Effect of different Processing and Preservation Techniques on Lycopene: A Mini Review

 

Shruti Rawat1, Arshi Siddiqui2*, Rajat Singh3

1Department of Food Technology, School of Applied and Life sciences,

Uttaranchal University, Dehradun, Uttarakhand, 248007 India.

2Department of Post Harvest Process and Food Engineering,

G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, 263145 India.

3College of Horticulture and Forestry, Thunag, Mandi, Himachal Pradesh, 175048 India.

*Corresponding Author E-mail: arshi669@gmail.com

 

ABSTRACT:

Lycopene is the principle pigment found in the majority of the red fruits and vegetables. It is rich in so many medicinal properties. Tomato and its processed products are also a good source of lycopene. Around 85% lycopene is found in tomato and its processed products. The bright red, eye catching hue of ripen tomato is a gift of this lycopene to the tomato.The growing demand of lycopene results in the major production of its products. Processing temperatures leads to the decreased quality of the lycopene in the final product. Isomerization and oxidation are mainly responsible for this. So, a proper processing time and temperature is needed which will deliver the lycopene in its full potential form to the consumers.

 

KEYWORDS: Preservation, Lycopene, Tomato, Pigment, Isomerization, Oxidation.

 

 


INTRODUCTION:

Carotenoids are the pigments which gives diverse colours to the fruits and vegetables. They are generally produced by the plants, algae, certain bacteria and fungi. These pigments vary from red, orange and yellow in colour. The characteristic red colour of watermelon; orange colour of pumpkin and yellow colour of banana is due to the presence of carotenoids. Carotenoids are tetraterpenoids and are of 2 kinds: (a) Carotenes: having only carbon and hydrogen atom (e.g. alpha carotene, beta carotene and lycopene) (b) xanthophyll: having 1 extra oxygen atom in addition to the group (e.g. lutein and zeaxanthin)1.

 

Tomato is one such good source of carotenoid and is a popular crop after potato. Lycopersiconescentulumis a rich source of fibre and vitamins. It is consumed either freshly or in a processed form like ketchup, sauce, soup and puree.

 

Tomato and its products are the primary source of lycopene in a diet and around 85% lycopene is present in them2, making it enriched with many antioxidant properties. Lycopene is a red colour carotenoid, responsible for the red colour of certain fruits and vegetables such as tomato, watermelon, pink grapefruit3, papaya and apricot. The first ever lycopene in tomato was detected by Millardet (1876) and then named by Schunck4.

 

Lycopene (C40H56) has molecular mass 536.89 Daltons. It has 13 double bonds, of which eleven are conjugated and two are unconjugated double bonds5. Lycopene is a lipophilic and octaprene (containing 8 isoprene units)6. Among all the carotenoids found in nature, lycopene has the ultimate singlet quenching ability7 that is 2- folds more than Beta- carotene and ten- folds higher than Vitamin E8 which makes it an excellent antioxidant. Lycopene rich diet can reduce the chances of cancers (lung cancer)9. It also helps in reducing prostate cancer, cardiovascular diseases and gastrointestinal diseases10.

 

Nowadays, tomato is emerging as the potent lycopene rich food. Apart from tomato pulp, its seed and peel are used for the lycopene production. Its by-products (processed) are often neglected and either used as the animal feed or are thrown away which leads to the major wastage. Various studies have shown that its by-products also contain a good amount of lycopene in them. So utilising these by products can also lead to low wastage and sustainability.

 

Increasing demand leads the focus in the manufacturing process of this pigment. Its product as ketchup, sauce and juice are consumed worldwide. However, these processed products went through a lot of treatment (heating, cooking) which can lead to the loss or degradation of this valuable pigment thus, affecting the health benefits as well as their appearance (colour). So, these products should be processed in a way that it will lead to less deterioration and reach the consumer with its full potential. This review focuses on the lycopene, its sources, extraction methods, preservation methods and its impact on lycopene.

 

Sources of Lycopene:

Lycopene can be obtained by natural resources (plants, algae),chemical synthesis and microbially(fungi, bacteria).Human beings can not synthesize lycopene, they get it by their food which get stored in adipose tissue and liver (in large amount) and in kidney and lungs (in small amount)11.

 

Dietary sources:

Red colour fruits and vegetables are the primary dietary sources of lycopene. Ample amount of lycopene can be found in tomato, rosehip12, guava, watermelon, pink grapefruit3, dried apricots and papaya13 which give them their red colour. It can also be found in the seeds and peels14of some fruits and vegetables.

 

Tomato and tomato based products contain ample amount of lycopene in them. Major tomato products (processed) consist of tomato juice, soup, ketchup and sauce. Around 85% lycopene alone can be found in them2. However, the lycopene content varies in tomato from variety to variety. By products of tomato processing (including skin and seeds) also consists of high amount of lycopene in them. Dietary sources of lycopene are given in Table 1.

 

Table 1 Dietary sources of lycopene15,16,17,18

DietarySources

Content (mg/100g)

Tomatoes (Red)

3.1 7.44

Guava

5.23 5.50

Watermelon

23 72

Raw Rosehip

12.9 35.2

 

Microbial sources:

The lycopene produced by microbial sources has advantages such as high yield and high quality. It was reported in a study that Blakesleatrisporais an excellent lycopene source in nature and it produces lycopene which has high content, quality and nutritional value than tomatoes19.

 

It wasmentioned that Escherichia coli and Saccharomyces cerevisiaecan also be used for producing lycopene and the later one is considered as a safer host but the production of lycopene is higher in E.coli20. As reported by this study, there was a higher yield of 22- fold in lycopene in S.cerevisiae by combining host engineering with pathway engineering. Microbial lycopene sources are mentioned in Table 2.

 

Physicochemical Properties of Lycopene:

Lycopene is red in colour having molecular weight 536.89 g/mol14 and chemical formula C40H56. Its melting point is between 171C to 176C21 and it contains eleven (11) conjugated and two unconjugated bonds. These conjugated bonds are responsible for the colour in lycopene11. Due to lack of provitamin A activity (absence of terminal Beta-ionic ring)4, its biochemistry is different from alpha carotene and beta- carotene7.

 

Lycopene is lipophilic, containing elongated needles (red) in crystal form4. Its powder is dark-reddish brown in colour14. Due to its acyclic structure, it is water insoluble4and soluble in hexane, acetone and oil14.

 

Lycopene become highly unstable on exposure with light, heat and oxygen14. It gets oxidized in oxygens presence. Lycopene is predominantly found in all trans form but in presence of light and heat, it gets isomerized from trans-to-cis configuration4. Properties of lycopene are given in Table 3.

 

Table 2: Microbial sources of lycopene20,21,22

Sources

Content (mg/g)

Saccharomyces cerevisiae

2.43

Phycomyces

15

Yarrowialipolytica

16

 

Table 3: Properties of Lycopene23, 4, 14, 24

Properties

Result

Colour

Vibrant Red

Chemical Formula

C40H56

Stable at pH

3.5 4.5

Melting point

Between 171C and 176C

 

Extraction of Lycopene:

Solvent Extraction is the extraction method in which two (immiscible) liquids are used to separate the compounds (on solubility basis). This method includes uses of organic solvents like ether and hexane. This method is the most reliable and widely used method for the extraction of carotenoids. As lycopene get easily solubilized in solvents so extraction by this method is easy. Theresearch was done on extraction of lycopene from tomato pomace (using solvent extraction method) by optimizing the conditions favourable for the extraction. The maintained conditions by them were temperature at 40C, time of 5hours and Acetone and ethyl acetate in the ratio of 1:1. They obtained a 611.105 mg/100g yield of lycopene25.

 

Supercritical fluid extraction uses fluid above supercritical point for extraction26. This method is best for extracting and purifying low volatile and heat sensitive compounds27.The authorused tomato peel (by product) for extracting lycopene by supercritical fluid extraction28. In that paper, the authors detected the impact of various parameters (temperature, flow rate of CO2 and pressure) on extraction. They found that the favourable conditions were at the temperature of 90C and Pressure of 40 MPa in which around fifty six percent (56%) lycopene was retrieved. Supercritical liquids increase the rate and efficiency of the reaction. A similar method also performed using CO2 for extracting lycopene and beta carotene from the ripe tomatoes. The conditions maintained were 40C to 80C (temperature) and 2500 to 4000psi (pressure). Recovered lycopene was sixty five percent (65%) at 4000psi (Pressure) and 80 C (temperature)29. The flow diagram for supercriticalextraction of lycopene from tomato is shown in Figure 1.

 

Figure 1.SupercriticalExtraction of lycopene from tomato

 

Enzymes are well known for their specificity and efficiency. The plant cell wall consists of polysaccharides in them due to which the diffusivity of solute decreases30. Enzymes usage improves the yield as they act on these polysaccharides and help in loosening the structure31 and increasing porosity. This method is highly efficient for inflammable compounds and lacks toxicity.Theresearch was done on extraction of lycopene from the processed waste of tomato using enzymes. Tomato peels were treated with the pectinases and cellulases (enzymes) followed by extraction with solvent (hexane). They found the maximum lycopene (which was 8 18 times high than non treated peel) was at 30C with enzyme load of 0.16 kg/kg32.

 

Microwave Assisted Extraction uses microwaves (which ranged between 300 Megahertz to 300 Gigahertz33. Microwave radiation heat the sample and rise in temperature causes release of solutes by cell rupturing34. This process is also referred as ― Green Technology due to less usage of solvents33. In this method, high pressure (inside cell) builds up and causes their disruption due to which inside material (solute) diffuse out34.

 

Ultrasound Assisted Extraction method uses the phenomenon of cavitation. Ultrasound waves (> 20 Kilohertz) are used for extraction of valuable compounds. This technique involves placing of mixture of sample and solvent in ultrasonic bath33. Then waves are generated and lead to the formation of bubbles which on rupturing, causes breakage of plant cells35. This allows the increased permeability of solvents. Maximum lycopene content (100%) found at temperature (45C) for 50 min (extraction time)36. The various advantages and disadvantages of different extraction methods of lycopene are given in Table 4.

 

Table 4: Advantages and disadvantages of extraction methods of lycopene37, 26, 38, 14, 39, 35

Method

Advantage

Limitation

Solvent

Extraction Method

    Easytouse

    Expensive

    Time consuming

Supercritical fluid

Extraction

    Best for lowvolatile compounds

    Highyield

    Need cosolvent

    Plant setup cost is high

Enzyme

Assisted

Extraction

 

    Environment friendly

    No toxicity

    Enzyme unstability

    Costly enzyme recovery

Microwave

Assisted

Extraction

    Less solventusage

    High yield

    Costly equipment

Ultrasonic

Assisted

Extraction

    Rapid

    Energy saving

    Depend on

particle size

 

Preservation Techniques:

Food preservation is the method of prolonging product life by elimination or inhibition of microbes from the food. It preserves the nutritive values and colour of the product so that it can be used later in the off season. Pickling and salting are the traditional method of preserving food which uses oil and salt as a tool for microbial prevention. Application of various methods ensure the retainment of nutritional qualities of food as well as provide varieties like jam, pickles which can be enjoyed in any season. Withdraw of total water from the food is termed as Dehydration. This method removes all the water which can be used by microbes for their survival thus extending the shelf life of food.Some preservation techniques are:

 

Freeze drying:

Freeze drying, popularly known as Lyophilisation dehydrates the product by withdrawing the ice at lower pressure using the sublimation process. Sublimation involves conversion from solid to gaseous state40. This technique offers a superior quality produce with an extended shelf life. This method completely removes water making it unavailable for the microbes to sustain and producing a dehydrated produce.

 

The process of Lyophilisation includes 3 steps41. First step involves freezing of solvent at a much reduced temperature (nearly around -70 C to -80 C). Second step contain partly drying of solvent by lowering pressure. Lastly, the remaining water is removed by desorption (Secondary Drying).Freeze drying ensures that the freshness and initial quality of the produce remain preserved. That is possible because of the inhibition of the chemical and microbial activity.

 

Vacuum drying:

Vacuum drying withdraws all the moisture and creates a vacuum. This method prohibits the produce from getting oxidized and retains their colour and aroma42.This technique is ideal for thermo liable materials43. It need less drying time as it operates at reduced temperature.

 

Microwave Drying:

This method involves usage of microwaves which enter the material and convert moisture into heat. In this process, microwaves penetrate the material surface and cause the reorientation of water molecules (dipole moment) which creates heat energy and evaporates the moisture of the food. Microwave drying is used to dry chips.

 

Effect of Preservation Techniques on Lycopene:

Lycopene is the principle pigment of tomato and its products which gives them red colour. It has many beneficial health effects and is widely known for its antioxidant activity. Tomato and its products are the primary dietary sources of lycopene. More lycopene is available in its processed form as compared to the fresh form, so the demand of these processed products (as a lycopene rich food or as a functional food) is increasing. However, these processed products went through a lot of treatment (heating, cooking) which can lead to the loss or degradation of this valuable pigment thus, affecting the health benefits as well as their appearance (colour).

Isomerization and Oxidation are the two major reasons behind the destruction of lycopene. At extreme temperature, lycopene undergoes isomerization which has major role in affecting quality. Lycopene naturally exists as all trans isomer but under these conditions, it get transformed into the cis-form44. These cis- forms are very sensitive to oxidation which creates an undesirable effect of lycopene. Autoxidation leads to the lycopene fragmentation and formation of different undesirable compounds and forms an undesirable flavour45. It is an irreversible process.

 

Various researches till now have been taken place to find a suitable process which can preserve maximum lycopene. The researcher foundthat a rise in the temperature of drying (70C to 80C) in a cabinet air drier will speed up the deterioration of lycopene46. So, drying of tomatoes should be done below 70C for better retention of lycopene. It wasreporteddryingof tomato at 3 different temperatures (40C, 50C and 60C) by convection hot air drying with an air velocity of 1.5 m/s. The result was that the highest lycopene was found at 60C47.

 

The research was done to investigate the effect of microwave drying on antioxidant activities of tomato in which they subjected tomato to 2 different time (30s and 300s). Results showed that highest lycopene was found in tomato treated at 300s i.e. 40.71 mg/kg fresh matter which showed that increase in treatment time provides good results48.

 

The author studied the effect of heating and exposure to light on lycopene by placing tomato puree to various temperatures i.e., 60C, 80C, 100C and 120C for 1 to 6 hours and exposure to light for 1 to 6 days. He found that exposure at 60C and 80C temperature increased the lycopene isomerization. However light exposure did not showed much change3.

 

The researchers evaluated the lycopene and antioxidant activities subjected to 2 methods of drying i.e., Oven drying and Freeze Drying. They found that oven drying cause less damage to lycopene in comparison to freeze drying and cause an increase in it49. The rise is because of withdrawal of pigments from the matrix (due to thermal treatment)50. Another researcher also mentioned that air dried tomatoes had more extractable lycopene than freeze dried tomatoes51.

 

However there is so inconsistency in these results which can be because of different variety, treatment time and temperature and softness of tomato. Damage caused to the lycopene totally depends on the type of treatment used.

 

CONCLUSION:

Lycopene is the pigment which impart colour to the many plants and algae. It is a red hue which gives many fruits and vegetables their characteristic colour. Apart from colour, it also offers many health benefits. Its unique structure is responsible for its antioxidant activity. This red hue is predominantly found in all trans form which is known as the most thermostable form. Tomatoes are cheap and easily available which make them consumed widely around the globe. They possess many nutritive values due to presence of lycopene in them. As the primary source of lycopene and a healthy food, its demand is increasing as a functional food. Due to which the main focus is to develop a product with the high nutritional value. It is becoming popular as a functional food due to high level of nutritional value. Tomatoes have high moisture content due to which they easily get spoiled by the microbes. So, preservation is required for them. Thats why they are converted into powders, ketchup and other products. These processed products are passed through a number of steps exposing them to high temperature. However lycopene is stable at low temperature but extreme conditions causes theunstability and isomerization of lycopene by changing it from trans to cis form which is very reactive to oxygen and causes oxidation resulting in off- flavour and dull appearance along with reduced health benefits. High temperature causes changes in the lycopene and indirectly degrades the bioactive compounds and a low quality product is obtained.So, to ensure that the lycopene should reach safely in its fully potential form to the customers, a suitable processing time and temperature is needed. A process that maintains the quality of lycopene throughout its processing will benefit to the food industry.

 

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Received on 23.12.2021 Modified on 02.07.2022

Accepted on 10.12.2022 RJPT All right reserved

Research J. Pharm. and Tech 2023; 16(5):2537-2542.

DOI: 10.52711/0974-360X.2023.00417