CHEMICAL ENGINEERING TRANSACTIONS VOL. 57, 2017 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Sauro Pierucci, Jiří Jaromír Klemeš, Laura Piazza, Serafim Bakalis Copyright © 2017, AIDIC Servizi S.r.l. ISBN 978-88-95608- 48-8; ISSN 2283-9216 Fish Processing by Ozone Treatment - Is Further Investigation of Domestic Applications Needful? Charles Odilichukwu R. Okpala Educare and Skills Training Network, Middlesex HA8 8EJ, United Kingdom charlesokpala@gmail.com Over the years globally, the trends of fish product utilization have been diverse. On the other hand, a number of process technologies have helped to actualize fish product development. Besides ozone processing showing high preservation promise, ozone after declared Generally Recognized As Safe (GRAS), has steadily evolved up to domestic facilities for home use. Recent tests performed on a domestic facility reported promising results on some characteristic properties of ozone-processed shrimp with storage time. In this terse opinion communication, the need for further investigations into other commercially available domestic ozone facilities is justified. 1. Introduction: Fish Processing Methods – A Modest Tabulation Over the years globally, the trends of fish product utilization have been diverse. In particular, fish products have served great healthful uses owed to their chemical composition, providing global population with nourishment as well as industrial by-product resources (Okpala et al., 2014; Okpala, 2017a, d&e; Sen, 2005). To advance human health and product development, various food process technologies have been developed and evolved over time, probably to overcome the deficiencies of the traditional conventional methods such as drying, salting up to typical refrigeration (Hall, 1997; Okpala et al., 2014; Okpala, 2015a; Sen, 2005). Table 1: Some fish processing technologies by class with some terse remarks Technology name Technology class Terse remarks Modified Atmosphere Packaging Non-thermal The use of headspace gases to bring about food preservation Minced Processing Non-thermal Considerable recovery of edible fish flesh from waste using bone separator Retort Pouch Thermal Sealing of already prepared fish product using flexible multilayer plastic Irradiation Non-thermal The application of ionizing radiation energy of liberated electrons for targeted fish shelf preservation Ozone treatment Non-thermal The application of generated ozone on fish products targeted product shelf preservation Microwave Thermal The use of electromagnetic waves ranging between 300 MHz and 300GHz converted to heat, aimed at fish product preservation Examples of promising food technologies applied to fish products include Modified Atmosphere Packaging (MAP), Minced processing, Retort Pouch, Irradiation, Ozone treatment, and Microwave (Hall, 1997; Okpala, 2014 and 2015b; Sen, 2005). Some fish processing technologies by class with some terse remarks have been summarized in Table 1. Whilst these food processes possess both merits and demerits regardless of class, that is, non-thermal up to thermal, all put together have received massive research attention/interest across DOI: 10.3303/CET1757303 Please cite this article as: Okpala C.O.R., 2017, Fish processing by ozone treatment – is further investigation of domesticc applications needful?, Chemical Engineering Transactions, 57, 1813-1818 DOI: 10.3303/CET1757303 1813 the globe and have either individually and/or collectively played diverse function(s) towards fish product development (Hall, 1997; Okpala et al., 2016a-c; Okpala, 2016a-b; Sen, 2005). 2. Ozone Processing declared ‘GRAS’ and thereafter Figure 1 shows the technological progress of ozone since discovery indicating key inventors, locations and context/situation. From the early times when ozone was recognized as odour, assigned ‘O3’ as simplest formula, early applications to food and non-food materials, it was only when US Food Drug Administration (FDA) declared it as ‘Generally Recognized As Safe (GRAS)’ and amended their food additive regulations to ensure that either aqueous and/or gaseous ozone would be safe, that the globe embraced this bio-based broad-spectrum antimicrobial. Since then, pursuits have continued for ozone to attain more environmental friendly process (O’Donnell et al., 2012; Okpala, 2017a-b). Ozone in food industry remains driven by factors such as consumer and processor acceptability, environmental impact, food safety and shelf life extension, as well as regulatory and legislative concerns. It is well understood that to obtain optimal results, ozone is better discharged on a fresh produce (O’Donnell et al., 2012; Okpala, 2014 and 2015b). Whilst the chemical and physical properties of ozone has greatly influenced its efficacy, how ozone is generated today, whether it is corona discharge or ultraviolet methods, has not so much deterred researchers from attempting its application on wide range of foods such as fruits and vegetable, grains, meat, seafood as well as non-food aspects such as food industry sanitization, water treatment, food waste and odour treatment and so on (O’Donnell et al., 2012; Okpala, 2015b and 2017a). In addition to ozone already considered as non-destructive to biochemical properties of fish flesh, it is also ascribed among most powerful oxidizing substances commercially available (Okpala, 2014, 2015a and 2017a). Figure 1: Technological progress of ozone since discovery indicating key inventors, locations and contexts/situations. 3. Ozone Discharge up to Applications/Treatments Ozone discharge occurs in three forms, namely: corona, ultraviolet and electrochemical. The most common is the corona type, which is widely applied in either laboratory and/or industrial settings. Ozone reaction processes have been well discussed by other authors (Goncalves, 2009; Guzel-Seydim et al., 2004a&b; Kim et al., 2003; O’Donnell et al., 2012). Ozonation – when ozone is pumped into liquid/water medium at specific flow rate and time – has also been reported elsewhere (Jiang et al., 1998). As a triatomic molecule, ozone, not 1814 only classed as allotrophic modification of oxygen, it remains in gaseous form at refrigerated/room temperature with oxidation-reduction potential of 2.07 v (Kim et al., 2003). Respectively, concentration ratio of ozone in gas and water is 1.13 and 0.26 – all of which are dependent on water temperature (Okpala, 2017d). Whilst ozone stays more stable in gas compared to aqueous (O’Donnell et al., 2012; Tomiyasu et al., 1985), if there be high pH in medium to interfere with stability of ozone molecule, its stability in water would take place with an increase in pH (O’Donnell et al., 2012; Okpala, 2017d; Ouederni et al., 1987). Figure 2 shows the schematic diagram for set-up of ozone generator highlighting corona discharge approach/methodology. The connection of various components is shown, from oxygen cylinder up to the electrodes (high and low tension). Also shown is the use of about 4% used to capture excess ozone, which has been reported (Okpala et al., 2015; Okpala, 2017d). Some ozone application on food material(s)/product(s) by purpose/type(s) are presented in Table 2. It is shown that nature of ozone on foods, i.e., aqueous and gas, focus on decontamination as well as shelflife extension (Kim et al., 1999; Kim and Yousef, 2000; O’Donnell et al., 2012; Okpala et al., 2015; Okpala, 2017d). Some ozone-food processing facilities are presented in Table 3. It is showed that regardless of ozone application/combinations, whilst ozone discharge on food process facilities/system involve equipment surfaces, confectionary plants, sanitizer for dairy/food plants up to domestic types, the microbial reduction still remains considerable. Clearly, there is useful evidence of microbiological efficacy of ozone when applied on food and non-food surfaces. This microbiological efficacy of ozone treatment has also been dealt with in Khadre et al (2002), especially how it relates with reactivity, temperature and pH. Anyways, considering the working operation of ozone generator regardless of application, whilst the passage of air through generated feed gas can result in production of 1 – 4% ozone, the use of pure oxygen can equally result in production of up to between 6 – 14% ozone. Notwithstanding this, the free radicals well known to associate with ozone are the core of its high reactivity and oxidizing power (Guzel-Seydim et al., 2004 a&b; Khadre et al., 2001; Kim et al., 1999; Kim and Yousef, 2000; O’Donnell et al., 2012; Okpala, 2014 a&b; Okpala, 2017d). Figure 2: Schematic diagram for set-up of ozone generator highlighting corona discharge instrument; Key: A= Oxygen cylinder; B= Flow Rate Controller; C= Bubble Type Flow Meter; D= Ozone Generator; E = Transformer; F& G= Excess Ozone Traps (4% KI); H= Rotating Vessel (90 rpm); V = Valve; X= High Tension Electrode; Y= Dielectric; Z= Low Tension Electrode (Adapted from Okpala et al., 2015; and Okpala, 2017d). Despite the differences in production of ozone, its concentration in particular is believed not to go up beyond the point where both the rate of formation equals with that of destruction. Therefore, there is a higher chance that the storage of gaseous ozone would be almost impossible given its nature of spontaneous degradation into oxygen atoms (Goncalves, 2009; Guzel-Seydim et al., 2004 a&b; Jiang et al., 1998; Okpala et al., 2015). Particularly, as per this current communication, the use of domestic types of ozone application has been of increasing/keen interest to the author. Also, in the view that this facility type is now commercially available around the world, it therefore becomes more imperative for makers of ozone equipment to continue to search for ‘best’ safe applications that would deliver the needs of consumers as well as industry. Also, the use of domestic ozone facility contributes well to the fact that ozone is gaining stronger grounds as a sanitizing agent for the food industry (Okpala, 2017d). 1815 Table 2: Some ozone treatment applications on food material(s)/product(s) by purpose/type(s). Ozone treatment/type Food material Product Purpose of application References Aqueous Meat; beef; fish, poultry meat 1) Decontamination 2) Extension of shelflife and quality O’Donnell et al. (2012) Okpala et al. (2015) Okpala (2017d) Aqueous and gas Applies; blackberries; strawberries and grapes 1) Decontamination; 2) Extension of shelf-life and quality improvement O’Donnell et al. (2012) Kim et al. (1999) Kim and Yousef (2000) Gas + vacuum + Heat Eggs 1) Hyper-pasteurization process; 2) Decontamination Kim et al. (1999) Kim and Yousef (2000) Okpala (2017d) Table 3: Some ozone-food processing facilities with microbial reduction impact Ozone application/combinations Food process facility/system Microbial reduction impact References Ozone (aqueous) Food processing equipment surfaces Up to 95% microbial plate count reduction O’Donnell et al. (2012) Ozone + H2O2 Confectionary plant; Hatchery equipment; Packaging film Up to between 95 – 99% microbial plat count reduction Kim et al. (2003) O’Donnell et al. (2012) Ozone (aqueous) Domestic ozone facility; Sanitizer for dairy and food plants Up to between <3 - <5 log reduction Okpala (2014a-b) Okpala (2017d) O’Donnell et al. (2012) 4. Domestic Ozone Facility used for Fish Processing: Some Reported Points As quest for societal welfare continually rises, the food industry continues to pursue innovative design of bio- based materials (Okpala, 2017d). Clearly, relevant literature presents ozone treatment as promising preservative candidate for the fish industry. The declaration of ozone as GRAS by FDA, not only paved way for its application to the fish industry, but also, has greatly contributed to advance this preservative technology (O’Donnell et al., 2012). Health regulatory standards continually advise manufacturers of ozone generating facilities to authenticate, establish, and verify the optimum amounts that would produce significant effects on food. This is because the concentration of residual quantities of ozone in direct contact with food flesh has to be insignificant (O’Donnell et al., 2012; Okpala, 2014 and 2017a). In recent times, ozone use has evolved up to household generating devices capable of purifying tap water, and clean fruits and vegetables. This form of ozone process technology (OPT), not only an additional intervention and promising for food industry, the author recently used a household ozone-generating device (O3 Fresh TM, Model SQ-8-BA, Ovoproducts, Leicestershire, UK) to investigate ozone-processed shrimp subject to iced storage. Complying with European Council Directive 73/23/EEC and 93/68/EEC (as amended), this device is commercially available and increasingly situated in many home kitchens. It has built-in ozone concentration discharge of 100 mg/h into water, wash and spin capacity of 4 L, and three exposure levels/wash cycles of 1, 3, and 5 min – all fixed by manufacturer. Typically, by adjusting ozone exposure/wash cycles, the treatment levels can be determined (Okpala, 2014; Okpala, 2017a-c,&e). To operate this facility (at ~ 25 °C), the shrimp (fish) product was placed in the evenly perforated removable basket and filled with (recommended) tap water up to the indicated level. When wash cycles is switched-on, the removable basket revolves/spins concurrently with ozone discharge to ensure rapid, regular and even distribution of ozone constituent particles within the water medium (Okpala, 2014, 2015b, 2016, 2017a-b). The characteristic properties determined on the tested ozone-processed shrimp samples ranged from chemical, physical, and microbiological parameters. The resultant data showed promising preservation trends (Okpala, 2014, 2015b, 2016, 2017a-b). Besides the characteristic trends showing promising preservation potential of the household ozone facility with storage time (Okpala et al., 2016b), there were some energy considerations of ozone-processed shrimp, such as total energy, which showed no significant differences (Okpala et al. 2015). The authors understood that it was fairly difficult to ascertain the total energy outcomes in the ozone- processed shrimp, which in that publication was indicated as good justification for future research. 1816 5. Concluding Remarks: Is Further Investigation Needful? To best of author’s knowledge, it appears that only shrimp product has been tested using domestic ozone facility. The latter, whilst increasingly becoming commercially available and promising candidate for food safety, the results evidenced on one fish-food type (that is, shrimp) would definitely not suffice to make strong food technological case, but can only be for a start. As a matter of fact, other domestic/home ozone facilities that may or may not resemble that reported by the author, might well possess different concentration discharge as well as treatment levels/wash cycles. This creates avenue for new research questions to emerge, which according to Okpala (2017c), may help to actualize specific (researchable) objectives, and then consolidates to build-up an overall aim. In this context therefore, there is need to encourage other researchers to use domestic ozone facilities to engage in further studies. It is important that such further studies are warranted to involve other commercially available domestic ozone facilities, to test it on a wide range of economically important fish products not only to generate more robust data towards product development but also to authenticate, consolidate and validate the preservation potential of domestic facility in food processing technology. 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