyme was stable at a broad pH range (5.0–10). The enzyme proved to be an exo-polygalacturonase, releasing galacturonic acid by hydrolysis of polygalacturonic acid. Moreover, the exo-polygalacturonase was able to enhance the clarification of both apple and citrus juice. As a result, an economical polygalacturonase production process was defined and proposed using an industrial food by-product.

Fractionate analysis of the phytochemical composition and antioxidant activities in advanced breeding lines of high-lycopene tomatoes

The results of the first study characterizing new high-lycopene tomato advanced breeding lines, to determine the phytochemical content as well asin vitroantioxidant activities of peel, pulp and seed fractions are presented.

Use of time-resolved spectroscopy as a method to monitor carotenoids present in tomato extract obtained using ultrasound treatment

INTRODUCTION

Compounds exhibiting antioxidant activity have received much interest in the food industry because of their potential health benefits. Carotenoids such as lycopene, which in the human diet mainly derives from tomatoes (Solanum lycopersicum), have attracted much attention in this aspect and the study of their extraction, processing and storage procedures is of importance. Optical techniques potentially offer advantageous non-invasive and specific methods to monitor them.

OBJECTIVES

To obtain both fluorescence and Raman information to ascertain if ultrasound assisted extraction from tomato pulp has a detrimental effect on lycopene.

METHOD

Use of time-resolved fluorescence spectroscopy to monitor carotenoids in a hexane extract obtained from tomato pulp with application of ultrasound treatment (583 kHz). The resultant spectra were a combination of scattering and fluorescence. Because of their different timescales, decay associated spectra could be used to separate fluorescence and Raman information. This simultaneous acquisition of two complementary techniques was coupled with a very high time-resolution fluorescence lifetime measurement of the lycopene.

RESULTS

Spectroscopic data showed the presence of phytofluene and chlorophyll in addition to lycopene in the tomato extract. The time-resolved spectral measurement containing both fluorescence and Raman data, coupled with high resolution time-resolved measurements, where a lifetime of ~5 ps was attributed to lycopene, indicated lycopene appeared unaltered by ultrasound treatment. Detrimental changes were, however, observed in both chlorophyll and phytofluene contributions.

CONCLUSION

Extracted lycopene appeared unaffected by ultrasound treatment, while other constituents (chlorophyll and phytofluene) were degraded.

Mitigation strategies in the agro-food sector: The anaerobic digestion of tomato purée by-products. An Italian case study

Tomato processing involves a significant production of residues, mainly constituted by discarded tomatoes, skins, seeds and pulp. Often, these residues are not valorized and represent an added cost for manufacturing companies because of disposal processes, with environmental issues due to the difficult management. The exploitation of these residual materials results complex as their availability is mainly concentrated in few months. A possible solution is the production of biogas employed in a Combine Heat and Power engine for energy production, in line with the 2020 targets of European Union in terms of promotion of energy from renewable resources and greenhouse gas emission reduction. The tomato by-product utilization for energy production as a strategy to reduce the environmental load of tomato purée was evaluated by means of Life Cycle Assessment. Two scenarios were considered: Baseline Scenario - tomato by-products are sent back to the tomato fields as organic fertilizers; Alternative Scenario - tomato by-products are employed in a nearby biogas plant for energy production. Methane production of tomato by-products was assessed by means of specific laboratory tests. The comparison between the two scenarios highlighted reductions for all the impact categories with the Alternative Scenario. The most important reductions are related to particulate matter (-5.3%), climate change (-6.4%) and ozone depletion (-13.4%). Although small, the reduction of the environmental impact cannot be neglected; for example for climate change, the anaerobic digestion of by-products allows a saving of GHG emissions that, over the whole year, is equal to 1.567 tons of CO2 eq. The results of this study could be up-scaled to the food industries with high heat demand producing considerable amounts of fermentable by-products employable as feedstock for biogas production.

Use of Time-Resolved Fluorescence to Monitor Bioactive Compounds in Plant Based Foodstuffs

The study of compounds that exhibit antioxidant activity has recently received much interest in the food industry because of their potential health benefits. Most of these compounds are plant based, such as polyphenolics and carotenoids, and there is a need to monitor them from the field through processing and into the body. Ideally, a monitoring technique should be non-invasive with the potential for remote capabilities. The application of the phenomenon of fluorescence has proved to be well suited, as many plant associated compounds exhibit fluorescence. The photophysical behaviour of fluorescent molecules is also highly dependent on their microenvironment, making them suitable probes to monitor changes in pH, viscosity and polarity, for example. Time-resolved fluorescence techniques have recently come to the fore, as they offer the ability to obtain more information, coupled with the fact that the fluorescence lifetime is an absolute measure, while steady state just provides relative and average information. In this work, we will present illustrative time-resolved measurements, rather than a comprehensive review, to show the potential of time-resolved fluorescence applied to the study of bioactive substances. The aim is to help assess if any changes occur in their form, going from extraction via storage and cooking to the interaction with serum albumin, a principal blood transport protein.