The aim of the study was to consider the suitability of a mixture of juices from jicama, winter melon, and carrot as a raw medium for producing probiotic juice by Lactobacillus strains ( Lactobacillus plantarum CICC22696 and Lactobacillus acidophilus CICC20710), as well as evaluate changes of physicochemical and microbiological characteristics during fermentation and cold storage (4 °C, 28 days). Both strains grew well in juice mixtures after 24 h of fermentation at 37 °C, reaching nearly 9 and 8 log CFU/mL when inoculated with L. plantarum and L. acidophilus respectively. The viability of L. plantarum was near 8 log CFU/mL at the end of storage whereas viability of L. acidophilus only remained 4.57 log CFU/mL. Degradation of total carotenoids was in the range of 12% - 23% in fermentation periods and 16% - 23% during cold storage depending on the strain used. The values of lightness, redness, and yellowness increased during fermentation. However, this tendency was variable during cold storage when the values of redness and yellowness decreased. Sensory acceptability of the products was enhanced by adding sucrose or multi fruit juice (containing mainly tropical fruit juices). The fermented juice with L. plantarum is efficient to produce a functional probiotic beverage.
Probiotics are defined as live organisms, which provide a benefit to the host when administered in adequate quantities [
Through fermentation, fruit and vegetable juices are preserved and maintained, while improving the nutritive and sensory properties of the products. Various studies have been conducted to investigate the suitability of fruit and vegetable juices as a medium to develop new probiotic beverages from fruits such as pineapple [
Vegetables are rich sources of bioactive compounds which have beneficial effects in prevention of some diseases and certain types of cancer [
To our knowledge, studies dealing with the fermented drink/juice made from jicama and/or winter melon have not been explored. Most fermented juices from fruits and vegetables in past studies used lactic acid bacteria, researchers just limited investigation scope at considering the suitability for producing probiotic juice. Therefore, this study had three main objectives:
1) To investigate the suitability of a vegetable juice medium composed of jicama, winter melon and carrot juices as raw material for production of probiotic vegetable juice by lactic acid bacteria.
2) To determine physicochemical and microbiological changes during fermentation and cold storage of the vegetable juice mixture.
3) To evaluate sensory acceptability of products, furthermore, to confirm whether the addition of sucrose or multi fruit juice (mainly tropical fruit juices) improves sensory quality and hedonics.
Jicamas, winter melon with sparser wax covering its surface, and orange carrots were purchased from the supermarket Auchan and local market in Binhu district, kept at 4˚C, and used in the experiment as quickly as possible. Vegetables were careful washed and peeled. The seeds and cavity tissues were removed from the winter melon. Juices were extracted from jicama, winter melon and carrots using a Philips Viva Collection juicer (Shengzheng, China). The extracted juices were filtered separately through a cheesecloth. The clarified juices from jicama, winter melon, carrots were combined in a ratio of 1:1:1 by volume. The juice mixture was analyzed yielding the following characteristics: titratable acidity of 0.09% (expressed as lactic acid), pH of 6.05 and total soluble solid content of 6.0˚Brix. The fresh juice mixture was subjected to pasteurization in a TOMY SX-500-high pressure steam sterilizer (Tomy Kogyo Co. Ltd, Fukushima, Japan) at 80˚C for 15 min [
Lactic acid bacteria (L. plantarum CICC 22696, L. acidophilus CICC 20710) were supplied by China Center of Industrial Culture Collection (CICC), Beijing, China. Both bacterial cultures were stored frozen at −20˚C in MRS (De Man, Rogosa and Sharpe) medium containing 20% glycerol. The strains were reactivated by means of double passage on MRS when needed according to the instructions in the user’s manual.
Lactobacillus strains were cultivated on MRS broth at 37˚C. When used for fermentation, lactic acid bacteria were cultivated until the late exponential phase of growth was reached. The exponential phase was determined from bacterial growth curve. Erlenmeyer flasks containing 100 mL of pasteurized juice mixture were then inoculated the culture to nearly 7.00 log CFU/mL, this concentration was chosen based on the recommendation for probiotic foods: minimal counts of 7.00 log CFU/mL for better efficacy in regulating beneficial effects [
To determine the effects of cold storage on cell viability and physicochemical properties after completion of appropriate fermentation time, samples of fermented juice mixture were transfer to storage at 4˚C for 28 days. Viable counts, color and total carotenoids of fermented vegetable juice were recorded at intervals of 7 days, during the 28 days. The microbial population was expressed as log CFU/mL.
A digital F2-standard pH meter (Mettler-Toledo Instruments (Shanghai) Ltd, China) was used for pH measurements. The total soluble solid (˚Brix) of the juice was measured using a refractometer (Master-20M, ATAGO Co., Ltd., Tokyo, Japan).
Total acidity expressed as percent of lactic acid, was determined by titrating the juice sample (10 mL) with 0.1 N NaOH to the end point (pH 8.2 ± 0.1) [
The total carotenoid content of the sample was determined by a slightly modified method of Adiamo, Ghafoor [
Carotenoids content ( mg / L ) = A × V ( mL ) × 10 4 E 1cm 1% × P
where A = absorbance; V = total extract volume; P = analyzed juice volume (mL); E 1cm 1% = 2592 (β-carotene extinction coefficient in petroleum ether).
Viable cell counts were obtained by serial dilution with saline until 107 dilution was reached. Aliquots of 0.1 ml of dilution were plated in triplicate on petri-dishes containing MRS agar. The petri-dishes were incubated for 48 h (L. plantarum CICC22696) and for 72 h (L. acidophilus CICC20710) at 37˚C. Plates containing 20 - 350 colonies were measured and recorded as colony forming units (log CFU/mL). L. acidophilus appears on agar as irregular light brown colonies ranging in diameter from 0.9 to 1.5 mm [
The juice color was determined by using an UltraScan Pro1166 spectrophotometer (Hunterlab, America), and readings were taken in triplicate. The reflectance instruments determined three color parameters: lightness (L*), redness (a*), and yellowness (b*). The index of total color difference (ΔE) was calculated by the equation [(L − Lo)2 + (a − ao)2 + (b − bo)2]1/2. Where Lo, ao, and bo are referred to the color reading of control sample. A larger ΔE value indicates the greater color change compared with the control sample.
Seven formulations of vegetable juice mixture were prepared for assessment shown as
The sensory characteristics were evaluated by a panel of 21 judges involved students in faculty of food science and technology who were not familiar with
Formulations | Fermented juice by Lactobacillus strain | Sucrose | Multi fruit juice |
---|---|---|---|
CON | - | - | - |
PFJ | L. plantarum | - | - |
AFJ | L. acidophilus | - | - |
SUC-PFJ | L. plantarum | Added to 10˚Brix | - |
SUC-AFJ | L. acidophilus | Added to 10˚Brix | - |
MASK-PFJ | L. plantarum | - | 10% v/v |
MASK-AFJ | L. acidophilus | - | 10% v/v |
characteristics of fermented non-dairy beverage. The judges (13 women, 8 men) ranged from 24 - 35 years old. Two evaluation sessions were conducted in individual booths. All samples of 40 ml were coded with 3-digit random numbers, presented to the panelists at room temperature and evaluated one at a time, in random order. Room temperature spring water was provided to panel members for rinsing the mouth between samples. The acceptance testing of attributes (color, texture, flavor, taste and overall acceptance) used a 9-point hedonic scale, ranging from 1 to 9 where 9 = like extremely and 1 = dislike extremely. The evaluation data were recorded and mean scores for each attribute were calculated to compare with the samples.
All experimental results were the mean of triplicate. The data were recorded as the mean ± standard deviation (mean ± SD) and the statistical analysis was conducted with IBM SPSS software (version 24, Statsoft, America). Data analysis was done by one-way ANOVA followed by Duncan’s post hoc test. Results were regarded as significant differences at p < 0.05.
Time (h) | pH | TTS ( Brix) | Titratable acidity (%lactic acid) | Log CFU/mL | Total sugar (mg/mL) | Total carotenoids (mg/L) |
---|---|---|---|---|---|---|
0 h | 5.97 ± 0.01a | 6.4 ± 0.06a | 0.09 ± 0.01c | 6.80 ± 0.09c | 48.76 ± 0.71a | 24.22 ± 0.13a |
24 h | 3.68 ± 0.01b | 5.3 ± 0.06b | 0.61 ± 0.01b | 8.98 ± 0.04a | 37.02 ± 1.01b | 21.32 ± 0.29b |
48 h | 3.40 ± 0.01c | 5.0 ± 0.00c | 0.95 ± 0.05a | 8.77 ± 0.11b | 34.66 ± 1.04c | 19.54 ± 0.14c |
Data expressed as means ± standard deviation (n = 3). Values in the same column followed by different superscript letters indicate statistically significant differences at p < 0.05. TSS: total soluble solid.
Time (h) | pH | TTS ( Brix) | Titratable acidity (%lactic acid) | Log CFU/mL | Total sugar (mg/mL) | Total carotenoids (mg/L) |
---|---|---|---|---|---|---|
0 h | 5.98 ± 0.04a | 6.4 ± 0.10a | 0.09 ± 0.01c | 6.59 ± 0.05c | 47.93 ± 1.07a | 23.63 ± 0.22a |
24 h | 3.96 ± 0.01b | 5.6 ± 0.06b | 0.49 ± 0.02b | 7.89 ± 0.01a | 40.27 ± 0.89b | 20.19 ± 0.24b |
48 h | 3.83 ± 0.01c | 5.4 ± 0.00c | 0.59 ± 0.01a | 7.42 ± 0.03b | 38.67 ± 0.77b | 18.25 ± 0.38c |
Data expressed as means ± standard deviation (n = 3). Values in the same column followed by different superscript letters indicate statistically significant differences at p < 0.05. TSS: total soluble solid.
CFU/mL after 24 h then slightly decreased to 8.77 and 7.42 log CFU/mL after 48h of fermentation at 37˚C. Extending the growth period to 48 h did not increase the number of viable cells of any tested starter but did reduce cell viability. For maximum health benefits, scientists have suggested the minimum probiotic organism level in probiotic food products should be 106 - 107 CFU/mL at the time of consumption [
The pH and TSS of vegetable juice decreased during the fermentation process (
The strains rapidly fermented the vegetable juice mixture and resulted the reduction of total sugar and carotenoids. The greater growth and metabolism of L. plantarum have led to higher sugar consumption than L. acidophilus, and decreased the initial sugar content of 48.76 mg/mL to 34.66 mg/mL. There was about 29.70 mg of carotenoids in 1 L of fresh vegetable juice mixture extracted with the Philips Viva Collection juicer. Pasteurizing (80˚C, 15 min) substantially reduced total carotenoid content in fresh juice mixture to ~23 - 24 mg/L (
The fermentation also resulted an increase in a* and b*, indicating the redness and yellowness of vegetable juice mixture increased. Carotenoids are the main pigments responsible for the color of carrot roots and juices. Trans carotenoid isomers are predominant in nature and under extreme pH values (acid and alkali), can be transformed to cis carotenoid isomers and cause color change in carrot juice [
The juice mixtures after 24 h fermentation were stored at 4˚C for 28 days showed the different cell viability between two strains (
Lactobacillus strain | Time (h) | L* | a* | b* | ΔE |
---|---|---|---|---|---|
L. plantarum | 0 | 44.57 ± 0.06c | 24.38 ± 0.03c | 35.72 ± 0.07b | ̶ |
24 | 45.75 ± 0.07b | 24.77 ± 0.10b | 35.94 ± 0.04a | 1.26 ± 0.07 | |
48 | 46.22 ± 0.07a | 25.15 ± 0.05a | 35.99 ± 0.03a | 1.84 ± 0.04 | |
L. acidophilus | 0 | 43.52 ± 0.09b | 24.04 ± 0.09c | 33.54 ± 0.09b | ̶ |
24 | 43.67 ± 0.14ab | 24.56 ± 0.08b | 33.72 ± 0.08a | 0.57 ± 0.04 | |
48 | 43.92 ± 0.19a | 24.87 ± 0.09a | 33.88 ± 0.09a | 0.98 ± 0.14 |
Data expressed as means ± standard deviation (n = 3). Values in the same column followed by different superscript letters indicate statistically significant differences at p < 0.05. The values within column that do not have a common superscript are also significant different (p < 0.05). Unfermented vegetable juice mixture at 0h is used as the control.
Time (days) | Log CFU/mL | |
---|---|---|
L.plantarum | L.acidophilus | |
1 | 8.88 ± 0.06a | 7.57 ± 0.01a |
7 | 8.75 ± 0.04b | 6.99 ± 0.04b |
14 | 8.56 ± 0.05c | 6.31 ± 0.09c |
21 | 8.27 ± 0.07d | 5.47 ± 0.07d |
28 | 7.95 ± 0.08e | 4.57 ± 0.07e |
Data expressed as means ± standard deviation (n = 3). Values in the same column followed by different superscript letters indicate statistically significant differences at p < 0.05.
storage, which is considered a great value for fermented products containing probiotics. In contrast, viable cell count of L. acidophilus decreased significantly during cold storage and remained at only 4.57 log CFU/mL after 28 days. Pasteurization for the long period (80˚C, 15 min) could cause nutritional loss in the material which might have contributed to L. acidophilus viability loss. L. plantarum demonstrates a stronger viability than other Lactobacillus strains during cold storage time in fruit and vegetable juices [
After 28 days of cold storage, fermented vegetable juice mixtures with L. plantarum and L. acidophilus presented a loss about 23% and 16% of their initial total carotenoid content, respectively (
The results of color component (L*, a*, b* and ΔE) in the fermented vegetable juice mixture during storage (4˚C, 28 days) were shown
The sensory assessment of vegetable mixture juices was conducted on 14th day of storage because all formulations (except CON) need to have culture counts high enough to be considered probiotic foods (>6 log CFU/mL) (
with sucrose and multi fruit juice (mainly tropical fruit juice) had no effect (p > 0.05) on acceptability of color and texture. The highest acceptability was the CON formulation. The formulations without any supplements got low acceptability (odor, taste, overall acceptance). This is likely because the metabolism of the cultures results changes to the components in the juices that negatively contribute to the aroma and flavor of the final products. Probiotification of juices from fruits and vegetables were characterized as “medicinal”, “acid”, “bitter”, “astringent”, “salty” or “dairy”. Fermented juices with L. plantarum had a stronger sour taste (
In vegetable juice mixtures fermented with L. plantarum by adding the multi fruit juice (MASK-PFJ) or sucrose (SUC-PFJ) while the vegetable juice mixtures fermented with L. acidophilus by only adding sucrose (SUC-AFJ). The results indicated that the preference might be related to sweetness and the addition of pleasant aroma and volatile compounds is able to mask the presence of probiotics. However, the commercial juice was used in adding isn’t a good choice to mask unpleasant flavor and change considerably sensory attributes of probiotic juices. A set of tests for mixing the vegetable juice mixture with a wide variety of commercial vegetable juice or fruit juice should be done to find the best option in improving effectively sensory quality. Herein, our study didn’t reveal any information about the juices they evaluated which has a significant impact on consumer liking. Exposure and health information have positive effects on the overall liking of juices containing probiotic cultures [
This research demonstrated both Lactobacillus strains were capable of having biochemical activities in vegetable juice mixture without any nutrient supplementation. Change in levels of physicochemical and microbiological characteristics in vegetable juice mixture during fermentation and cold storage depended on the strain used. As sensory analysis, acceptance of the probiotic vegetable juice mixtures was in range of 5 to 8 on a 9-point hedonic scale, which differed between the attribute evaluated and the strain used. Moreover, the sensory quality was improved positively by sucrose addition or adding multi fruit juice (10% v/v, mainly tropical fruit juices). Based on the present findings, L. plantarum could be used as a culture for production of probiotic drink from vegetable juice mixture with high nutrient values and health benefits. Optimizing fermentation, improving survival of probiotics during cold storage, as well as enhancement of sensory traits for this vegetable juice mixture require further studies.
This research was supported by the financial support of the Six-Talent Peaks Project in Jiangsu Province and Qinglan Project, which has enabled us to carry out this study.
Authors declare that they have not any conflicts of interest.
Do, T.V.T. and Fan, L.P. (2019) Probiotic Viability, Qualitative Characteristics, and Sensory Acceptability of Vegetable Juice Mixture Fermented with Lactobacillus Strains. Food and Nutrition Sciences, 10, 412-427. https://doi.org/10.4236/fns.2019.103031