Effects of Inulin and Oligofructose on the Rheological Characteristics

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					JFS M: Food Microbiology and Safety


Effects of Inulin and Oligofructose on the
Rheological Characteristics and Probiotic Culture
Survival in Low-Fat Probiotic Ice Cream
                      ¸
A.S. AKALIN AND D. ERISIR



    ABSTRACT: The effects of supplementation of oligofructose or inulin on the rheological characteristics and survival
    of Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 in low-fat ice cream stored at –18 ◦ C for 90
    d were studied. Addition of oligofructose or inulin to ice cream mix significantly increased apparent viscosity and
    overrun and developed the melting properties in ice cream during storage (P < 0.05). However, the highest increase
    in firmness, the lowest change in melting properties, and the longest 1st dripping time were obtained in probiotic
    ice cream containing inulin (P < 0.05). Some textural properties have also improved especially by the end of storage.
    Freezing process caused a significant decrease in the viability of Lactobacillus acidophilus La-5 and Bifidobacterium
    animalis Bb-12 (P < 0.05). Oligofructose significantly improved the viability of L. acidophilus La-5 and B. animalis
    Bb-12 in ice cream mix (P < 0.05). Although the viable numbers for both bacteria decreased throughout the storage,
    the minimum level of 106 CFU/g was maintained for B. animalis Bb-12 in only ice cream with oligofructose during
    storage.
       Keywords: Bifidobacterium animalis Bb-12, inulin, Lactobacillus acidophilus La-5, low-fat ice cream, oligofruc-




                                                                                                                                                   M: Food Microbiology
    tose




                                                                                                                                                         & Safety
                                   Introduction                           gestible food ingredients or prebiotics that selectively stimulate

D     airy products with incorporated probiotic bacteria are gaining
      popularity and the probiotics comprise approximately 65%
of the world functional food market (Agrawal 2005). The species
                                                                          growth and/or activity of probiotic bacteria have been used to in-
                                                                          crease the viability of probiotic bacteria in dairy products.
                                                                             On the other hand, by decreasing the fat content in frozen dairy
of bacteria most commonly used in dairy products for probiotic            product formulations, quality characteristics on body and texture
effect are Lactobacillus and Bifidobacterium (Saxelin and others          are affected (Ohmes and others 1998). In this respect, inulin and
2005). Standards requiring a minimum of 106 to 107 CFU/g of Lacto-        oligofructose, the best-known prebiotics and also fat replacers, pos-
bacillus acidophilus and/or bifidobacteria in fermented dairy prod-       sess several functional and nutritional properties that may be used
ucts have been introduced by several food organizations worldwide         to formulate innovative healthy foods for today’s consumer. Inulin
(Shah 2000). Therefore, it is important to ensure a high survival         is a term applied to a heterogeneous blend of fructose polymers
rate of these bacteria during the product shelf life to maintain con-     found widely distributed in nature as plant storage carbohydrates.
sumer confidence in probiotic products (Saxelin and others 1999).         It has a degree of polymerization (DP) of 2 to 60. Oligofructose
Ice cream seems suitable for delivering probiotics in human diet          is a subgroup of inulin, consisting of polymers within a DP ≤ 10.
because of its pleasant taste and attractive texture. However, in or-     Both inulin and oligofructose are widely used in functional foods
der to ensure that the product provides an adequate content of            throughout the world (Sangeetha and others 2005). Their structure
microorganisms, cells must survive in freezing and frozen storage.        is similar to corn sweeteners, principal carbohydrates used in ice
Freezing and thawing cause various degrees of damage to cells, in-        cream technology. Classed as fat replacers, inulin and oligofructose
cluding microorganism death, inhibition of its development, re-           influence the bulk and mouthfeel of the products. Also they are re-
duction, or interruption of metabolic activity (Davies and Obafemi        sistant to hydrolysis in both the stomach and small intestine, and
1985).                                                                    are classified as dietary fiber ingredients (Spiegel and others 1994;
   Recent studies have focused on the survival of probiotic bac-          Niness 1999).
teria in ice cream produced by different techniques such as cul-             The main uses of inulin and oligofructose are as texturizing
turing ice cream mix (Hekmat and McMahon 1992; Davidson and               agents, particularly in low-fat foods such as ice cream (Devereux
others 2000; Akın 2005; Favaro-Trindade and others 2006), nonfer-         and others 2003). Some studies have been reported on the function-
mented ice cream mix (Alamprese and others 2002; Haynes and               ality of inulin as a fat replacer in reduced fat ice cream (Schaller-
Playne 2002), or adding fermented milk to regular ice cream mix           Povolny and Smith 2001), in yog-ice cream (El-Nagar and oth-
(Christiansen and others 1996; Hagen and Narvhus 1999). Nondi-            ers 2002), and in fat-free starch-based dairy dessert (Tarrega and
                                                                          Costell 2006). However, no research has been reported on both
                                                                          functional and prebiotic effects of inulin and oligofructose as a food
MS 20070590 Submitted 7/27/2007, Accepted 2/7/2008. Authors are with Ege ingredient in low-fat probiotic ice cream. Thus, our objective was to
Univ., Faculty of Agriculture, Dept. of Dairy Technology, 35100, Bornova, compare the effects of inulin or oligofructose supplementation es-
Izmir, Turkey. Direct inquiries to author Akalın (E-mail: sakalin21@ pecially on the survival of probiotic starter culture and also the rhe-
yahoo.com).
                                                                          ological characteristics of low-fat probiotic ice cream. In addition,


C 2008 Institute of Food Technologists                                               Vol. 00, Nr. 0, 2008—JOURNAL OF FOOD SCIENCE           M1
doi: 10.1111/j.1750-3841.2008.00728.x
Further reproduction without permission is prohibited
                       Probiotic culture survival in ice cream . . .

                       we aimed to compare the rheological characteristics of regular low-        Overrun% = (weight of ice cream mix) – (weight of ice cream)
                       fat ice cream and probiotic ice cream.                                  × 100 × (weight of ice cream)−1 (Marshall and others 2003).
                                                                                               Apparent viscosities of the mixes were evaluated at 4 ◦ C after
                                           Materials and Methods                               24 h aging using a Brookfield RV Viscometer fitted with spindle no:5
                                                                                               at 20 rpm (Brookfield Engineering Laboratories, Stoughton, Mass.,
                       Ingredients and formulation for ice cream                               U.S.A.). Results were multiplied by RV viscometer factor (2000/N,
                          In the production of ice cream, cow’s milk was supplied from N = 20 rpm) and given as Pa.s. Firmness of ice cream was de-
                       Ege Univ., Agricultural Faculty, Menemen Research Farm (Izmir, termined by a Surberlin PNR 6 Penetrometer (Sommer Runge KG,
                       Turkey), pasteurized cream containing 35% milk fat, and non- Berlin, Germany). Penetrations of a conical spindle weighing 91.6
                       fat milk powder was supplied from Pınar Dairy Industry (Izmir, g (× 0.1 mm) to ice cream at –18 ◦ C were measured after 5 s. Be-
                       Turkey), and freeze-dried DVS starter cultures of Lactobacillus fore the measurements were taken, penetrations of the probe were
                       acidophilus La-5 and Bifidobacterium animalis subs. lactis Bb- conducted 4 cm from the side of each cup and were repeated twice.
                       12 were obtained from Chr. Hansen Lab. (Hoersholm, Denmark). Firmness was measured as the depth (in mm) of penetration of con-
                       Other ingredients for low-fat ice cream mix included sucrose and ical spindle into the ice cream and then a firmness index (g/mm)
                       corn syrup (G-40) (Cargill, ˙  Istanbul, Turkey), stabilizer–emulsifier was calculated by dividing the conical spindle weight (91.6 g) to the
                       mixture of Cremodan SE 30 (Danisco AS, Copenhagen, Denmark), depth of penetration (mm).
                       inulin (Fibruline XL, molecular weight: 3300, degree of polymer-           Melting behavior, expressed as 1st dripping time and melting
                       ization > 20), and oligofructose (Fibrulose F97, molecular weight: properties, was evaluated on ice cream samples stored at –18 ◦ C.
                       1000, degree of polymerization < 20) (Cosucra AS, Fontenoy, Bel- Melting properties were determined by carefully cutting the plastic
                       gium).                                                                  cups from the ice cream samples (preweighed as 25 g), placing the
                                                                                               ice cream onto 1-mm stainless steel screen over a cup, and weigh-
                       Manufacture of ice cream                                                ing the amount of ice cream drained into the cup over a 90-min
                          All ice creams were manufactured in the pilot plant of Dairy period at 20 ± 0.5 ◦ C. The time for the 1st drop of melted ice cream
                       Technology Dept., Faculty of Agriculture, Univ. of Ege. Mix formu- was also determined (Christiansen and others 1996).
M: Food Microbiology




                       lation was 4% (w/w) milk fat, 12% (w/w) milk solids nonfat, 13%
                       (w/w) sucrose, 0.65% (w/w) stabilizer/emulsifier, 4% (w/w) 42 Dex- Enumeration of probiotic bacteria
      & Safety




                       trose Equivalent corn syrup for regular ice cream (R) and probiotic        The count of viable probiotic bacteria was determined after ag-
                       ice cream (P), 4% (w/w) oligofructose for probiotic ice cream with ing of the mix for 24 h at 4 ◦ C, and then during the storage days of
                       oligofructose (PO), and 4% (w/w) inulin for probiotic ice cream the samples. One gram of probiotic ice cream sample was diluted
                       with inulin (PI).                                                       with 9 mL of sterile 0.1% (w/v) peptone water (Oxoid, Basingstoke,
                          Raw milk and cream were weighed into stainless steel milk Hampshire, U.K.) and mixed uniformly with a vortex mixer. Subse-
                       cans. All dry ingredients were mixed into the cold liquid ingre- quent serial dilutions were made and viable cell numbers enumer-
                       dients and complete incorporation was ensured. The mixes were ated using the pour plate technique. The counts of L. acidophilus
                       pasteurized at 68 ◦ C for 30 min. L. acidophilus La-5 and B. an- La-5 were enumerated on MRS agar (Merck, KGaA 64271, Darm-
                       imalis Bb-12 cultures were added to the mixes (0.3%) except for stadt, Germany) incubated aerobically at 37 ◦ C for 72 h. (Chris-
                       the regular sample (R), after cooling to 40 ◦ C, to achieve ap- tiansen and others 1996). B. animalis Bb-12 was enumerated ac-
                       proximately 108 CFU/g, mixed well, and fermented for approx- cording to the method of Lankaputhra and others (1996) using
                       imately 4 h at 40 ◦ C until the desired pH of 5.5 was reached. MRS-NNLP (nalidixic acid, 15 mg/L; neomycin sulphate, 100 mg/L;
                       Hekmat and McMahon (1992) reported that probiotic ice cream lithium chloride, 3 mg/L and paramomycin sulphate, 200 mg/L)
                       was preferred at pH 5.5 regarding overall acceptance by judges. agar. Filter sterilized NNLP was added to the autoclaved MRS base
                       The fermented mixes were then cooled in an ice bath to 5 ◦ C. just before pouring (Laroia and Martin 1991). The inoculated plates
                       All mixes were aged at 4 ◦ C for 24 h to ensure complete hydra- were incubated anaerobically at 37 ◦ C for 72 h using an oxygen
                       tion of all ingredients. Mixes were frozen in random order using free gas mixture of anaerobic jars (Merck). Plates containing 25 to
                                                                     g
                       a batch ice cream freezer (4 L capacity, U˘ ur, Nazilli, Turkey) for 250 colonies were enumerated and recorded as logarithm of colony
                       35 min. The ice cream was packaged into 150-mL plastic cups and forming units (CFU)/g of sample.
                       50-mL plastic cups (as 25 g for melting behavior), and then placed
                       in a hardening room at –18 ◦ C. The experiment was conducted in Statistical analysis
                       triplicate.                                                                Each experiment was independently replicated 3 times and all
                                                                                               analysis and enumerations were done in duplicate. Analysis of vari-
                       Compositional analyses                                                  ance for each set of data was conducted as a factorial arrangement
                          Total solids in the ice cream was determined by drying the sam- of treatments in a completely randomized block design to deter-
                       ples for 3.5 h at 100 ◦ C and fat contents were analyzed by means of mine whether significant differences existed. For the storage ex-
                       the Gerber method (AOAC 1990). The pH values of ice cream sam- periment, the set of data was conducted as a split plot in a ran-
                       ples were measured with a pH-meter combined with a glass elec- domized complete block design. Each replication was a block; milk
                       trode (Beckman Zeromatic SS-3, Beckman Instruments Inc., Fuller- treatment was the main unit treatment, and days of storage were
                       ton, Calif., U.S.A.). The titratable acidity in ice cream was deter- the subunit treatment. The model equation was Yi jk = µ + αi +
                       mined with N/10 natrium hydroxide in the presence of phenolph- βj(i) + δk + (αδ)ik + εi jk where µ, αi , β j(i) , δk , (αδ)ik , and εi jk repre-
                       thalein and expressed as percent lactic acid.                           sent overall mean effect, effect of milk treatment i, random ef-
                                                                                               fect of block j receiving milk treatment i, effect of storage time k,
                       Rheological analyses                                                    milk treatment by storage time interaction, and experimental error,
                          Overrun was measured with a comparison of the weight of ice respectively.
                       cream mixture before and after freezing. The formula for overrun is        Data were analyzed using the general linear model procedure of
                       as follows:                                                             the SPSS Win 9.0 program, and Duncan’s multiple range test was

                       M2    JOURNAL OF FOOD SCIENCE—Vol. 00, Nr. 0, 2008
Probiotic culture survival in ice cream . . .

Table 1 --- Results (mean ± SD, n = 3) of compositional and physical analyses on aged mix and ice cream.
                                     Mix
                                                                                                             Ice cream
Mix or                               Apparent viscosity
ice cream             pH                  (Pa.s)                 Total solids (%)          Fat (%)         Lactic acid (%)              pH            Overrun (%)
R                6.90 ± 0.00b            1.76 ± 0.0a               33.38 ± 0.04a          4.0 ± 0.0a        0.14 ± 0.01a          6.90 ± 0.01b         23.6 ± 4.0a
P                5.52 ± 0.05a            2.68 ± 0.03b              33.42 ± 0.02a          4.0 ± 0.1a        0.51 ± 0.01b          5.45 ± 0.06a         27.6 ± 1.9ab
PO               5.52 ± 0.05a            3.35 ± 0.01c              33.47 ± 0.11a          4.1 ± 0.1a        0.51 ± 0.01b          5.45 ± 0.17a         31.7 ± 1.3b
PI               5.47 ± 0.05a            3.91 ± 0.04d              33.49 ± 0.05a          4.1 ± 0.1a        0.52 ± 0.02b          5.35 ± 0.17a         50.6 ± 2.5c
R = regular mix or ice cream; P = probiotic mix or ice cream; PO = probiotic mix or ice cream with oligofructose; PI = probiotic mix or ice cream with inulin.
a,b,c
      Means with different letters in the same column are different (P < 0.05).

used to compare means when the effect was significant (P < 0.05).
In addition, statistical significance was given in terms of P values,
with differences at the 95% confidence interval (P < 0.05) being
considered statistically significant (SPSS 1997).


                      Results and Discussion

C     ompositional analyses of ice cream samples performed in the
      1st day of storage revealed that the targeted total solids and
fat levels were achieved (Table 1). As expected, pH and lactic acid
contents of regular and probiotic ice cream samples were signif-
icantly different (P < 0.05) while similar lactic acid contents and
pH values were determined in all probiotic ice creams (P > 0.05).
Regular ice cream sample had a mean pH value of 6.90 ± 0.01 and




                                                                                                                                                                      M: Food Microbiology
lactic acid percentage of 0.14 ± 0.01. There were significant differ-
ences in viscosities among all mixes, including probiotic ice cream




                                                                                                                                                                            & Safety
mixes, and viscosity increased by addition of oligofructose or in-
ulin to mix (P < 0.05) (Table 1). High apparent viscosity in the
                                                                                    Figure 1 --- Firmness index of ice cream during storage.
probiotic ice cream mix containing oligofructose or inulin can be                   R = regular ice cream; P = probiotic ice cream; PO =
explained by the interactions of the dietary fiber and liquid com-                  probiotic ice cream with oligofructose; PI = probiotic ice
ponents of the probiotic ice cream mix. Ice cream mixes contain-                    cream with inulin. The error bars represent the standard
                                                                                    deviation (n = 3). a,b,c Means with different letters in the
ing carbohydrate-based fat replacers exhibit a viscous behavior be-                 same storage day are different (P < 0.05).
cause of the capability for imbibing water, which would increase
the viscosity of the system (Schmidt and others 1993). The high-
est mean apparent viscosity of 3905 MPa.s (P < 0.05) was obtained                   cream. Addition of oligofructose or inulin increased the firmness
in the probiotic mixes containing inulin (Table 1). Similar to our                  in probiotic ice cream. (P < 0.05) (Figure 1). However, ice cream
findings, significantly higher apparent viscosity was obtained by                   supplemented with inulin was significantly firmer than other prod-
replacing 100% of the 42 DE corn syrup with inulin in a reduced                     ucts throughout the storage except the 1st day (P < 0.05). Due to
fat ice cream mix (Schaller-Povolny and Smith 2001). The authors                    its longer chain length, inulin is less soluble than oligofructose and
reported that higher apparent viscosity resulted from the higher                    has the ability to form inulin microcrystals when sheared in wa-
molecular weight of inulin and that a potential interaction between                 ter or milk. These crystals interact to form a creamy texture (Niness
the inulin and milk proteins could also be present in the system.                   1999). In addition, the ability of inulin to bind water molecules and
Higher molecular weight of inulin may be related to higher ap-                      form a particle gel network can improve the firmness of the prod-
parent viscosity of the ice cream mix with inulin in our study. In-                 uct (Franck 2002). Although it seems that firmness was improved in
ulin, being highly hygroscopic, would bind water and form a gel-                    all products by extension of storage, significant increases were not
like network that, in addition to other components (like corn syrup                 found (P > 0.05) except for the 60th day for the P sample, the 60th
or emulsifier–stabilizer mixture), would modify the rheology of the                 and 90th days for the PI sample, and the 90th day for the R and PO
mix. Similar results in relation to the effect of inulin on viscosity               samples.
were also reported by El-Nagar and others (2002) and Akın (2005)                        A slower change in melting properties was observed in probi-
for yog-ice cream and probiotic-fermented ice cream, respectively.                  otic ice creams when compared to control sample during storage
   The highest overrun value was also obtained in probiotic ice                     (P < 0.05) (Figure 2). Melting properties were also improved by
cream mix containing inulin (P < 0.05), indicating its responsibil-                 using oligofructose and inulin (P < 0.05). However, the most re-
ity for the increased air incorporation (Table 1). The overrun value                markable improvement in melting behavior was obtained in the
increased approximately 2 times when inulin was used in the man-                    product containing inulin (P < 0.05). The change in melting prop-
ufacture, in contrast to the findings of Akın (2005) for probiotic-                 erties decreased in all samples as storage time increased, and the
fermented ice creams. The addition of L. acidophilus La-5 and B.                    least change was obtained at the 60th and 90th days for the PI sam-
animalis Bb-12 and fermentation of the mix did not significantly af-                ple and the 90th day for the other products (P < 0.05). The 1st drip-
fect the overrun values (Table 1). Alamprese and others (2002) also                 ping time was also longer in probiotic ice creams supplemented
reported that Lactobacillus johnsonii La1 addition did not modify                   with oligofructose and inulin in comparison to the control sample
the overrun of ice cream.                                                           (Figure 3). However, inulin increased the 1st dripping time more
   In the current study, a direct correlation has been determined                   than oligofructose, which was found to be statistically signif-
between firmness and melting behavior. Our results indicated that                   icant for all storage days (P < 0.05). Additionally, the times
all probiotic ice creams were found to be firmer than regular ice                   prolonged in all samples as storage time increased while the

                                                                                                 Vol. 00, Nr. 0, 2008—JOURNAL OF FOOD SCIENCE                    M3
                       Probiotic culture survival in ice cream . . .

                       longest time was reported at the 60th and the 90th days for                 product. These observations are consistent with those of El-Nagar
                                ,
                       the R, P and PO samples and at the 90th day for the PI sam-                 and others (2002) who demonstrated that inulin supplementation
                       ple (P < 0.05). Typically, ice crystal size increases by about              reduced the melting rate and increased firmness in yog-ice cream.
                       30% to 40% during hardening of ice cream. In the storage, ice               Akın (2005) also reported that addition of inulin retarded the melt-
                       recrystallization occurs. The small crystals melt at the same time          ing time of probiotic-fermented ice cream. This study has verified
                       that large crystals grow. The changes in ice crystals due to the ther-      that the highest values for the apparent viscosity, overrun, and firm-
                       modynamic ripening process are enhanced by temperature fluctu-              ness and the most remarkable improvement in the meltdown char-
                       ations. Small crystals, with a slightly lower melting point, are more       acteristics were obtained in the mix or ice cream containing probi-
                       sensitive to temperature fluctuations than larger crystals (Marshall        otics and inulin (P < 0.05). Ice creams containing a high amount of
                       and others 2003). Inulin or oligofructose can control ice recrystal-        air (high overrun) tend to melt slowly. Air cells act as an insulator
                       lization like a stabilizer agent. Therefore, the 1st dripping time of all   (Marshall and others 2003).
                       samples can be improved by these interactions as storage time in-              The viable counts of probiotic bacteria were 7.74 ± 0.51, 8.44 ±
                       creased. Addition of inulin led to the lowest change in melting prop-       0.16, and 8.24 ± 0.04 log CFU/g for L. acidophilus La-5 and 7.58 ±
                       erties and longest 1st dripping time as well as the most increase           0.62, 8.49 ± 0.14, and 8.12±0.28 log CFU/g for B. animalis Bb-12 in
                       in firmness (P < 0.05), due probably to the high molecular weight                                  ,
                                                                                                   the ice cream mixes P PO, and PI, respectively. When compared to
                       and hygroscopic properties of inulin. The gelling properties of in-         the control sample, the viable counts for both L. acidophilus La-5
                       ulin improve the consistency of mix and retard the melting of the           and B. animalis Bb-12 significantly increased in the probiotic ice
                                                                                                   cream mix by addition of oligofructose (P < 0.05) due to the pos-
                                                                                                   sible prebiotic effects of oligofructose in the ice cream mix. Fruc-
                                                                                                   tooligosaccharides (FOS), especially oligofructose, are preferred by
                                                                                                   bifidobacteria as a source of carbon and energy. Growth rates of bi-
                                                                                                   fidobacteria cultivated on either oligofructose or inulin were eval-
                                                                                                   uated and better growth was obtained on oligofructose than inulin
                                                                                                   (Wang and Gibson 1993; Gibson and Wang 1994). In addition, in
M: Food Microbiology




                                                                                                   vitro fermentation of inulin revealed that molecules with a shorter
                                                                                                   chain length are fermented quicker than molecules with a longer
      & Safety




                                                                                                   chain length (Roberfroid and others 1998). Therefore, higher sur-
                                                                                                   vival of these probiotics in ice cream mix containing oligofructose
                                                                                                   can be sourced from shorter chain length or lower polymerization
                                                                                                   degree of oligofructose than inulin.
                                                                                                      The changes in the viable counts of L. acidophilus La-5 and B.
                                                                                                   animalis Bb-12 in ice cream samples during storage are presented
                                                                                                   in Table 2. During freezing of the mix, the counts of both viable bac-
                                                                                                   teria decreased by 1.5 to 2.0 log units, and their numbers in the
                                                                                                   frozen ice cream were found to be in the range of 5.96 to 6.60 log
                                                                                                   CFU/g for B. animalis Bb-12 and 5.98 to 6.21 log CFU/g for L. aci-
                       Figure 2 --- Melting properties of ice cream during storage.
                       R = regular ice cream; P = probiotic ice cream; PO =                        dophilus La-5. The decline in bacterial counts, as a result of freez-
                       probiotic ice cream with oligofructose; PI = probiotic ice                  ing, is most likely due to the freeze injury of cells leading eventually
                       cream with inulin. The error bars represent the standard                    the death of cells. Furthermore, the incorporation of oxygen into
                       deviation (n = 3). a,b,c,d Means with different letters in the              the mix may have resulted in an additional decrease in viable cell
                       same storage day are different (P < 0.05).
                                                                                                   counts as well as the mechanical stresses of the mixing and freez-
                                                                                                   ing process. The counts also significantly decreased (0.3 to 0.9 log
                                                                                                   CFU/g) throughout the storage (P < 0.05); however, freezing and
                                                                                                   mixing involved in converting the mix into ice cream had a greater
                                                                                                   effect on culture viability than storage in ice cream (P < 0.05). A
                                                                                                   similar finding was reported by Hagen and Narvhus (1999), Alam-
                                                                                                   prese and others (2002), and Haynes and Playne (2002), but not by
                                                                                                   Hekmat and McMahon (1992). During freezing and storage of ice
                                                                                                   cream, more or less reduction in the survival of probiotic bacte-
                                                                                                   ria was also reported (Hekmat and McMahon 1992; Christiansen
                                                                                                   and others 1996; Hagen and Narvhus 1999) for different microor-
                                                                                                   ganisms, different production technologies and formulations, and
                                                                                                   pH. On the other hand, Davidson and others (2000) and Alamprese
                                                                                                   and others (2002) reported that starter culture bacteria in low-fat
                                                                                                   ice cream did not change significantly during storage.
                                                                                                      In our study, B. animalis Bb-12 survived better than L. aci-
                                                                                                   dophilus La-5 in ice cream over 90 d (Table 2). However, the viable
                                                                                                   counts of B. animalis Bb-12 were higher than the recommended
                       Figure 3 --- First dripping times of ice cream during stor-                 minimum limit of 106 CFU/g only in ice cream containing
                       age. R = regular ice cream; P = probiotic ice cream; PO =                   oligofructose during storage. In addition, according to the general
                       probiotic ice cream with oligofructose; PI = probiotic ice                  mean value of storage, the ice cream products supplemented with
                       cream with inulin. The error bars represent the standard
                       deviation (n = 3). a,b,c Means with different letters in the                oligofructose contained higher viable counts of both probiotic bac-
                       same storage day are different (P < 0.05).                                  teria during the storage, possibly depending on the higher viable

                       M4    JOURNAL OF FOOD SCIENCE—Vol. 00, Nr. 0, 2008
Probiotic culture survival in ice cream . . .

Table 2 --- Viable counts of L. acidophilus La-5 and B. animalis Bb 12 (mean ± SD, n = 3) in ice cream during storage
(log CFU/g).
Ice cream                      1st day                         30th day                          60th day                        90th day                     Mean of storage
L. acidophilus La-5
   P                       5.98 ± 0.25aB                    5.53 ± 0.18aAB                    5.02 ± 0.48aA                    5.13 ± 0.28aA                     5.41 ± 0.48a
   PO                      6.21 ± 0.02aB                    5.77 ± 0.11bA                     5.79 ± 0.15bA                    5.70 ± 0.10bA                     5.87 ± 0.23b
   PI                      6.00 ± 0.09aB                    5.47 ± 0.14aA                     5.24 ± 0.10aA                    5.12 ± 0.46aA                     5.46 ± 0.41a
B. animalis Bb-12
   P                       6.27 ± 0.19bB                    5.97 ± 0.07bA                     5.93 ± 0.26bA                    5.94 ± 0.20abA                    6.03 ± 0.23b
   PO                      6.60 ± 0.20cB                    6.40 ± 0.17cAB                    6.45 ± 0.28cAB                   6.25 ± 0.11bA                     6.43 ± 0.22c
   PI                      5.96 ± 0.13aB                    5.36 ± 0.35aA                     5.51 ± 0.19aAB                   5.47 ± 0.55aAB                    5.57 ± 0.39a
P = probiotic ice cream; PO = probiotic ice cream with oligofructose; PI = probiotic ice cream with inulin.
a,b,c
      Means with different letters in the same column are different (P < 0.05).
A–C
     Means in the same row with different superscripts are significantly different (P < 0.05).


counts in mixes with oligofructose and more conducive structure of                            Devereux HM, Jones GP, McCormack L, Hunter WC. 2003. Consumer accept-
                                                                                                ability of low fat foods containing inulin and oligofructose. J Food Sci 68:
oligofructose to cell viability during storage (P < 0.05). The lowest                           1850–4.
viable counts of B. animalis Bb-12 obtained in the products with                              El-Nagar G, Clowes G, Tudorica CM, Kurı V, Brennan CS. 2002. Rheological qual-
inulin in the first and other days of storage (P < 0.05) can be caused                          ity and stability of yog-ice cream with added inulin. Int J Dairy Technol 55:
                                                                                                89–93.
by the higher overrun rate of these samples (Table 2). In general,                            Favaro-Trindade CS, Bernardi S, Bodini RB, de Carvalho Balieiro JC, de Almeida E.
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                                                                                                2:287–91.
                                  Conclusions                                                 Gibson GR, Wang X. 1994. Bifidogenic properties of different types of fructo-
                                                                                                oligosaccharides. Food Microbiol 11:491–8.

T    he best improvement in textural characteristics in terms of                              Hagen M, Narvhus JA. 1999. Production of ice cream containing probiotic bacteria.




                                                                                                                                                                                       M: Food Microbiology
     firmness, melting properties, and 1st dripping time was ob-                                Milchwissenschaft 54:265–8.
                                                                                              Haynes N, Playne MJ. 2002. Survival of probiotic cultures in low-fat ice-cream. Aust J
tained in probiotic ice cream with inulin during storage (P < 0.05).                            Dairy Technol 57:10–4.




                                                                                                                                                                                             & Safety
Viable starter culture counts reduced (0.3 to 0.9 log CFU/g) during                           Hekmat S, McMahon DJ. 1992. Survival of Lactobacillus acidophilus and Bifidobac-
                                                                                                terium bifidum in ice cream for use as a probiotic food. J Dairy Sci 75:1415–
the storage, but at the initial freezing and churning stage of convert-                         22.
ing mix into ice cream a greater decrease (1.5 to 2.0 log unit) in the                        Lankaputhra WEV, Shah NP, Britz ML. 1996. Evaluation of media for selective enu-
                                                                                                meration of Lactobacillus acidophilus and Bifidobacterium species. Food Aust
counts L. acidophilus La-5 and B. animalis Bb-12 (P < 0.05) was ob-                             48:113–8.
served. Survival of L. acidophilus La-5 and B. animalis Bb-12 in ice                          Laroia S, Martin JH. 1991. Methods for enumerating and propagating bifidobacteria.
                                                                                                Cultured DairyProd J 26:32–3.
cream was significantly enhanced with oligofructose (P < 0.05) and                            Marshall RT, Goff HD, Hartel RW. 2003. Ice cream. 6th ed. New York: Kluwer Aca-
the recommended minimum limit of 106 CFU/g was maintained                                       demic/Plenum Publishers.
                                                                                              Niness KR. 1999. Inulin and oligofructose: what are they? J Nutr 129:1402–6.
for B. animalis Bb-12 in only probiotic ice cream with oligofructose                          Ohmes RL, Marshall RT, Heymann H. 1998. Sensory and physical properties of ice
during storage.                                                                                 creams containing milk fat or fat replacers. J Dairy Sci 81:1222–8.
                                                                                              Roberfroid MB, Van Loo JAE, Gibson GR. 1998. The bifidogenic nature of chicory in-
                                                                                                ulin and its hydrolysis products. J Nutr 128:11–9.
                             Acknowledgments                                                  Sangeetha PT, Ramesh MN, Prapulla SG. 2005. Recent trends in the microbial produc-
The authors thank the Ege Univ., Faculty of Agriculture, and Re-                                tion, analysis and application of fructooligosaccharides. Trends Food Sci Technol
                                                                                                16:442–57.
search Fund Council for financial support to this study.                                      Saxelin M, Grenov B, Svensson U, Fonden R, Reniero R, Mattila-Sandholm T. 1999.
                                                                                                The technology of probiotics. Trends Food Sci Technol 10:387–92.
                                                                                              Saxelin M, Tynkkynen S, Mattila-Sandholm T, de Vos WM. 2005. Probiotic and other
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                                                                                                            Vol. 00, Nr. 0, 2008—JOURNAL OF FOOD SCIENCE                        M5

				
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