banana yogurt.pdf

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S. AKMAKI, B. EN, . URGU, M. GRSES, A. ERDOAN

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urk. J. Vet. Anim. Sci.2012; 36(3): 231-237 BAKdoi:10.3906/vet-1007-2

Probiotic properties, sensory qualities, and storage stability ofprobiotic banana yogurts

Songl AKMAKI1,*, Blent EN1, amer URGU2, Mustaa GRSES1, Ahmet ERDOAN2

1Department o Food Engineering, Agricultural Faculty, Atatrk University, Erzurum 25240 - URKEY

2Atatrk University, Vocational School o Erzurum, 25240 Erzurum - URKEY

Received: 01.07.2010

Abstract: Te quality properties o probiotic yogurt samples made with banana marmalade (BM), which can be aprobiotic product, were examined. Yogurt samples were produced rom cow milk inoculated with yogurt cultures andprobiotic cultures (Lactobacillus acidophilus, Bifdobacterium bifdum, and an equal mixture o the 2 strains), and then15% BM was added to each yogurt sample. Acidity, pH, bacteria counts, and sensory analysis o the yogurt samples wereinvestigated on days 1, 3, 5, 7, 10, and 14 during storage at 4 C. Lactobacillus delbrueckii subsp. bulgaricus, Streptococcusthermophilus, L. acidophilus, and B. bifdum counts generally decreased during the storage period. Te highest L.acidophilus count (8.145 log cu/g) was ound in L. acidophilus + B. bifdum-mixed yogurt on the third day. Te highestB. bifdum count (6.38 log cu/g) was recorded in B. bifdum-ermented yogurt on the frst day. Yeast and mold countso all yogurts increased during the storage period. Coliorm bacteria and Staphylococcus aureus were not ound in theyogurt samples. Te sensory quality and probiotic properties o all o the yogurts decreased aer 7days. Te highestsensory score was observed in the control and the yogurts produced by adding B. bifdum.

Key words: Probiotic yogurt, banana yogurt, banana, Lactobacillus acidophilus, Bifdobacterium bifdum

Probiyotikli muzlu yourtlarn probiyotik zellikleri, duyusal kalitesi ve depolamastabilitesi

zet: Bu aratrmada, probiyotik bir rn olabilmesi mmkn, muz marmelat ile retilen probiyotik yourtrneklerinin baz kalite zellikleri incelenmitir. nek stnden yourt kltrleri (Lactobacillus delbrueckii subsp.bulgaricus ve Streptococcus salivarius subsp. thermophilus) ve arkl probiyotik kltrler (Lactobacillus acidophilus,Bifdobacterium bifdum ve ikisinin eit karm) ile yourtlar retilmitir. Daha sonra yourtlara % 15 orannda muzmarmelad (MM) ilave edilmitir. Btn yourt rnekleri 4 Cde 14 gn depolanm ve depolamann 1, 3, 5, 7, 10 ve14. gnlerinde; asitlik, pH, mikroorganizma saylar ve duyusal analizler yaplmtr. Lactobacillus delbrueckii subsp.bulgaricus, Streptococcus salivarius subsp. thermophilus, L. acidophilus and B. bifdum saylar genel olarak azalmtr. EnyksekL. acidophilus (8,145 log kob/g) says L. acidophilus + B. bifdum karm ile retilen yourtlarda depolamann 3.gnnde ve en yksekB. bifdum says 6,38 log kob/g olarakB. bifdum ile retilen yourtta ilk gnde tespit edilmitir.Probiyotik kltrl muzlu yourtlar, 7. gnden sonra probiyotik zelliklerini kaybetmitir. Maya ve k saylar isebtn yourt rneklerinde depolama sresince artmtr. Hi bir yourt rneinde koliorm ve Staphylococcus aureustespit edilememitir. m yourt rneklerinin duyusal kalitesi 7. gnden sonra azalmtr. En yksek duyusal deerlerikontrol ve B. bifdum ilaveli yourtlar almtr.

Anahtar szckler: Probiyotik yourt, muzlu yourt, muz, Lactobacillus acidophilus, Bifdobacterium bifdum

Research Article

* E-mail: [email protected]


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Probiotic properties, sensory qualities, and storage stability o probiotic banana yogurts

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Introduction

Most strains o classic yogurt cultures cannot survivein the intestinal tract, and thus their prophylactic

use is limited. Microbiological investigations oyogurt report poor microbial survival due to thelow pH o the yogurt media, and this has led to theinvestigation o probiotic ormulations in dierentyogurt preparations (1). Probiotic yogurt is a classicexample o a unctional ood (2). Special types oyogurts are oen manuactured or dietetic and/ortherapeutic purposes and are known as bioyogurts.Yogurt contains live probiotic microorganisms, whichreportedly have benefcial health eects (3-5). Teincorporation oL. acidophilus and Bifdobacterium

species into yogurt starter culture may contravenesome existing handicaps o yogurt and lead to greatertherapeutic value in the resultant milk product (6).Te presence o viable lactic acid bacteria in a highconcentration in ermented milks, such as yogurt,has been correlated with several consumer healthbenefts (7,8).

Tere are several studies on yogurt spoilage (9,10)and the benefcial eects o lactic acid bacteria (11).Due to the presence o both low pH levels and lactic

acid bacteria, yogurt is a selective environment orthe growth o certain contaminating microorgan-isms; the introduction o ruit and sugar into yogurtamplifes the risk o spoilage by providing additionalermentable substrates (10). Tis makes yogurt a lessselective growth environment, and yogurt productsare likely to support the growth o a number oyeastspecies (12).

Fruit mixes improve the nutritional value andthe taste o yogurt, and ruit enhancement plays a

considerable role in yogurt consumption and sales.Varieties o ruit yogurts have been ormulated asprobiotic ruit yogurts, and the survival o probioticbacteria in yogurts has been investigated duringcold storage (13). Banana (Musa sp.) ruit containsconsiderable amounts o amylose, starch, dietaryfber, protein, vitamins, and minerals (14,15). Teproduction o ruit juices, concentrates, and pureesmay be a good use or excess and rejected stocks.Common processed banana products include bananapuree, banana powder or our, banana chips, canned

banana slices, banana jam, banana vinegar, andbanana wine (16,17). Among these, banana puree is

the most important product and is used in the bakery,ice cream, and baby ood industries (14). In addition,banana puree is used in ruit-avored yogurtproduction. Te unctionality o yogurt increaseswith the addition o probiotic microorganisms. Temost commonly used probiotic microorganisms indairy ood are L. acidophilus and B. bifdum, whichare chosen or their nutritive, therapeutic, andsymbiotic characteristics (18,19).

Te aim o this study was to investigate the pos-sibility o using probiotic bacteria (L. acidophilus, B.bifdum, or an equal mixture o these 2 strains) inthe production o banana marmalade (BM)-mixedyogurt products and to contribute to the manuac-turing o new unctional oods. Tis study will alsohelp increase the ruit-avored probiotic yogurt con-sumption o children and improve consumer health.

Materials and methods

Bacterial cultures, raw cow milk, and banana

L. acidophilus DSMZ 20079 and B. bifdum DSMZ20456 strains were imported rom the German

Collection o Microorganisms and Cell Cultures(DSMZ, Braunschweig, Germany). Yogurt cultures(L. delbrueckii subsp. bulgaricus and S. thermophilus)were provided by the Atatrk University Departmento Food Engineering (Erzurum, urkey). Eachculture was maintained in 12% sterile reconstitutedskim milk supplemented with 2% glucose and 1%yeast extract. All cultures were stored at 4 C, andworking cultures were propagated successively 3times prior to use (20).

Te cow milk used in this study was supplied bythe Atatrk University Agricultural Facultys FoodEngineering Department Pilot Dairy Plant (Erzurum,urkey). Banana was obtained rom a supermarket inErzurum.

Manuacture o yogurts

Yogurt samples were manuactured rom cow milk.Te dry matter o homogenized milk was increased to17.32% by evaporation under vacuum pressure (450mmHg) at 60 C. Evaporated milk was heated to 90

C or 5 min and cooled to 37 1 C or incubation.Te yogurt culture was added to the milk, and the


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milk was divided into 4 equal parts o 10 kg each. Tefrst part was le unaltered or the control group. L.acidophilus was added to the second part (3%, w/w),B. bifdum was added to the third part (3%, w/w),and L. acidophilus + B. bifdum culture was addedto ourth part (1:1, 3%, w/w). L. acidophilus and B.bifdum were added to the milk aer the preliminaryincubation at 37 1 C or 18 h. All o the culturedmilk groups were then le or a fnal ermentation at43 1 C. Te ermentations were terminated whenthe acidity level reached a pH value o 4.7. Followingincubation, yogurt samples were cooled to 5 C andheld at this temperature or 1 day.

A mixture o banana puree and an equal amount

o sucrose was heated at 85 C or 20 min and thencooled to 5 C. Te resulting BM mixture was addedto the yogurts at a ratio o 15 g BM to 100 g yogurt(dry matter was 23.29% aer the addition o BM).Te fnal product was mixed and then placed in 150-mL sterile glass jars and stored at 4 C. All yogurtsamples were subjected to microbiological, sensory,acidity, and pH analyses on days 1, 3, 5, 7, 10, and 14.

Microbiological analysis

Te samples studied (25 g) were weighed aseptically

into sterile Stomacher bags diluted with 225 mL obuered peptone water and homogenized using aStomacher (HG 400, Mayo International, Milan, It-aly). Tus, the frst dilution o 101

was obtained; the

other dilutions were prepared rom this frst 101di-lution

to dilutions o 107. Plate count agar, violet red

bile agar, potato dextrose agar, and Baird-Parker me-dium were used or the enumeration o total aerobicmesophilic bacteria (AMB), coliorm bacteria, yeastand mold, and S. aureus, as described by Harrigan

(21). De Man, Rogosa, and Sharpe (MRS agar, Merck,Darmstadt, Germany), MRS LP, MRS bile, and M17agars were used or the enumeration o lactic acidbacteria, B. bifdum, L. acidophilus, and S. thermophi-lus, respectively, as described by Vinderola and Re-inheimer (22). Te agar plates were incubated or 2days at 30-32 C (AMB), 1 day at 35-37 C (coliormbacteria), 5-7 days at room temperature (yeast andmold), 1 day at 35-37 C (S. aureus), 3 days at 35-37C in an anaerobic jar (lactic acid bacteria and bifdo-bacteria), or 2 days at 35-37 C (S. thermophilus). All

media were provided by Merck except or the Baird-Parker medium (Fluka, Steinheim, Germany).

Physical and chemical analysis

Te pH value o the yogurt samples was measuredat 17-20 C with a digital pH meter (pH 211,

Hanna Instruments, Amorim, Portugal). Tetitratable acidity (lactic acid, %) was determinedaer mixing yogurt samples with 10 mL odistilledwater and titrating with 0.1 N NaOH using 0.5%phenolphthalein indicator. Yogurt and milk sampleswere then analyzed or total dry matter by thegravimetric method (23).

Confrmation o identity o L. acidophilus and B.bifdum

Identifcation o L. acidophilus and B. bifdum

colonies was perormed by microscopic analysisand with an API identifcation test kit. Te API 50CH system (re.: 50300; bioMerieux, Marcy lEtoile,France) was used to identiyL. acidophilus,andAPI20 A was used or B. bifdum. Te API identifcationsystems were used according to the manuacturersdirections. est identifcation rates were 94.6% or L.acidophilus and 97.2% or B. bifdum.

Sensory analysis

Stored yogurt samples were assessed by 6 panelistsusing a sensory rating scale o 1 (poor) to 9 (excellent)or some sensory parameters (odor, texture, syneresis,avor, acidity, sweetness, and overall acceptability),as described by Bodyelt et al. (24). All yogurtsamples were presented to the panelists in the glassjars (150 mL) and at 4-6 C. Te panel o assessorswas an external group o nonsmokers who were veryamiliar with ermented dairy products and whowere evaluated or sensory acuity and consistency.

Water and bread wereprovided to panel members tocleanse their palates between samples.

Statistical analysis

A actorial arrangement was set up to study theinuence o probiotic treatments (4) and storagetime (6) using 2 replicates. A total o 48 samples wereinvestigated or microbiological, sensory, acidity, andpH analyses on days 1, 3, 5, 7, 10, and 14. All analyseswere conducted twice. Data obtained rom analysiso the samples were evaluated by variance analysis,

and the dierences among means were detected byDuncans multiple range tests (SPSS 1999).


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Probiotic properties, sensory qualities, and storage stability o probiotic banana yogurts

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Results

Te initial titratable acidity values o the controlsamples and yogurts with L. acidophilus,B. bifdum,

and L. acidophilus + B. bifdum were 0.85%, 0.83%,0.74%, and 0.85%, respectively; these values hadincreased to 1.04%, 1.00%, 1.10%, and 0.94% at theend o 14 days.

Changes in counts o AMB, yeast and mold, S.thermophilus,and L. delbrueckii subsp. bulgaricus inyogurt samples are shown in Figures 1-4. Coliormbacteria and S. aureus were below the detection limitor all yogurt samples (


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High sweetness scores, acidity, and generalacceptance were obtained by the control yogurts;BM yogurt with L. acidophilus received a low scoreo general acceptance. Statistically signifcantdierences (P < 0.01) were ound among the control

and the other yogurts or the score o sweetness andacidity; however, statistically signifcant dierences(P < 0.05) were not ound in BM yogurts with L.acidophilus, B. bifdum, or the L. acidophilus andB. bifdum combination. A high score o generalacceptance was ound in the control yogurts andyogurts with B. bifdum. High sweetness scores,acidity, and general acceptance were obtained on thefrst day o storage and decreased up until day 14. Nosignifcant dierences (P < 0.05) were ound amongthe control and other yogurts between days 1 and7. However, statistically signifcant dierences (P 6 log cu/g to achieve optimal potential therapeutic

eects (9). Vinderola et al. (28) also stated thatprobiotic microora counts decrease during storage.Te rate o this loss in cell viability depended on theyogurt type and the use o lactic starter. Con et al. (30)stated that dierent ruit-avored yogurts should notbe stored longer than 7 days. In this research, countsoL. acidophilus and B. bifdum decreased graduallywith storage time; the yogurt samples had probioticvalues o 106 log cu/gup until day 7, and then sensoryqualities decreased.

Sensory analysis results

A positive correlation was ound between generalacceptability and S. thermophilus count, and anegative correlation was observed between generalacceptability and yeast and mold count (P < 0.01).Tesensory quality o all yogurts decreased aer 7 days.Te sensory quality o control yogurts was higher thanthat o the yogurts with probiotic cultures. Yogurtswith B. bifdum were preerred to probiotic yogurtsamples by the panelists. At the beginning o storage,all yogurts were superior, mainly because o theirmore intense avor and better consistency. However,aer 7 days, the acidity o the yogurts increased, andthe sensory scores o all samples began to decrease.

Te overall acceptability scores o samples increasedduring storage or up to 7 days (scores greater than 7)and then decreased (highest score: 9). Tis could beattributed to the development o acidity. Te highestsensory scores occurred in the control yogurt and theyogurts produced by adding B. bifdum.

Te results suggest that the probiotic culturestested in this study have the potential to contributeto ruit-avored yogurt production technology andproduct taste. Yogurt samples retained probiotic

values o 106

log cu/g up until day 7 o storage at 4 C;aer 7 days, sensory qualities also began to decrease.Te highest sensory scores were recorded in thecontrol and in yogurts produced with B. bifdum.

Acknowledgment

Te authors would like to thank the Atatrk UniversityResearch Fund or supporting this research.


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