Synergetic effect of microwave blanching and modified atmosphere packaging using laser micro-perforated bags on the storage quality of carrot

Abstract

Fresh food products such as vegetables and fruits are a remarkable source of vital nutrients including micronutrients, vitamins, fibres and various phytochemicals which are essential for human health. In general, due to their high moisture content, fruits and vegetables are highly perishable, hence reduced quality and shelf life are a major challenge for storage purposes and limit the availability of these fresh products (Hussein et al., 2015). Some studies have reported that this reduction in quality and shelf life may occur as a result of continued life processes in fruits and vegetables even after harvest as a result of ongoing metabolic activities such as respiration, ripening and also from presence of mechanical damage and physiological disorders (Irtwange, 2006; Sandhya et al., 2010; Siddiqui, 2011). These underlying causes of deterioration lead to undesirable quality changes in factors such as texture, colour, flavour and beneficial healthy values (Defilippi et al., 2005). Overall, if these factors are not properly controlled, they might eventually lead to reductions in edibility, availability, food losses, and subsequently in financial losses (Defilippi et al., 2005; Fallik, 2004; Irtwange, 2006; Mahajan et al., 2014; Opara et al, 2009; Opara et al., 2012). © 2021 Institute of Agrophysics, Polish Academy of Sciences M.C. EZEANAKA et al. 188 Carrots are one of the most preferred root crops because of their high nutrient content such as beta-carotene, dietary fibre, vitamins and minerals as well as their versatility in culinary uses due to their special taste (Gaggiotti et al., 2019). However, carrots are highly susceptible to moisture loss which leads to freshness and quality degradation (Larsen and Wold, 2016). Hence, an effective preservation technique is required to preserve such food products and maintain their quality while extending shelf life to make them readily available even during off seasons. Many food preservation techniques have been applied to date and have in turn been reviewed by many researchers. Chemical based treatments such as antioxidant treatments and washing with ozonized water and sanitizers for food pretreatment are among the preservation techniques which have been effective in the preservation of food products (Beltrán et al., 2005; Garcia et al., 2003; Garcia and Barrett, 2002). However, consumer awareness concerning food safety and health benefits has resulted in the minimization of the use of these chemicals in the food industry (Hussein et al., 2015). Moreover, research has shown that using these chemical washings and sanitizers cannot guarantee the production of foods free from microbial contamination and without affecting the sensory quality of food products (Martin-Diana et al., 2007). As a result, most of these washing sanitizers and inorganic chemical treatments presently face serious challenges to gain widespread acceptance in the fresh produce industry (Martin-Diana et al., 2007; Worth et al., 2002). Smart packaging, also referred to as IP (intelligent packaging) is another remarkable innovation primarily designed to track food, sense the internal and external surroundings of the package and is capable of conveying any notable changes to the food manufacturer or producer, hence it effectively monitors the safety status and quality of the food product (Aindongo et al., 2014; Yam et al., 2005). Active packaging is also another recognized innovation which involves the use of emitters and absorbers or a discharging system of active components, ethylene emitters/ scavengers and also moisture absorbers in the packaging material (Rodriguez-Aguilera and Oliveira, 2009). The active ingredients extend shelf-life by modifying the atmosphere surrounding the product inside the package (Jacxsens et al., 2003). However, the extensive use of these intelligent and active packaging methods and their practical application is limited mainly because of regulatory issues and practical limitations including high costs (Realini and Marcos, 2014; Yam et al., 2005). The need for appropriate pretreatment and non-invasive easily available packaging that will prevent desiccation, reduce contamination as well as retaining the appeal of freshness and prolonging shelf life continues to gain more interest in the food industry. Blanching treatment stabilizes the texture, flavour, colour and nutritional quality content of the product and inactivates enzymes which catalyse deleterious changes. According to (Terefe et al., 2014) the activity of deteriorative enzymes such as peroxidase (POD), Polyphenol oxidase (PPO), lipase, chlorophyllase, and lipoxygenase (LOX), together with the presence of microorganisms associated with enzymatic activity may be responsible for colour changes, adverse changes in flavour and a reduced shelf life in fresh vegetables and fruit. Some studies have reported that browning discoloration and anthocyanin degradation in lychee fruit correlated to a significant extent with increased POD activity during storage (Zhang et al., 2003; Zhang et al., 2005). (Funamoto et al., 2002; Funamoto et al., 2003) reported that chlorophyll degradation in broccoli correlated with increased POD activity. (Xiao et al., 2017) stated that blanching helps to inactivate both enzymes and microorganisms. Hence, this process maintains quality while extending the shelf life of food (Anthon and Barrett, 2002; Begum and Brewer, 2001; Tunde-Akintunde, 2010). Some researchers have reported on the effects of blanching in various food products. Others have reported on the preferred influence of microwave blanching compared to other blanching methods (Bhattacharya et al., 2017; Bingol et al., 2014; Quarcoo and Manu, 2016; Ruiz-Ojeda and Peñas, 2013; Severini et al., 2016). Moreover, it reduces microbial load and does not affect sensory quality. The application of various aspects of modified atmosphere packaging (MAP) on different fresh produce has been examined by many researchers. This technique involves the use of gas mixtures to preserve food according to a particular food requirement. Many researchers have also reported on advancements in the use of MAP and its potential to extend shelf-life and preserve the quality of fresh food products (Aindongo et al., 2014; Oms-Oliu et al., 2008; Qu et al., 2020; Sandhya et al., 2010; Soliva-Fortuny and MartinBelloso, 2003). Others have examined the influence of MAP on subsequent outbreaks of foodborne diseases and the growth of resistant foodborne pathogens (Aindongo et al., 2014; Harris et al., 2003). Additionally, MAP is known to be comparatively cheap and easier to use as it does not involve any protocols which have a long duration. Permeability is one of the factors to be considered when using MAP, which is particularly the case for produce with a high rate of respiration. In some cases, the levels of the components of the packaging atmosphere attained using traditional MAP are not sufficient to maintain quality of produce for a sufficient length of time (Jarvis et al., 2017; Mangaraj et al., 2009; Sandhya et al., 2010). Also, moisture condensation can occur as a result of fluctuating temperatures (Linke and Geyer, 2013). This may lead to the development of undesirable properties such as off-odours and anaerobiosis and can severely modify the volatile profile of packaged food product (Aindongo et al., 2014, Martín-Belloso et al., 2013). Alternatively, the use of a perforated MAP has been proposed as a technique to overcome these limitations (Hussein et al., 2015; Rodriguez-Aguilera and Oliveira, 2009). It is important to note that several MICROWAVE BLANCHING AND MAP FOR STORAGE QUALITY OF CARROT 189 authors have reported on the use of blanching as a viable pretreatment of fresh food products and also highlighted the use of MAP for extending shelf life. However, as yet, no research has been conducted on the combined effect of blanching and micro-perforated-MAP on carrot storage quality. This research aims to evaluate the synergetic effect of microwave blanching and micro-perforated MAP on carrot quality during storage. MATERIALS AND METHODS Fresh carrots (Daucus carota ) were purchased from Auchan supermarket (Wuxi, China), at the full ripeness stage. The carrots were refrigerated at 4°C, less than 24 hours prior to processing. The carrots were first washed, peeled and finally sliced into 8-mm pieces before being blanched in water at 360 W for 300 secs using a microwave oven (Panasonic Co., Ltd, China) with a maximum rated power of 800 W at 2450 MHz. The internal dimensions of the microwave oven were approximately 302×509×348 mm (Başkaya et al., 2015). The actual microwave power level was 669 W using the IMPI-2L method (Saifullah et al., 2019). For the experiment, 100 g of carrot slices was blanched and cooled immediately in ice. Afterwards, the surface water was removed using a water removal machine (Shandong Duckling Group Home Appliance Co. LTD China, Model T 68-188 dehydrator) at 50 W for 2 min.