ORIGINAL PAPER

Inactivation of Spoiling Yeasts of Fruit Juicesby Pulsed Ultrasound

Antonio Bevilacqua & Barbara Speranza &

Daniela Campaniello & Milena Sinigaglia &

Maria Rosaria Corbo

Received: 18 June 2013 /Accepted: 19 August 2013# Springer Science+Business Media New York 2013

Abstract This paper reports on the use of ultrasound (US) asa suitable strategy to control the growth of spoiling yeasts infruit juices. In a first phase, US technique was tested towardsSaccharomyces cerevisiae inoculated in different juices(strawberry, orange, apple, pineapple and red-fruits): the treat-ment was performed by modulating the level of the power(20–60 %), the duration of the treatment (2–6 min) and thepulse (2–6 s), according to a fractional design. Then, the besttreatment was applied against some other spoiling yeasts(Pichia membranifaciens , Wickerhamomyces anomalus ,Zygosaccharomyces bailii , Zygosaccharomyces rouxii ,Candida norvegica). Finally, a challenge test for a commer-cial beverage (red-fruit juice), inoculated with Z. bailii andcontaining a citrus extract, was conducted evaluating theeffect of US on the sensory scores of the beverage. The resultsshowed that the effect of US was mainly influenced by thepower and the duration of the treatment; on the other hand, theeffect of pulse was less significant and slight. The highestreduction of S. cerevisiae was found in the following combi-nation of the design: power 60 %/time 4 min/pulse 2 s andpower 60%/time 6min/pulse 6 s; this result was confirmed forthe other spoiling yeasts. US and citrus extract could becombined to prolong the shelf life of the red-fruit juice andcontrol the growth of Z. bailii . The two hurdles exerted adifferent role and acted in different times: US reduced theinitial contamination, whilst citrus extract controlled the yeastwithin the storage.

Keywords Fruit juices . Yeasts . Ultrasound . Combinedapproach

Introduction

Spoilage of fruit and vegetable juices is generally attributed to thepresence and proliferation of a natural acid-tolerant microflora(yeasts, molds and acid-tolerant bacteria). Zygosaccharomycesrouxii , Zygosaccharomyces bailii , Pichia membranifaciens ,Saccharomyces spp., Candida spp. and Rhodotorula spp. arethe yeasts generally isolated from spoiled juices (Jay et al. 2005);in particular, Saccharomyces andPichia are responsible for juicespoilage, as a consequence of ethanol production from sugars orfilm formation onto the surface (Bevilacqua et al. 2010; Jay et al.2005). Moreover, anaerobic and aerobic bacilli (Clostridiumbutyricum and Clostridium pasteurianum, Bacillus coagulansand Bacillus megaterium ; Alicyclobacillus spp.), lactobacilli,and heat-resistant species of mycelial fungi, are also involvedin the spoilage of fruit juices (Jay et al. 2005).

Even if heat remains the technique most extensively used forinactivation of microorganisms in foods, there is recently agrowing interest in the development of alternative approachesin response to the desires of consumers for products which areless organoleptically and nutritionally damaged during process-ing and less reliant on additives than in the past (Corbo et al.2009). The new approaches mostly involve non-thermal foodpreservation technologies that offer full or partial (reducingtreatment time and/or temperatures) alternatives to heat. Someexamples of non-conventional methods are the use of electric ormagnetic fields, microwave radiation, ionizing radiation, high-intensity light pulses and high-hydrostatic pressure (Corbo et al.2009; Di Benedetto et al. 2010). Ultrasound (US) is one of theseemerging technologies able to minimize processing, maximizequality and ensure the safety of food products while maintaininga high level of proprieties and sensory qualities. It can be definedas a pressure wave with a frequency of 20 kHz or more;generally, it uses frequencies from 20 kHz to 10 MHz, and forindustrial purposes, it has two main requirements: a liquidmedium, even if the liquid element forms only 5% of the overall

A. Bevilacqua : B. Speranza :D. Campaniello :M. Sinigaglia :M. R. Corbo (*)Department of the Science of Agriculture, Food and Environment(SAFE), University of Foggia, Via Napoli 25, 71122 Foggia, Italye-mail: mariarosaria.corbo@unifg.it

Food Bioprocess TechnolDOI 10.1007/s11947-013-1178-5

medium, and a source of high energy vibrations (the ultrasound)(Patist and Bates 2008). US can be divided into two groups:destructive (high-power US) and non-destructive US (low-in-tensity and diagnostic US); the effects of destructive US relyupon the acoustic cavitation (Cárcel et al. 2012; Leighton 1998;Soria and Villamiel 2010). There are some factors able toinfluence the antimicrobial effect of this technique: the ampli-tude of waves, the temperature and the duration of the treatment,and the volume and composition of the food. Another importantfactor is the shape and the dimension of microorganisms: largercells are more sensitive than the small ones, probably due totheir larger surface areas (Bevilacqua et al. 2012b). Gram-positive bacteria are more resistant than Gram-negative ones(Drakopoulou et al. 2009); cocci are more resistant than rods(Chemat et al. 2011). Finally, spores are resistant and can beinactivated only through the use of combined treatments, likeultrasound+heat (thermo-sonication) or ultrasound+pressure(mano-sonication) (Butz and Tauscher 2002; Chemat et al.2011).

US approach was proposed for the stabilization of fruit juicesand the inhibition of naturally occurring microflora (Adekunteet al. 2010a, b; Valero et al. 2007), Pichia fermentans ,Alicyclobacillus acidoterrestris , Alicyclobacillus acidiphilus(Wang et al. 2010; Gabriel 2012), Listeria innocua (Gastélumet al. 2011), Salmonella sp. (Mukhopadhyay and Ramaswamy2012), Cronobacter sakazakii (in infant formula) (Adekunteet al. 2010c), Saccharomyces cerevisiae (Bermúdez-Aguirreand Barbosa-Cánovas 2012) and Fusarium oxysporum(Bevilacqua et al. 2013a) or to inactivate pectin methylesteraseand polygalacturonase (Shiferaw Terefe et al. 2009). Despitethese reports, to the best of our knowledge, few data are avail-able on yeasts; thus, this research was aimed to study theapplication of US towards yeasts in fruit juices, as a singlehurdle or combined with a natural extract (citrus extract).Namely, the specific aims of the research were: (1) the optimi-zation of US towards S. cerevisiae in different juices (strawber-ry, orange, apple, pineapple and red-fruits); (2) the validation ofthe treatment towards other spoiling yeasts (Candida norvegica ,Wickerhamomyces anomalus ,P. membranifaciens , Z. bailii andZ. rouxii); (3) a challenge test in a commercial beverage (red-fruit juice) using Z. bailii as the microbial target and by com-bining US with citrus extract.

Materials and Methods

Microorganisms

The following yeasts were used throughout this research:

1. C. norvegica , a wild strain belonging to the culture collec-tion of the laboratory of Applied Microbiology, Universityof Foggia.

2. S. cerevisiae EC 1118, a commercial strain purchasedfrom Lallemand (Montreal, Canada).

3. Some strains from Deutsche Sammlung von Mikroorganis-mem und Zellkulturen's collection-DSMZ (Braunschweig,Germany):W. anomalus DSMZ70130;P.membranifaciensDSMZ 70169; Z. bailii DSMZ 70492; Z. rouxii DSMZ2532.

The strains were maintained on Yeast Peptone Glucoseagar (YPG: bacteriological peptone, 20 g/l; yeast extract,10 g/l; glucose, 20 g/l; agar, 12 g/l. All the ingredients werefrom Oxoid, Milan, Italy) at 4 °C and monthly transferred.Before each assay, the strains were grown in YPG broth,incubated at 25 °C for 48–72 h.

Citrus Extract

A commercial citrus extract, named biocitro (citrus extract)(Quinabra, Probena, Spain), was used in this research. Biocitrowas produced from Citrus paradisi (grapefruit), Citrus sinensis(sweet orange) and Citrus reticulata (tangerine); the composi-tionwas the following: ascorbic acid and ascorbates (vitamin C),linked with citrus bioflavonoids, 4.0–7.20 %; hydrated glycerinlinked with other traces of citrus polyphenols, carbohydrates,bio-flavoproteins, pectin, citrus sugars, citric acid, 30.80–36.60 %; water, 6.00–11.00 %. Stock solutions of the extract(5,000 and 10,000 ppm) were prepared in sterile distilled water.

Effect of Ultrasound on S. cerevisiae

Aliquots (20 ml) of apple, pineapple, orange, strawberry andred-fruit juices (a commercial beverage containing 20 % of redorange juice, 20 % of blueberry juice, 10 % of pomegranatejuice) were inoculated to 5 log cfu/ml with S. cerevisiae ; there-after, the samples were treated by a VC Vibra Cell Ultrasound(US) equipment, model VC 130 (Sonics and Materials Inc.,Newtown, CT, USA); the equipment works at 20 kHz(frequency)–130 W (acoustic energy). The probe (5×60 mm;diameter×the active component of horn) was put 2–3 cm belowthe surface of the juices; US treatments differed for the duration(from 2 to 6 min), the pulse (from 2 to 6 s) and the percentage ofacoustic energy used for sample processing (from 20 to 60 %).Power level, the duration of the treatment and pulse werecombined through a fractional design 3k−p (Table 1).

Supposing a mean transducer efficiency of 70 % (η ), theacoustic power or energy supplied (WA) into the media was:

WA ¼ η� Pe

with P e being the power input (130 W). Thus, the real energysupplied by transducer varied from 18.2 W (20 % of totalpower applied) to 54.6 W (60 % of acoustic energy).

Before each treatment, the ultrasonic probe was washedwith sterile distilled water; immediately after the processing

Food Bioprocess Technol

the temperature increased to 40 °C and the samples werecooled in ice. The number of surviving yeasts was evaluatedthrough the spread plate method on YPG agar (25 °C for2 days). Aliquots of juices, inoculated with S. cerevisiae butnot treated through ultrasound, were used as controls. Theexperiments were performed twice over two different batches;moreover, the whole design was repeated two times.

Data were modelled as decrease of yeast count referred tothe control (ΔN , log cfu/ml) and then used as input values tobuild a polynomial equation, reading as follows:

y ¼X

i¼1

3

βixi þX

i≤

3 X

j

3

βijxix j þX

i≤

3 X

j≤

3 X

k

3

βijkxix jxk

þX

i¼1

3

βixi2 þ ε ð1Þ

where β i, β ij, and β ijk are the coefficients of the individual(x i), quadratic (x i

2) and interactive effects (x ix j–x ix jxk) of theindependent variables (energy, pulse and duration of ultra-sound treatment); ε is the standard error of the model; y isthe dependent variable (i.e. the decrease of S. cerevisiae ,ΔN ).

The significance of each term of the equation was evaluat-ed through the Pareto chart of standardized effects, whilst thequantitative effects of each factor of the design were assessedthrough 3D plots. Statistical analysis was performed throughthe software Statistica for Windows (Statsoft, Tulsa, OK).

Optimization on Some Other Spoiling Yeasts

In the second step of the research, apple, orange, strawberry andred-fruit juices were inoculated withW. anomalus , P. membrani-faciens , Z. bailii , Z. rouxii , and C. norvegica (5 log cfu/ml) andprocessed through US equipment, using only two combinations:C (power, 60 %; time, 4 min; pulse, 2 s) and L (power, 60 %;

time, 6 min; pulse 6 s); each strain was tested individually. Thenumber of surviving yeasts was assessed through the spread platecount (YPG agar incubated at 25 °C for 2–4 days); aliquots ofjuices, inoculated with yeast but not processed, were used ascontrols. The experiments were performed in duplicate.

Combined Effects of Ultrasound and Biocitro Towards Z.bailii

Z. bailii was inoculated to 5 log cfu/ml in the commercial red-fruit juice, added with biocitro (50 or 100 ppm); thereafter, thejuice was processed through US equipment. The duration andthe power of the treatment, along with the amount of biocitro,varied according to a 3k−p fractional design (Table 2). Thepulse was set to 2 s.

Then, the juice was stored at 25 °C for 13 days and the levelof the yeast was assessed through the spread plate method(YPG agar, incubated at 25 °C for 4 days) (immediately afterthe treatment and after 2, 6, 9 and 13 days of storage). Cellcounts of Z. bailii were used as input values to build apolynomial equation (a model for each time of sampling), asreported above. The experiments were performed twice overtwo different batches.

Sensory Analysis

A sensory analysis was conducted to evaluate the acceptabilityof red-fruit juice processed through ultrasound and added withbiocitro, using the approach proposed by Luckow andDelahunty (2004a, b). In particular, 20 untrained assessors (stu-dents and researchers from University of Foggia; 23–50 yearsold; 13 women and 7 men), analyzed 4 samples, identified by aletter, as follows:

A Control;B Juice treated by ultrasound (power, 60 %; time, 6 min);C Juice with biocitro (100 ppm);D Juice with biocitro and treated with ultrasound.

They were requested to give a score for colour, odour andoverall acceptability from 0 (bad) to 5 (very good), being 2 thebreak point for the acceptability. As a final step of the sensorytest, panelists were requested to answer this question: “Wouldyou buy this product?” Consumers could choose three possi-ble answers: “definitely would buy”, “maybe buy/maybe notbuy”, “definitely would not buy” (Bevilacqua et al. 2012b).

Results and Discussion

Model Building with S. cerevisiae

The main goal of the first step of the research was the evalu-ation of the possibility of using US (ultrasound) as a

Table 1 Combinations of power, duration of US treatment and pulseused to treat juices inoculated with S. cerevisiae

Combinations of thedesign

Power(%)

Duration of the treatment(min)

Pulse(s)

A (control) – – –

B 20 6 4

C 60 4 2

D 20 4 6

E 20 2 2

F 40 2 6

G 40 6 2

H 60 2 4

I 40 4 4

L 60 6 6

Food Bioprocess Technol

processing treatment to reduce the level of spoiling yeasts infruit juices; thus, S. cerevisiae was used as the target andinoculated onto different beverages (apple, orange, pineappleand strawberry), as well as in a commercial and popular drink,prepared as a mix of different fruits (red-fruit juice).

After US treatment, data were modelled as decrease of cellcount referred to the control; the results are shown in theFig. 1. The highest reduction of yeast (2–2.5 log cfu/ml) wasachieved in the combination L (power, 60 %; pulse, 6 s;duration of the treatment, 6 min) for all the juices and also inthe combination C (power, 60 %; time, 4 min; pulse, 2 s) forapple juice; in the other runs of the design the effect of USwaslower.

S. cerevisiae experienced the same resistance/sensitivity toUS in orange, strawberry and red-fruit juices, whilst somedifferences were recovered in apple and pineapple juices. Inapple juice, a higher effect of US in the combination C (power,60 %; pulse, 2 s; time, 4 min) was found, as S. cerevisiae wasreduced by 2.16±0.59 log cfu/ml, whereas in the pineapplejuice the effect was always lower (0.2–1 log cfu/ml).

Data from strawberry, orange and red-fruit juices were usedto build a simple polynomial model, able to describe theeffects of power, time and pulse on the anti-yeast effectexerted by US towards S. cerevisiae . The model was signif-icant, with an adjusted regression coefficient of 0.828 and amean square residual of 0.075; Fig. 2 shows the Pareto chartfor the statistical weight of the factors of the design (power,time, pulse). The most significant terms were the power andthe time, followed by the interaction power/time and by theindividual term of pulse.

Figure 3 shows the 3D plots for the interaction power/time;pulse was set to different values: 2 s (A), 4 s (B) and 6 s (C).As expected, anti-yeast effect of US increased following theincrease of power and time; the highest reduction of S.

cerevisiae was found for the combination power 60 %/time6 min. Another interesting trait was the slight effect of pulse,as the inactivation of S. cerevisiae varied from 1.5 to 2.2. logcfu/ml depending on the pulse (from 2 to 6 s, respectively).

Data from strawberry, orange and red-fruit juices con-firmed that anti-yeast activity relies upon the total acousticenergy, i.e. by power and time, as the acoustic energy is afunction of these factors (Bevilacqua et al. 2013a; Jomdechaand Prateepasen 2010; Valero et al. 2007). A deviation fromthis general trend was found in apple and pineapple juices; inpineapple juice the effect of US was probably lowered by thepronounced cavitation induced by the treatment, whilst forapple juice there are no literature reports able to explain thistrend.

Effects of US Towards Some other Spoiling Yeasts

The aim of the second step of the research was the evaluationof the effects of US towards some other yeasts (Z. bailii , Z.rouxii , P. membranifaciens , W. anomalus , C. norvegica ),representative of the spoiling microflora of juices.

Two combinations (C and L) were chosen for this purpose.In the combination C (Fig. 4a) the effect of US relied uponboth the kind of juice and the yeast: P. membranifaciens andZ. bailii were reduced by 1.2–2 log cfu/ml, without anysignificant difference amongst the different juices. On theother hand, Z. rouxii was reduced by 1.7 log cfu/ml in orangejuice, whilst the effect was not significant in apple, red-fruitand strawberry juices.

W. anomalus was less affected by the treatment and wasreduced by 1.0±0.58 log cfu/ml only in apple juice; finally,C.norvegica was reduced by 1.5–2 log cfu/ml in apple andorange juices.

The results from the combination C highlighted that W.anomalus was the most resistant yeast, followed by S.cerevisiae and Z. rouxii . However, these two yeasts weresignificantly affected by the kind of juice, as S. cerevisiaewas more sensitive in apple juice and Z. rouxii in orange juice.Finally, P. membranifaciens and Z. bailii were the most sensi-tive yeasts and were less affected by the kind of juice. Thisdifferent trend was not related to cell shape, as yeasts with thesame shape (Pichia anomala vs. P. membranifaciens and Z.bailii vs. Z. rouxii) showed different levels of reduction.

The effect of the kind of microorganismwas not significantwhen a stronger treatment was used (combination L) (Fig. 4b)as the yeasts showed similar trend being reduced by 1.6–2.6log cfu/ml.

Step 3: Challenge Test for the Red-Fruit Juice

In the last step of the research a challenge test was performedin the red fruit juice; Z. bailii was used as target, as it is one ofthe most serious spoiling microorganism for juices (Patrignani

Table 2 Fractional design for the last step of the research (red-fruit juiceinoculated with Z. bailii)

Combinations of thedesign

Power(%)

Duration of the treatment(min)

Biocitro(ppm)

A1 (control 1) 60 6

A2 (control 2) – – 100

A3 (control 3) – – –

B 20 6 50

C 60 4 –

D 20 4 100

E 20 2 –

F 40 2 100

G 40 6 –

H 60 2 50

I 40 4 50

L 60 6 100

Food Bioprocess Technol

et al. 2010). The experiments were performed at the optimaltemperature of Z. bailii (accelerated shelf life test) and biocitrowas used as an additional hurdle to control the yeast, due to itspromising effects towards yeasts (Bevilacqua et al. 2010,2013b) and the ability to increase the effect of some physicaltreatments like homogenization (Bevilacqua et al. 2012a).

Figure 5 reports the evolution of Z. bailii in some selectedcombinations of the design: the controls (A1, A2, A3), theruns I (power, 40 %; time, 4 min; biocitro, 50 ppm) and L(power, 60%; time, 6 min; biocitro, 100 ppm). As expected, inA1 (US treatment without biocitro), Z. bailii was significantlyreduced immediately after the treatment; however, the survi-vors were able to grow and attain a level similar to thatreported for A3 (not processed juice) after few days. In A2

(biocitro at 100 ppm), the extract was able to control Z. bailiifor at least 6 days.

Data from this challenge test (the combinations showed inFig. 5 and the others) were used as input values for a staticapproach (Bevilacqua et al. 2012a, 2013b) andmodel the levelof Z. bailii for each time of sampling. Table 3 shows thestatistical effects of the factors of the design (power andduration of US, concentration of biocitro); US played animportant role immediately after the treatment, whilst its effectwas not significant throughout the storage. On the other hand,the effect of biocitro was significant throughout the entirestorage time.

Figure 6 shows the 3D plot for the interaction power/timeon the level of Z. bailii immediately after the treatment with

0

0.5

1

1.5

2

2.5

3

yeas

t re

duct

ion

(con

trol

-tre

ated

sam

ple)

(lo

g cf

u/m

l)

apple

red-fruit

strawberry

orange

pineapple

Fig. 1 Reduction of S. cerevisiaein the different combinations ofthe design (power×duration ofthe treatment×pulse). Meanvalues±standard deviation

Fig. 2 Pareto chart for the effectof power, duration of UStreatment and pulse on thereduction of S. cerevisiae in red-fruit, strawberry and orangejuices. L linear effect;Q quadraticeffect

Food Bioprocess Technol

US: the use of the highest power, combined with a time of6 min, reduced the yeast by more than 2 log cfu/ml, whilst theuse of biocitro (Fig. 7) determined after 13 days a level of Z.bailii 1.5–2 log cfu/ml lower than in the samples not contain-ing the extract.

As a final assay of this step, a preliminary sensory analysiswas performed, following the approach by Luckow and

Fig. 3 3D plots for the interaction power/time on the reduction of S.cerevisiae in red-fruit, strawberry and orange juice. Pulse was set to 2, 4and 6 s

0

0.5

1

1.5

2

2.5

3

yeas

t red

ucti

on(c

ontr

ol-t

reat

ed s

ampl

e) (

log

cfu/

ml)

apple

red-fruit

strawberry

orange

C

0

0.5

1

1.5

2

2.5

3

3.5

yeas

t red

ucti

on(c

ontr

ol- t

reat

ed s

ampl

e) (

log

cfu/

ml)

apple

red-fruit

strawberry

orange

L

a

b

Fig. 4 Validation of US treatment towards some spoiling yeasts. Cpower: 60 %, time, 4 min; pulse, 2 s. L power, 60 %; time, 6 min; pulse,6 s. Mean values±standard deviation

Fig. 5 Evolution of Z. bailii in a commercial red-fruit juice, treated withultrasound and added with biocitro. I power, 40 %; time, 4 min; biocitro,50 ppm. L power, 60%; time, 6 min; biocitro, 100 ppm. A1 power, 60%;time, 6 min. A2 biocitro, 100 ppm. A3 control. Mean values±standarddeviation

Food Bioprocess Technol

Delahunty (2004a, b). Some untrained assessors were asked togive a score to the colour and odour of the samples of the red-fruit juice processed by US and/or containing biocitro (Fig. 8);the differences amongst the samples (one-way ANOVA andTukey's test) were not significant. However, when the asses-sors were asked to give a purchase intent, they reported thatthey wished to buy the control, as well as the samples con-taining biocitro or treated with US (samples B and C), but theyhad some doubts for the sample D (biocitro+US) (data notshown).

The idea of combining physical treatments and antimicro-bials is quite old and has its background on the theory ofhurdle technology by Leistner (1978). The real effect of thecombination of some hurdles is a matter of debate, as manyresearchers stated that different variables could interact. Onthe other hand, Zwietering et al. (1992) and Lambert andBidlas (2007a, b) stated that different hurdles combine togeth-er independently, thus no synergistic effect could be recovered

and each hurdle can act primarily on its target at cell level(gamma theory) (Corbo et al. 2009). In the past, Bevilacquaet al. (2012c) found that biocitro and homogenization acted assingle hurdles towards P. membranifaciens in a model system,whilst biocitro increased the effect of homogenization towardsthe spores of F. oxysporum (Bevilacqua et al. 2013a).

The data of this research showed that US and biocitro actedas single hurdles against Z. bailii in a red-fruit juice; more-over, they played a role in different moments: US reduced theinitial contamination whilst biocitro could control the yeastwithin the storage.

Just a highlight on the sensory test: although the assayperformed in this research was not a real consumer test, butonly a preliminary experiment, the results pointed out that USdid not affect significantly the sensory attributes of juice.Some problems rose up for the combination biocitro+US:

Table 3 Standardized effects of power, duration of US (ultrasound) treat-ment and concentration of biocitro on the viability of Zygosaccharomycesbailii inoculated in a commercial red-fruit juice, stored at 25 °C for 13 days

Immediatelyafter UStreatment

2 days 6 days 9 days 13 days

Intercept 3.87 4.22 5.28 5.54 6.37

Time −0.91 –a

– – –

Power −1.42 – – – –

Biocitro - −1.73 −2.42 −1.93 −1.22

Significance of themodel (R2adjusted)

0.868 0.930 0.826 0.926 0.887

a Not significant

Fig. 6 3D plot for the interaction power/duration of US treatment on thelevel of Z. bailii in the commercial red-fruit juice immediately after thetreatment

Fig. 7 3D plot for the interaction biocitro/duration of US treatment onthe level of Z. bailii in a commercial red-fruit juice after 13 days ofstorage at 25 °C

0

1

2

3

4

5

6

colour odour overall quality

Sens

ory

scor

es

A

B

C

D

Fig. 8 Sensory scores for a red-fruit juice containing biocitro and/ortreated with US. Mean values±standard deviation. A control; B juicetreated by ultrasound; C juice with biocitro; D juice with biocitro andtreated with ultrasound

Food Bioprocess Technol

maybe, the time of the addition of the extract could play a role.Biocitro, in fact, was added before the physical treatment, thussuggesting a modification induced by cavitation on the ex-tract. A possible way to overcome this issue could be the useof a different flow sheet: performing before US treatment,thereafter adding biocitro.

Conclusions

The US approach was tested towards different spoiling yeasts(S. cerevisiae , P. membranifaciens , W. anomalus , Z. bailii ,and Z. rouxii ) on some juice. Its effect relied upon the acousticenergy, i.e. on the power, duration of the treatment and pulse;however, the effect of pulse was less significant. Concerningthe differences amongst the different yeasts,W. anomalus wasthe most resistant target, followed by S. cerevisiae and Z.rouxii and finally by P. membranifaciens and Z. bailii ; how-ever, the different trend was not related to cell shape, as similaryeasts showed a different behaviour.

Finally, US could be combined successfully with biocitroto inhibit Z. bailii , as US acted as a tool to reduce the initialcontamination, whilst the extract acted as a controlling factorthroughout the storage.

References

Adekunte, A. O., Tiwari, N. K., Cullen, P. J., Scannell, A. G. M., &O’Donnell, C. P. (2010a). Effect of sonication on colour, ascorbicacid and yeast inactivation in tomato juice. Food Chemistry, 122 ,500–507.

Adekunte, A. O., Tiwari, N. K., Scannell, A. G. M., Cullen, P. J., &O’Donnell, C. P. (2010b). Modelling yeast inactivation in sonicatedtomato juice. International Journal of Food Microbiology, 137 ,116–120.

Adekunte, A. O., Valdramis, V. P., Tiwari, N. K., Slone, N., Cullen, P. J.,O’Donnell, C. P., et al. (2010c). Resistance of Cronobacter sakazakiiin reconstituted powdered infant formula during ultrasound at con-trolled temperature: a quantitative approach on microbial responses.International Journal of Food Microbiology, 142, 53–59.

Bermúdez-Aguirre, D., & Barbosa-Cánovas, G. V. (2012). Inactivation ofSaccharomyces cerevisiae in pineapple, grape and cranberry juicesunder pulsed and continued thermo-sonication treatments. Journalof Food Engineering, 108 , 383–392.

Bevilacqua, A., Campaniello, D., Sinigaglia, M., Ciccarone, C., & Corbo,M. R. (2012a). Sodium benzoate and citrus extract increase theeffect of homogenization towards spores of Fusarium oxysporumin pineapple juice. Food Control, 28 , 199–204.

Bevilacqua, A., Corbo, M. R., & Sinigaglia, M. (2010). In vitro evalua-tion of the antimicrobial activity of eugenol, limonene and citrusextract against bacteria and yeasts, representative of the spoilingmicroflora of fruit juices. Journal of Food Protection, 73, 888–894.

Bevilacqua, A., Corbo, M. R., & Sinigaglia, M. (2012b). Use of naturalantimicrobials and high pressure homogenization to control thegrowth of Saccharomyces bayanus in apple juice. Food Control,24, 109–115.

Bevilacqua, A., Corbo, M. R., & Sinigaglia, M. (2012c). Inhibition ofPichia membranifaciens by homogenization and antimicrobials.Food and Bioprocess Technology: an International Journal, 5 ,1061–1067.

Bevilacqua, A., Sinigaglia, M., & Corbo, M. R. (2013a). Ultrasound andantimicrobial compounds: a suitable way to control Fusariumoxysporum in fruit juices? Food and Bioprocess Technology, 6 ,1153–1163.

Bevilacqua, A., Speranza, B., Campaniello, D., Corbo, M. R., &Sinigaglia, M. (2013b). Inhibition of spoiling yeasts of fruit juicesthrough citrus extracts. Journal of Food Protection. doi:10.4315/0362-028X.JFP-13-034.

Butz, P., & Tauscher, B. (2002). Emerging technologies: chemical as-pects. Food Research International, 35, 279–284.

Cárcel, J. A., García-Peréz, J. V., Benedito, J., & Mulet, A. (2012). Foodprocess innovation through new technologies: use of ultrasound.Journal of Food Engineering, 110 , 200–207.

Chemat, F., Zill-e-Huma, & Khan, M. K. (2011). Applications of ultra-sound in food technology: processing, preservation and extraction.Ultrasonics Sonochemistry, 18, 813–835.

Corbo, M. R., Bevilacqua, A., Campaniello, D., D’Amato, D., Speranza,B., & Sinigaglia, M. (2009). Prolonging microbial shelf life of foodsthrough the use of natural compounds and non-thermal ap-proaches—a review. International Journal of Food Science andTechnology, 44 , 223–241.

Di Benedetto, N., Perricone, M., & Corbo, M. R. (2010). AlternativeNon-Thermal Approaches: Microwave, Ultrasound, Pulsed ElectricFields, Irradiation. In A. Bevilacqua, M. R. Corbo, & M. Sinigaglia(Eds.), Application of alternative food-preservation technologies toenhance food safety and stability (pp. 143–160). Saif Zone, Sharjah,UAE: Bentham.

Drakopoulou, S., Terzakis, S., Fountoulakis, M. S., Mantzavinos, D., &Manios, T. (2009). Ultrasound-induced inactivation of gram-negative and gram-positive bacteria in secondary treated municipalwastewater. Ultrasonics Sonochemistry, 16, 629–634.

Gabriel, A. A. (2012). Microbial inactivation in cloudy apple juice bymulti-frequency Dynashock power ultrasound. UltrasonicsSonochemistry, 19, 346–351.

Gastélum, G. G., Avila-Sosa, R., López-Malo, A., & Palou, E. (2011).Listeria innocua multi-target inactivation by thermo-sonication andvanillin. Food and Bioprocess Technology, 5 , 665–671.

Jay, J. M., Loessner, M. J., & Golden, D. A. (2005). Modern foodmicrobiology (6th ed.). New York: Springer.

Jomdecha, C., & Prateepasen, A. (2010). Effects of pulse ultrasonicirradiation on the lag phase of Saccharomyces cerevisiae growth.Letters in Applied Microbiology, 52, 62–69.

Lambert, R. J. W., & Bidlas, E. (2007a). An investigation of the Gammahypothesis. A predictive modeling study of the effect of combinedinhibitors (salt, pH and weak acids) on the growth of Aeromonashydrophila. International Journal of Food Microbiology, 115, 12–28.

Lambert, R. J. W., & Bidlas, E. (2007b). A study of the Gamma hypothesis:predictive modeling of the growth and inhibition of Enterobactersakazakii. International Journal of FoodMicrobiology, 115, 204–213.

Leighton, T. G. (1998). The principles of cavitation. In M. J. W. Povey &T. J. Mason (Eds.), Ultrasound in food processing (pp. 151–182).London: Chapman & Hall.

Leistner, L. (1978). Hurdle effect and energy saving. In W. K. Downey(Ed.), Food quality and nutrition . London: Applied SciencePublishers. p 553.

Luckow, T., & Delahunty, C. (2004a). Consumer acceptance of orangejuice containing functional ingredients. Food Research International,37 , 805–814.

Luckow, T., & Delahunty, C. (2004b). Which juice is healthier? Aconsumer study of probiotic non-dairy juice drinks. Food QualityPreference, 15, 751–759.

Food Bioprocess Technol

Mukhopadhyay, S., & Ramaswamy, R. (2012). Application of emergingtechnologies to control Salmonella in foods: a review. FoodResearch International, 45, 666–677.

Patist, A., & Bates, D. (2008). Ultrasonic innovations in the food indus-try: from the laboratory to commercial production. Innovative FoodScience and Emerging Technologies, 9 , 147–154.

Patrignani, F., Vannini, L., Kamdem, S. L. S., Lanciotti, R., &Guerzoni,M.E. (2010). Potentialities of high-pressure homogenization to inactivateZygosaccharomyces bailii in fruit juices. Journal of Food Science,75 , M116–M120.

Shiferaw Terefe, N., Gamage, M., Vilkhu, K., Simons, L., Mawson, R., &Versteeg, C. (2009). The kinetics of inactivation of pectinmethylesteraseand polygalacturonase in tomato juice by thermosonication. FoodChemistry, 117, 20–27.

Soria, A. C., & Villamiel, M. (2010). Effect of ultrasound on the techno-logical properties and bioactivity of food: a review. Trends in FoodScience & Technology, 21 , 323–331.

Valero, M., Recrosio, N., Saura, D., Muñoz, N., Martí, N., & Lizama, V.(2007). Effects of ultrasonic treatments in orange juice processing.Journal of Food Engineering, 80, 509–516.

Wang, J., Hu, X., & Wang, Z. (2010). Kinetics models for theinactivation of Alicyclobacillus acidiphilus DSM 14558 andAlicyclobacillus acidoterrestris DSM 3922T in apple juice byultrasound. International Journal of Food Microbiology, 139 ,177–181.

Zwietering, M. H., Wijtzes, T., De Wit, J. C., & van’t Riet, K. (1992). Adecision support system for prediction of the microbial spoilage infoods. Journal of Food Protection, 55 , 973–979.

Food Bioprocess Technol