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Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2020 Aug 18;58(6):2078–2088. doi: 10.1007/s13197-020-04716-8

Ready-to-prepare soup mix enriched with sea cucumbers: production, sensory attributes and nutritional composition

G Nishanthan 1,✉, I Wickramasinghe 2, S B Navaratne 2, D C T Dissanayake 1
PMCID: PMC8076401  PMID: 33967306

Abstract

Sea cucumbers are considered healthy and high in nutritive value. Conversely however, limited consumption of sea cucumbers has been reported in many parts of the world. This study was done to produce a ready-to-prepare soup mix incorporating the sea cucumber aiming to popularize the sea cucumber consumption. The highly abundant low-value Bohadschia vitiensis in the coastal waters of Sri Lanka was selected to prepare this soup mix. Fresh B. vitiensis samples (n = 250) were collected from major sea cucumber landing sites of the northwest coast. Out of the seven compositions prepared initially, three compositions; 20%, 40% and 60% were selected. The best composition among these was selected through a sensory test performed using a semi-trained panel (n = 30) at the University of Sri Jayewardenepura, Sri Lanka. The initial chemical and microbial qualities of the selected soup mix were analyzed and the best packaging material was selected. Results showed that the soup mix with 40% sea cucumber flour was the best composition as it reported significantly higher sensory scores than the other two mixes (p ≤ 0.05, Friedman). This soup mix exhibited high protein (21.43 ± 1.21%), low fat (4.98 ± 0.23%) and its oxygen radical absorbance capacity was 1.04 ± 0.13 mg Trolox equivalents/g. Coliforms and Staphylococcus aureus colonies were absent in the soup mix. The total plate count (1.9 × 102 CFU/g), yeast and mold count (0.7 × 102 CFU/g) and the heavy metal contents were within the safe limit for human consumption. The Polyester–Aluminum–PE was selected as the best packaging material which ensured 6 weeks storage time at room temperature.

Keywords: Sea cucumber, Soup mix, Heavy metal, Antioxidant

Introduction

Sea cucumbers belonging to the class Holothuroidea of the Phylum Echinodermata are a highly diverse group of marine invertebrates. Around 1400 sea cucumber species partitioned into six orders; Aspidochirotida, Apodida, Dactylochirotida, Dendrochirotida, Elasipodida and Molpadiida are reported worldwide (Bordbar et al. 2011). All sea cucumbers are ocean dwellers and some inhabit shallow coastal waters while others live in the deep ocean. Usually, sea cucumbers are benthic except for some pelagic Elasipodia species (Conand 2018; Purcell et al. 2012). The exploitation history of sea cucumbers dates back to several centuries, and they first became commoditized in China and India more than 1000 years ago (Conand 1990). According to Purcell et al. (2016), the total sea cucumber production in the year 2012 was 100,000 tons of live animal.

Sea cucumbers are considered a good source of food, especially in most cultures in the East and Southeast Asia (Kelly 2005). The processed body wall of sea cucumbers known as bêche-de-mer or trepang is considered an ideal tonic food in China. An extract of boiled skin is also very popular among the Malaysians as a tonic (Choo 2008). The fermented sea cucumber viscera, known as "konowata", is a delicacy in Japan (Kinch et al. 2008). Sea cucumbers are well known for their medicinal values and widely used in Chinese and Malaysian traditional medicinal practices as a remedy for hypertension, asthma, rheumatism, cuts, burns, impotence and constipation (Bordbar et al. 2011; Rahman 2014). The presence of considerable amounts of bioactive compounds such as triterpene glycosides (saponins), glycosaminoglycan, cerebrosides, sulfated polysaccharides, chondroitin sulfates, sterols (glycosides and sulfates), phenolics, peptides, lectins, glycoproteins, glycosphingolipids and essential fatty acids have been reported in sea cucumbers (Bordbar et al. 2011; Mamelona et al. 2007; Rahman 2014). These components have been reported to be responsible for several unique biological and pharmacological activities such as anticancer, anti-angiogenic, anti-hypertension, anticoagulant, anti-inflammatory, antimicrobial, antioxidant, antitumor, antithrombotic and wound healing (Bordbar et al. 2011). From the western medical viewpoint, sea cucumbers serve as a rich source of polysaccharide chondroitin sulfate, which is well-known for its ability to reduce arthritic pain (Choo 2008). In addition to medicinal uses, there is a demand for sea cucumbers as an aphrodisiac to improve sexual performance (Bordbar et al. 2011).

Although sea cucumbers have high nutritional and medicinal values, consumption of sea cucumbers is limited to some ethnic groups. Furthermore, large scale sea cucumber producing nations have limited or no local consumption mainly due to its unpleasant odour and external appearance (Nishanthan et al. 2018; Dissanayake and Stefansson 2010). On the other hand, due to over-harvesting of sea cucumbers worldwide, the current catches mainly consist of low-value species which are not in demand and fetch lower prices when compared to the high and medium-value species in both local and international markets (Kinch et al. 2008; Conand 2018). As stated by Singh and Azam (2013), value addition seems to be a good solution to overcome these problems. This study, therefore, aims to produce a sea cucumber incorporated ready-to-prepare soup mix using a highly abundant low-value Bohadschia vitiensis in the coastal waters of Sri Lanka. It is assumed that this new product will help to enhance the local consumption of sea cucumbers as their unpleasant qualities have been suppressed to some extent. Further, this will lead to maximizing the economic return of low-value species through new market avenues.

Materials and methods

Ingredients collection and storage

Marketable size (weight ranged from 250 to 280 g) fresh Bohadschia vitiensis samples (n = 250) were collected from major sea cucumber landing sites of the northwest coast of Sri Lanka, packed in insulated regiform boxes with ice and transported to the laboratory of the Department of Zoology, University of Sri Jayewardenepura, Sri Lanka under chilled condition. Other ingredients used for the soup mix preparation including tomatoes, carrots, garlic, coriander seeds, pepper seeds, parsley leaves, corn flour, cow milk powder, table salt and citric acid crystals were purchased from the local market and stored at room temperature (27 °C).

Preparation of sea cucumber flour and other ingredients

Individual weight of each fresh B. vitiensis was recorded and internal organs were removed by making a small slit on the ventral body region using a sharp stainless-steel knife. The eviscerated individuals were washed with potable water to remove slime, sand and remaining gut contents and their body weights were measured individually. The cleaned sea cucumber meat was sliced into 1.5–2.0 cm pieces. A mixture of 12 g turmeric powder and 22 g table salt were mixed well with 1 kg slice sea cucumber meat and marinated for 30 min in a closed container. The treated meat was washed with lime juice (1 kg meat: 1 L lime juice) to tenderize the sliced meat, and then steam-boiled for 20 min using a steamer (Phillips-Netherlands, model: HD9125). The resultant product was dried in a cabinet dryer (Xingtai-China, model: XTDQ-101-5A) at 45 ± 5 °C for 24 h. The dried meat was then ground and sieved to obtain sea cucumber powder with the particle size of 210 microns. The weight of the prepared powder was measured, packed in Low-density polyethylene (LDPE) pouches and stored under room temperature. The percentage yield obtained from the fresh sea cucumbers was calculated using the following equation:

Yield%=w1w0×100

here W1 = Weight of sea cucumber flour obtained, W0 = Fresh weight of sea cucumbers used.

The other ingredients such as dehydrated carrots, tomato powder, spice mix and dehydrated parsley leaves were prepared by pre-processing of the fresh forms of these ingredients. The percentage yield obtained from each ingredient after the pre-processing was calculated using the following equation:

Yield%=w1w0×100

here W1 = The dehydrated weight of the ingredient, W0 = The fresh weight of the ingredient.

The initial weight of fresh tomatoes, fresh carrots, spices used in spice mix (garlic, dried coriander and pepper seeds) and fresh parsley leaves were measured and washed with potable water. Tomato powder was prepared by grinding dehydrated tomato slices. In this process, fresh tomatoes were blanched for 3 min in 1% sodium meta-bi-sulphate (Na2S2O5, SMS), cut into slices, deseeded and dehydrated in a cabinet dryer at 45 ± 5 °C for 24 h. Similarly, dehydrated carrots were prepared by drying blanched carrot slices (1.5–2 cm) in a cabinet dryer at 60 ± 5 °C for 6 h. Cleaned garlic cloves, dried coriander seeds and pepper seeds were weighed into a ratio of 2:2:1, dried in a cabinet dryer at 60 ± 5 °C for a period of 4 h and ground to obtain spice powder mix. Finally, dehydrated parsley leaves were obtained by dehydrating cleaned parsley leaves in a cabinet dryer at 60 ± 5 °C for 6 h. Other ingredients such as corn flour, cow milk powder, table salt and citric acid crystals were used directly in the soup mixes without any further processing.

Preparation of different soup mix compositions

Sea cucumber flour and corn flour were mixed to obtain seven different soup mix compositions as shown in Table 1. Out of the seven compositions, the three best; 20%, 40% and 60% were selected from pre-trials performed to check reconstitutability with the aid of a 5-member expert sensory panel of the Department of Food Science and Technology, University of Sri Jayewardenepura. Suitable quantities of other ingredients were determined based on the feedback of pre-trials and these quantities were kept constant in all three soup mixes. The detailed experimental design of this study is given in Fig. 1.

Table 1.

Different compositions of sea cucumber flour incorporated soup mixes

Sample no. % Sea cucumber flour % corn flour % other ingredients
456 10 60 30
521 20 50 30
589 30 40 30
664 40 30 30
698 50 20 30
754 60 10 30
765 70 0 30
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Fig. 1.

Fig. 1

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Experimental for formulating a ready-to-prepare soup mix incorporated with sea cucumber (Bohadschia vitiensis ) flour

Selection of the best soup mix composition

To find the best soup mix composition, three soup mixtures were served to a semi-trained panel (n = 30) at the University of Sri Jayewardenepura and an untrained panel of Chinese (n = 30) workers at the Coal power plant, Nuraichcholai, Sri Lanka. Each soup mix was prepared as a creamy paste by adding 100 g of the soup mix into 1 L of water and by heating under a low flame until it boiled. Each panel member was served 30 mL of each soup mix and asked to report their taste preferences in a given datasheet.

An acceptance sensory test with the help of a 30-member semi-trained panel using a five-point hedonic scale was performed for several sensory attributes such as colour, appearance, odour, mouthfeel, taste and overall acceptability. Based on the results of this experiment, the best soup mix composition was selected and it was further developed through a series of biochemical and microbial tests.

Analysis of biochemical and microbial properties of the selected soup mix

Analysis of proximate composition

The proximate composition (i.e. percentages of moisture, crude ash, crude protein and crude fat contents) of the selected soup mix was analyzed at the accredited laboratory of the Industrial Technology Institute (ITI) of Sri Lanka by following the methods described in Pearson's chemical analysis of foods. The conversion factor 6.25 was used to convert total nitrogen into crude protein (Pearson et al. 1987). The percentage of carbohydrate content was estimated by subtracting percentages of protein, fat, ash and moisture from 100 (Pearson et al. 1987). The calorific value of the soup mix was estimated by multiplying the percentages of protein, fat and carbohydrate with their respective physiological fuel value. The fiber content was analyzed following the method described by Pearson et al. (1987). All these analyses were conducted in triplicate.

Analysis of peroxide value, heavy metal contents and antioxidant properties

The peroxide value of the selected soup mix was estimated using a titrimetric method (AOAC 1990). The contents of Cadmium, Lead, Zinc and Arsenic in the soup mix were detected using an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and the values were reported in mg/kg sample (AOAC 2002). The DPPH (1,1-diphenyl-2-picrylhydrazyl) assay was used to estimate the antioxidant content and the value was reported as oxygen radical absorbance capacity (ORAC) in mg Trolox equivalents/g of methanol extract. All these analyses were conducted in triplicate.

Analysis of initial microbial quality

The microbial quality i.e. total plate count (TPC), enumeration of yeast and molds, enumeration of Staphylococcus aureus, total coliform count and Escherichia coli count of the selected soup mix was analyzed. The total plate count (TPC) was determined by pour plate technique according to the ISO 4833-1:2013 standard (ISO 2013). The enumeration of yeast and molds was done according to the ISO 16212:2017 standard (ISO 2008). Enumeration of Staphylococcus aureus (ISO 6888-3:2003 standard), total coliform count (ISO 4831: 2006 standard) and E. coli count (ISO 7251:2005 standard) were carried out using the MPN (Most Probable Number) technique (ISO 2003, 2005, 2006). All these analyses were conducted in triplicate.

Selection of the best packaging material

In order to select a suitable packaging material for the selected soup mix, three packaging materials; Polyester–Aluminum–Polyethylene, Polyester-Metalized Polyester Polyethylene and Nylon-low density polyethylene (LDPE) were tested. Seventy-five packets were prepared from each packaging material and each packet was filled with 20 g of soup mix. Packets were properly sealed and kept at room temperature (27 °C) in order to determine the time period that soup mix can be stored under each packaging material without losing its biochemical, microbial and sensory qualities. Percentage moisture, peroxide value, total plate count (TPC) and enumeration of yeast and molds of sample packets representing each soup mix were tested at a 2-week interval for a period of 8 weeks. A sensory test was performed after 45 days of storage using the semi-trained panel (n = 30) at the University of Sri Jayewardenepura as described in “Selection of the best soup mix composition” section.

Analysis of the production cost of the selected soup mix

The weight of each ingredient required to produce 100 g of soup mix was estimated and the respective cost of each ingredient was calculated using their market price. The following equation was used to calculate the cost of each ingredient.

Ci=WYCu

here Ci = Cost of ingredient (US$), W = Weight of dehydrated ingredient used (g), Y = The yield after dehydration (%), Cu = The market price of the fresh ingredient (US$/g).

Statistical analysis

The web diagram prepared using the mean score values obtained from the semi-trained panel members for each sensory attribute was used to determine the best soup mix composition. Differences in sensory attributes of the three different soup mix compositions were compared using the Friedman non-parametric test followed by the Wilcoxon test. Similarly, sensory attributes of the selected soup mix packed in three different packaging materials were also compared after 45 days of storage. Bonferroni correction was done to adjust the p value in order to reduce type 1 error (McDonald 2009). Percentage taste preference of Chinese was considered when selecting the best soup powder composition. The moisture content and peroxide value of the soup mix packed in different packaging materials were compared using Analysis of Variance (ANOVA). The cost of producing 100 g of the selected soup mix was calculated. All the statistical analyses were carried out using SPSS 22 for Windows software.

Results

Selection of the best soup mix composition

The prepared soup mixes were light brown in colour with a mild fishy odour. The soup mix with 60% sea cucumber flour appeared to be grainier than the other two mixes. Pieces of dehydrated carrots and parsley leaves were scattered in all three soup mixes.

Sensory attributes except for odour were significantly different among the three soup mixes (Table 2, p ≤ 0.05, Friedman). Soup mixes with 20% and 40% sea cucumber flour received significantly higher scores for colour and appearance than the soup mix prepared using 60% sea cucumber flour. However, the soup mix with 40% sea cucumber flour showed significantly higher scores for mouthfeel, taste and overall acceptability than the other two products (p ≤ 0.016, Wilcoxon). Furthermore, the soup mix with 40% sea cucumber flour occupied a larger area in the web diagram than the other two compositions (Fig. 2) and 76% of Chinese people showed their preference for this composition. Therefore, the soup mix with 40% sea cucumber flour was selected as the best composition for further development.

Table 2.

Mean scores obtained for each sensory attribute studied using sensory evaluation for three compositions (20%, 40% and 60%) of soup mixes and changes in sensory attributes of 40% sea cucumber flour incorporated ready-to-prepare soup mix packed in Polyester–Aluminum–PE (PAPE), Polyester-Metalized polyester PE (PMPE) and Nylon-LDPE (NPE) after 45 days of storage

Attributes Mean scores
Sensory evaluation for three compositions of soup mixes Sensory evaluation for 40% ready-to-prepare soup mix packed in 3 different packing materials after 45 days of storage
20% (521) 40% (664) 60% (754) NPE PMPE PAPE
Colour 3.7a 3.6a 2.5b 2.9a 3.0a 3.1a
Appearance 3.6a 3.5a 2.5b 2.8a 3.0a 3.1a
Odour 2.7a 3.0a 2.4a 2.3a 2.4a 2.6a
Mouth feeling 2.8a 3.6b 2.5a 2.6a 3.0b 3.4b
Taste 3.0a 3.8b 2.7a 2.4a 3.3b 3.6b
Overall Acceptability 3.0a 3.9b 2.5a 2.5a 3.2b 3.5b
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For each sensory evaluation test values in the same row bearing different letters are significantly different (p ≤ 0.016, Friedman test followed by post hoc Wilcoxon test with Bonferroni Correction)

Fig. 2.

Fig. 2

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Web diagram constructed using mean scores obtained for each sensory attribute studied using sensory evaluation for three compositions of soup mix

Proximate composition, peroxide value, heavy metal contents and antioxidant properties of the selected soup mix composition

The average moisture content of the selected soup mix composition was 7.6 ± 0.01%. The crude values of ash, protein, fat and carbohydrate on a dry matter basis were 19.48 ± 1.04%, 21.43 ± 1.21%, 4.98 ± 0.23% and 54.11 ± 0.83% respectively (Table 3). The estimated calorie value was 346.98 kcal/100 g and the crude fiber content was 1.19 ± 0.08% on a dry weight basis (Table 3).

Table 3.

The initial biochemical test results of 40% sea cucumber flour incorporated ready-to-prepare soup mix

Parameter Values
Moisture (%) 7.60 ± 0.01
Crude protein (%) 21.43 ± 1.21
Crude fat (%) 4.98 ± 0.23
Crude ash (%) 19.48 ± 1.04
Crude carbohydrate (%) 54.11 ± 0.83
Crude fiber (%) 1.19 ± 0.08
Pb (mg/kg) 1.1
Zn (mg/kg) 1.9
Cd (mg/kg) ND
As (mg/kg) 0.1
Antioxidant value (mg Trolox equivalents/g of methanol extract) 1.04 ± 0.13
Peroxide value (meq) 0
Total plate count (CFU/g) 1.9 × 102
Yeast and mold count (CFU/g) 0.7 × 102
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ND not detected

The peroxide value of the selected soup mix was 0.0 meq. The estimated Lead (Pb), Zinc (Zn) and Arsenic (As) contents in the soup mix were 1.1 mg/kg, 1.9 mg/kg and 0.1 mg/kg, respectively, while Cadmium (Cd) was not detected (Table 3). The antioxidant value (ORAC) was reported as 1.04 ± 0.13 mg Trolox equivalents/g of methanol extract (Table 3).

Initial microbial quality of the selected soup mix composition

The total plate count (TPC) and the enumeration of yeast and molds in the selected soup mix were 1.9 × 102 CFU/g and 0.7 × 102 CFU/g, respectively (Table 3). Neither gas production nor colour change was recorded for the presumptive coliform test and no colonies of Staphylococcus aureus were detected in this soup mix.

Selection of the best packaging material

Variations in moisture content, peroxide value, total plate count, yeast and mold count of the soup mix packed in three different packaging materials with respect to storage time are given in Table 4. The peroxide value remained 0.0 meq throughout the storage period, however, a gradual increase in moisture content was reported in all soup mix packets after 2 weeks of storage time. A significant increase in moisture content with respect to the initial value was reported in the soup mix packed in Nylon-LDPE after 4 weeks storage period while this was evident for soup mixes in the other two packaging materials after 8 weeks (p ≤ 0.05, ANOVA).

Table 4.

Changes in moisture content, peroxide value (PV), total plate count (TPC) and yeast and mold count (YMC) of 40% sea cucumber flour incorporated ready-to-prepare soup mix packed in polyester–aluminum–PE (PMPE), polyester-metalized polyester PE (PAPE) and nylon-LDPE (NPE) during storage

Parameter Initial 2 weeks 4 weeks 6 weeks 8 weeks
NPE PMPE PAPE NPE PMPE PAPE NPE PMPE PAPE NPE PMPE PAPE
Moisture (%) 7.60 ± 0.01a 7.74 ± 0.41a 7.72 ± 0.19a 7.51 ± 0.07a 9.07 ± 0.07b 8.59 ± 0.11a 7.69 ± 0.57a 9.37 ± 3.17c 8.63 ± 0.94a 8.57 ± 0.01a 9.83 ± 0.02c 8.81 ± 0.05b 8.64 ± 0.05b
PV (meq) 0 0 0 0 0 0 0 0 0 0 0 0 0
TPC (CFU/g) 1.9 × 102 1.0 × 103 9.7 × 102 7.8 × 102 1.30 × 103 1.20 × 103 1.17 × 103 6.80 × 103 6.50 × 103 5.00 × 103 1.00 × 106 7.20 × 105 6.00 × 105
YMC (CFU/g) 0.7 × 102 3.1 × 102 1.3 × 102 1.0 × 102 8.0 × 102 3.20 × 102 2.4 × 102 4.30 × 103 3.90 × 102 3.1 × 102 TNTC 5.10 × 102 4.50 × 102
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Values in the same row bearing different letters are significantly different (ANOVA, p ≤ 0.05), TNTC: Too much in number to count

The total plate count of the soup mix packed in all three packaging materials was within the safe limits for human consumption (< 1 × 104 CFU/g) for up to 6 weeks, however, it increased rapidly thereafter and exceeded the safe limit by the 8th week. Although yeast and mold count of the soup mix packed in Nylon-LDPE exceeded the safe limit for human consumption (< 1 × 103 CFU/g) by the 6th week of storage, others were within the safe limit until the end of the study period (Table 4). The soup mix packed with Polyester–Aluminum–PE showed the lowest microbial growth.

The results of the sensory test performed on the 45th day of storage disclosed that there were no significant differences in colour, appearance and odour of the soup mix packed in different packaging materials (Table 2). However, the soup mix packed in Nylon-LDPE obtained significantly lower scores for mouthfeel, taste and overall acceptability than the other two (p ≤ 0.016, Wilcoxon). After analyzing these results, Polyester–Aluminum–PE was selected as the best packaging material to store the prepared ready-to-prepare soup mix for a period of 6 weeks under the ambient condition.

The unit (100 g) production cost of the soup mix was estimated as 2.5 US$. Approximately 82.4% of the total production cost was constituted by the process of dried sea cucumber flour preparation.

Discussion

When preparing sea cucumber flour, turmeric powder and salt were used to marinate the sea cucumber meat. Lime juice can penetrate the raw flesh and break down the meat's connective tissues with its acidic nature. Therefore, lime juice was used to tenderize the sea cucumber meat. In addition to lime juice, turmeric powder also acts as a tenderizing agent. The tenderizing process made it easy to grind the firm sea cucumber meat after dehydration (Ciriminna et al. 2017).

Ingredients such as tomatoes, carrots, cow milk powder, table salt and parsley leaves were used to improve the taste of the soup mix. Furthermore, dehydrated carrots and parsley leaves improve the appearance of the soup mix. Corn flour was used as a thickening agent and citric acid crystals were used as both a flavoring and preserving agent. The unpleasant fishy odour, one of the major reasons for very low consumption of sea cucumbers, especially in sea cucumber producing nations. This odour was suppressed to some extent in this soup mix by adding a spicy powder mix. However, the addition of excess spicy powder can affect the taste, smell, appearance and demand of the soup powder. Therefore, all the ingredients used in this soup mix were standardized using pre-sensory evaluations. Standardization of ingredients used in soup mixes is a common practice. Sawant and Krishi (2017) followed a similar procedure when preparing a tilapia incorporated soup mix.

At the beginning of this experiment, only three soup mix compositions out of the seven were filtered out with the help of an expert sensory panel. Only these three soup mixes were given to the sensory panel as more choices can reduce the accuracy of ranking on the different sensory parameters and too many samples are rather challenging to the panelist (Hobson 1990). According to the expert sensory panel, increasing the level of sea cucumber flour to more than 60% (very low thickness) and reducing it to less than 20% (very high thickness) can severely affect to the reconstitutability.

Selection of the best soup composition was initially done by using sensory attributes such as taste, odour and mouthfeel as one of the aims of this study is to promote local consumption of sea cucumbers which is very limited at present due to its unpleasant shape, taste, odour and mouthfeel. The selected soup mix was further developed by performing standard biochemical and microbial experiments to make it a safe product for human consumption. Two levels of sensory tests were performed in this study using a 30-member semi-trained local panel and a 30-member untrained Chinese panel. This was done to check the preference for this ready-to-prepare sea cucumber incorporated soup mix by both locals and Chinese. The Chinese panel was used as they are the major sea cucumber importers as well as major sea cucumber consumers in the world. The size of the sensory panels was decided by following standard sizes recommended by Hobson (1990).

The ready-to-prepare soup mix prepared in this study contains a high level of carbohydrate (54.11 ± 0.83%), protein (21.43 ± 1.21%) and relatively low level of fat (4.98 ± 0.23). Some soup mixes, prepared using Indian borage (Coleus aromaticus) and tilapia fish also reported similar levels of carbohydrate (54.4% and 49.8%, respectively) as this soup mix. However, those products contained lower levels of protein (19.1% and 17.59%) and higher levels of fat (6.3% and 12.65%) than this soup mix (Wadikar and Premavalli 2013; Sawant and Krishi 2017). Singh and Azam (2013) on the other hand reported relatively lower levels of protein and fat than this soup mix for their sea cucumber value-added sweetened sandfish biscuits (12.29% and 3.46% respectively) and salted sandfish biscuits (11.27% and 2.07% respectively). The shelf-stability of this soup mix can be ensured as it contains relatively low-fat content and similar results have been reported in many previous studies (Wadikar and Premavalli 2013). The moisture content of this soup mix was higher than the moisture contents reported for Tilapia (1.74%) and prawn (4.72%) soup mixes by Sawant and Krishi (2017) and Niththiya et al. (2017). The fiber content of the soup mix is relatively lower than the fiber percentages reported by Niththiya et al. (2017) for vegetable (4.8%) and prawn (5.10%) added soup mix prepared with Palmyra tuber flour. However, the calorie values of these products were in a similar range (351.32 kcal/100 g and 333.42 kcal/100 g) of the current product.

Heavy metals can cause deleterious effects on animal and human health when their concentrations are highly amplified (Mohammadizadeh et al. 2016). Even though the risk of heavy metal accumulation was evident from sea cucumbers (Mohammadizadeh et al. 2016), the contents of heavy metals (Cd, Pb, Zn and As) in this soup mix were well below the minimum permissible limits (1.5 mg/kg, 3 mg/kg, 200 mg/kg and 0.25 mg/kg, respectively) imposed by the US Food and Drug Administration (Food and Drugs Administration 2014; Mohammadizadeh et al. 2016). Therefore, it can be confirmed that the ready-to-prepare soup mix, enriched with sea cucumber flour is safe for human consumption.

The antioxidants can protect human cells from oxidative stress and degenerative diseases, including certain cancers (Bordbar et al. 2011). Several previous studies reported the availability of antioxidant functionality in sea cucumbers (Bordbar et al. 2011; Mamelona et al. 2007). Mamelona et al. (2007) reported that antioxidants (as oxygen radical absorbance capacity, ORAC) in Atlantic sea cucumbers ranged from 35.04 to 200.2 mg Trolox equivalents/g. The ORAC value obtained for this soup mix is lower (1.04 ± 0.13 mg Trolox equivalents/g) than their findings. This could be due to the presence of a small amount of sea cucumber flour (~ 40 g) in 100 g of our soup mix. However, the soup mix, prepared in the current study can be considered as a source of antioxidants. In addition to sea cucumber flour, the other ingredients such as tomatoes (Toor and Savage 2005), carrots (Sun et al. 2009) and spices (Yashin et al. 2017) used in this soup mix may have some contribution to the reported overall antioxidant value.

The present study indicated that the initial peroxide value of the selected soup mix remained 0 meq throughout the study period irrespective of the packaging material and storage period. Rapid changes in peroxide value in soup mixes with respect to packaging materials and storage period was evidenced in some previous studies (Sawant and Krishi 2017; Wartha et al. 2013), and the resultant constant peroxide value in our soup mix could be due to the presence of low levels of fat content.

According to the standards of the Sri Lanka Standards Institutes (SLSI), the total plate count, yeast and mold count of any food products should be below 1 × 104 CFU/g and 1 × 103 CFU/g, respectively (SLS 643: 2007). Further, Coliforms and Staphylococcus aureus colonies should be absent (SLS 643: 2007). As the sea cucumber incorporated soup mix prepared in this study satisfied SLSI requirements, it is safe for human consumption. According to Wartha et al. (2013), no changes in total plate count were evident for tilapia soup mix packed in metalized film pouches till 12 weeks and HDPE pouches for 10 weeks although they reported rapid changes in LDPE pouches after 4 weeks storage period. Niththiya et al. (2017) reported the initial total plate count of fresh vegetable soup mix and prawn added soup mix as 2.1 × 103 CFU/g and 2.9 × 103 CFU/g respectively. They observed a slight increment in total plate count in both samples packed in high-density polyethylene packs at 2 months storage period.

This study reported a significant reduction in sensory scores (p ≤ 0.016) of the soup mix packed in Nylon-LDPE. A similar observation was reported by Wartha et al. (2013) for tilapia soup mix. However, Chacko et al. (2005) did not report remarkable changes in sensory attributes of the soup mix prepared using squids and packed in Nylon-LDPE.

The estimated shelf life of ready-to-prepare soup mix enriched with sea cucumbers is 6 weeks in Polyester–Aluminum–PE and this is lower than the storage periods reported by Wartha et al. (2013) for tilapia soup mix and Chacko et al. (2005) for squid soup mix. The reasons for the short shelf life of our product cannot be explained as there were no previous studies. When selecting an ideal packaging material, there are several factors need to be considered such as thicknesses, oxygen transmission rates (OTR) and water vapour transmission rates (WVTR) and these properties influence the quality of the product stored in that packaging material. Out of three packaging materials tested in this study, Polyester–Aluminum–PE has the highest thickness values (100–105 microns) than Polyester-Metalized Polyester–PE (85–90 microns) and Nylon-LDPE (60–66 microns). The oxygen transmission rates (OTR) and water vapour transmission rates (WVTR) of Polyester–Aluminum–PE are between 0–0.0001 gm−2 day−1 and 0–0.0001 gm−2 day−1 respectively and the above values are very lower than Polyester-Metalized Polyester–PE (41–62 gm−2 day−1 and 3.9–6.2 gm−2 day−1 respectively) and Nylon-LDPE (25–39 gm−2 day−1 and 16–23 gm−2 day−1 respectively). These values evident that the Polyester–Aluminum–PE has better barrier properties than the other two packaging materials. Furthermore, the shelf life can be increased by employing novel packaging techniques such as vacuum packaging and nitrogen gas packaging (Koseki and Itoh 2002).

This study proved that highly abundant low-value B. vitiensis in the coastal waters of Sri Lanka (Dissanayake and Stefansson 2010) can be successfully utilized for value addition. It is believed that some issues related to the sea cucumber industry such as limited local consumption of sea cucumbers, especially among some sea cucumber producing nations (i.e. Seychelles, Nicaragua, French Polynesia and Sri Lanka) can be addressed through this new invention. According to Morrissey and Dewitt (2013), value addition is an ideal way to reach different types of consumers. Therefore, this product would help to attract a new group of consumers both locally and internationally. Since it is an instant product, this could be easily promoted and popularized. On the other hand, nutritional and medicinal compounds (i.e. anti-tumoral, anticoagulant and antimicrobial properties) of sea cucumbers can be distributed to a broader range of consumers through this newly invented product (Kelly 2005). All these opportunities may ensure the new market for low-value sea cucumber species like B. vitiensis (Morrissey and Dewitt 2013) providing a better solution to overcome the existing low market demand for these species.

Conclusion

A ready-to-prepare soup mix, prepared by incorporating 40% sea cucumber flour obtained from highly abundant low-value B. vitiensis in the coastal waters of Sri Lanka is an organoleptically acceptable, nutritionally rich, safe product for human consumption. The unit production cost (100 g) of this soup mix was 2.5 US$ and this can be stored in Polyester–Aluminum–PE pouches up to 6 weeks at room temperature. This invention will be a good initiative to popularize the consumption of nutritionally rich sea cucumbers among many people and to find new markets for highly abundant low-value sea cucumber species in order to maximize their net economic return than that at present.

Acknowledgement

This work was supported by the National Research Council of Sri Lanka [Grant number NRC 15-50]. The support given by Suganth International (Pvt.) Ltd. during the sample collection was highly appreciated.

Compliance with ethical standards

Conflict of interest

The authors have declared no conflicts of interest for this article. This invention received a local Patent Numbered LK/P/1/19793.

Footnotes

Publisher's Note

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