Food Engineering
Mohsen Zandi; Ali Ganjloo; Mandana Bimakr; Abolfazl Gharebaghi
Abstract
Introduction: Grape is a non-climacteric fruit with a low rate of physiological activity but is subject to serious physiological and parasitic disorders after harvest and during long term storage (Ciccarese et al., 2013). Currently, Edible coatings have been studied as potential substitutes for conventional ...
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Introduction: Grape is a non-climacteric fruit with a low rate of physiological activity but is subject to serious physiological and parasitic disorders after harvest and during long term storage (Ciccarese et al., 2013). Currently, Edible coatings have been studied as potential substitutes for conventional plastics in food packaging. Edible coating is a thin layer of edible material formed as a coating on a food product. Edible coating can offer several advantages to the fresh fruit and vegetable industry such as improvement in the retention of color, acids, sugar and flavor components, the maintenance of quality during shipping and storage, the reduction of storage disorders and improved consumer appeal (Antoniou et al., 2015; Cazon et al., 2017; Fakhouri et al., 2015; Galus & Kadzińska, 2015). Farsi gum as a novel source of polysaccharides has drawn much attention in a wide range of various fields such as pharmaceutics, food and cosmetics industries. Functional properties of Farsi gum are influenced by its structure and molecular weight (Hadian et al., 2016; Joukar et al., 2017). By inclusion of bioactive compounds in the Farsi gum network the aforementioned impairments could be overcome and moreover, new protective and functional valences could be added. The inclusion of lipid-based component in Farsi gum gives it excellent light and moisture barrier properties. The benefic impact on human health of hemp seed oil is worldwide recognized. A recent study demonstrated the antimicrobial properties of hemp seed oil. Due to their abundance in biologically active compounds, hemp seed oil is promising natural alternatives that may extend the shelf-life, microbiological safety and nutritional values of food (Cozmuta et al., 2015; Leizer et al., 2000; Salarnia et al., 2018). Growing awareness of the quality of fruit has necessitated increasing effort to develop rapid and non-destructive methods for evaluating fruit quality (Bhargava & Bansal, 2020; Rachmawati et al., 2017; Tao & Zhou, 2017; Wu & Sun, 2013). The aim of this study was the consideration of image processing application for grape sorting based on visual surface characterize. Materials and Methods: Coating emulsion was prepared using (Farsi gum (0%, 1.5% and 3%), hemp seed oil (0%, 0.075% and 0.15%) and glyceride (0.3%)). grape fruit were coated by immersion in coating dispersion for 5 min. Samples were then allowed to loss the excess coating dispersion. Coatings were developed at room temperature during an hour. Samples were refrigerated at 4± 1°C for 28 days and analyses were performed at days 0 and 28. Defect identification and maturity detection of grape fruits are challenging task for the computer vision to achieve near human levels of recognition. The image acquisition was performed in a homogenously controlled lighting condition. Considering the camera lens’s focal length, the samples were placed 25 cm under the camera’s lens to be under camera’s field of view. The images of grape were segmented from the background using thresholding of the high contrast images via MATLAB software (R2019a, image processing toolbox). The optimum threshold value was obtained to be 0.35, 0.45 and 0.30 for R, G and B channel, respectively. Results and Discussion: The proposed techniques can separate between the defected and the healthy grape fruits, and then detect and classify the actual defected area. Classification is performed in two manners which in the first one, an input grape is classified with two different algorithms (RGB and binary). The Result showed that the accuracies for detecting the surface defects on grape were 97.73% and 96.30% using RGB and binary algorithms, respectively. Proposed method can be used to detect the visible defects of coated grape, and to grade the grape in high speed and precision. Conclusions: The results of this research and similar ones can provide helpful recommendations in grading fruits for fresh consumption. The simplicity and the efficiency of the proposed techniques make them appropriate for designing a low-cost hardware kit that can be used for real applications.
Hadise Karimi; Hojatollah Bodaghi; Ahmad Rajaei; Shideh Mojerlou
Abstract
Introduction: Fresh grapes (Vitis vinifera L.) show severe lesions at the post-harvest stage and during the storage period. Decreasing the quality of grapes in the post-harvest stage limits its consumption and commercialization. Some methods such as using bio-control agents, natural antimicrobials, physical ...
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Introduction: Fresh grapes (Vitis vinifera L.) show severe lesions at the post-harvest stage and during the storage period. Decreasing the quality of grapes in the post-harvest stage limits its consumption and commercialization. Some methods such as using bio-control agents, natural antimicrobials, physical methods, disinfectants agents ,GRAS, (ozone, ethanol, acetic acid) have been used to control Botrytis cinerea after harvest. Encapsulation of the essential oils will increase their ability by increasing the effectiveness of the essential oils. Currently, chitosan has been interested for encapsulating bioactive compounds, as they are generally known to be safe and possess superior biological properties such as biodegradability, biocompatibility and non-toxicity. The aim of this study was to encapsulate thyme essential oil in chitosan nanogels to enhance and maintain its antifungal effect against B. cinerea in vitro and in vitro on Shahroodi red grape. Materials and methods: For the purpose of this study, chitosan nanogels were first prepared and the infrared spectrum of chitosan-meric acid nanogels was measured using FT-IR430 infrared spectrophotometer at 20 ° C. The morphology of chitosan-meric acid nanogels and encapsulated essential oil was analyzed by SEM. Release test was then performed to determine the release rate of thyme essential oil encapsulated in chitosan-meric acid nanogels. Effect of chitosan-meristic acid nanogels at three levels of 0, 150 and 300 µl/L, pure thyme essential oil and thyme essential oil encapsulated in chitosan-meristic acid nanogels at three levels of 0, 75 and 150 µl / L in vitro and on the shelf life of grape fruits was studied under modified atmospheric conditions during 72 days storage at 2 to 4 °C. During storage, some traits such as firmness by manual penetrometer, electrical conductivity of fruit tissue, some components of fruit skin color and soluble solids were assessed by a refrectometer. Results and discusion: Infrared spectroscopy (FTIR) results confirmed the successful coupling between chitosan amin groups and carboxylic acid-meristic acid groups and scanning electron microscopy image showed that the particle size of chitosan-meric acid nanogel was than 100 nm. The Comparison of the particle size in the present study with the previous studies on the size of chitosan-meric acid nanogels was smaller and more uniform. These differences could be related to several reasons, transform the long chitosan chain into smaller fragments by initial sonication, the important role of ultrasound in the reduction of the particle size and passing the nanogels through the filter. Release test showed that the diffusion of thyme essential oil from chitosan-meric acid nanogels has a two-step process. The chitosan-meric acid nanogels prepared in this study have hydrophilic (chitosan polymer) and hydrophilic (meristic acid fatty acid chain) regions, which led to the gradual release of thyme essential oil due to their hydrophobic nature. The results of the infected packaged berries confirmed that with increasing concentration of thyme essential oil, the antifungal effect was also increased. Evaluation of the effects of essential oil and nanogels - essential oils on grape berries infected with pathogenic spores showed the highest number of spores in control treatment (10.125 × 105 per ml) and the lowest number in NE2 (1.375 × 105 per ml) were observed. Coating treatments of chitosan-meric acid nanogel and thyme essential oil encapsulated in chitosan-meric acid nanogels showed better results at higher concentrations, but in the case of essential oil, lower spores were observed. The lowest electrical conductivity and discoloration, the highest L * component and chroma index were observed in thyme essential oil treatment with concentration of 75 µl/l. The results showed that the lower concentrations of the essential oil in the control of botrytis cinerea was better than the pure essential oils, whereas in the experiments on the storage of grape fruit, the treatment of thyme essential oil with a concentration of 75 µl/l It showed the most favorable result. Based on the results of the present study, the effect of essential oil nano-gel and essential oil alone on the shelf life after harvesting of grapes packed with polyethylene film confirmed that the essential oil performance was better than the essential oil nanogel. The lower performance of the essential oil nanogel than that of the essential oil alone can be due to inhibition of the essential oil diffusion through the packaging film while, the encapsulated essential oil release slower than the essential oil alone, it is likely to have an effect longer than expected in this study for the storage period of the grape. Considering this case and the antimicrobial capability of essential oil nanogel, it is necessary to investigate the effect of essential oil nanogel compared to essential oil on longevity of grapes for a longer of storage period.
Elnaz Ghaem far; Seyed Mahmoud Reza Hojjati
Abstract
Introduction: Adding color to Foods can make them more appealing to consumers, to allow consumers to identify what taste to expect from a product, and to protect sensitive flavors from light. Color has always played a vital role in food selection and acceptance, and colorants are added to foods to alleviate ...
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Introduction: Adding color to Foods can make them more appealing to consumers, to allow consumers to identify what taste to expect from a product, and to protect sensitive flavors from light. Color has always played a vital role in food selection and acceptance, and colorants are added to foods to alleviate color lost during processing. Caramel color, from the palest yellow to the deepest brown, accounts for more than 80% (by weight) of all colorants added to the foods we eat and drink (Sengar, et al., 2014).Because of sensitivity of liquid colors to oxidation, light and heat and difficulties in their handling and incorporating, dried pigments have been developed. Microencapsulation is a technique to package materials in the form of micro- and nano-particles. There are different methods for encapsulation in the food industry. Freeze drying which has a long dehydration period, has been used as a simple technique in encapsulating water-soluble essential oils and natural aromas or drugs (Khazaei, et al., 2014). In this work, in addition to liquid caramel color production, encapsulation of liquid color with freeze drying technique through wall materials of maltodextrin and Arabic gum were carried out. The stability of microencapsulated color was then evaluated.
Materials and Methods: Rish baba grape and Kabkab date syrup were obtained from local market. Ammonium chloride, citric acid, sodium hydroxide, tween 80, Arabic gum were purchased from Merck (Germany). Glycine and maltodextrin were obtained from Sigma-Aldrich (USA) and Dextrose Company (Iran), respectively. In this study, the effect of factors such as type of catalyst (ammonium chloride-glycine), concentration of catalyst (0.5-2 molar), the pH of reaction (4-5), reaction time (60-120 minutes) on liquid color intensity of caramel produced from two natural sources of date and grape were investigated based on fractional factorial experimental design. For production of liquid caramel color, grape/date syrup was heated while being stirred to 65ᵒ C. Catalysts were then added to syrup and heated to 110ᵒC. water was added to reaction product and centrifuged. The solvent was removed by rotary evaporator (IKA HB 10, Germany).The resulting caramel color was stored under refrigeration at 4ᵒ C. In order to produce powder of caramel color, wall materials including Arabic gum and maltodextrin were dissolved in distilled water at ambient temperature to obtain 20% total solids concentration and stirred for 30 minutes at 60ᵒC. The mixture of liquid caramel color, tween80, and wall material solution was mixed in a ratio (w/w) of 1:4 (liquid caramel color: wall material) and stirred for 15 minutes. The mixture was then dried in a freeze dryer (ALPHA 1-2 LD PLUS, Germany) for 24 hours. The blank sample was prepared without wall materials and freeze-dried in similar conditions with other samples in 24 hours. Dried materials were collected and stored in brown glass bottles with screwed caps at 4⁰C until analysis. The powders were characterized using TGA/DSC thermogravimetric analysis (METTLER TOLEDO, USA), scanning electron microscopy (SEM) (TESCAN vegar, Czech Republic) and X-ray diffraction (XRD) (Billerica, MA, USA) to confirm the structural and morphological aspects of powders.
Results & Discussion: The results showed that the type of catalyst had no effect on the intensity of the colors and maximum color intensity (0.174 for color produced from grape and 0.15 for color produced from date) was obtained under these conditions: 120 minutes for reaction time, pH value = 4 and catalyst concentration of 2 molar. Results of thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC) indicated the increase of thermal resistance by microencapsulation process so that initial decomposition temperature for liquid form, without wall material, with Arabic gum and with maltodextrin for grape source were 114,138,162,185°C respectively and for date source were 113,131, 143, 180°C respectively. Results of Scanning electron microscope demonstrated that size of the powders were 11-55 μm. In conclusion, microencapsulation by freeze drying could be recommended as a suitable method for stabilizing caramel color.
