Food Biotechnology
Asma Entezari; Nasser Sedaghat; Golshan Shakeri
Abstract
Introduction The main sources of Salmonella for humans are pork, beef, chicken, eggs, fruits, vegetables, and their derivatives such as mayonnaise, and peanut butter. Different species of Salmonella can adapt, grow or survive at different environmental conditions. Salmonella enterica is a majorcause ...
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Introduction The main sources of Salmonella for humans are pork, beef, chicken, eggs, fruits, vegetables, and their derivatives such as mayonnaise, and peanut butter. Different species of Salmonella can adapt, grow or survive at different environmental conditions. Salmonella enterica is a majorcause of food borne illness in humans, and Salmonella typhimurium and Salmonella enteritidis serovars are the most prevalent. One strategy is to use active packaging to reduce the microbial load or prevent the growth of microorganisms on food. Recently, antimicrobial active packaging has received much attention due to maintaining food quality, safety, and increasing shelf life. Among the antimicrobials used in the food industry, bacteriophages have a very good efficiency to control pathogenic bacteria. Pullulan has a good ability to form a film, its film has good characteristics such as transparency, odorlessness, tastelessness, solubility in water, and low permeability to oxygen and fat, However, the major obstacle is related to its price. The combination of polysaccharides with proteins has been done in order to improve the performance and reduce the costs of films. Gelatin is a suitable option to combine with pullulan in terms of good mechanical properties, reduced permeability, and its good price. Different ratios of gelatin and pullulan were studied and suitable film selected, but it needed to modify, so nanofibers cellulose was added in order to improve the mechanical properties and water resistance. Adding cellulose nano fiber can be a good and appropriate option. The aim of this research was to evaluate theantibacterial effectiveness of gelatin-pullulan- nanofibers cellulose composite film containing bacteriophage against Salmonella typhimurium at two different temperatures. Materials and MethodsGelatin and pullulan powders were weighted separately and mixed together (20gelatin-80pullulan). Nanofiber cellulose was extracted from rice bran and was used at three different levels (1%, 3%, and 5%). Commercial bacteriophage solution was added to each of the films separately and the films were prepared by molding method. Thickness, moisture content, solubility, swelling, tensile strength, and elongation of gelatin-pullulan film containing nanofibers were studied. Zone inhibitory of films containing different percentage of cellulose nanofibers on the agar media against Salmonella typhimurium (104 CFU.ml-1) was evaluated. The, antibacterial effect of selected film on the poultry meat inoculated with S. typhimurium (104 CFU.g-1) and several phages on the surface meat at 4 and 12 was also investigated. Results and Discussion The results indicated that gelatin-pullulan films containing different percentages of cellulose were showed approximately 2 mm of zone inhibitory compare to films free of phages. Also, inhibitory among films at different percentage of nanofiber cellulose did not show significant change. Antibacterial effect on poultry meat was dependent on temperature, films loaded with bacteriophages at higher temperature (12 ) was more effective compare to lower temperature (4 ). The populations of S. typhimurium were decreased 1 log and 0.7 log than control samples at 4 after 7 and 9 days respectively, while at 12 , 1 log and around 2.55 log decrease was found after 1 and 9 days, respectively. In a study, beef inoculated with salmonella was treated by SALMONELEXTM bacteriophage and resulted in 1.29 log reduction of pathogenic bacteria compared to the control sample (Yeh et al., 2017). In another study, the antibacterial effect of double-layer poly lactic acid/xanthan film at 10 °C compared to 4 °C against pathogenic bacteria of Salmonella and Listeria was determined and found that at10 °C, the number of pathogenic bacteria was decreased more than at 4 °C (Radford et al., 2017).. Kamali et al. (2022b) reported that the release of phages from the film of 30 poly lactic acid/70 whey protein to the meat surface after one hour was 63.22 % and 63.18 % at 4 °C and 10 °C, respectively, which means no significant difference, after one day at both temperatures.
Food Technology
Amir Rezaie; Masoud Rezaei; Mahdi Albooftileh
Abstract
Introduction: Films with appropriate mechanical properties and low permeability are very important for food packaging. Natural polymers have gained increasing attention for the development of biodegradable films due to the environmental problems caused by petroleum-based polymers. Carboxymethyl cellulose ...
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Introduction: Films with appropriate mechanical properties and low permeability are very important for food packaging. Natural polymers have gained increasing attention for the development of biodegradable films due to the environmental problems caused by petroleum-based polymers. Carboxymethyl cellulose (CMC) is a linear polysaccharide that exhibited good film forming properties. Gum Arabic (GA) is another polysaccharide that can be used for preparing the edible and biodegradable films. However, several studies have shown that biopolymers like CMC and GA films have high water vapor permeability and poor mechanical properties in moist conditions. One of the strategies that can be used for improving the properties of biopolymers films is blending the different polymers and formation the composite films. Various studies on the preparation of biocomposite films have been performed, however, to the best of our knowledge, studies on combinations of the CMC and AG have not been reported yet. Thus, the main objectives of this study were to prepare CMC/AG composite films using solvent casting method and investigate the effect of different CMC/AG blending ratio on the physical (water vapor permeability (WVP), water contact angle (WCA), color, opacity and light-barrier properties), mechanical and thermal properties. Furthermore, in order to determine the structural characteristics of the films, fourier-transform infrared spectroscopy (FT-IR) and x-ray diffraction (XRD) measurements were also performed. Material & Method: The CMC and AG solutions were prepared by dissolving 1 g in 100 mL of distilled water at 45 °C for 24 h under magnetic stirring. The prepared solutions were then blended in different proportions (75:25, 50:50, and 25:75). After mixing, glycerol (0.3% w/w) was added as a plasticizer and the solution was stirred for 15 min. The prepared solutions were poured into a glass plate, then dried at 45 °C for 24 h in the oven. Finally, the properties of CMC, GA and composite films were determined. Result and Discussion: In this study, biodegradable films composed of CMC and AG were successfully prepared. Results showed that some properties of the composite films were greatly influenced by addition of AG. So that, WVP of films was decreased significantly in the blend films and the lowest WVP was observed in the 25:75 (AG: CMC) films (p < 0.05). The films hydrophobicity was significantly increased from 41.33o to 61.10o by addition of AG to the CMC films (p < 0.05). With increasing the ratio of AG, the tensile strength (TS) of blend films decreased. Opacity and light transmission of the composite films increased and decreased, respectively with increasing the AG ratio. The differential scanning calorimetry (DSC) test demonstrated that the thermal properties of blend films improved with increasing the AG content. The FT-IR analysis indicated that new interaction was generated between the components of the blend films. Generally, it can be concluded that blending the AG and CMC can improve some of the physico-mechanical properties of the blend films
Tooraj Mehdizadeh; Hossein Tajik; Ali Mojaddar Langroodi
Abstract
Introduction: Meat is sensitive to microbial spoilage and chemical oxidation, so it is favorable to use a natural preservative with antioxidant and antimicrobial effects. The objective of this study was to prepare composite films from chitosan and starch containing pomegranate peel extract (PPE) and ...
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Introduction: Meat is sensitive to microbial spoilage and chemical oxidation, so it is favorable to use a natural preservative with antioxidant and antimicrobial effects. The objective of this study was to prepare composite films from chitosan and starch containing pomegranate peel extract (PPE) and Thymus kotschyanus EO alone and in combination to evaluate their effects on shelf-life characteristics, including physico-chemical (pH, aw and lipid oxidation), sensorial (color, odor and general appearance) and microbial (lactic acid bacteria, aerobic mesophiles, pseudomonas) on meat at 4°C for 21 days.
Materials and methods: Fresh pomegranate fruits (Punica granatum) were purchased from a local hypermarket. After separation, the peels were washed and dried. Thus 700 ml alcohol and 300 ml distilled water were added to 250g of powdered peel. The mixture was left in a shaker for 24 hr. After cooling and filtration using a paper filter, the solvent was removed in a rotary evaporator and the extract was stored at 4 °C until use. The Thymus kotschyanus was purchased a local market in Urmia. Hydrodistilation of dried parts of plant was performed in a Clevenger-type apparatus for 3 hr. Sodium sulfate was used for dehydration of the oil, then oil was filtered using 0.22 μm filters and stored in colored glass tubes in the dark at refrigerated temperature. Chitosan film solution was prepared by dissolving 1.5% (w/v) of chitosan in 1% (v/v) of glacial acetic acid solution with constant agitation using a magnetic stir plate during 24 h at room temperature. As a plasticizer, glycerol was added in the proportion of 30% (w/w) to chitosan powder, and the system was agitated for 5 min to complete homogenization. Starch solutions with concentrations of 3.5 % (w/v) were prepared by dispersing 27% amylose corn starch (Sigma-Aldrich Chemie GmbH, Steinheim, Germany) in distilled water and heating the mixtures on hotplates 95 ˚C during 30 min with stirring until it gelatinized, and then cooling to 40 ˚C. Composite films were prepared by mixing 100 mL of 2% chitosan solution with 100 mL of 3.5% starch solutions. For the films incorporated with the essential oils, tween 80 at a level of 0.2% w/v of essential oil was used as emulsifier. EO or hydro-alcoholic extracts were incorporated to the system at the level of 1% (v/v) of film form solution and homogenized in magnetic stir plate during more 5 min at room temperature. For microbial tests ten grams of each sample was diluted in 90 ml sterile 0.1 % ml peptone water (Merck, Darmstadt, Germany) and homogenized using shaker for 3 min at room temperature. Then, 0.1 mL of serial dilutions (0.1 % peptone water) of beef meat homogenates were transferred to agar plates. Pseudomonas were counted on Pseudomonas agar supplemented with CFC at 25 °C for 48 h (CFC, Merck, Darmstadt, Germany). Lactobacillus were enumerated on MRS agar (Merck, Darmstadt, Germany, Oxoid) incubated at 30 °C for 48 h. Finally, total mesophilic counts were determined using Plate Count Agar (PCA, Merck, Darmstadt, Germany), after kept for 2 days at 30°C. Level of lipid oxidation was investigated using thiobarbituric acid reactive substances (TBARS) method as described by Pikul et al (1989). Ten grams of sample was homogenized with 1 mL BHT (1 mg/mL) and 35 mL trichloroacetic acid (5%) in a blender. The mixture was filtered using Whatman no 1. Five mL TBA solution (0.02 M) of filtrate solution was added to 5 mL of filtrate solution and kept in a water bath at 100°C for 60 min to expand the malondialdehyde–TBA complex. After cooling the tube, the absorbance of the samples were determined at 532 nm. The pH values were determined using a digital pH meter. A 5 g of beef meat sample containing 25 ml of distilled water was homogenized for up to 1 min. The sensory analysis of meat samples was carried out with 10 trained PhD students. After preparation of treatments, the samples were offered to each panelist separately. Fresh beef meat was used as a control. Panelists were asked to evaluate texture, color, flavor and odor and overall acceptance on a nine-point Hedonic scale, with 9 being so good and 1 being so poor.
Results and discussion: The incorporation of PPE and EO into composite film showed that aerobic mesophiles and lactic acid bacteria were the most sensitive and resistant groups to films by 7.11 and 6.92 log cycles reduction after 21 days’ storage, respectively. In addition, meat wrapped by 1% PPE films had the lowest degrees of lipid oxidation (1.11 mg MDA/kg samples) which was 61% lower than the control samples (2.90 mg MDA/kg samples). This study showed that starch-chitosan composite films containing of pomegranate peel extract and Thymus kotschyanus EO was significantly antibacterial properties, while shows the higher antioxidant effect. PPE also improves some physical properties of the film. Our results indicated that incorporation of pomegranate peel extract (PPE) and Thymus kotschyanus EO as a natural antibacterial agents have a potential to prolong the shelf-life of meat.
