ABSTRACT
Hibiscus sabdariffa L. (Malvaceae) calyx is a valuable food resource in Africa. This herb is rich in phenolic compounds and a good source of natural antioxidants. Concentrated extract prepared with Hibiscus sabdariffa L. calyx is commonly used in traditional African and Asian diets and medicines. However, the organoleptic properties of these extracts are degraded during storage. Therefore, the stability of these products is one of the problems faced by roselle calyx extracts users. Stabilization of the H. sabdariffa extract to prevent or reduce quality changes and to extend shelf-life of these products is a challenge to food processors. In this study, strategies for minimizing or eliminating these alterations were evaluated. Concentrated extract of hibiscus calyx (60 °Brix) was divided into three parts: control, pasteurized and addition of potassium sorbate. The samples were stored at 4, 30 or 45°C for three months. Reducing sugars, pH, titratable acidity and total anthocyanins were determined during 0, 15, 30, 45, 60, 75 and 90 days of storage. The results showed that hibiscus calyx extracts can be stored at 4°C for three months without any changes in organoleptic properties. Pasteurization and addition of potassium sorbate did not improve significantly, the stability of the concentrated extracts during storage periods at high temperature. However, these treatments extended the shelf-life at cooling temperature (4°C) without serious changes.
Key words: Hibiscus sabdariffa L., calyx extracts, stability, storage, temperature.
Nowadays, food quality is no longer limited to organoleptic, nutritional and functional quality, but also entails that foods can be transported over long distances, stored and distributed without changes. Products must therefore have sufficient shelf-life to reach consumers in good quality. Thus, novel techniques have to be developed to increase the time to keep food products intact (Singh, 2018).
Roselle, Hibiscus sabdariffa L, is an annual herbaceous plant that belongs to the Malvaceae family with important health properties (Ali and El-Anany, 2017). Bissap (H. sabdariffa L.) is cultivated throughout the Senegalese territory and more particularly in the central and northern regions (Cisse et al., 2009a). Red H. sabdariffa calyx is
used to produce a variety of food products like: jam, jelly and red soft drinks with tangy taste depending on the variety (Cisse et al., 2009b). The red color is due to anthocyanins present in the calyx. Anthocyanins are known to have nutritional and health properties (Chiu et al., 2015; Worawattananutai et al., 2014; Abdul Hamid et al., 2014; Rodriguez-Perez et al., 2017) and can be used as natural colorants in food, pharmaceutical and cosmetic products (Pinsuwan et al., 2010). The hibiscus based juices are known for their color instability during storage in correlation with changes in anthocyanin contents (Vankar and Shukla, 2011). The instability of these anthocyanins could be influenced by the quantity of solids in suspension and dissolved oxygen (Cisse et al., 2009c; Kane et al., 2015). Anthocyanins degradation during storage depends also on extraction methods and storage temperatures (Cisse et al., 2012).
Concentration process by water evaporation makes hibiscus extracts more stable. Pasteurization and food additives are methods for preservation to stabilize food products during storage. Sorbic acid and its salts kill yeasts, molds and bacteria by accumulating in microorganisms’ cytoplasm, causing acidification of the cytosol (Van Beilen et al., 2014). Therefore, they preserve the organoleptic, nutritional and microbiological properties of food during storage. These changes cause a lot of losses to the value chain hibiscus.
Therefore, the objective of this study is to evaluate the impacts of pasteurization and potassium sorbate (E202) on the stability of concentrated extracts of H. sabdariffa during storage at 4, 30 and 45°C for 3 months.
Production of extracts of H. sabdariffa L
The concentrated extracts were made with calyx of a local variety of H. sabdariffa L called Bissap Vimto. Twenty kilograms of calyx purchased from local market in Dakar, Senegal were mixed with 100 L of water and soaked for 4 h. The resulting mixture was filtered with a 0.2 mm diameter steel filter and a cotton filter to obtain a clear extract. The extract with 8.8 °Brix was then concentrated with an evaporator (AURIOL, France) to 60 °Brix. The concentrated extracts were divided into three: concentrated extract without treatment (NTC), concentrated extract with addition of 0.16% potassium sorbate (CSP) and the pasteurization of the concentrated extract at 70 C for 30 min (PC). Samples were stored in glass bottles wrapped in aluminum foil and stored at 4, 30 and 45°C. From zero time to day-90, every 15 days, up to 90 days, the concentrated calyx extracts were determined for: reducing sugars, pH, titratable acidity and total anthocyanins.
pH was determined with a pH-meter (Hanna HI 223, USA) dipped into the bottles (AOAC, 2005). The amount of titratable acid was determined by potentiometric titration using sodium hydroxide solution with a potentiometer titrator (Titroline Schott T23230 N° M 011287, Germany) (AOAC, 2005). Reducing sugars were measured with the Luff-Schoorl method (Kowalski et al., 2013). The sugars were extracted in aqueous ethanol. After eliminating the ethanol, the solutions were clarified and the sugars were determined before and after inversion. All analyses were performed in triplicate.
The anthocyanins concentrations of the hibiscus extracts were also determined during storage (Lee et al., 2005). The principle of determination was based on the properties of anthocyanins to change color depending on the pH (pH differential method). After dilution of the extract in two buffer solutions at pH 1.0 and 4.5 purchased from Fisher Scientific, USA, the absorbance was measured at 510 and 700 nm in triplicate. The anthocyanin’s concentration was calculated using the following formula:
Ca: Anthocyanin concentration (mg/L); MW: molecular weight of Delphinidin 3-sambubioside, the major anthocyanin in H. sabdariffa extract, (597 g/mol); ε: molar extinction coefficient (26 000 L mol-1. cm-1); dF: dilution factor; A: absorbance, calculated using the formula:
A = (A1 - A2) - (A3 - A4)
Where, A1 = Absorbance measured at pH = 1 and 510 nm; A2 = absorbance measured at pH = 1 and 700 nm; A3 = absorbance measured at pH = 4.5 and 510 nm; A4 = Absorbance measured at pH = 4.5 and 700 nm.
Statistical analysis
Results are expressed as mean ± SD. The Fisher's protected least significant difference (PLSD) for multiple comparisoncomparisons after one-way ANOVA was used to analyze the data (SPSS Version 14.0J, SPSS, Chicago, IL). Differences were considered significant at P <0.05.
Characterization of the H. sabdariffa extracts
The effect of concentration process on some physiochemical properties of the hibiscus extracts are shown in Table 1. The results showed that the evaporation process increased the Brix from 8.8 to 60 °Bx. Non-concentrated extract (NC) had a significantly higher pH (2.1±0.01) than the concentrated extract (1.4±0.04). The concentration process decreased the pH and significantly increased reducing sugars and anthocyanins in the samples.
pH variation during storage
The pH of the samples decreased during storage (Table 2). This decrease was significant (P <0.05) for CSP samples stored at different temperatures at day-90 as compared to zero time. There were no differences between the pH of NTC, CSP and PC at day-90 of storage at 4, 30 and 45°C Table 3. between samples during storage at different temperatures. At day-90, the titratable acidity in samples stored at 4°C was non-significantly different from that on zero time. During storage at 45°C, titratable acidity significantly (P <0.05) increased in CSP and PC samples at day 90.
Evaluation of reducing sugars during storage
The concentration of reducing sugars in the hibiscus concentrates during storage is shown in Table 4. At day 90, CSP samples stored at 45°C showed the lowest concentration of reducing sugars (113.635±0.007 g/L ) as compared to NTC and PC stored at the same temperature (117.955±0.007 and 117.955±0.006 g/L, respectively).
Variation of anthocyanin during storage
As shown in Table 5, at 4°C, all the treatments kept most of the anthocyanin levels [13.708 g/L (NTC), 13.111 g/L (CSP) and 13.800 g/L (PC)]. Table 6 shows the effect of temperature storage (30°C) on the anthocyanin levels of hibiscus extract samples. From the results, all the treatments affected the level of anthocyanin. The residual level of anthocyanin was 49, 31 and 26% for NTC, PC and CPS, respectively. Table 7 shows that the highest destruction of anthocyanin among the storage temperatures was at 45°C in all the samples.
The concentration process decreased pH. This process also significantly increased titratable acididy, reducing sugars and anthocyanins in the samples. These results are in accordance with Youssef and Shatta (2006). Samples of hibiscus concentrated extracts had a very low pH (1.4 to 1.6). This acidity was due to organic acids such as the succinic and oxalic acids contained in the calyces of H. sabdariffa (Cisse et al., 2009b). Hibiscus extracts also contain other organic acids such citric, hydroxycitric, hibiscus, malic, tartaric and ascorbic acids (Da-Costa-Rocha et al., 2014). The increase in titratable acidity during storage at 45°C did not influence significantly, the final pH of the samples. The low pH of these concentrates makes it possible to avoid growth of certain microorganisms because the minimal pH of growth for most bacteria is 4.5 with some exceptions like lactic and acetic acid bacteria which can grow at pH lower than 4. The yeasts and molds have a minimum growth pH of 1.5 to 3.5 (Oyarzabal and Backert, 2011). Pasteurization and addition of food preservatives like potassium sorbate are means to inhibit the multiplication of these microorganisms which are the main agents influencing the conservation of food products (Yang et al., 2017).
The calices also contain sugars with glucose as the major sugar present (Peng-Kong et al., 2002). Reducing sugars were shown to decrease during storage. This reduction tended to increase during storage at 30 and 45°C than at 4°C (Table 4). Microorganisms can grow rapidly at favorable temperature and use these sugars in their metabolism, leading to the reduction of the sugar content (Pokusaeva et al., 2011). Changes in reducing sugars can influence sensory acceptability of hibiscus drinks by the consumers (Bechoff et al., 2014).
Hibiscus calyces are rich in anthocyanin used as natural colorant and functional food ingredient (Idham et al., 2012). These anthocyanins are responsible for the red color of H. sabdariffa calyx products. The concentration of anthocyanin is influenced by the storage conditions and has an impact on the shelf-life (Sinela et al., 2016). Samples stored at 45°C for three months lost more than 99% of their anthocyanin content, while those kept at 4°C retained almost all their anthocyanins. Temperature is an essential factor in the degradation of anthocyanins. Indeed, temperature was also the determining factor in the deterioration of the phenolic pigments (Fernandez-Lopez et al., 2013; Al-Sanabani et al., 2016). In the case of anthocyanin, high temperatures favor the opening of the heterocyclic anthocyanins with the formation of chalcones which are colorless products (Dziezak, 1986). The degradation of these pigments causes disappearance of the chromatic characteristics since they determine the color of the products (Camelo-Mendez et al., 2016). Pasteurization, addition of potassium sorbate and the pH of hibiscus extracts affected anthocyanin stability. Food preservatives such as potassium sorbate were shown earlier to have a slight influence on the anthocyanins stability (Moldovan and David, 2014). High pressure processing and thermal pasteurization were reported to influence polyphenols and anthocyanins stability during storage (Marszalek et al., 2017). West and Mauer (2013) showed that the stability of anthocyanins in solution was inversely correlated to increasing pH and temperature and was related to the common destruction of anthocyanins and ascorbic acid in solution. Finally, the use of low temperature (4°C) besides pasteurization and/or addition of potassium sorbate could extend the shelf-life of these concentrates without changes.
In conclusion, concentrated hibiscus extracts can be stored at an optimal temperature of 4°C for 3 months without serious changes in the extracts. Pasteurization and addition of potassium sorbate to the concentrated extracts of H. sabdarifa did not improve significantly, the stability of these products during storage at higher temperature.
The authors have not declared any conflict of interests.
REFERENCES
|
Abdul Hamid Z, Lin Lin WH, Abdalla BJ, Bee Yuen O, Latif ES, Mohamed J, Rajab NF, Paik Wah C, Wak Harto MK, Budin SB (2014). The role of Hibiscus sabdariffa L. (Roselle) in maintenance of ex vivo murine bone marrow-derived hematopoietic stem cells. Scientific World Journal 2014:1-10.
Crossref
|
|
|
|
Ali RF, El-Anany AM (2017). Hypolipidemic and hypocholesterolemic effect of roselle (Hibiscus sabdariffa L.) seeds oil in experimental male rats. Journal of Oleo Science, 66(1):41-49.
Crossref
|
|
|
|
|
Al-Sanabani, AS, Youssef KM, Shatta A A, El-Samahy SK (2016). Impact of freezing and freeze-drying processes on color, phytochemical contents and antioxidant capacity of pomegranate arils. Journal of Food Science Suez Canal University 3(1):27-34.
Crossref
|
|
|
|
|
AOAC (2005). Official method of analysis (18th Ed.). Association of Official Analytical Chemists, Washington DC.
|
|
|
|
|
Bechoff A, Cissé M, Fliedel G, Declemy AL, Ayessou N, Akissoe N, Touré C, Bennett B, Pintado M, Pallet D, Tomlins KI (2014). Relationships between anthocyanins and other compounds and sensory acceptability of hibiscus drinks. Food Chemistry 148:112-119.
Crossref
|
|
|
|
|
Camelo-Méndez GA, Jara-Palacios MJ, Escudero-Gilete ML, Gordillo B, Hernanz D, Paredes-López O, Vanegas-Espinoza PE, Del Villar-Martínez AA, Heredia FJ (2016). Comparative study of phenolic profile, antioxidant capacity, and color-composition relation of roselle cultivars with contrasting pigmentation. Plant Foods for Human Nutrition 71(1):109-114.
Crossref
|
|
|
|
|
Chiu CT, Hsuan SW, Lin HH, Hsu CC, Chou FP, Chen JH (2015). Hibiscus sabdariffa leaf polyphenolic extract induces human melanoma cell death, apoptosis, and autophagy. Journal of Food Science 80(3):649-658.
Crossref
|
|
|
|
|
Cisse M, Dornier M, Sakho M, Mar Diop C, Reynes M, Sock O (2009a). La production de bissap (Hibiscus sabdariffa) au Sénégal. Fruits 64(2):111-124.
Crossref
|
|
|
|
|
Cisse M, Dornier M, Sakho M, Ndiaye A, Reynes M., Sock, O (2009b). Le bissap (Hibiscus sabdariffa L.): composition et principales utilisations. Fruits 64(2):179-193.
Crossref
|
|
|
|
|
Cisse M, Vaillant F, Acosta O, Dhuique-Mayer C, Dornier M (2009c). Thermal degradation kinetics of anthocyanins from blood orange, blackberry, and roselle, using the Arrhenius, Eyring, and Ball Models. Journal of Agricultural and Food Chemistry 57(14):6285-6291.
Crossref
|
|
|
|
|
Cisse M, Vaillant F, Kane A, Ndiaye O, Dornier M (2012). Impact of the extraction procedure on the kinetics of anthocyanin and colour degradation of roselle extracts during storage. Journal of the Science of Food and Agriculture 92(6):1214-1221.
Crossref
|
|
|
|
|
Da-Costa-Rocha I, Bonnlaender B, Sievers H, Pischel I, Heinrich M (2014). Hibiscus sabdariffa L. A phytochemical and pharmacological review. Food Chemistry 165:424-443.
Crossref
|
|
|
|
|
Fernández-López JA, Angosto JM, Giménez PJ, León G (2013). Thermal stability of selected natural red extracts used as food colorants. Plant Foods for Human Nutrition 68(1):11-17.
Crossref
|
|
|
|
|
Idham Z, Muhamad II, Sarmidi MR (2012). Degradation kinetics and color stability of spray-dried encapsulated anthocyanins from Hibiscus sabdariffa L. Journal of Food Process Engineering 35(4):522-542.
Crossref
|
|
|
|
|
Kane A, Driss Y, Ndiaye NA, Cisse M, Sakho M, Dornier M (2015). Impact de la teneur en extrait sec soluble sur la dégradation thermique des anthocyanes d'extraits aqueux d'Hibiscus sabdariffa L. Afrique Science 11(6):308-319.
|
|
|
|
|
Kowalski S, Åukasiewicz M, Berski W (2013). Applicability of physico-chemical parameters of honey for identification of the botanical origin. ACTA Scientiarum Polonorum Technologia Alimentaria 12(1):51-59.
|
|
|
|
|
Lee J, Durst RW, Wrolstad RE (2005). Determination of total monomeric anthocyanin pigment content of fruit juices, beverages, natural colorants, and wines by the pH differential method: Collaborative study. Journal of AOAC international 88(5):1269-1278.
|
|
|
|
|
Marszalek K, Woźniak Å, SkÄ…pska S, Mitek M (2017). High pressure processing and thermal pasteurization of strawberry purée: quality parameters and shelf life evaluation during cold storage. Journal of Food Science and Technology 54(3):832-841.
Crossref
|
|
|
|
|
Moldovan B, David L (2014). Influence of temperature and preserving agents on the stability of cornelian cherries anthocyanins. Molecules 19(6):8177-8188.
Crossref
|
|
|
|
|
Oyarzabal OA, Backert S (2011). Microbial Food Safety: An Introduction. Springer Science and Business Media. P 191. Available at:
View
|
|
|
|
|
Peng-Kong W, Salmah Y, Salmah Yusof, Ghazali HM, Che Man YB (2002). Physicoâ€chemical characteristics of roselle (Hibiscus sabdariffa L.). Nutrition and Food Science 32(2):68-73.
Crossref
|
|
|
|
|
Pinsuwan S, Amnuaikit T, Ungphaiboon S, Itharat A (2010). Liposome-containing Hibiscus sabdariffa calyx extract formulations with increased antioxidant activity, improved dermal penetration and reduced dermal toxicity. Journal of the Medical Association of Thailand Chotmaihet Thangphaet 93:216-226.
|
|
|
|
|
Pokusaeva K, Fitzgerald GF, van Sinderen D (2011). Carbohydrate metabolism in Bifidobacteria. Genes and Nutrition 6(3):285-306.
Crossref
|
|
|
|
|
Rodriguez-Pérez C, Segura-Carretero A, Del Mar Contreras M (2017). Phenolic compounds as natural and multifunctional anti-obesity agents: A review. Critical Reviews in Food Science and Nutrition 2017:1-18.
Crossref
|
|
|
|
|
Sinela A, Rawat N, Mertz C, Achir N, Fulcrand H, Dornier M (2016). Anthocyanins degradation during storage of Hibiscus sabdariffa extract and evolution of its degradation products. Food Chemistry 214:234-241.
Crossref
|
|
|
|
|
Singh VP (2018). Recent approaches in food bio-preservation - A review. Open Veterinary Journal 8(1):104-111.
Crossref
|
|
|
|
|
Van Beilen JW, Teixeira de Mattos MJ, Hellingwerf KJ, Brul S (2014). Distinct effects of sorbic acid and acetic acid on the electrophysiology and metabolism of Bacillus subtilis. Applied and Environmental Microbiology 80(19):5918-5926.
Crossref
|
|
|
|
|
Vankar PS, Shukla D (2011). Natural dyeing with anthocyanins from Hibiscus rosa sinensis flowers. Journal of Applied Polymer Science 122(5):3361-3368.
Crossref
|
|
|
|
|
West ME, Mauer LJ (2013). Color and chemical stability of a variety of anthocyanins and ascorbic acid in solution and powder forms. Journal of Agricultural and Food Chemistry 61(17):4169-4179.
Crossref
|
|
|
|
|
Worawattananutai P, Itharat A, Ruangnoo S (2014). In-vitro antioxidant, anti-inflammatory, cytotoxic activities against prostate cancer of extracts from Hibiscus sabdariffa leave. Journal of the Medical Association of Thailand 297(8):81-87.
|
|
|
|
|
Yang W, Wu Z, Huang ZY, Miao X (2017). Preservation of orange juice using propolis. Journal of Food Science and Technology 54(11):3375-3383.
Crossref
|
|
|
|
|
Youssef KM, Shatta AA (2006). Some physical, chemical and rheological characteristics of watermelon juice, concentrate and syrup. Journal of Agricultural Science Mansoura University 31(9):6101-6110.
|
|
