Abstract

Comparative studies on proximate, phytochemical and sensory evaluation of Asystasia gangetica and market herbal tea were investigated. Fresh leaf, herbal tea powder and hot water tea extract samples were subjected to proximate and phytochemical composition while hot water tea extract samples were subjected to sensory evaluation using conventional standard methods. Result obtained from the investigation ranged as follows: 10.94 to 91.96, 2.09 to 18.72, 4.94 to 7.95, 0.55 to 2.38, 1.31 to 2.99 and 3.22 to 63.38 %; 1.08 to 2.47, 0.45 to 3.89, 1.69 to 8.28, 1.01 to 6.84, 0.86 to 4.29%; 0.52 to 2.43 mg/100g for moisture, crude protein, crude fiber, fat, ash, carbohydrate, flavonoids, alkaloids, saponins, tannins, steroids and hydrogen cyanide, respectively. Sensory evaluation results for A. gangetica and market herbal tea hot water extract were 4.88 and 5.12; 5.6 and 5.68; 4.96 and 5.92; 5.72 and 5.88; 5.92 and 5.72; and 5.76 and 5.72 for colour, taste, astringency, aftertaste, flavour and overall acceptability, respectively. The result findings revealed that herbal tea from A. gangetica favourably competed (nutritionally) with the market herbal tea and was also liked slightly in overall acceptability (on a 7 point Hedonic scale). This implies that this indigenous herbal plant could be commercially used for herbal tea production since it is packed with viable bioactive ingredients.

1. Introduction

Tea is an aromatic non-alcoholic beverage with a functional food effect and prepared by pouring boiled water into the fresh or cured leaves of Camellia sinensis ¹. It is reported that tea consumption started about five thousand years ago in China and India ². Traditionally, tea was consumed to improve blood flow, eliminate toxins and improve resistance to diseases ³ while several epidemiological studies have linked tea consumption to the reduction of cardiovascular disease risk, diabetes, cholesterol level ⁴, arthritis ⁵, osteoporosis and dental carriers ⁶. Tea is categorized into several types such as white, green, oolong, black, puerrh, scented and herbal teas ⁷.

Herbal tea is made with fresh or dried flowers, leaves, seeds or roots of plants which are generally known to possess medicinal values when allowed to steep in boiled water for a few minutes before consumption. Adeyemi et al. ⁸ reported that Asystasia gangetica is a herbal plant commonly known as Ganges primrose, widely seen across Nigeria, South Asia, Sub-Saharan Africa, Oceania and scientifically proven edible ⁹. This herbal plant is a widely used concoction in some localities in Nigeria for the management and treatment of so many ailments and was reported to have anti-diabetic and hypolipidemic properties both at acute and sub-acute levels with no toxicity infliction after seven days of study at the maximum tested dose level of 5000 mg/kg body weight ⁹. The consumption of this herb is usually faced with the challenge of its odour, colour and taste as it is prepared as a crude aqueous extract thus limiting its consumption despite its huge benefits medicinally due to vital bioactive nutrients. Thus, the processing of this herbal plant to tea help decrease this offensive odour, taste and colour thereby increasing its acceptability and utilization. Sequel to the above research findings, thus the drive to this study on the comparing the proximate, phytochemical and sensory evaluation of Asystasia gangetica and market herbal tea,

2. Material and Methods

The Asystasia gangetica leaves were collected in March from the Nnamdi Azikiwe University Awka environment and were identified and authenticated by a taxonomist with a voucher specimen Number: MOUAU/VPP/16/016.

The picked fresh leaves from the plants were washed with distilled water and processed into herbal tea according to the method of Gabriel and Nkemakonam ¹⁰ with little modification. The picked leaves were weighed, washed, drained and withered for 6 hours under room temperature open air. It was then dried at 50°C for six hours, cooled, rolled and packaged in a teabag.

The percentage moisture, fat, crude protein, ash and crude fiber content of the samples were determined according to the conventional standard method of AOAC ¹¹. Moisture content was determined by air oven drying. Fat content was by the Soxhlet fat extraction method. Crude protein was determined using the Micro Kjeldahl method. The crude fibre was determined by hydrolysis while ash content was by muffle furnace. Carbohydrate determination was by difference according to the method of Pearson ¹² as %carbohydrate = 100 – (%moisture content + %fat + %ash + %crude protein + %crude fiber).

The tannins, flavonoids and saponins contents of the samples were determined according to the standard conventional method of AOAC ¹³ in percentage. The steroids content was determined according to the conventional standard method of Kirk and Sawyer ¹⁴ in percentage. The alkaloids of the samples were determined according to the conventional standard method of Harbone ¹⁵ in percentage while the hydrogen cyanide (HCN) content of the samples was determined according to the standard conventional method of Bradbury et al. ¹⁶ in mg/100g.

The sensory properties (colour, taste, astringency, flavour, after taste and overall acceptability) of the herbal tea hot water extracts samples were evaluated using a conventional standard method of seven-point Hedonic scale and scores as 1 = strongly dislike, 2= moderately dislike, 3= slightly disliked, 4= indifferent, 5= slightly like, 6= moderately liked and 7= strongly liked. The panel was made of 25 students and staff of the Department of Food Science and Technology, Faculty of Agriculture, Nnamdi Azikiwe University Awka, Nigeria who are conversant with herbal tea.

Data analysis results generated from the study was expressed as mean ± standard deviation of three replicate determinations. Statistical analysis was performed on the data using one-way analysis of variance (ANOVA) using statistical package for social sciences (SPSS) software version 18.0 and differences in means were compared by Duncan’s multiple range test. Significance was accepted at P < 0.05.

3. Results and Discussion

The proximate composition of fresh Asystasian gangetica leaves, herbal tea powder and herbal tea hot water extract; market herbal tea powder and herbal tea hot water extract in percentage is shown in Table 1. The samples studied significantly (p<0.05) differed in all the proximate parameters except the ash content of both tea hot water extracts. The moisture content of the herbal tea powder is below that reported by Ifemeje et al. ¹⁷ while the tea extract is higher, which could be due to water used for the extraction. The moisture content of the powdered herbal tea samples studied was higher than the proposed standard value of 6.5% ¹⁸ for a good storage value. This finding denotes a negative implication on the shelflife of the herbal tea powder studied. The protein and fat content of the herbal tea powder samples analyzed were higher and not in agreement with the report of Rehman et al. ¹⁹ who suggested 1 to 2% and 0.9 to 1.62% of protein and fat for a better quality of tea sample. However, the protein values were also higher than that reported by Ifemeje et al., ¹⁷ (0.3 to 1.06%) but the fat content (3.6 to 5.8%) is lower than that. The ash content of the studied samples was in line with the report of Rehman et al. ¹⁹ who proposed that ash content should not exceed 5.54% to maintain the quality of tea during storage while the studied samples were in close range with that reported by Ifemeje et al. ¹⁷ (1 to 2.5%). Though crude fiber was not present in the hot water herbal extract, the values in powdered herbal samples were below that reported by Ifemeje et al., ¹⁷ (76.63 to 80.35%) but were within the range proposed by Venkatesan et al., ²⁰ (16.5%) for maintenance of high-quality tea during storage. The high values of carbohydrates in the sample could be due to other nutrients packed together with it since it was determined by difference.

The phytochemical content of Asystasia gangetica leaves, herbal tea powder and herbal tea hot water extract; market herbal tea powder and tea hot water extract are shown in Table 2. Generally, hot water herbal tea extract from A. gangetica was compared significantly (p<0.05) with market tea extract. It is observed that all the phytochemicals in the fresh A. gangetica leaves were higher than the values found in the tea powder and extract. This could be due to the negative and positive (hydrogen cyanide) effects of heat involved in the processing. It is also discovered the phytonutrients in both the tea powder and hot water extract of A. gangetica are significantly (p<0.05) higher when compared with the market sample. The resulting trend of this study disagrees with the trend reported by Gabriel and Nkemakonam ¹⁰ who reported an increase in the phytochemical composition with heat processing during tea production as a result of nutrient concentration. This could also be related to the moisture content of the tea, as Gaberiel and Nkemakonam ¹⁰ reported 10.37% while this finding had 11.45%, meaning that theirs was more concentrated than in this study. Both the herbal tea powder and hot water tea extract from A. gangetica leaves were favourably higher in all the phytochemical (flavonoid, alkaloid, saponin, tannin, steroids and hydrogen cyanide) analyzed when compared with market samples. The results obtained from the tea samples for saponins, steroids, alkaloids and hydrogen cyanide are within the same range as that reported by Gabriel and Nkemakonam ¹⁰ for moringa black and green tea as 2.25 to 5.5, 1.05 to 5.05, 0.65 to 2.20 and 0.55 to 2%, respectively while tannins and flavonoids are higher and below, respectively when compared with the same work by the above-named author as 0.22 to 1.32 and 6 to 16.50 %, respectively.

The sensory evaluation of the hot water herbal tea extract from A. gangetica and market samples is shown in Table 3. The herbal tea hot water extract from A. gangetica significantly differed in colour, taste, astringency and after taste when compared with the market sample but was the same at p<0.05 for flavour and overall acceptability. This means that the A. gangetica herbal tea competed favourably based on its higher values of flavour (5.92) and overall acceptability (5.76) showing liked slightly based on the seven-point Hedonic scale. It implies that if A. gangetica herbal tea is commercialized it could sell competitively in the market.

4. Conclusion

The comparative investigation revealed that A. gangetica herbal tea has an advantage over market herbal tea samples in terms of proximate composition, phytochemical composition and sensory evaluation. The findings suggest that this A. gangetica herbal tea could enhance the nutrition, antioxidant properties and immune system of the body. Sequel to these research findings on A. gangetica ethanolic extract, further in vivo animal assay to ascertain also its hot water extract efficacy be encouraged.

Competing Interest

The authors declared that no conflicts of interest exist.

Acknowledgements

Sincere appreciation goes to Tertiary Education Fund, Nnamdi Azikiwe University Awka, Nigeria.

Funding

This work was sponsored by the Tertiary Education Fund (TETFUND) (Grant number: 9^th batch, 2014-2016 merged TETFUND Research Project (RP) Intervention)

References