Impact of acoustic cavitation on food emulsions

Ultrasonics Sonochemistry 30 (2016) 98–102

Contents lists available at ScienceDirect

Ultrasonics Sonochemistry journal homepage: www.elsevier.com/locate/ultson

Impact of acoustic cavitation on food emulsions Olga Krasulya a,⇑, Vladimir Bogush a, Victoria Trishina a, Irina Potoroko b, Sergey Khmelev c, Palani Sivashanmugam d, Sambandam Anandan e a

Moscow State University of Technology and Management, Moscow, Russia Federal State Funded Educational Institution of Higher Professional Education, ‘‘South Ural State University’’ Sub-division: Quality Expertise of Consumer Products, Chelyabinsk, Russia c Altai Technical University, Biysk, Russia d Department of Chemical Engineering, National Institute of Technology, Tiruchirappalli 620 015, India e Nanomaterials and Solar Energy Conversion Lab, Department of Chemistry, National Institute of Technology, Tiruchirappalli 620 015, India b

a r t i c l e

i n f o

a b s t r a c t

Article history: Received 13 October 2015 Received in revised form 11 November 2015 Accepted 12 November 2015 Available online 12 November 2015

The work explores the experimental and theoretical aspects of emulsification capability of ultrasound to deliver stable emulsions of sunflower oil in water and meat sausages. In order to determine optimal parameters for direct ultrasonic emulsification of food emulsions, a model was developed based on the stability of emulsion droplets in acoustic cavitation field. The study is further extended to investigate the ultrasound induced changes to the inherent properties of raw materials under the experimental conditions of sono-emulsification. Ó 2015 Elsevier B.V. All rights reserved.

Keywords: Food sonochemistry Cavitation reactor Theoretical approach Viscosity measurement Meat sausage

1. Introduction Emulsions are obtained by mixing of two or more immiscible liquids, in which one is dispersed (the dispersed phase) into another (the continuous phase) in the form of very small droplets. Examples of emulsified products include margarine and low-fat spreads, salad cream and mayonnaise, meat sausages, ice-cream and cakes. Two types of relatively simple liquid–liquid emulsions are oil-in-water (O/W) (for example, milk) and water-in-oil (W/O) (for example, margarine) in comparison to cake and mayonnaise which are multiple emulsions. Meat emulsions are ground meat containing a mixture of water, protein, fat, salt and small amounts of other ingredients [1–3] which are important human diet. The role of food industry is to provide improved bioactives/nutraceuticals in complex food matrices by choosing suitable delivery vehicles including simple solutions, association colloids, emulsions, suspensions, gels, solid matrices etc [4]. Most bioactive/nutraceuticals have poor water solubility and hence new approaches of delivering them in the form of emulsions are growing [5,6]. Researchers have identified the use of ultrasound

(US) for creating emulsions in food. Much of the existing research work in the area of ultrasonic emulsification has focused mainly on simple matrix such as an emulsion of sun flower oil in water [7–10]. Delivery of nutraceuticals in milk and juice has recently been reported [11]. The application of US in food processing is discussed in several review articles [12–18]. They have discussed its usage in a range of processes such as extraction, food analysis and quality control, microbial cell reduction, meat tenderization, filtration, viscosity reduction, enzyme inhibition, drying, osmodehydration and crystallization. US emulsification is used in liquid food processing and only limited number of reviews exclusively focus on the ‘‘emulsification capability” of US in broader areas involving pharma, food and chemical systems [19,20]. The purpose of this work is to provide theoretical and experimental approach to deliver stable emulsions of bioactives in simple and complex food matrices, viz., sunflower oil in water and meat sausages by using US. In addition, the possibility of the physical effects of US affecting the inherent properties of the food system during the emulsification process is also discussed. 2. Experimental section

⇑ Corresponding author. E-mail addresses: (S. Anandan).

[email protected]

(O.

http://dx.doi.org/10.1016/j.ultsonch.2015.11.013 1350-4177/Ó 2015 Elsevier B.V. All rights reserved.

Krasulya),

[email protected]

Meat samples were prepared from ground meat (50% beef, 50% pork) of regular as well as PSE (pale soft exudative) and DFD (dark

99

O. Krasulya et al. / Ultrasonics Sonochemistry 30 (2016) 98–102

firm and dry) quality. The amount of brine (NaCl) in meat samples was adjusted to the value of 3.85 g per 100 g. Brine treatment was carried at ambient temperature for 30 min. Water holding capacity was evaluated as described below: weighed test tubes with meat samples were placed in water a bath and kept for 20 min at 98 °C, upon cooling to ambient temperature released moisture drops were collected with filter paper and test tubes were reweighed. All chemicals for brine preparation were purchased from fosfate-ABASTOL and were the purest grade available. Bottled drinking water was used in all experiments. Ultrasound treatment of water was carried at operating frequency of 20 kHz. pH measurements were performed on pH-213 (Hanna Instruments, Germany). Standard viscometer (A&G, Japan) was used to measure absolute viscosity. All parameters for brine processing reactor such as ultrasound intensity, frequency, and flow rate based on dissolving ability of US treated water were previously optimized and reported elsewhere [21,22]. It is also important to note that experimental conditions were set up in such a way that final meat product would not contain more than 10% of brine by volume. The brine was treated in brine processing reactor with a piezoceramic converter, with the capacity of 5 l/min, and subject to the recipe the brine was added at the first chopping stage. The received minced sausage was formed in a nylon cover, compressed within 2 h and then exposed to thermal treatment in the modes provided by the regulatory documentation (GOST R 52196-2011). ‘‘Milk” complex supplement consisting of phosphates, sodium glutamate, sodium erythorbate, natural colorant and extracts of spices was also added at the first chopping stage. The brine prepared in the ratio of 1:12 (culinary salt:water) was used in the test sample. A thermostated SV-100 vibroviscosimeter (manufactured by A&G Co., Japan, measurement range from 1 to 100 Pa s, the temperature in the cell comprised 85 °C) was used to measure the viscosity at various temperatures. The data were recorded on a PC and processed by Excel software. SV-100 vibroviscosimeter was selected because viscosity measurement by this device does not lead to the destruction of the forming structure as opposed to coaxial-cylinder viscosimeters.

3. Results and discussion The preparation of food emulsions using acoustic cavitation is widespread as a basic technique to upgrade the quality of finished products, improve their organoleptic characteristics and boost economy of the production process. Two approaches to the ultrasonic preparation of food emulsions were considered: (1) direct sonication of the system by immersion of the operating tool of the ultrasonic oscillatory system (radiator) into a medium containing disperse and continuous phases, and generation of emulsion by acoustic cavitation; (2) cavitation activation of the continuos medium (for example, brines, syrups, etc.) in the cavitation reactor, as a result of which water acquires unique properties related to its structural changes. In order to determine optimal conditions for ultrasonic emulsification of food emulsions (approach 1: sunflower oil in water), an emulsion drop decay model in an acoustic cavitation field was developed. The model is based on the droplet deformation Eq. (1), a mathematical model developed by Taylor [23]. The surface of a droplet is presented as a load with weight m on a spring (equivalent to surface forces) with a damping device (equivalent to viscosity of the disperse phase):

_ m€x ¼ F  kx  dx;

ð1Þ

where m – drop weight in kg; F – external force acting on the drop from the side of the fluid flow, N; k – elastic coefficient of the drop, n/m; d – damping coefficient of the drop, kg/s; x – deformation value, m. The elastic coefficient of the drop is calculated by the following formula:

k r ¼ Ck ; m qd R3

ð2Þ

where Ck – proportionality coefficient depending on the drop deformation mode; r – surface tension on the border of the carrier and the disperse phase interface, N/m; qd – density of the disperse phase, kg/m3; R – drop radius, m. The damping coefficient of the drop is calculated by the following formula:

d l ¼ Cd d 2 ; m qd R

ð3Þ

where Cd – proportionality coefficient depending on the drop deformation mode; ld – viscosity of the disperse phase, Pa s. At ultrasonic cavitation external force F is proportional to the pressure amplitude of the shock waves generated on cavitation bubble collapse. The solution to differential Eq. (1) allows to find the maximum drop deformation value and to determine its potential decay. Subject to the earlier published work [23], if maximum drop deformation exceeds one fourth of its diameter d, the drop is decayed into 2 equal drops with the diameter of p3dffiffi. 2

Therefore, the dependence of the drop diameter on time is described by the following differential equation:

@d 1 ffiffiffi ¼ dt bu ðdÞ ln p 3 @t 2

ð4Þ

where tbu(d) – dependence of the individual drop decay time on its diameter. The dependence of the individual drop decay time on its diameter is determined as follows. Subject to Eq. (1), the maximum drop deformation value is proportional to the external force acting on the drop from the side of the fluid flow. This force is proportionate to the shock wave pressure amplitude [24], when it reaches the drop’s surface. Whereas the drop is decayed only when its maximum deformation exceeds a half of its radius, the decay will accordingly pass when the shock wave pressure amplitude near the drop’s surface exceeds some threshold value. It means that the drop will decay on the impact of cavitation bubbles formed around it due to diffusion of the shock wave as shown in Fig. 1. Based on the above mentioned layout, the drop decay time is determined by the interval, during which at least one cavitation bubble is formed in area Vb. The time interval of bubble formation resulting in the drop decay is calculated on the basis of the probabilistic approach using the formula mentioned below:

t

T ; nV b

ð5Þ

where n – number of cavitation bubbles determined as reported earlier [25], m3; T – bubble collapse period, s; Vb – volume of the area of bubble collapse leading to the drop decay, m3. The drop decay time calculated by Eq. (5) allows to find the dependence of the drop diameter on time (Fig. 2) at emulsification of exemplary food emulsion ‘‘sunflower oil in water”. The physical

100

O. Krasulya et al. / Ultrasonics Sonochemistry 30 (2016) 98–102

Fig. 1. Layout of the impact of cavitation bubbles on emulsion drops.

120

100 Drop diameter, micron 80

1,5 W/cm^2 3 W/cm^2

60

6 W/cm^2 9 W/cm^2

40

20

0 0

5

10

15

20

25

30

Time, min Fig. 2. Dependence of the emulsion’s drop diameter on time at different impact intensities.

Table 1 Physical properties of the exemplary emulsion (sunflower oil in water). Viscosity of the carrier phase, mPa s Viscosity of the disperse phase, mPa s Surface tension on the border of phase interface, mN/m Volume content of the disperse phase, %

0.82 57 39

properties or characteristics of the exemplary emulsion are presented in Table 1. According to the observed dependencies (Fig. 2) at the impact intensity of 1.5 W/cm2, even at treatment during 20 min the drop diameter still exceeds 20 lm, which is insufficient for generation of a stable emulsion. The impact with the intensity of 3 W/cm2 allows to generate emulsions with the drop diameter of 15 lm during 20 min. The impact with the intensity of 6 W/cm2 and higher allows to generate emulsion drops with the diameter of less than 15 lm already during 13 min. Thus, we can affirm that the model developed by us (after its validation for adequacy) is correct

Density of the carrier phase, kg/m3 Density of the disperse phase, kg/m3 Starting drop diameter, micron

1000 920 100

and such optimal parameters can be used for determination of emulsification of food emulsions in further applied research. The cavitation effect on fluid food media for their further application in food emulsions (approach 2: minced sausage in cooked sausage products) was studied by taking example of minced sausage in cooked sausage products, which, according to Zharinov [26], can be referred to the class of ‘‘food emulsions”. Earlier work [27] proves that application of ultrasonic brine treatment at production of sausage products allows to improve their customer attributes, however, the mechanism of the impact of fluid food media (brine) treated in the cavitation reactor on

101

O. Krasulya et al. / Ultrasonics Sonochemistry 30 (2016) 98–102 Table 3 Kinetic constants of the food emulsion’s structure recovery process.

Table 2 Recipes of minced sausages. Raw materials and ingredients Semi-fat pork Beef of grade 1 Dry cow milk, whole or nonfat Chicken eggs or chicken egg mixture Process water Brine White salt ‘‘Milk” complex supplement

Content, kg/100 kg (control)

Content, kg/100 kg (test)

60 35 3 2 24 – 2.0 0.8

60 35 3 2 – 26

Control

Test

g1, Pa s g2, Pa s

41 57 0.004 0.9998

52 69 0.004 0.9999

k, c1 r2

r2 – value characterizing authenticity of the approximant depending on the test data set.

0.8

formation of the food emulsion structure has not been studied. Here we made an attempt to study the mechanism of the impact of the brine exposed to cavitation treatment on structural and mechanical properties on the minced meat as a food emulsion in the course of cooking. Table 2 shows the recipes of samples used in this study. Brine solution, added to the samples at first chopping stage (after adding of beef of grade 1 to the chopper), was used as a control sample. ‘‘Milk” consisting of phosphates, sodium glutamate, sodium erythorbate, natural colorant and extracts of spices was also added at the first chopping stage. The brine solution prepared with salt: water ratio of 1:12 was used in the test sample. It is clear from the data shown in Fig. 3 that viscosity of minced sausage at thermal treatment changes in a complex way and has three typical areas, the durations of which do not coincide with those of the control sample. The first area (1a, 2a), in Fig. 3, gives evidence of increasing viscosity of the emulsion at almost constant temperature. Such behavior could be explained by the recovery of the structure of the minced sausage emulsion after its destruction in the vibroviscometer cell. In this case, kinetics of viscosity change can be described by the following equation:

g ¼ g1 þ ðg2  g1 Þ  eks

Constants

ð6Þ

where g1, g2 – viscosity in the initial time and at achievement of maximum in the first process area Pa s, k - constant characterizing the structure recovery process s1, s – time, s.

Methods of non-liner regression analysis [28] were used for determination of the equation constant (6) for two variants of minced sausage (Table 2). The constant (k) of the process of structure recovery (Table 3) of the food emulsion – minced sausage containing the cavitation-treated brine is slightly less than that of the control sample. In our opinion, it can be related, firstly, to an increase in the volume and degree of structure of hydrated film of protein macromolecules in the test sample [29], which complicates the structure recovery process. Secondly, the recovery temperature of structure of minced sausage in the test sample is less than that in the control sample. The second area (1b, 2b) in Fig. 3, connected with reduction of the viscosity factor is preconditioned by destruction of the emulsion’s structure on exposure to heat. In this case reduction of viscosity of the control minced sausage begins earlier and at a higher temperature, (time 445 s, t = 19.48 °C). For the test sample containing the brine exposed to cavitation treatment reduction of the emulsion’s viscosity begins later and at a lower temperature (time 645 s, t = 16.23 °C). As it is clear from Fig. 3 (area (1b, 2b)), the process flows with different intensities for the control and the test samples. For the test sample, viscosity reduces smoothly and finishes earlier at a lower temperature (time 1355 s, t = 25 °C) than for the control sample (time 1530 s, t = 30 °C). In our opinion, such difference in the change in viscosity factor for the control and test samples of the food emulsion can be explained as follows. In the test sample, aqueous solution of brine that was exposed to cavitation treatment interacts with protein molecules of the minced sausage (forming hydrated films with it) [26], which leads to its structuring and, as a consequence, to higher viscosity factors as opposed to the control sample. Besides, in such water

Fig. 3. Kinetics of viscosity and temperature change in the food emulsion – minced sausage on thermal treatment.

102

O. Krasulya et al. / Ultrasonics Sonochemistry 30 (2016) 98–102

medium (after ultrasonic treatment) chemical reactions occur faster than in a control medium, which ensures earlier beginning of protein denaturation processes at lower temperatures (for the food emulsion of the test sample as opposed to the control sample). In the third area (1c, 2c) the viscosity factor is increased upon heating, which is preconditioned by the formation of food emulsion structure on account of muscular tissue protein denaturation. For the control sample the structuring process begins at 32–33 °C, and for the test sample at 26–27 °C (Fig. 3). Fig. 3 shows that viscosity is increased monotonously. At the values of 70–75 Pa s, the viscosity changes significantly: such behavior is likely related to relaxation of shear stresses in the food system, such phenomena are described earlier [30]. Formation of the food emulsion structure at the final product stage begins from the surface and flows more intensely than inside the sample. Such unevenness in structure formation leads to appearances of stresses relieved in the food system on account of their relaxation. Thus, at structure formation during cooking of the food emulsion – minced sausage – a dual process occurs: structure formation and relaxation.

4. Conclusions We have shown based on experimental results that relaxation processes flow more actively in a food emulsion (minced sausage) prepared using cavitation-treated brine, which leads to weakening of the structure formation in sausage product. The impact with the intensity allows to generate emulsion drops with the diameter of less than 15 lm and such optimal parameters can be used for determination of emulsification of food emulsions in further applied researches. The obtained product has a smooth elastic texture and a pronounced taste, which makes it more preferable for the customer. Acknowledgements The author SA and OK thank DST, India for the sanction of India–Russia collaborative research grant (INT/RUS/RFBR/P-209 dated 15-6-15) and NSC (Russia) for the financial support through (research grant No. 15-58-45028/15 dated 19-6-2015). References [1] D. Álvarez, M. Castillo, F.A. Payne, M.D. Garrido, S. Bañón, Y.L. Xiong, Prediction of meat emulsion stability using reflection photometry, J. Food Eng. 82 (2007) 310–315. [2] D. Santhi, A. Kalaikannan, S. Sureshkumar, Factors influencing meat emulsion properties and product texture: a review, Crit. Rev. Food Sci. Nutr. (2015), http://dx.doi.org/10.1080/10408398.2013.858027. [3] O. Krasulya, S. Shestakov, V. Bogush, I. Potoroko, P. Cherepanov, B. Krasulya, Applications of sonochemistry in Russian food processing industry, Ultrason. Sonochem. 21 (2014) 2112–2116. [4] D.J. McClements, E.A. Decker, Y. Park, J. Weiss, Structural design principles for delivery of bioactive components in nutraceuticals and functional foods, Crit. Rev. Food Sci. Nutr. 49 (2009) 577–606. [5] N. Garti, Delivery and controlled release of bioactives in foods and nutraceuticals, first ed., Woodhead Publishing, 2008.

[6] L. Couëdelo, C. Boué-Vaysse, L. Fonseca, E. Montesinos, S. Djoukitch, N. Combe, M. Cansell, Lymphatic absorption of a-linolenic acid in rats fed flaxseed oilbased emulsion, Br. J. Nutr. 105 (2011) 1026–1035. [7] T.S. Leong, T.J. Wooster, S.E. Kentish, M. Ashokkumar, Minimising oil droplet size using ultrasonic emulsification, Ultrason. Sonochem. 16 (2009) 721–727. [8] S. Kentish, T.J. Wooster, M. Ashokkumar, S. Balachandran, R. Mawson, L. Simons, The use of ultrasonics for nanoemulsion preparation, Innov. Food Sci. Emerg. Technol. 9 (2008) 170–175. [9] S.M. Jafari, Y. He, B. Bhandari, Nano-emulsion production by sonication and microfluidization – a comparison, Int. J. Food Prop. 9 (2006) 475–485. [10] N. Porova, V. Botvinnikova, O. Krasulya, P. Cherepanov, I. Potoroko, Effect of ultrasonic treatment on heavy metal decontamination in milk, Ultrason. Sonochem. 21 (2014) 2107–2111. [11] S. Akalya, M. Ashokkumar, Characterization of ultrasonically prepared flaxseed oil enriched beverage/carrot juice emulsions and process-induced changes to the functional properties of carrot juice, Food Bioprocess Technol. 8 (2015) 1258–1266. [12] D.J. McClements, Advances in the application of ultrasound in food analysis and processing, Trends Food Sci. Technol. 6 (1995) 293–299. [13] M. Ashokkumar, F. Grieser, Ultrasound assisted chemical processes, Rev. Chem. Eng. 15 (1999) 41. [14] G. Kaur, S.P. Jaiswal, K.S. Brar, J.C. Kumar, Physico-chemical characteristics of some important varieties of carrot, Indian Food Pack 30 (1976) 5–8. [15] A.C. Soria, M. Villamiel, Effect of ultrasound on the technological properties and bioactivity of food: a review, Trends Food Sci. Technol. 21 (2010) 323–331. [16] J. Chandrapala, C.M. Oliver, S. Kentish, M. Ashokkumar, Use of power ultrasound to improve extraction and modify phase transitions in food processing, Food Rev. Int. 29 (2012) 67–91. [17] J. Chandrapala, C. Oliver, S. Kentish, M. Ashokkumar, Ultrasonics in food processing, Ultrason. Sonochem. 19 (2012) 975–983. [18] J. Chandrapala, C. Oliver, S. Kentish, M. Ashokkumar, Ultrasonics in food processing – food quality assurance and food safety, Trends Food Sci. Technol. 26 (2012) 88–98. [19] A. Brotchie, F. Grieser, M. Ashokkumar, Effect of power and frequency on bubble-size distributions in acoustic cavitation, Phys. Rev. Lett. 102 (2009) 084302. [20] S. Abbas, K. Hayat, E. Karangwa, M. Bashari, X. Zhang, An overview of ultrasound-assisted food-grade nanoemulsions, Food Eng. Rev. 5 (2013) 139– 157. [21] S. Shestakov, O. Krasulya, V. Bogush, Sonochemical treatment of brine, RU Patent 2402909, Russia, 2010. [22] T. Shlenskaya, T. Baulina, O. Krasulya, S. Shestakov, Equipment for using the sonochemistry into the fattening of pigs, Int. J. Eng. Innov. Technol. 3 (2013) 380–384. [23] G.I. Taylor, The shape and acceleration of a drop in a high speed air stream, in: G.K. Batchelor (Ed.), The Scientific Papers of GI Taylor, vol. 3, University Press, Cambridge, 1963, pp. 457–464. [24] V.N. Khmelev, R.N. Golykh, A.V. Shalunov, Optimization of these modes and conditions of ultrasonic influence on various technological mediums by mathematical modeling, Micro/Nanotechnologies and Electron Devices (EDM), in: 2012 IEEE 13th International Conference and Seminar of Young Specialists on, DOI: 10.1109/EDM.2012.6310202, pp. 124-134. [25] V.N. Khmelev, R.N. Golykh, A.V. Shalunov, S.S. Khmelev, K.A. Karzakova, Determination of ultrasonic effect mode providing formation of cavitation area in high-viscous and non-newtonian liquids, Micro/Nanotechnologies and Electron Devices (EDM), in: 2012 IEEE 13th International Conference and Seminar of Young Specialists on, DOI: 10.1109/EDM.2014.6882511, pp. 203207. [26] I.A. Rogov, A.I. Zharinov, L.A. Tekut’eva, T.A. Shepel’, Biotechnology Meat and Meat Products: A Course of Lectures, DeLiprint, Moscow, 2009. 296 p. [27] O.N. Krasulya, V.I. Bogush, O.A. Dolgova, T.A. Misharina, Use of sonochemistry at production of cooked sausage products, Meat Ind. J. 7 (2013) 20–24. [28] R.W. Larsen, Engineering with Excel, Williams Publishing House, Moscow, 2004. 544 p. [29] A.M. Evtushenko, N.A. Drozdova, I.G. Krasheninnikova, O.N. Krasulya, Impact of sonochemical treatment of the brine on properties of meat emulsions, Meat Ind. J. 10 (2011) 54–56. [30] A.M. Evtushenko, I.G. Krasheninnikova, T.V. Shlenskaya, Peculiar features of the sol-gel transition at formation of berry jellies with wheat germ oil, in: 27th Symposium on Rheology, A.V. Topchiev Institute of Petrochemical Synthesis at the Russian Academy of Sciences, 2014.