Impact of non-processing technology in dairy products for microbial safety | Foo

1. Impact Of Non-Processing Technology In Dairy Products For Microbial Safety Dr. Nancy Agnes, Head, Technical Operations, FoodResearchLab, info@foodresearchlab.com temperature processing have been investigated in great depths to inactivate and destroy the pathogenic and spore-forming microorganisms. Researchers have worked closely on pathogenic organisms such as Listeria monocytogenes, Staphylococcus aureus, Escherichia coli,Bacillus cereus, Salmonella spp., Campylobacter spp, which are the major causes for the occurrences of foodborne illness worldwide. I. INTRODUCTION Dairy products, especially milk is highly perishable as it contains ample nutrition and high in moisture content for the microorganism to grow and multiply. To enhance food safety and protect the quality, non-thermal processing technologies are gaining significant attention in the Food Industry. Currently, consumers are opting for minimally processed foods that are close to natural tastes. Hence the dairy industries are moving towards non-thermal processing technologies which deliver fresh and nutritious foods with better shelf-stability. The microbial inactivation during the processing is critical for improving the shelf-life of milk. Common methods such as pasteurization, The main challenge with thermal treatments is that they damage some nutritional components while microbial inactivation, which also involves undesirable flavour changes. To avoid these nutritional and organoleptic changes, non-thermal treatments such as pulsed electric field (PEF), high- pressure processing (HPP), ultrasound, membrane ultra-high 1 Copyright © 2021 Food Research Lab. All rights reserved

2. filtration and non-thermal plasma have been deployed. and taste. PEF treatment (35 kV/cm, 2.3 μs pulse width, at 65 °C for < 10 sec) shown significant pasteurization results similar to a high-temperature short time (HTST) pasteurization. Moreover, the sensory properties of PEF treated products were found to have a better consumer acceptance rate compared to the thermal counterparts. II. PULSED ELECTRIC FIELD (PEF): PEF has gained significant popularity as it destroys both spoilage and pathogenic bacteria and fungi. PEF also inactivates enzymes related to quality deterioration without causing any changes in flavour Table 1 Effect of PEF on microbes present in dairy products. Adapted from 1 Treatment conditions Reduction Microorganisms Dairy food References Milk submitted to ultrafiltration 50 pulses of 60 kV/cm or80 pulses of 70 kV/cm 6 and 9-log Qin et al. (1998) E. coli 36 kV/cm, 50 pulses Pasteurized skim milk Fernández-Molina (2001) 200 μs at 50 kV/cm 2.6-2.7-log L. innocua 15 to 28 °C, 0.5 L/min100 pulses, 50 kV/cm 0.5 μF,2 μsec, 3.5 Hz Exponential decay Fernández-Molina et al. (1999a) Cregenzán-Alberti et al. (2015) Raw bovine milk 89 μs at 40 kV/cm at 32.5 °C 5-log –E. coli K12 2 Copyright © 2021 Food Research Lab. All rights reserved

3. Raw whole milk 30 kV/cm after 200 μs 2.1-Log Zhao et al. (2013) E. Coli Sobrino-López Martin-Belloso (2006) & UHT milk 5-Log L. monocytogenes 150 bipolar pulses of 8 μs at35 kV/cm 4.5-Log S. aureus Michalac (2003) et al. Skim milk 35 kV/cm, 90 μs, 22 °C 1-log L. lactis K (x10-2/μs) = 0.054-0.52,15- 40 kV/cm, Temp = 15-40 °C 4-42.4 μs D value Skim milk Sensoy et al. (1997) Salmonella Dublin L. (Scott A) monocytogenes Milk Reina et al. (1998) 150-200 μs D value K (x10-2/μs) = 0.077-0.092,16 kV/cm, Temp < 30 °C 2500-3000 μs D value SMUF Pothakamury, (1995) E. coli Raw skim milk (0.2% milkfat) Qin et al. (1994) L. innocua 425-520 μs D value Fernández-Molina et al. (1999b) B. subtilis Milk L. delbrueckii 4-7 Log P. fluorescens S. Dublin Dunn & Pearlman (1987) Yogurt (50 °C, 1.8 V/μm 2.0-log Lactobacillus brevis B. stearothermophilus 3.4% fat milk 60 kV/cm, 200μs, 50 °C (Tin) 3-log Shin et al. (2007) P. fluorescens Michalac (2003) et al. Skim milk 35 kV/cm, 90 μs, 22 °C 1-log L. lactis Infant milk formula Pina-Perez (2009) et al. Cronobacter sakazakii 35 kV/cm, 500μs, 5 °C (Tin) 1.2-log 3.6% Fat whole milk 29 kV/cm, 250 μs, < 45 °C 1.5-2-log Picart et al. (2002) L. innocua Guerrero-Beltrán et al. (2010) Whole milk 40 kV/cm, 43.75 μs, 68 °C 5.5-log L. innocua Sobrino-López Martín-Belloso (2008) & Skim milk 25 kV/cm, 100 μs, ~50 °C 3-log S. aureus pathogenic and spoilage microorganisms to increase the stability and shelf life of food Product development. HPP can characteristics depending on the duration of treatment and the temperature applied, creating irreversible changes in the structure. The particle size of skim III. HIGH PRESSURE PROCESSING (HPP): alter the protein HPP employs high pressure in the range of 100-600 MPa for up to 20 min duration to eliminate 3 Copyright © 2021 Food Research Lab. All rights reserved

4. milk decreases substantially from 200 to 100nm, when subjected to HPP treatment at 300MPa. HPP is also mainly chosen for minimal nutrient loss and significant microbial load reduction. To maintain the organoleptic properties of the milk, HPP treatment combinations could be used to provide an increased shelf-life and fresh sensory properties. Table 2 Effect of HPP on microbes present in dairy products. Adapted from 1 Treatment conditions Microorganisms Dairy Food Reduction References B. stearothermophilus Skim milk 84 °C at 300 MPa 0.67-log Pinho et al. (2011) Commercial sterile milk 300 MPa at 75-85 °C ~5-log CFU/mL Amador Espejo et al. (2014) Bacillus spores Milk K (1/min) = 3 min D value Patterson et al. (1995) S. typhimurium 0.6 min D value Patterson & Kilpatrick (1998) 0.768, 350 MPa Y. enterocolitica 0.768, 375 MPa E. coli Gervilla et al. (1997) 2.303,300 MPa S. aureus Kalchayanand et al. (1998) 3.838, 345 MPa L. monocytogenes P. fluorescens 9.21 min D value Raw milk 25 °C, 300 MPa Erkmen, (2009) S. typhimurium 13.6 min D value Shao & Ramaswamy, (2011) Milk 90 °C, 700 MPa C. sporogenes Raw milk with 15% fat 300 MPa, 25 °C 1.2 to 4.0-log Briñez et al. (2007) E. coli MG1655 100 MPa, 2-4 °C L. innocua S. aureus chemical functional properties. The use of the US in the food industry is limited compared to the other non-thermal processing techniques. However, the US can be used in the removal of gases and homogenization of fat and also improve the availability of antioxidants. IV. ULTRASOUND (US): The US technology is the most commonly used technology in the food industry around the globe as it is eco-friendly, non-toxic and showcases various applications in the food industry. The US is greatly used in the homogenization and inactivation of microbes (via sonication) present in milk and in novel dairy products which have unique physio- Microorganisms Dairy Food Table 3 Effect of US on microbes present in dairy products. Adapted from 1. Reduction Treatment conditions 20 kHz, 120 μm,12 min, 60 °C 20 kHz, 10 min, 750 W References 3.1-log Herceg et al. (2012) E. coli Raw whole 4% fat cow’s milk Raw milk (pasteurization) 2 to 5.34-log CFU/g Cameron et al. (2009) E. coli P. fluorescens 4 Copyright © 2021 Food Research Lab. All rights reserved

5. L. monocytogenes L. monocytogenes S. typhimurium UHT milk Heat at 60 °C with Sonication at 20 kHz 30 min at 50 °C 30 min at 40 °C 110 μm, 60 °C D60&S = 0.3 min 3-log 2.5-log D60&S = 23s Earnshaw et al. (1995) Skim milk Wrigley and Llorca (1992) Zenker et al. (2003) UHT milk (pH 6.7) E. coli K12DH5 go mainstream; however, manufacturers should look into the drawbacks which are holding them back. V. PLASMA AND LOW PLASMA TECHNOLOGY (PT): PT is the newest addition to the non-thermal technologies, having various application to the food and dairy industry. PT has proven to improve the quality of the end product with enhanced microbial safety from both pathogenic and spoilage microbes. Just like HPP and PEF, PT has also shown to preserve the sensorial, organoleptic and nutritional properties of the foods. The mechanism of PT is based on the additional gas energy which is getting fed by electrical discharge turning it into energy-rich plasma. Plasma consists of free radicals and electrons which is highly reactive. Moreover, it is important to note that PT induces modification on the surface of the food as the radicals react on the surface and are not capable of penetrating the matrix. PT is also used for enzyme modification and inactivation, wastewater treatments and modified food packaging. References: 1. Shabbir, M. A., Ahmed, H., Maan, A. A., Rehman, A., Afraz, M. T., Iqbal, M. W., ... & Aadil, R. M. (2021). Effect of non-thermal processing techniques on pathogenic and spoilage microorganisms of milk and milk products. Food Science and Technology, 41(2), 279-294. 2. Evrendilek, G. (2014). Non-thermal processing of milk and milk products for microbial safety. Dairy microbiology and biochemistry: recent developments, 322, 322-355. VI. CONCLUSION The operational cost of HPP continues to decrease due to its increased demand in the industry. The average processing cost of HPP ranges between 0.05 to 0.5US$ per kg of food. The operational cost of PEF ranges between 0.01 to 0.02 US$ per litre of food. This cost of non-thermal techniques operation is 10 times greater than conventional thermal processing cost. US technology can be used cost- efficiently for extraction and rapid crystallization procedures, providing increased yield in less time. Moreover, the current limitations with non-thermal processing technologies are that it involves huge investment and lack regulatory support in a few countries. To technologies are capable of reducing the microbial load similar to thermal processing techniques, with an added benefit of minimal loss of nutritional contents. A combination of these techniques called hurdle technology can be used to obtain massive results, such as destroying pathogenic microbes which is not possible otherwise. Therefore, there is great scope in the near future for these techniques to sum, although these novel non-thermal 5 Copyright © 2021 Food Research Lab. All rights reserved