In this study, the effects of different amounts of inulin and oat fiber addition on the properties of apricot probiotic drinking yoghurt (APDY) were investigated. Seven different APDY was produced. Six of them were produced by the addition of 0.5%, 1% and 2% inulin (B, C, D) and oat fiber (E, F, G) and one of them was produced as control sample. Pasteurized apricot pureed and sugar (10%) was added to fermented milk beverage. APDYs were analysed 1, 7, 14 and 21 days after production. Addition of fiber to APDYs had significantly affected on the pH, titratable acidity, water holding capacity, S. thermophilus, L. acidophilus Bifidobacterium BB-12 counts, and sensorial properties of the samples (p < 0.01). pH values decreased titratable acidity, water holding capasity, the viscosity values, L. acidophilus and Bifidobacterium BB-12 counts increase by the addition of fiber into samples.
Because of their attributed health benefits, probiotic bacteria have been increasingly included in yoghurts and fermented milks during the past three decades and they are consumed at appropriate levels and as part of a balanced diet. In order to produce therapeutic benefits, a suggested minimum level for probiotic bacteria in fermented milk is from 106 to 107 cfu mL−1 [
Inulin and oat fiber, the nondigestible carbohydrate containing naturally occuring fructooligosaccharides and β-glucan, respectively, possesses some characteristics of dietary fibers, and such is of particular interest for its metabolic properties [
The aim of this study was to establish the maximum level of fibre that could be incorporated into drinking yoghurt and thus, to produce an acceptable APDYs containing apricot and diatery fibers and high levels of probiotic bacteria (>106 - 107 cfu g−1, which is the recommended minimum daily intake).
APDYs production were done in the Dairy Pilot Plant of the Food Engineering Department of Harran University. The cow milks were inoculated with mixed probiotic culture (FD-DVS ABT-2 Probio-Tec) consisting of Streptococcus thermophilus, Lactobacillus acidophilus and Bifidobacterium BB-12. The starter cultures were obtained from Peyma-Chr. Hansen (Turkey). Inulin and oat fiber were supplied from Arosel Gıda (İstanbul). Apricot and sugar were purchased from markets. All reagents used in this work were of analytical grade and obtained from Sigma Chemicals (İstanbul, Turkey).
Drinking yoghurt was manufactured according to Tamime and Robinson [
The pH of the milk and APDYs was measured using a digital pH-meter. Titratable acidity, expressed as g of lactic acid per 100 g APDY, was evaluated by titration method and the total fat contents were determined by the Gerber method, respectively [
The water holding capacity (WHC) was determined with a procedure adapted from Remeuf et al. [
The viscosity of the APDYs was determined at 4˚C using a digital Brookfield Viscometer, Model DV-II (Brookfield Engineering Labrotories, Stoughton, MA, USA) [
Bacteriological analysis
APDY samples (10 g) were decimally diluted in 100 mL sterile peptone water (0.1%) and 1 mL aliquot dilutions were poured onto plates of the various selective and differential agars in triplicate. S. thermophilus, L. acidophilus and Bifidobacterium BB-12 were incubated by using M17 agar, MRS with sorbitol agar and MRS-NNLP [
The samples were organoleptically assessed by ten panelists using a 9-point hedonic scale was used to evaluate flavour, texture, appearance and general acceptability (1 = strongly unacceptable, 9 = very good) as described by Bodyfelt et al. [
The data were analysed statistically by means of SPSS statistical software program (version 5.0). Statistically different groups were determined by the LSD (Least Significant Difference) test [
The chemical composition of milk used for the production of APDY (data not shown) fell within the following averages: titratable acidity 0.18 (±0.01) % as lactic acid (L. A.), pH 6.68 (±0.02), total solids 11.78% (±0.06), fat 3.1% (±0.03), protein 3.34% (±0.07), lactose 4.58% (±0.06) and ash 0.73% (±0.01).
The changes of physico-chemical properties of APDY are shown in
Addition of fiber had a positive effect on the WHC of APDYs. The highest WHC was obtained for sample G, which fortified with 2% oat fiber. With the increase in fiber content, WHC values were increased (p < 0.01). Oat fiber and inulin are highly hygroscopic, could bind water and form a gel-like network [
Addition of fiber, especially oat fiber increased the viscosity of APDY (p < 0.01). The viscosity value of the sample F was the highest and the control sample was the least. Several authors reported that dietary fiber in fermented milk products increase the viscosity of the end product [
Sample* | Storage period | pH | Titratable acidity (%L. A) | Viscosity (Cp) | Water holding capacity (%) |
---|---|---|---|---|---|
A | 1.day | 4.62 ± 0.049a1A | 0.501 ± 0.001c2D | 1126 ± 8.485d4C | 77.91 ± 1.216e3A |
7.day | 4.54 ± 0.049a1B | 0.535 ± 0.006b2C | 1170 ± 19.799d3B | 77.08 ± 1.386e3A | |
14.day | 4.42 ± 0.064a1B | 0.581 ± 0.037c3B | 1200 ± 22.627c3A | 76.49 ± 1.054d2A | |
21.day | 4.33 ± 0.035a1C | 0.625 ± 0.004c3A | 1228 ± 11.314c2A | 75.39 ± 1.945e2B | |
B | 1.day | 4.56 ± 0.078a1A | 0.542 ± 0.006b1B | 1222 ± 31.113c3C | 81.47 ± 1.181d2A |
7.day | 4.49 ± 0.085a1A | 0.552 ± 0.006b2B | 1260 ± 11.314c2B | 79.90 ± 0.79d2A | |
14.day | 4.37 ± 0.049a1B | 0.633 ± 0.014b2A | 1308 ± 5.657c2A | 77.95 ± 1.301d2B | |
21.day | 4.30 ± 0.064b1C | 0.651 ± 0.029b2A | 1332 ± 5.657b1A | 76.90 ± 0.962e2B | |
C | 1.day | 4.49 ± 0.021b1A | 0.554 ± 0.004a1C | 1264 ± 11.314b2C | 88.35 ± 1.937c1A |
7.day | 4.38 ± 0.035b2B | 0.585 ± 0.005a1B | 1290 ± 8.485b2B | 86.64 ± 2.220c1A | |
14.day | 4.30 ± 0.021c1B | 0.674 ± 0.004a1A | 1330 ± 2.828c1A | 85.66 ± 0.955c1B | |
21.day | 4.21 ± 0.028c1C | 0.688 ± 0.011a1A | 1343 ± 4.243b1A | 84.16 ± 0.559d1B | |
D | 1.day | 4.46 ± 0.0072b1A | 0.564 ± 0.002a1C | 1331 ± 1.414a1A | 89.41 ± 0.919c1A |
7.day | 4.32 ± 0.028b2B | 0.592 ± 0.008a1B | 1352 ± 11.314a1A | 88.38 ± 0.742b1A | |
14.day | 4.24 ± 0.028c2C | 0.678 ± 0.002a1A | 1358 ± 8.485b1A | 86.93 ± 1.237c1B | |
21.day | 4.15 ± 0.042d2D | 0.697 ± 0.010a1A | 1359 ± 12.728a1A | 86.03 ± 0.933c1B | |
E | 1.day | 4.59 ± 0.007a1A | 0.548 ± 0.005b1C | 1280 ± 11.314b2B | 91.59 ± 0.785b2A |
7.day | 4.49 ± 0.042a1B | 0.571 ± 0.025a1C | 1294 ± 14.142b2B | 89.89 ± 1.117b2A | |
14.day | 4.43 ± 0.021a1B | 0.616 ± 0.008b1B | 1336 ± 11.314b2A | 87.15 ± 1.174b3B | |
21.day | 4.36 ± 0.028a1C | 0.641 ± 0.013c2A | 1358 ± 2.828a1A | 85.03 ± 0.127c3C | |
F | 1.day | 4.54 ± 0.021b1A | 0.568 ± 0.002a1C | 1304 ± 22.627a1B | 93.12 ± 1.259a1A |
7.day | 4.47 ± 0.035b1A | 0.587 ± 0.007a1C | 1350 ± 8.485a1A | 91.95 ± 0.870a1A | |
14.day | 4.36 ± 0.021b1B | 0.621 ± 0.008b1B | 1360 ± 5.657b1A | 89.69 ± 1.711b2B | |
21.day | 4.32 ± 0.028a1B | 0.657 ± 0.016b1A | 1376 ± 0.000a1A | 88.63 ± 0.594b2B | |
G | 1.day | 4.52 ± 0.078b12A | 0.576 ± 0.004a1C | 1334 ± 19.799a1B | 94.11 ± 1.351a1A |
7.day | 4.43 ± 0.035b1B | 0.584 ± 0.006a1C | 1362 ± 14.142a1A | 93.48 ± 1.690a1A | |
14.day | 4.32 ± 0.021b2C | 0.625 ± 0.001b1B | 1388 ± 5.657a1A | 92.21 ± 2.524a1B | |
21.day | 4.27 ± 0.014c2C | 0.672 ± 0.009b1A | 1384 ± 5.657a1A | 91.06 ± 1.803a1B |
*A: Control, B: Fortified with inulin at 0.5%, C: Fortified with inulin at 1.0%, D: Fortified with inulin at 2.0%, E: Fortified with oat fiber at 0.5%, F: Fortified with oat fiber at 1.0%, G: Fortified with oat fiber at 2.0%; a-dDifferent letters in the same column denote significant differences for fiber addition (P < 0.01). Different numbers in the same column denote significant differences for fiber rate storage period (P < 0.01). Different capital letters in the same column denote significant differences for storage period (P < 0.01).
Viable bacterial counts of APDY samples during storage are shown in
Sample* | Storage period | Streptococcus thermophilus | Lactobacillus acidophilus | Bifidobacterium BB-12 |
---|---|---|---|---|
A | 1.day | 6.93 ± 0.1061B | 6.04 ± 0.028d2A | 5.21 ± 0.035c2A |
7.day | 7.08 ± 0.1061B | 5.94 ± 0.007c1A | 5.09 ± 0.057c1A | |
14.day | 7.66 ± 0.1201A | 5.91 ± 0.014c1A | 4.99 ± 0.014b1B | |
21.day | 6.78 ± 0.2401A | 5.83 ± 0.028c2B | 4.93 ± 0.035b2B | |
B | 1.day | 6.98 ± 0.0851B | 6.15 ± 0.035d2A | 5.35 ± 0.021b1A |
7.day | 7.12 ± 0.0851B | 6.10 ± 0.021c1A | 5.13 ± 0.035c1B | |
14.day | 7.74 ± 0.0851A | 6.03 ± 0.035d1A | 4.97 ± 0.021b2C | |
21.day | 6.09 ± 0.1272C | 5.94 ± 0.021c1B | 4.98 ± 0.035b2B | |
C | 1.day | 7.06 ± 0.0641B | 6.48 ± 0.007c1A | 5.36 ± 0.028b1A |
7.day | 7.27 ± 0.0491B | 6.03 ± 0.035c1B | 5.21 ± 0.042b1B | |
14.day | 7.75 ± 0.0991A | 6.02 ± 0.085d1B | 5.00 ± 0.141b1C | |
21.day | 6.24 ± 0.0782C | 6.03 ± 0.035b1B | 5.03 ± 0.099b2C | |
D | 1.day | 7.07 ± 0.1481B | 6.54 ± 0.007b1A | 5.49 ± 0.332a1A |
7.day | 7.34 ± 0.0921B | 6.13 ± 0.028c1B | 5.26 ± 0.035b1B | |
14.day | 7.75 ± 0.1271A | 6.01 ± 0.057d1B | 5.14 ± 0.057a1B | |
21.day | 6.22 ± 0.0992C | 6.05 ± 0.071b1B | 5.22 ± 0.120a1B | |
E | 1.day | 6.88 ± 0.0351B | 6.51 ± 0.014c1A | 5.44 ± 0.014a1B |
7.day | 7.03 ± 0.1132B | 6.42 ± 0.021a1A | 4.97 ± 0.049d3C | |
14.day | 7.42 ± 0.0782A | 6.36 ± 0.007b2B | 4.82 ± 0.049c2C | |
21.day | 6.02 ± 0.1202C | 6.26 ± 0.127a1B | 5.10 ± 0.481a1B | |
F | 1.day | 7.00 ± 0.1201C | 6.66 ± 0.007b1A | 5.50 ± 0.049a1A |
7.day | 7.02 ± 0.1912B | 6.27 ± 0.014b1B | 5.24 ± 0.057b2B | |
14.day | 7.84 ± 0.0781A | 6.23 ± 0.035c2B | 5.05 ± 0.071b1C | |
21.day | 6.41 ± 0.0851D | 6.10 ± 0.141b2C | 5.04 ± 0.156b1C | |
G | 1.day | 7.04 ± 0.1341B | 6.80 ± 0.007a1A | 5.56 ± 0.035a1A |
7.day | 7.74 ± 0.0571A | 6.40 ± 0.007a1C | 5.48 ± 0.071a1A | |
14.day | 7.99 ± 0.0781A | 6.58 ± 0.000a1B | 5.21 ± 0.078a1B | |
21.day | 6.54 ± 0.0921C | 6.37 ± 0.304a1C | 5.14 ± 0.057a1B |
*A: Control, B: Fortified with inulin at 0.5%, C: Fortified with inulin at 1.0%, D: Fortified with inulin at 2.0%, E: Fortified with oat fiber at 0.5%, F: Fortified with oat fiber at 1.0%, G: Fortified with oat fiber at 2.0%; a-dDifferent letters in the same column denote significant differences for fiber addition (P < 0.01). Different numbers in the same column denote significant differences for fiber rate storage period (P < 0.01). Different capital letters in the same column denote significant differences for storage period (P < 0.01).
L. acidophilus counts of the samples fortified with oat fiber were higher than the other samples. Addition of inulin and oat fiber improve the viability of L. acidophilus. As increase in fiber content, L. acidophilus counts were increased (p < 0.01). Previous studies have reported on the ability of probiotic and yoghurt starter cultures to break down and utilise β-glucan or inulin [
Addition of fiber improved the viability of Bifidobacterium BB-12. Inulin is a prebiotic can stimulate the metabolism of LABs, which was metabolized as an additional carbon and energy source [
The sensory ratings for the APDYs for colour and appearance, consistency, aroma and general acceptability properties are detailed in Figures 1 (a)-(c), respectively. Because of growing yeast and mold, we couldn’t make sensorial analysis at 21st day of storage. The results on organoleptic evaluation indicated that the colour and appearance and consistency scores of APDYs with fiber received higher scores than the control samples (p < 0.01). It could be related to decrease of whey speration in the samples with fiber. So their appearance was more homogenous than control samples. On the other hand, WHC increased in the samples with fiber and their firmness was improved. As the fiber rates increased the colour and appaerance and consistency scores of the samples increased, except sample G. We think that, addition of oat fiber at the rate of 2% caused too much water binding and concluded the sample G had an appearance and consistency like a yoghurt. Fernandez-Garcia et al. [
The samples with inulin had the highest and the samples with oat fibers had the lowest aroma scores. Addition of inulin improved the aroma of APDYs. Güven et al. [
increased during storage up to 7 day, and then decreased. At the beginning of storage, APDYs were more intensive flavour. This could be associated with development of acidity and decreases in acetaldehyde contents of the samples at the end of storage. Guven et al. [
General acceptability scores of APDYs was influenced negatively by addition of fiber except sample B, which has 0.5% inulin (p < 0.01). Sample B had the highest general acceptability scores. Similar results were found by Guven et al. [
Addition of fiber improved physical properties of APDY such as viscosity and WHC. pH was lower, but titratable acidiy, viscosity and WHC were higher in APDY samples supplemented with oat fiber than the other samples. During the storage, whilst the pH and WHC values declined gradually, the titratable acidity and viscosity content increased at the same time.
While the counts of S. thermophilus weren’t influenced by fiber, the counts of L. acidophilus and Bifidobacterium BB-12 were adversely affected by addition of fiber. The counts of L. acidophilus and Bifidobacterium BB-12 remained higher in APDYs supplemented with oat fiber than the other samples. Higher level of fiber supplementation led to an improvement in viability of L. acidophilus and Bifidobacterium BB-12. The viability of the probiotic bacteria was the highest in fortified with 2% oat fiber (sample G). During the storage, the viable counts of probiotics and S. thermophilus dropped in all samples. However the counts of L. acidophilus in all samples fortified with fiber were found to be above the threshold for therapeutic minimum (106 - 107 cfu g−1).
APDYs supplemented with inulin or oat fiber addition showed different sensory profile. Whilst addition of inulin improved sensory properties of APDYs, addition of oat fiber affected the aroma and general acceptability of APDYs negatively. The sample fortified with 0.5% inulin received the highest sensory scores from the panelists. During storage, total sensory scores of APDYs decreased.
Consequently, the use of inulin and oat fiber in APDY production could be recommended due to theirs prebiotic effects on probiotic bacteria and physical properties in APDYs and the maximum level of them could be 0.5%.
This study was financially supported by the Research Fund of Harran University (Project No: 12153) and extracted from Ms. thesis of İsmet Ferliarslan.
Güler-Akın, M.B., Ferliarslan, I. and Akın, M.S. (2016) Apricot Probiotic Drinking Yoghurt Supplied with Inulin and Oat Fiber. Advances in Microbiology, 6, 999-1009. http://dx.doi.org/10.4236/aim.2016.614094