Standardisation and organoleptic evaluation of passion fruit and pineapple drink
The passion fruit and pineapple drink were standardised with different proportions of passion fruit juice and pineapple juice. The mean scores and the mean rank scores for organoleptic qualities of passion fruit and pineapple drink are presented in Table 2.
The mean scores and mean rank scores for appearance of passion fruit and pineapple drink varied from 8.40 (T
5) to 8.93 (T
3) and 2.97 to 4.60 respectively. The mean scores for colour varied from 8.00 (T
5) to 8.71 (T
4). The mean scores for taste varied from 7.44 (T
5) to 8.53 (T
3). The highest mean rank score for taste obtained was 4.73 for treatment T
3. The mean scores for overall acceptability varied from 7.88 (T
5) to 8.52 (T
3) with mean rank scores in the range of 2.47 to 4.90.
Among various treatments, the highest mean scores of 8.93 (appearance), 8.48 (flavour), 8.68 (texture), 8.53 (taste) and 8.52 (overall acceptability) were obtained for T
3 (70% passion fruit juice and 30% pineapple juice). Considering highest scores of organoleptic qualities passion fruit and pineapple drink (T
3-70% PFJ + 30% PJ) was selected as the best treatment for further studies.
Optimisation of condition for growth of Lactobacillus acidophilus in passion fruit and pineapple drink
The selected fruit drink along with control was inoculated with the probiotic strain
L.
acidophilus at various conditions and the optimum growth conditions were concluded from the results. Variables such as substrate concentration, time of incubation, temperature and inoculum concentration were optimised.
Table 3, represents the viable count of
L.
acidophilus with different variables at 10
9 dilution. 25 ml of the substrate concentration showed maximum growth of the probiotic organism with a colony count of 13.36 log cfu ml
-1 comparing to other substrates, 50 ml (13.15 log cfu ml
-1) and 75 ml (12.79 log cfu ml
-1). The number of colonies in control sample was 13.26, 12.99 and 12.38 log cfu ml
-1 in 25, 50 and 75 ml of juice sample respectively. One hour of incubation showed maximum growth (13.36 log cfu/ ml
-1) compared to 2 hours (13.14 log cfu ml
-1) and 3 hours (12.73 log cfu ml
-1) and also that of control sample with viability of 13.25, 12.89 and 12.34 cfu ml
-1 for 1, 2 and 3 hours respectively. The best temperature for probiotic growth was 37°C with a colony count of 13.33 log cfu ml
-1. Inoculation of 4 µl of culture had maximum growth (13.36 log cfu ml
-1) and minimum was 12.50 log cfu ml
-1 for 5 µl of inoculation. The number of colonies in control sample was 12.83, 13.27 and 12.44 log cfu ml
-1 for 3, 4 and 5 µl of inoculum respectively.
Physico chemical analysis of probiotic and non probiotic drinks
As per Table 4, TSS of the developed probiotic drinks differ significantly with their respective controls. TSS of the probiotic drink was found to be 12.80° Brix where as that of non probiotic drink was 13.50° Brix. Titratable acidity was higher in probiotic drink than non probiotic drink. The control probiotic drink contains 2.03 per cent titratable acidity, whereas the probiotic drink contains 2.28 per cent and there was significant difference in the titratable acidity of probiotic and non probiotic drinks.
Energy content of the probiotic fruit drink were lower when compared with that of the non probiotic drink. Energy content of non probiotic drink was 68.96 Kcal 100 g
-1 whereas that of probiotic drink was 59.32 Kcal 100 g
-1. The same situation was observed in the case of ascorbic acid content also. The non probiotic drink contain significantly higher amount of ascorbic acid than the probiotic drink (Table 4).
Organoleptic evaluation of passion fruit and pineapple drink
In the present study, the mean scores and mean rank scores for appearance of passion fruit based pineapple drink varied from 8.40 (T
5) to 8.93 (T
3) and 2.97 to 4.60 respectively. The texture of passion fruit based pineapple drink obtained a mean scores from 7.73 (T
5) to 8.68 (T
3) with mean rank scores in the range of 2.10 to 4.33. The mean scores for texture was the highest in T
3 (8.68). The mean scores for colour varied from 8.00 (T
5) to 8.71 (T
4). The mean scores and mean rank scores for flavour varied from 7.82 (T
4) to 8.48 (T
3) and 2.93 to 4.40 respectively. The mean scores for taste varied from 7.44 (T
5) to 8.53 (T
3). The highest mean rank score for taste obtained was 4.73 for treatment T
3. The mean scores for overall acceptability varied from 7.88 (T
5) to 8.52 (T
3) with mean rank scores in the range of 2.47 to 4.90. This was in accordance with
Seale and Sherman (1960) developed blended beverage of passion fruit with orange and pineapple which provided good texture and good flavour to the product and showed good physico chemical and sensory qualities.
Shaw and Wilson (1988) prepared passion fruit orange blended nectar concluded that nectar having high proportion of passion fruit have better acceptance.
Najumudeen (2015) developed blended fruit syrup of pineapple and passion fruit and reported that product were bright in colour and was highly acceptable by the consumers.
Among various treatments in the present study, the highest mean scores of 8.93 (appearance), 8.48 (flavour), 8.53 (taste), 8.68 (texture) and 8.52 (overall acceptability) were obtained for T
3 (70% passion fruit juice and 30% pineapple juice). Considering highest scores of organoleptic qualities passion fruit based pineapple drink (T
3-70% PFJ + 30% PJ) was selected as the best treatment for further studies.
Optimisation of condition for growth of Lactobacillus acidophilus in passion fruit and pineapple drink
Fruit juice act as a good medium for probiotic organism growth and also can maintain a minimum therapeutic level 10
9 cfu/g or ml (
WHO, 2001). According to
Manasi et al., (2013) the viability of
Lactobacillus acidophilus decreased upon refrigerated storage of probiotic pineapple juice. The initial count 3.8×10
7 cfu ml
-1 diminished to 1.8×10
7 cfu ml
-1, however the count doesn’t go below the minimum level. During storage at 30±1°C, the count expanded to 9.5×10
8 (in 48 hrs) and afterwards declined to 2.9×10
7 cfu ml
-1 after 120 hrs. A probiotic beverage with whey and pineapple juice was prepared by
Shukla et al., (2013) at a ratio of 65:35 and revealed that a good quality probiotic drink can be developed using one per cent of inoculum of
Lactobacillus acidophilus which can be stored for 24 days at 5±1°C and 48 hrs at 30±1°C.
Adebayotayo and Akpeji (2016) developed probiotic pineapple juice, were the juice supported the viability of the organism, lactic acid production, vitamin C production and antagonistic potential of the probiotic bacteria. The lactic acid bacteria were viable throughout the storage (1.05 to 1.10×10
9 cfu ml
-1) and there was no difference in taste, colour, aroma or appearance of the final product after a storage period of four weeks.
Gallina et al., (2019) developed and characterised probiotic fermented smoothie beverage and concluded that the viable count of the probiotic organism of passion fruit and mango blend after 1, 13 and 30 days of storage was 7, 7.5 and 6.5 log cfu ml
-1 respectively at a temperature of 8±2°C.
Nguyen et al., (2019) investigated that without any supplements
Lactobacillus and
Bifidobacterium were able to grow well in pineapple juice and acts itself as a matrix for the propagation of probiotic bacteria.
Monteiro et al., (2020), suggested that passion fruit pulp act as a good medium for probiotic culture, when fermented at a temperature of 30°C.
According to
Shukla et al., (2013), who developed whey based probiotic pineapple beverage, did not show much difference in sensory evaluation and also concluded that the main descriptors that characterised the probiotic product were acidity and sweetness. The mean score for overall acceptability of whey-pineapple juice blend was 8.87. Flavour and taste of the product was found to be enhanced due to probiotication. This may be due to the process of fermentation occurred in the beverage
Physico chemical analysis of passion fruit and pineapple drink
During probiotic fermentation, the organism convert glucose to lactic acid. This is responsible for the decrease in pH of the product. During fermentation, the probiotic organism produces lactic acid by hydrolyzing starch. This reduces the TSS content and starch in probiotic samples. This metabolic activity convert starch to fermentable simple sugars which is used by probiotic organisms
(Adams et al., 2008). Yan-li (2011) produced wine with combination of pawpaw and passion fruit and the pH was estimated as 4.0.
Fernandes et al., (2011) concluded that upon pasteurisation of passion fruit juice, there is increase in titrable acidity (3.06 g 100 ml
-1) were as the homogenised juice have 2.83 g 100 ml
-1. The titrable acidity of wine produced from mixed juice of passion fruit, mango and pineapple was 1.4 per cent after fermentation and TSS was 20° Brix (
Nzbuheraheza and Nyiramugwera, 2014).
Lactobacillus spp. is more effective in reducing pH than yeasts and other microbes (
Gautam and Sharma, 2014). The reduction may be due to the utilisation of sugars for the metabolic activity of probiotic LAB in the probiotic juice samples. Similar observation was reported by
Kumar et al., (2011), in fruit juice with
Lactobacillus casei. There was reduction in TSS content of probiotic pineapple juice formulated by
Adebayo Tayo and Akpeji (2016) from 15.28 to 12.68° Brix after storage of 4 weeks.
Stanton et al., (2005) reported that both genera
Lactobacillus and
Bifidobacterium were reported to have high requirements of free amino acids, peptides, vitamins and fermentable carbohydrates for their growth and development.
Lactobacillus and
Bifidobacterium strains grow well in pineapple juice meaning this matrix in itself was a suitable medium for propagation of probiotic bacteria. Pineapple juice acts as a good matrix for probiotic growth without any supplements of nutrients.
Nazarudeen (2010) suggested that, increased moisture content reduces the nutritive factors such as fat and carbohydrate, thereby reducing the energy value.
Shukla et al., (2013) reported that reduction in ascorbic acid content of probiotic drinks were may be due to pasteurisation of juice and exposure to light. The ascorbic acid content in RTS drink prepared by blending juices of passion fruit and cashew apple in different ratios such as 25:75, 50:50, 25:75 + ginger drops and 50:50 + ginger drops was 80.26 mg 100 g
-1, 79.73 mg 100 g
-1, 76.39 mg 100 g
-1 and 79.29 mg 100 g
-1 respectively
(Sobhana et al., 2011).