Frozen Food Industry Research Articles

Scheduling a single machine with concurrent jobs for the frozen food industry

This study examines the air blast freezing process of the frozen food industry, which processes multiple products with variable processing rates. The analysis depicts a new, single machine-scheduling problem in which the machine can process multiple jobs concurrently, within its capacity. The machine processes independent jobs arriving at various times while incurring interruption costs when allowing the jobs to enter or leave the machine. A mixed integer linear programming (MILP) model and a heuristic algorithm are developed for scheduling, the objectives of which are to minimize the costs associated with machine activities including that of waiting to load, waiting to unload and interruption time. The heuristic algorithm demonstrates the high potential of the computational time savings by obtaining the solution within one-fifth of the mathematical model computational time.

Unrelated Parallel Machine Scheduling with Sequence-Dependent Setup Times in Frozen Food Industry

In this paper, a scheduling problem in the freezing station of a frozen food industry is addressed. It is a case of the unrelated parallel machines with machine-dependent and job sequence-dependent setup times problem. In a production shift, each freezing machine is allowed to process only products in the same product family. A mathematical model is developed to solve the problem in order to minimize the production related cost including production cost, fixed production cost, setup cost, inventory holding cost, and backlog cost. The proposed model is tested with a set of various problems. The results demonstrate that the proposed mathematical model could optimally solve the small sized problems.

29. Ice-binding proteins and their interactions with ice crystals

Ice-binding proteins (IBPs) depress the freezing point of the body fluids below the melting point, resulting in a thermal hysteresis (TH) that prevents freezing of the organism in supercooled conditions and inhibits ice re-crystallization in frozen tissues. The potential of these proteins in the medical sector, in cryopreservation, in the frozen food industry, and in agriculture is enormous. The mechanisms by which IBPs interact with ice surfaces are still not completely understood and the potential of IBPs as cryoprotecting agents has not yet been realized. At the molecular level it was found that the IBPs coordinate and stabilize water molecules on their binding surface to form an ice-like water film. While this ice-like film is too small to nucleate supper-cooled water it serves as a mechanism of tight binding to ice. Still, the way these IBPs influence ice growth and the activity differences between difference types of IBPs is the subject of current research. We are investigating the interactions of IBPs with ice surfaces. In particular we are interested in the difference between hyperactive antifreeze proteins and moderately active ones, and the dynamic nature of the protein:ice interaction. We have developed novel methods to study these issues, including fluorescence microscopy techniques combined with temperature-controlled microfluidic devices (Celik et al., PNAS 2013, Drori et al., J.R. Soc. Interface 2014, Drori et al., RSC Adv. 2015). These techniques enable the replacement of the IBP solution surrounding an IBP-bound ice crystal by other solutions, without perturbing the system, which enables us to investigate the dynamic nature of the interactions between IBP and ice. The results show that binding of IBP to ice is irreversible, and that the TH-gap is sensitive to the time allowed for the proteins to accumulate on ice surfaces. This sensitivity changes dramatically between different types of IBPs. In a study of ice shaping during growth and melting we have demonstrated a correlation between ice crystal shapes, the shaping process, and the affinity of IBPs for the basal plane (Bar-Dolev et al., J.R. Soc. Interface 2012). Our results point to a connection between the dynamics and level of activity of different types of IBP to their ability to bind to specific ice orientations, in particularly to the basal plane of the ice. These results contribute to an understanding of the mechanisms by which diverse IBPs act that will be critical for the successful use of IBP in cryobiological applications. Supported by ERC, NSF, ISF, and CIHR.

A Study on Introduction of Unit Load System for Frozen Food Industry - Focus On Logistics Operation of Ice Cream of A’s Company -

A Study on Introduction of Unit Load System for Frozen Food Industry - Focus On Logistics Operation of Ice Cream of A’s Company -

Ice Growth Control with Ice-Binding Proteins

Ice-binding proteins (IBPs) depress the freezing point of body fluids below the melting point, resulting in a thermal hysteresis (TH) that prevents freezing of the organism. The potential of these proteins in the medical sector, in cryopreservation, in the frozen food industry, and in agriculture is enormous. We are investigating the mechanism by which IBPs interact with ice surfaces and inhibit ice growth and recrystallization. We have developed novel methods for these studies, including fluorescence microscopy techniques combined with temperature-controlled microfluidic devices. These techniques have enabled the replacement of the IBP solution surrounding an IBP-bound ice crystal by buffer, without losing the bound IBP or the TH activity. Our results show the irreversibility of the protein:ice interactions and the indirect dependence of TH activity on the protein concentration in solution. We found that the dynamics of the interactions with ice vary dramatically between different types of IBPs. From our results and other recent developments a new understanding of the mechanisms by which various IBPs act is emerging. This understanding is critical for the successful use of IBPs in cryobiological applications.Supported by the European-Research-Council (ERC), the National-Science-Foundation (NSF), and the Israel-Science-Foundation (ISF), Canadian Institutes of Helth (CIHR), The Lady Davis Foundation, and the Canada Research Chair program.Website: http://www.agri.huji.ac.il/∼braslavs/ReferencesDrori et al, Ice-Binding Proteins that Accumulate on Different Ice Crystal Planes Produces Distinct Thermal Hysteresis Dynamics, J. R. Soc. Interface (2014), 11:20140526.Celik, et al, Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth, PNAS (2013) 110, 1309-1314.

Effect of Novel Quick Freezing Techniques Combined with Different Thawing Processes on Beef Quality.

This study investigated the effect of various freezing and thawing techniques on the quality of beef. Meat samples were frozen using natural convection freezing (NF), individual quick freezing (IQF), or cryogenic freezing (CF) techniques, followed by natural convection thawing (NCT) or running water thawing (RT). The meat was frozen until the core temperature reached -12℃ and then stored at -24℃, followed by thawing until the temperature reached 5℃. Quality parameters, such as the pH, water binding properties, CIE color, shear force, and microstructure of the beef were elucidated. Although the freezing and thawing combinations did not cause remarkable changes in the quality parameters, rapid freezing, in the order of CF, IQF, and NF, was found to minimize the quality deterioration. In the case of thawing methods, NCT was better than RT and the meat quality was influence on the thawing temperature rather than the thawing rate. Although the microstructure of the frozen beef exhibited an excessive loss of integrity after the freezing and thawing, it did not cause any remarkable change in the beef quality. Taken together, these results demonstrate that CF and NCT form the best combination for beef processing; however, IQF and NCT may have practical applications in the frozen food industry.

Multiobjective Optimization of Cryogenic Freezing Conditions of Chicken Drumstick via Compromise Simplex Method

Because frozen foods have various quality characteristics, an optimization of a cryogenic freezing process is a complex task. This study proposes a compromise simplex method (CSM) using regression analysis to determine four optimal controllable process parameters corresponding to multiresponses for the level of three product quality characteristics. The results of the experimental process for the modified simplex method and multiple response surface optimization model both outperformed the results of the existing operating conditions, thus verifying that the CSM result in food preservation with the product quality measures close to customer satisfaction. The four recommended optimal conditions were as follows: the freezer set temperature of −100C, exhaust fan speed at 10 Hz, retention time of 12 min and counter-current nitrogen flow. Practical Applications This study optimized multiple responses for chicken drumsticks in a cryogenic freezing process. This optimization method has potential for practical application. All compromised quality characteristics are of topmost importance to the frozen food industry. This method, with some modifications, can also be used in further studies of related food products.

Study on Frozen Food Industry\'s Integrated Information Management Strategy Based on ERP

In order to study the causes of weak frozen food industry management in China, especially for the industry that produces the high repetitive and high corrosion production using information centres, we analyze that the approach of integrated information management strategy is emphasized in developing of computer integrated Enterprise Resource Plan (ERP). ERP comprises of HRM, financial management, manufacturing management and inventory management. This study focuses on computer integrated information and ERP has impacts on the information use in an organization and how ERP has impacts on the business strategy. We hope these can accelerate the construction of frozen food industry's integrated information management strategy based on ERP, promote sustained and rapid growth in frozen food industry, constantly improve the guarantees for product quality and safety and promote the simultaneous development of integration and informatization.

Thermal inactivation kinetics of hepatitis A virus in spinach

Leafy vegetables have been recognized as important vehicles for the transmission of foodborne viral pathogens. To control hepatitis A viral foodborne illness outbreaks associated with mildly heated (e.g., blanched) leafy vegetables such as spinach, generation of adequate thermal processes is important both for consumers and the food industry. Therefore, the objectives of this study were to determine the thermal inactivation behavior of hepatitis A virus (HAV) in spinach, and provide insights on HAV inactivation in spinach for future studies and industrial applications. The D-values calculated from the first-order model (50–72°C) ranged from 34.40±4.08 to 0.91±0.12min with a z-value of 13.92±0.87°C. The calculated activation energy value was 162±11kJ/mol. Using the information generated in the present study and the thermal parameters of industrial blanching conditions for spinach as a basis (100°C for 120–180s), the blanching of spinach in water at 100°C for 120–180s under atmospheric conditions will provide greater than 6 log reduction of HAV. The results of this study may be useful to the frozen food industry in designing blanching conditions for spinach to inactivate or control hepatitis A virus outbreaks.

Cold exposure and health effects among frozen food processing workers in eastern Thailand.

Frozen food processing workers work under a cold environment which can cause several adverse health effects.This study explored factors affecting workers' health in the frozen food industry in Thailand. Participants comprised 497 workers exposed to a cold working environment and 255 office workers who served as the controls.Data were collected by a survey on the work environment, and the interview of workers for abnormal symptoms. The exposed group had the following characteristics: 52.7% male, overall average age of 27 (SD 6.6) years old, attained elementary education (Grade 4 and Grade 6) (54.1%), married (48.9%), smokers (21.3%), alcohol consumption (31.0%), duration of work was between 1 and 5 years (65.2%), working 6 days a week (82.7%), 1–5 hours of overtime per week (33.8%), office workers (33.9%); work category: sizing (6.9%), peeling (28.3%) dissecting (22.2%), and in the warehouse (8.6%). The temperature in the work environment ranged from 17.2°C to 19.2°C in most sections, −18.0°C in the warehouse, and 25°C in the office areas. Warehouse workers had more abnormal symptoms than controls including repeated pain in the musculoskeletal system (OR 11.9; 95% CI 6.12–23.45), disturbance throughout the body (OR 4.60; 95% CI 2.00–10.56), respiratory symptoms (OR 9.73; 95% CI 3.53–26.80), episodic finger symptoms (OR 13.51; 95% CI 5.17–35.33).The study results suggest that workers' health should be monitored especially with regard to back and muscle pain, respiratory symptoms, episodic finger symptoms, and cardiovascular symptoms. Health promotion campaigns such as antismoking and reduction of alcohol consumption should be established because smoking and alcohol consumption are contributing factors to the pathogenesis of Raynaud's phenomenon and peripheral vascular disorders such as hypertension and heart disease.

A new approach for the preservation of apple tissue by using a combined method of xenon hydrate formation and freezing

Abstract Freezing usually causes cell and tissue damage in frozen fruits. This study attempted to use a combined method of xenon hydrate formation and freezing (CXF) for the preservation of apple parenchyma tissue and to compare it with the freezing alone process (FAP). CXF included two steps. The first step was to initiate a certain amount of xenon hydrate by introducing the apple parenchyma tissue to the xenon gas at 1.0 MPa and 1 °C for 0, 1, 2, 3, 4, 5, 6 and 7 d. It was found that the amount of xenon hydrate in apple parenchyma tissue increased with storage time and 2 d was optimum to obtain the certain amount of xenon hydrate. In the second step, the sample with optimum xenon hydrate formation was frozen at − 20 °C. The results showed that CXF was more effective in maintaining firmness, turgor pressure, and cell membrane integrity of the apple parenchyma tissue than FAP. A typical restricted diffusion phenomenon which indicates that water molecules are maintained in the apple parenchyma cells was found in the CXF samples, while the FAP samples showed an unrestricted diffusion phenomenon. In addition, firmness, turgor pressure, cell membrane integrity, and restricted diffusion phenomenon of the CXF samples were similar to those of the fresh samples. The CXF could preserve the apple parenchyma tissue because of the bulk water inside the cells and the water surrounding the cells which transformed to ice crystals is limited. Thus, cell and tissue damage due to the formation of ice crystals was reduced. The obtained results indicated that the CXF is effective for the preservation of the apple parenchyma tissue. Industrial relevance There has been an attempt to improve the quality of frozen fruit by using innovative techniques, in opposition to simply freezing. This present work proposed xenon hydrate formation for the reduction of bulk water before freezing in order to reduce freezing damage due to a large amount of ice crystal formation. The combined method of xenon hydrate formation and freezing has been proved to be able to reduce cell membrane damage usually occurring in frozen fruit. Thus this new technique has potential to be used for improving the quality of frozen fruit. The xenon hydrate formation is considered as an innovative technique for the preservation of fruit, which is expected to be useful for the frozen food industry.

Antifreeze Effect of Carboxylated ε-Poly-l-lysine on the Growth Kinetics of Ice Crystals

Some biological substances control the nucleation and growth of inorganic crystals. Antifreeze proteins, which prohibit ice crystal growth in living organisms, promise are also important as biological antifreezes for medical applications and in the frozen food industries. In this work, we investigated the crystallization of ice in the presence of a new cryoprotector, carboxylated ε-poly-L-lysine (COOH-PLL). In order to reveal the characteristics and the mechanism of its antifreeze effect, free-growth experiments of ice crystals were carried out in solutions with various COOH-PLL concentrations and degrees of supercooling, and the depression of the freezing point and growth rates of the tips of ice dendrites were obtained using optical microscopy. Hysteresis of growth rates and depression of the freezing point was revealed in the presence of COOH-PLL. The growth-inhibition effect of COOH-PLL molecules could be explained on the basis of the Gibbs-Thomson law and the use of Langmuir's adsorption isotherm. Theoretical kinetic curves for hysteresis calculated on the basis of Punin-Artamonova's model were in good agreement with experimental data. We conclude that adsorption of large biological molecules in the case of ice crystallization has a non-steady-state character and occurs more slowly than the process of embedding of crystal growth units.

Business strategies used by Micro-SMEs in a Bangkok street market

Purpose – This paper aims to report on research aimed at determining the nature of business strategies employed by micro small and medium-sized street vendors in a local market area in Bangkok. Design/methodology/approach – The research consisted of a longitudinal study of the defined research site, involving ethnographic interaction and observation mediated by the use of a research diary. Findings – The research found that the use of business strategies was quite limited and varied in line with the street vendor's relationships with other actors and business practitioners. Research limitations/implications – The research was deliberately limited in terms of space and is ongoing in terms of time. Additional areas of Bangkok will also be studied for comparative purposes. Practical implications – Street vending and markets offer valuable opportunities for informal employment and for part-time employment to provide additional income generation for the working poor. Vendors also help sustain a decent standard of living for migrant workers. Social implications – Street vending of this sort reflects the nature of underlying changes in urban life: the building of new mass transit routes, the opening of condominiums in place of shop houses and the flourishing of the frozen food industry. Many street vendors are mobile and flexible but not all of them. Originality/value – This paper contributes to the literature on street vending and urban micro-entrepreneurs and will be of interest not just to scholars of business but also in planning for social policy and urban management.

Thermal Inactivation of Human Norovirus Surrogates in Spinach and Measurement of Its Uncertainty

Leafy greens, including spinach, have potential for human norovirus transmission through improper handling and/or contact with contaminated water. Inactivation of norovirus prior to consumption is essential to protect public health. Because of the inability to propagate human noroviruses in vitro, murine norovirus (MNV-1) and feline calicivirus (FCV-F9) have been used as surrogates to model human norovirus behavior under laboratory conditions. The objectives of this study were to determine thermal inactivation kinetics of MNV-1 and FCV-F9 in spinach, compare first-order and Weibull models, and measure the uncertainty associated with the process. D-values were determined for viruses at 50, 56, 60, 65, and 72 °C in 2-ml vials. The D-values calculated from the first-order model (50 to 72 °C) ranged from 0.16 to 14.57 min for MNV-1 and 0.15 to 17.39 min for FCV-9. Using the Weibull model, the tD for MNV-1 and FCV-F9 to destroy 1 log (D ≈ 1) at the same temperatures ranged from 0.22 to 15.26 and 0.27 to 20.71 min, respectively. The z-values determined for MNV-1 were 11.66 ± 0.42 °C using the Weibull model and 10.98 ± 0.58 °C for the first-order model and for FCV-F9 were 10.85 ± 0.67 °C and 9.89 ± 0.79 °C, respectively. There was no difference in D- or z-value using the two models (P > 0.05). Relative uncertainty for dilution factor, personal counting, and test volume were 0.005, 0.0004, and ca. 0.84%, respectively. The major contribution to total uncertainty was from the model selected. Total uncertainties for FCV-F9 for the Weibull and first-order models were 3.53 to 7.56% and 11.99 to 21.01%, respectively, and for MNV-1, 3.10 to 7.01% and 13.14 to 16.94%, respectively. Novel and precise information on thermal inactivation of human norovirus surrogates in spinach was generated, enabling more reliable thermal process calculations to control noroviruses. The results of this study may be useful to the frozen food industry in designing blanching processes for spinach to inactivate or control noroviruses.

NEG モデルを用いた日系冷凍食品企業の海外立地と優遇措置に関する経済分析

NEG モデルを用いた日系冷凍食品企業の海外立地と優遇措置に関する経済分析

141 Inhibition of ice recrystallization by antifreeze proteins

Ice recrystallization (IR) is a process in which large ice crystals grow at the expense of smaller ones. It occurs constantly in nature and in industrial processes in conditions of moderate cooling of a partially frozen environment or at accelerated rate due to temperature fluctuations of frozen substances. IR is one of the major causes of smooth texture loss and deterioration of frozen food such as ice cream during storage. In cryopreservation, recrystallization during thawing, damages the cells and tissues due to membrane rapture and cell dehydration, reducing the survival rates. Organisms inhabiting cold environments and prone to IR injuries, such as freeze-tolerating plants and freeze-avoiding organisms like fish and insects have developed antifreeze proteins (AFPs), a subset of the Ice Binding Proteins group which interact with ice for various biological purposes. The AFPs adsorb to ice surfaces and restrict the growth of ice to the areas between bound protein molecules. Such proteins were shown to block IR effectively [Knight and Duman, 1986], and may serve as additives in many applications in which ice recrystallization is an obstacle. Although ice recrystallization inhibition (IRI) activity of a variety of AFPs was studied [Knight et al., 1995], the mechanism by which AFPs inhibit IR is unknown. Particularly, it has been shown that although insect AFPs have considerably higher freezing point depression activity relative to AFPs from fish and plants, their IRI activity is in the same range or lower [Yu et al., 2010]. We intend to study the mechanism of IRI in order to explain the inconsistency between this activity and the freezing point depression activity of insect AFPs. In our study the IRI activity of AFPs from mealworm Tenebriomolitor (TmAFP) was investigated. Sucrose solutions containing various concentration of TmAFP were cooled to −50 °C, then the temperature was elevated and sustained constant for annealing. During annealing, images of recrystallization were acquired using a light microscope equipped with fluorescence illumination and cold-stage. Initial results show an accumulation of TmAFP onto ice crystals and IRI in a range of AFPs concentrations. Our next goals are to develop test methods that will provide reliable, quantitative information on recrystallization and on the accumulation of the protein on the crystals, as well as depletion of the protein from the solution. Such methods will enable quantification of the ice recrystallization phenomena and subsequently quantification of the differences between the IRI activities of various types of AFPs. Understanding the mechanism of ice recrystallization and the effects of AFPs on it may improve and expand the use of AFPs in many applications in the medical sector, in cryopreservation, and in the frozen food industry. Source of funding: European Research Council (ERC). Conflict of interest: None declared. ido.braslavsky@mail.huji.ac.il

137 Controlling freezing using infrared radiation

Controlling ice growth is a significant tool in many fields such as preventing frost damage to plants, improving cryo-preservation of cells, tissues and organs, the frozen food industry, and cryopreservation procedures. We suggest a control of ice growth in super-cooled solutions by a combination of infrared (IR) radiation and antifreeze materials, such as antifreeze proteins (AFPs), for the purpose of cryobiology and food science. AFPs, which are part of the ice-binding proteins family, inhibit the growth of an ice crystal. As a result, the freezing temperature is reduced below the melting point. The hypothesis is that ice crystals can be stabilized in super-cooled solution by the use of the difference in the IR absorption of ice and water. Additional super-cooling can be achieved by AFPs. We use a homemade temperature-controlled system that allows fine control of the temperature of small amounts of liquid enclosed in a microdevice (Celik, Drori et al., 2013). The system includes an IR radiation to selectively heat and melt ice, due to the ability of IR radiation to heat ice more than water when a particular wavelength is chosen (Ullman, 2001). To measure the temperature within the device, we use a near-IR (NIR) camera and a band filter. This method is based on the temperature dependence of the NIR absorption of water (Kakuta, Fukuhara et al., 2011). Initial results show the ability to melt ice within microfluidic devices. We also were able to measure temperature field within the water using the IR camera. Simulation guided experiments are developed to show the control of ice growth using IR radiation in coexistence of ice crystals in super-cooled water. The combination we propose to control ice within miniature samples with an IR radiation and AFPs, opens the possibility of a new method for cryopreservation of cells and tissues. Source of funding: The Israel Science Foundation (ISF). Conflict of interest: None declared. ido.braslavsky@mail.huji.ac.il

143 Ice shaping in solutions of ice-binding proteins – Melting vs growing morphologies

A fundamental strategy evolved by organisms in cold habitats, obliged to cope with ice and freeze injuries, is ice-binding proteins (IBP). These proteins directly interact with ice surfaces and serve to depress the freezing point of the body fluids, to inhibit ice recrystallization, or to promote ice nucleation. The delicate control over ice growth make these proteins applicable in any field that requires control over ice growth, namely, in cryopreservation of cells, tissues and organs, in cryosurgery and in agriculture, in the frozen food industry and in complex material engineering. A variety of IBPs have been studied in the past decade, differing in sequences, structures, and specific activities. Most IBPs are grossly classified to moderate and hyperactive according to their thermal hysteresis activity, which is the gap between the equilibrium melting point and the freezing point of an ice crystal grown in IBP solution. We have studied the ability of IBPs to shape ice crystals in distinguishable forms characteristic of the particular protein type. IBPs with moderate thermal hysteresis activities induce elongated bipyramidal crystals – often with well-defined facets – while hyperactive IBPs produce more varied crystal shapes, such as the “lemon-like” crystals typically observed with Tenebrio molitor IBP. These unique morphologies are frequently considered to be growth shapes. We conducted a systematic study of ice shaping in solutions containing a wide range of IBPs. We found that although ice crystals in solutions of moderate IBPs do indeed grow into their faceted shapes, in the presence of most hyperactive IBPs, ice melts into its final shape. These melting shapes result from the affinity of the hyperactive IBPs for the basal planes of ice. A 3D simulation of a melting process using a velocity profile that reflects melting perpendicular to the basal plane confirmed our findings. Our results show a clear difference in the ice shaping mechanisms of moderate and hyperactive IBPs. This study implies that basal plane affinity may be predicted by simple observation of an ice crystal. Understanding the differences between the interactions of the various IBPs and ice is important for the future utilization of these proteins in industry and medicine. Source of funding: M.B.D was supported by The Lady Davis Fellowship thrust and The Valazzi-Pikovsky Fellowship Fund. The research was funded by the National Science Foundation (NSF), the Israel Science Foundation (ISF), the European Research Council (ERC). Conflict of interest: None declared. maya.bar1@mail.huji.ac.il

The Market Potential of Frozen Food Products in Bangalore

India is a large producer of food and is offering different opportunities and business propositions in food and food processing technologies, skills and equipment. The food-based industries encompass canning, dairy and food processing, specialty processing, packaging, frozen food/refrigeration. Products which come under the frozen food industry are fruits, vegetables, fisheries, milk products, meat, poultry and other packaged and convenience foods. Although it is a huge producer of food products, India still has immense untapped potential in the frozen food export industry. The demand for Indian recipes from the Indian settled across the globe has served as an impetus to development of the frozen food industry in recent years. Vegetables like drumsticks and okra and prepared food like chapattis and paratha’s are nowadays available in frozen form in neat packets all over the world. The frozen food market consists of the retail sale of frozen bakery and desserts, frozen fish/seafood, frozen fruit and vegetables, frozen meat products, frozen potato products and frozen ready meals and pizza. The availability of frozen foods in the Indian market has brought about great change in the life-style of the people of India. Earlier, women were spending lots of time in the kitchen and with the introduction of frozen foods; they are able to prepare a variety of mouth-watering dishes within no time to meet the taste of their family members. Among the different reasons for the popularity of frozen foods in India, the improving standard of living of the middle-income grouped people in India has also contributed towards the development of companies in the frozen food industry in India.

Effects of pre-existing bubbles on ice nucleation and crystallization during ultrasound-assisted freezing of water and sucrose solution

Abstract Power ultrasound has been proved to be a potential method to monitor and control crystallization phenomena, although it is a stochastic and probabilistic process. Cavitation plays a vital role during ultrasound assisting freezing processes since the collapse of cavitation bubbles can initiate nucleation and enhance heat transfer between cooling medium and frozen products. In the current study, water and sucrose solutions with or without pre-existing bubbles were frozen with ultrasound application for 3–5 s at 0.21 W/cm2 during the supercooling stage. The nucleation temperature and the delay from irradiation to nucleation at various ultrasound irradiation temperatures were studied. Statistical analysis of the results showed that nucleation temperature of liquid samples with bubbles exhibited a better fit to linear equation, while samples without bubbles did not. The nucleation of samples containing bubbles occurred at temperatures close to the irradiation temperatures with a short delay less than 1 s, which was shorter than that without bubbles. In addition, the lagging time between the start of ultrasound irradiation to the occurrence of nucleation was shortened with the decrease in ultrasound irradiation temperatures. In addition, under the influence of ultrasound, water saturated with air bubbles nucleated at − 1 °C with a shorter delay than water subsaturated with air bubbles, while nucleation of water subsaturated with air bubbles occurred after a shorter delay than water saturated with air bubbles at the temperature of − 2, − 3, − 4 and − 5 °C, indicating that a number of pre-existing bubbles in liquid samples may also turn into cavitation bubbles similar to the ones generated by ultrasound. Results of the current study implied that the method of injecting bubbles into liquids before freezing could be used to initiate and control the nucleation process for liquid samples during ultrasound assisting freezing. Industrial relevance The study indicated that adding bubbles to liquid samples could be a promising and feasible approach to improve the effectiveness of ultrasound irradiation on the initiation of nucleation. This approach could have great potential for the frozen food industry.