Despite the food packaging was employed as part of food preservation concept. Exposed surfaces of cheese are vulnerable to mold contamination from several sources. Thus, cheese spoilage is generally confined to molds. Four mycotoxigenic fungal isolates were used in this study; new method was applied in this study as a safe alternative cover to conventional covers in certain semi hard cheeses which are based on chitosan/potato starch and / or thyme, safflower and sesame powders. These new covers were adjusted for thickness homogeneity, covers permeability to water vapor was tested using the standard methods of ASTM, with certain modification .
Other new cover properties were adjusted.
This study aimed to investigate the effects of these covers on fungal growth and Mycotoxins migration to medium which mimicked cheese structure. Our results illustrated that The enriched chitosan covers with (HPPs) proved to be an efficient method to increase the antifungal activity and to reduce the inherently high water vapor permeability of plasticized chitosan packaging covers .
The use of chitosan cover alone or enriched with HPPs succeeded also to control the growth of the tested fungi invading cheese and reduced the mycotoxins migrated amounts cheese which . The response of EVOH with and without herbal plant parts powders (Hppps) addition was also discussed, the addition of these plant material ameliorated the capability of EVOH to reduce fungal growth and the majority of the tested mycotoxins migration amounts. Our results may be realized a significant impact on shelf-life extension and cheese safety during transport and trade.
Keywords: Hpps , cheese interior cover, Fungi ,Mycotoxins migration.
Cheese is considered a very important food. Semi hard cheese like Edam and Gouda cheese are among the very popular cheese around the world. (Official Edam Town website, 2007, Edam com., 2007, European commission, 2010, Miller et al., 2013and Marriam Webster, 2015). Gouda cheese is very susceptible to mold growth and is normally kept under refrigeration. Both of two semi hard cheese was surrounded by an interior coat or packs which permitted gas exchange. However, molds are ubiquitous in cheese. Mold mycelia and mold spores are dispersed by air currents in the cheese plants. Molds also grow on damp surfaces such as walls and shelves in cheese curing rooms and in storage room too. Exposed surfaces of cheese are vulnerable to mold contamination from these sources.
Thus, cheese spoilage is generally confined to molds, which are psychro tolerant and can grow under conditions of relatively Low oxygen. The low aw requirements of molds allow them to grow at relatively high salt concentrations. Those properties allow molds to grow well on Cheese surface. Certain researchers were studied hard, semi hard and semi soft cheeses from Denmark, France, Greece, and U K. they found that the main fungal isolates were Penicillium species such as P.citrinum and P. verrucosum followed by Aspergillus species.. Mycotoxins are secondary metabolites of molds that have adverse effects on humans that result in illnesses and economic losses. Aflatoxins ,ochratoxins are mycotoxins of greatest importance (Kure et al., 2001 and 2004;EFSA,2012 and Doughari,2015).
Petrochemical-based polymers predominate in food packaging due to their easy processing, excellent barrier properties, low cost and the need to use plasticizing agents to obtain stretchable ?lms (Kowalczyk and Baraniak, 2011; and Tapia, 2013). The composition of Flexible multilayer film packaging cheese consists of EVOH (Ethylene-vinyl alcohol) copolymer which is used in coextruded plastic film to improve oxygen barrier properties (Bendall,2007, Gordon ,2009). Embodiments of the present invention for using a core layer having a greater amount of EVOH ( a saponified or hydrolyzed copolymer of ethylene and vinyl acetate 70-80%) and lesser amounts of nylon (20-30%) to produce a film having a low CO2 gas transmitting rate, particularly when using an EVOH copolymer having an ethylene content of about 48 mole percent. which are suitable for packaging articles which respire low levels of CO2 such as gouda, , edam, butter kase and cheddar cheeses, by blending lower amounts of EVOH with higher amounts of nylon.(Edwards et al.,2003).
Certain reports (Levitt,1998, Goulas et al., 2000, Goulas et al., 2007, Bendall et al.,2007, Cruz et al.,2008 and Kanishka et al.,2013) illustrated the migration of undesirable substances to cheese like phtallate, dioxin and diethyl hexyl adipate (DEHA) plasticizer , ink and hormone-mimicking chemicals, from interior coats into hard and soft cheese. But the migration of mycotoxins throw these packs are not studied enough. However, simple changes in packaging materials are required to solve all these problems and to avoid aggravating this draw back. Environmental concerns enhance and stimulate the use of renewable and safe resources for producing economically convenient applications that could also improve life quality (Garca? et al.2004). Chitin is the natural polysaccharide biologically produced by living creatures on the earth in huge quantities. It is estimated that total production of Chitin on the earth annually is about 1 to 100 billion ton which is available for commercial use annually.
However, only a few thousand tons are actually used in the world. Chitosan, the N-deacetylated form of chitin, is a natural cationic polysaccharide, which is edible, non-toxic, biodegradable, biocompatible (No et al., 2007) and commercially available, that has been employed in a variety of applications (Muzzarelli, 2010&Muzzarelli et al., 2012). Moreover, chitosan is also well-known for its broad antimicrobial activity against bacteria and fungi (Muzzarelli et al. 1990, Cagri et al. 2004; C?rdenas et al.,2008). Chitosan ?lms have a low permeability to gases (CO2 and O2) and good mechanical properties. (Ojagh et al., 2010). Its safety has been verified scientifically through many tests. This food waste transformation not only reduces the waste from industries, it also reduces the cost of raw materials (Siracusa et al., 2008 and Janjarasskul et al,.2010). Essential oils (EOs) have been long recognized for their antibacterial, antifungal, antiviral, insecticidal and antioxidant properties.
They are widely used in medicine and the food industry for these purposes. (Henri et al.,2012 and Zareef et al.,2018). It has been reported that EOs containing aldehydes or phenols, such as cinnamaldehyde, citral, carvacrol, eugenol or thymol as major components showed the highest antibacterial activity, followed by EOs containing terpene alcohols. Other EOs, containing ketones or esters, such as ?-myrcetene, -thujone or geranyl acetate had much weaker activity. (Dorman and Deans.2000; oussalah et al.,2007; Dicko.2010 ; Aiouazzou, 2011and Bopitiya and Madhujith, (2013). Phenolic acids are a major class of phenolic compounds, widely occurring in the plant kingdom (Cai etal.,2004). predominant phenolic acids include hydroxybenzoic acids (e.g., gallic acid, p-hydroxybenzoic acid, protocatechuic acid, vanillic acid, and syringic acid) and hydroxycinnamic acids (e.g., ferulic acid, caffeic acid, p-coumaric acid, chlorogenic acid, and sinapic acid) (Cai et al., 2006).
Natural phenolic acids, either occurring in the free or conjugated forms, usually appear as esters or amides (Karimkhan et al., 2016) Sesame seeds (seasamum indicum), Safflower petals (Carthamus tinctorius L and and thyme leaves (Thymus vulgarisL ) are containing phenolic acid ,oils such as oleic and linoleic, palmitic acid and stearic acid in sesame Sesamum indicum (Hall, 2003; Zengin and Ayse, .2014). It is also rich in various bioactive compounds and phytochemicals (Cho et al.,,2000 Zuo etal.,2013,Chen et al.,,2013and Furumoto etal.,2016) which are known to play an important role in providing stability against oxidation of oil and contribute to antioxidative activity (Shahidi et al., 1997; Philip et al., 2010;Wu et al.,2013and Nidhal etal.,2014). Currently mold control in cheese generally involves the use of approved chemical preservatives (generally recognized as safe, GRAS). These special packaging techniques add to the cost of production, which is passed onto consumers.( Magnusson et al., 2003 and DanZhao, 2011 ).
So, to solve this problem further cheap and safe package structures are needed ,therefore, the objective of this work was to evaluate the combined use of chitosan, potato starch and /or herbal plant powder (hpp) as enriched chitosan potato starch cover surrounding semi hard cheeses to reduce the water vapor permeability of chitosan ?lms intended as edible food cover packaging improving at the same time, their antimicrobial to reduce the food spoilage rate and the migration of mycotoxins to cheese. Moreover, this antimicrobial covers may be improve the concept of active packaging which can be reduce , or delay the growth of microorganisms on the surface of food in contact with the package and consequently inhibit the mycotoxin transition to packaged cheese . This work aimed also to study the performance of biodegradable and edible biopolymers and their combination with (hpp) as natural packages for selected food products.
Preparation of the tested covers: Three kinds of cover are used in this experiment
All the used covers were cut similarly to have the same surface. Then, three cells containing silica gel (1g) each were covered with one of the tested cover coated with molten paraffin as a blank [c]. Afterwards, another twelve cells were placed inside the desiccators containing silica gel (1g) and each cell was covered by one tested cover (three cells) but the other cells were covered by one hpp enriched cover . Water at 25°C produces 100% moisture. So, water was poured into the cell permeability measurement. The difference in moisture on the two sides of each cover varied according to the cover structure. The difference in moisture was registered after 24hrs. by weighing the silica gel under each tested cover before[A] and after heating it [B] in oven at 105 ? C for one hour then the resulted water vapor desorbed from each cover and absorbed by silica gel was calculated according to the equations [A- B]) /A x100 . The difference between them was the water vapor permeability (WVP) or desorption amount of WV reached food.
Where B= Weight of the oven dried cell containing silica gel coated with cover
C= Weight of the cover+ molten paraffin film.
C’= Weight of the oven dried cell containing silica gel and covered with one tested cover+ molten paraffin film.
N.B= -The difference between c and c’ = zero.
Changes in cell weight are relative to time.
This experiment was carried out according to Elad et al.,1983 with certain modification to determine the capability of the conventional cover and the proposed cover to prevent the tested mycotoxins to reached the medium (which represented cheese) in comparison to cellophane (a very thin sheet) to investigate the role of cover thickness in mycotoxin migration during storage process. A modified medium consisting of Dextrose casein peptone-Agar medium (Merk, Germany) (15g) and PDA (125g) added to 1L.distilled water are used in this experiment. Four groups of petri dishes 13 dishes each were filled with the mention medium and then the tested cover was placed upon the solidified medium. Each dish was inoculated by the tested fungus. All dishes groups are stored for six weeks in a cooling incubator at 40?F and RH 68% as recommended by cheese producers.
At the of the storage period, dishes are taken then the radial growth of each fungus was measured. Data are registered as shown in table n?=5.
Each tested cover was gently removed then plugs 4 mm each was taken from the medium of each petri dish (ten plugs from each perti dish). The mycotoxins migrated to the medium through each tested cover was determined individually using plug method agar according to Bragulat et al.,2001 then each mycotoxin was quantitatively detected using HPLC according to Turnera et al., 2009.Data are registered as a illustrated in table n?=6.
The experiment was carried out in three replications in a completely randomized design. The data were subjected to statistical analysis using Costat computer package (CoHort Software, Berkeley, CA, USA). One way ANOVA was used and comparison between the resulted data was done using least significant difference (LSD) according to Duncan’s Multiple Range test was applied to compare the treatment mean values according to McDonald, (2009).
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