Incorporation of apricot (Prunus armeniaca) kernel essential oil into chitosan films displaying antimicrobial effect against Listeria monocytogenes and improving quality indices of spiced beef
Introduction
As one of traditional meat products cooked by the addition of spices in China, spiced beef is quite popular with young consumers owing to its attractive taste and entrancing flavor [1]. In shopping centers and agricultural markets, spiced beef is placed on the chopping boards so that the consumers can purchase as their wishes [2,3]. Nevertheless, although spiced beef was cooked using some spices that containing phenolic compounds with antimicrobial effect, it is still confronted with challenge of the invading of spoilage bacteria including Listeria monocytogenes [4,5].
L. monocytogenes can tolerate the living environment of low pH and high concentration of salt and survive in refrigeration condition, and lead to odorous smells, shadowy colors and undesirable sensory attributes of meat products [6,7]. When the meat products contaminated with L. monocytogenes are digested, they can affect pregnant women, newborn babies and elder adults with weak immune system, and result in meningitis, septicemia, or even the spontaneous abortions [8,9]. What is worse, it can cause a quite serious illness with a mortality rate of 12.7%, listeriosis [10]. Naturally, in order to prevent the contamination of L. monocytogenes during the preparation of meat products, several synthetic substances have long been employed as additives. However, people have expressed strong anxiety about the employment of these substances because of the carcinogenic and teratogenic diseases associated with them [11]. Meanwhile, the secondary metabolites of vegetables/fruits with antibacterial effects against L. monocytogenes have obvious potential as meat product preservatives owing to their high safety index, especially essential oils [12]. For instance, Coriandrum sativum essential oil was demonstrated to display prominent antibacterial activity against L. monocytogenes in cooked pork sausages [13]. Thymus capitata essential oil was found to reveal apparent preservative effect against L. monocytogenes in minced beef meat [14]. Therefore, it's quite meritorious and indispensable to search for antibacterial agents from vegetables/fruits for L. monocytogenes.
As reported, when vegetable/fruit essential oils directly added to food including meat products, their antibacterial effect may be quite limited [15]. The good news is that application of the edible films incorporating essential oils is more efficient than the direct addition of essential oils to the food including meat products [16]. By this way, they can selectively migrate from the packaging onto the surface of the meat products, thereby maintaining high concentrations where they are most necessary, and overcoming the disadvantages as follow: (1) The high volatility may reduce the efficiency because of their thermally instability and special requirement for encapsulation to obtain prolonged release [17]. (2) The low solubility may reduce the efficiency so that their antibacterial effects in vivo are lower than in vitro [18]. (3) The intense aroma may change the sensory properties of meat products so that reduce consumers' acceptability [19]. (4) Together with the potential toxicity, the application cost may cause their limitation in the preservation of meat products [20]. Among them, the antibacterial effect of the chitosan (CS) films incorporating essential oils has been frequently investigated [21,22]. In fact, CS is a linear polysaccharide of randomly distributed N-acetyl-d-glucosamine and β-(1-4)-linked d-glucosamine, which has been recommended to be an edible packaging material owing to its biodegradability, biocompatibility, non-toxicity and good film-forming properties [23]. Quite interestingly, the incorporation of essential oils in CS films has been reported to have strong antibacterial activity [16]. Therefore, it should be meaningful to explore the antibacterial of CS films incorporating with essential oils from vegetables/fruits in meat products.
As an everyday fruit, apricot (Prunus armeniaca) has an immensely popularity for its attractive aroma and great taste [24]. Recently, the CS films incorporating apricot kernel essential oil (AKEO) were demonstrated to exhibit antibacterial effect [25]. Consequently, the aim of the investigation was to explore the influence of CS films incorporating AKEO on L. monocytogenes and the quality of spiced beef.
Section snippets
Materials
Apricot seed kernels harvested from the countryside of Xinxiang, China and spiced beef produced by Dennis Group were purchased from Hongzhuanlu Shop of Dennis Supermarket at Zhengzhou, China in July 2019. CS (molecular weight 2.9 × 105 g/mol) and the foodborne pathogen L. monocytogenes (ATCC 7644) were provided by Institute of Chinese Medicine Health Care, Guangdong Food and Drug Vocational College, Guangzhou, China. Additionally, all the other chemicals and reagents of HPLC or analytical grade
Chemical composition of AKEO
In China, apricot kernel has been applied as a traditional Chinese medicine (TCM) to treat asthma, nausea, leprosy, bronchitis, constipation, emphysema and leucoderma, so that the exploration of its secondary metabolites have been frequently carried out, including essential oil [28,36]. In this study, 22.4 g of AKEO was extracted, with an extraction yield of 2.2% (w/w). Besides, 14 compounds were found in AKEO, and the main compounds of the essential oil were benzaldehyde (69.5%, w/w), benzoic
Conclusion
In summary, the CS films incorporated AKEO at 0.5% and 1.0% could display antimicrobial effects against L. monocytogenes in solid medium, micro-atmosphere, liquid media and sliced beef, and the CS film incorporated AKEO 1.0% not only inhibit the increase for the levels of PV, TBA, pH and TC of spiced beef, but also improve the sensory attributes including taste, color, texture and overall acceptance of spiced beef. Therefore, the CS film incorporating AKEO 1.0% can be employed as one promising
CRediT authorship contribution statement
Dongying Wang:Conceptualization, Supervision, Writing - review & editing.Ying Dong:Methodology, Visualization, Investigation.Xinpei Chen:Methodology, Visualization, Investigation.Yang Liu:Data curation.Junhui Wang:Software.Xuede Wang:Validation.Chenxin Wang:Writing - original draft, Writing - review & editing.Hongquan Song:Visualization.
Acknowledgements
This research was supported by the Fundamental Research Fund for the Henan Provincial Colleges and Universities (2018QNJH20), the Doctor Research Fund of Henan University of Technology (2017BS032), the Key Research Fund in Science and Technology of Henan Province, China (192102110210) and the Research Fund from China Agriculture Research System (CARS14-1-29).
Declaration of competing interest
None.
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