APPLICATION OF EDIBLE FILM AND COATING BASED ON ALOE VERA GEL FOR PRESERVATION OF PHYSICOCHEMICAL PROPERTIES OF PHYSALIS PERUVIANA L. FRUITS

The calyx removing of Physalis peruviana  fruits for production of fresh cut fruit makes its shelf life shorter. So, Aloe vera gel (AV) used as edible film and coating for increasing the fruit shelf life of fresh cut Physalis fruit. The physical parameter of prepared AV films was investigated such as: Thickness, water vapor permeability (WVP) and water solubility. The current study evaluates the effect of AV film and coating for maintain the Physalis peruviana fruits without calyx at 5±1°C and 95 % RH for 30 days. AV gel film was effective in controlling the fungal decay. which recorded the lowest value (4%) and reduced deterioration in all other physicochemical properties of Physalis fruit comparing with control. This study showed that the AV gel could be suitable for producing an edible film and coating with good physical characteristics such as low WVP (0.0037g/m2.h.mmHg). AV's low WVP appeared to have a great impact on maintaining post-harvest quality especially reducing the percentage of weight loss of coated fruit during storage.

hot for 10 min with mechanical stirring. 100 ml of the film-forming solution was poured and spread evenly over a Teflon plate (23 X 22 cm) by stainless steel spreader and dried for further evaluation at room temperature for 24 hours.

Film thicknesses
The film thickness was measured using the micrometer (Model 49 -50 -02, Messmer Instrument, Germany). Five measurements were done for each film sample and expressed as µm (Abd El Magied et al. 2009).

Water solubility (%)
The film scuttle in water was defined as the dry matter content which lost in water after 24 h of immersion. Two pieces of each film (1 4 cm diameter) were cut and weighed. One piece was dried at 105˚C / 24 h for determining the initial dry matter percentage. The other piece was immersed in 50 ml of distilled water for 24 at 25 0 C with sporadic stirring. After that, the pieces of film were removed and dried to constant weight at 105 º C for 24 h to determine the weight of dry matter that was dispersed in water. The water solubility % was determined as the average value of 3 measurements as follows (Sadegh et al. 2012).: WS (%) =[Initial dry matter(g) − Final dry matter(g) / Initial dry matter(g)] 100

Water vapor permeability (WVP)
The WVP of AV film was determined according to an ASTM E96-00 procedure (2000). WVP defined as the easing of penetration of moisture and passing through the film hydrophilic portion.

Preparation of Physalis fruits
Physalis fruits were harvested and stored and 95 % RH, then treated in the next day. 360 fruits with uniform size, physical damage and fungal injury free were used. The calyx of the Physalis fruits were removed then the fruits dipped in chlorinated water then dried using tissue paper. About 120 fruits, randomly distributed in 6 Polypropylene trays (10 x 20 cm) with 20 fruits in each tray, for each treatment. Two tray of each treatment was taken for analyses every 6 days until the 30 days of storage period completed. Three treatments conducted, the first treatment was the control (fruit without coating); the second treatment: packaging fruits in AV pouch film and the third treatment: packaging of Physalis fruits in AV pouch film. The third treatment: coating of Physalis fruits with AV coating by dipping into the AV gel solution at 25•C for 1 min.

Decay
The decay was observed and determined visually as recommended by Shehata et al. (2020) . The decay percent of coated and uncoated Physalis fruit was calculated as follows: [The number of decayed fruits / the number of total fruits] X 100

Weight loss
The weight loss percentage was calculated by the difference between the initial weight of fruits and the weight of fruits at 0, 6, 12, 18, 24 and 30 d multiplied by 100 (Awad et al. 2021).

Texture analysis
Fruits firmness was determined using a texture analyzer as described by Licodiedoff et al. (2016). Tissue firmness was measured by a texture analyzer (Force Gauge, Model M4-200, USA) with a 50 kg charge cell. A 2 mm-diameter cylinder pointer was used to analyze perforation. Speeds during the test were respectively, 3.3 mm.s -1 , with a 5 mm penetration depth for the 30s. Results were given in N. The results were expressed as the mean of 3 determinations for each treatment.

Browning Index
The fruit's color was measured using a colorimeter with a Minolta standard (KONICA MINOLTA, Japan) according to the method described by Ganjloo et al., (2009). The color coordinates a*, b* and L were used to calculate the browning index (BI) for the mean of 3 determinations for each treatment according to the method described by Palou et al., (1999

Titrable acidity % (TA%)
Ten grams of fruit was homogenized and made up to 100 ml with distilled water. Then 10 ml of the aliquot was taken and titrated with 0.1 N NaOH in present of Phenolphthalein as an indicator in triplicates, from the titer, the Titrable acidity % was calculated (El -Mogy et al. 2019).

Maturity index (MI)
The maturity index was calculated according to Catarina et al. (2015) according to the following equation: MI = TSS/ %TA

Sensory evaluation
The consumer panels were used in this study consisted of untrained ten panelists from the staff of Food Science Department, Faculty of Agriculture, Cairo University, Giza, Egypt (6 females and 4 males, aged ranged from 25 to 45 y) was used for evaluating sensory quality of Physalis fruit after one day of coating and every 6 days of cold storage. The panelists do not know the experimental approach and the fruits were blind to artificial light at 25ºC. The sensory criteria as color, texture, taste and overall acceptability were carried out based on a ninepoint hedonic scale(1=dislike extremely, 3-4 = mild dislike, 5 = reasonable, 6 8 = moderate dislike, 9, like extremely) (Ali and EL Said, 2020).

Statistical analysis
The results were presented as mean ± SD. The statistical analysis was performed using One-Way Analysis of Variance (ANOVA). Statistical significance was determined at (P < 0.05). Statistical analyses were performed using Co-stat Statistics Software, version 6.4 (Co Hort Software, California, USA).

Film Thickness
Results show that AV film was flexible and transparent. The prepared AV film thickness was 65 µm. The obtained results are in accordance with Ortega-Toro et al. (2017) who reported that starch-based film containing the highest ratio of AV gel (1:1) and plasticized with 0.15 g glycerol/g starch were more homogenous and had a higher gloss and transparency. Also, Pinzon et al. (2018) was shown that the thickness of starch-chitosan-Aloe vera gel film was increased 59.3 to 174.5 m with increasing of AV gel concentration 0 to 500 g/l. Abugoch et al. (2011) reported that the film thickness depends on the film chemical composition and the film-forming polymer nature. Also, Silva-Weiss et al. (2013) reported that the addition of polyphenolic compounds to starchchitosan films have a crosslinking effect that leads to increase in thickness. A similar result was observed in this study of the AV film solution which contains 5g starch/ 200ml (as a thickening agent).

Water solubility
The obtained results were shown that the water solubility (WS) of AV gel was relatively low (20.65 %) in comparison with other types of polysaccharides polymer films. These can be observed by Sadegh et al. (2012) who noticed that an increment in the portion of AV gel was followed by a decreasing in the water solubility of Aloe vera gel incorporated into Chitosan films. A similar effect was also shown when Pinzon et al. (2018) added AV gel into the chitosan film at 50% concentration. The edible films with low water vapor permeability usually tend to have low water solubility. Even though it is important to know that the most components of the AV gel are polysaccharides, organic acids and amino acids, which have highwater solubility, so they could easily soluble from the edible films. So, the lower water solubility of AV gel film or how the addition of AV to different types of edible polymers decreasing water solubility still unknown and need more study.

Water vapor permeability (WVP)
The film composition hydrophilic-hydrophobic ratio plays an important role in water vapor permeability (WVP). The water vapor permeability of AV gel film at 30 °C and 0/100 % relative humidity was recorded as 0.0037 g.m -2 .h.mmHg, which is considered relatively low in comparison with other polysaccharides polymer films. So, the AV gel addition could be used for reducing WVP with other types of polysaccharide polymer film as shown in the study of Sadegh et al. (2012) who found that AV gel incorporation had the potential role in enhancing the chitosan film barrier property to water vapor. Ortega-Toro et al. (2017) showed that the addition of AV gel into starch based Film (1:1 w/w) reduced water vapor permeability. Also, Pinzon et al. (2018) reported that, the addition of AV gel significantly decreases the water vapor permeability values of the banana starch-chitosan films 2.85 g Pa −1 s −1 m −1 in films without AV gel to 1.99 g Pa −1 s −1 m −1 . Also, he explained that, with the interaction between the AV gel components and starch-chitosan molecules, reducing the availability of the hydrophilic groups in all of starch and chitosan to interact with water and reducing the film's WVP.

Physico-chemical properties of Physalis fruits Decay
The maximum shelf life of fruits was defined as the time pass away between the application of coatings or films and the visual decay. Results in Table (1) showed that the decay increased significantly during storage. Percentage of decayed fruits was 12% for the control fruit after 18 days of storage period, however, shelf-life of the AV coated fruit and fruits packed in AV pouch film extended up to 18 days without decay. These results are in accordance with Licodiedoff et al. (2016) who reported that the edible coating of gelatin and calcium chloride markedly reduced the number of decayed fruits and prolonged the storage time up to 17 days without decay. This result is similar to the result of Tripathi et al. (2004), who reported that AV gel was successful in reducing microorganism proliferation in table grape, the effect is higher for yeast and molds than for mesophillic aerobics. Moreover, Brishti et al. (2014) reported that decay percentage reached 27% of papaya fruits coated with AV gel compared with the control which reached to 100% at the end of storage. Also, Ortega-Toro et al. (2017) showed that, the starch-based film containing AV gel (1:1 w/w) was more effective for controlling fungal decay in cherry tomatoes because he found that, the AV gel has a good effect as antifungal especially for Fusarium oxysporum. The AV film was more effective for reducing the number of infected physalis fruits than the coated fruits. That was explained by Cock, (2008) who identified 26 bioactive phytochemical compounds in AV gel such as anthraquinones, dihydroxyanthraquinones, saponins, acemannan. Means ± SD (n=3) in the same column followed by the same small letter are not significantly different (p ˂0.05).

Weight Loss
The results of weight loss% of all samples "Control (Non-coated fruits), coated and packed with the film" are shown in the  al. (2002) explained that, the main cause of weight loss of fruit as a result of migration of water from the fruit to the environment during storage. The essential mechanism participating to weight loss is the water evaporation which activated by a flair of water vapor pressure at different sites in bell pepper. The mechanism is based on the coating hygroscopic properties, which has the ability for forming a barrier to water diffusion between the fruit and environment to avoid its external transference. From the previous result we found that the AV film had a lower WVP so, that may be the cause of reducing the weight loss % of coated or packed physalis fruits.

Firmness
Results in the reported that using of AV and gum tragacanth as a coating delayed the changes in texture and no excessive softness was noticed in bell peppers after 30 days of storage at 4 ˚C. The coating may also inhibit the activities of pectin-degrading enzymes closely related to decrease in texture by reducing the metabolic processes rate during senescence, which also participated in the maintenance of fruit hardness (Gwanpua et al. 2014).

Total soluble solids content
The total soluble solids content (Birixº) of different physalis fruits, either coated or pouched and the control sample was presented in Table (1). It could be shown from the results that there were a significant differences between all the tested samples during storage times for the three treatments. As the storage time increased as directly proportional for the entire sample under investigation as shown in Table ( Ahmed et al. 2009) also, they suggested that the AV gel coating or film created a modified atmosphere around the fruits which reduced the production rate of ethylene, which, delay ripening, degradation of chlorophyll, accumulation of anthocyanin and synthesis of carotenoid and that lower fruits color surface changes.

Figure 1 Effect of Aloe vera gel film and coating on browning index (BI) of
Physalis fruit during storage at 5±1°C for 30 days.
Means followed by different letters are significantly different (P<0.05%).

Titratable acidity
The total titratable acidity (TA) was calculated as citric acid, which is the dominant acid in physalis fruits. Results in Fig. (2) show the changes of titratable acidity (TA%) of different tested physalis fruits, either coated or packed with the AV as well as the control sample through different storage times (up to 30 days) at 5˚C. A significant difference could be shown among all the tested samples. Data in Fig (2) show that the titratable acidity for all the samples recorded the highest percentage of the initial storage (after one-day storage). However, as the storage time (days) increased, the titratable acidity (%) decreased. The lower level of titratable acidity could be noticed in the control sample at the end of storage time, which recorded 2.10 %. Meanwhile, the coated or packed samples with AV had almost the same percentage of titratable acidity after 30 days of storage 2.27 and 2.30 %, respectively. Also, Sharmin et al. (2015), reported that papaya fruits coated AV gel (0.5%) recorded the minimum change of titrable acidity (0.39 %). This retention of TA content by coated papaya was due to the protective effect of AV coating as a barrier to O2 from the surrounding atmosphere and reduction of respiration (Srinu et al. 2012). Andrea et al. (2017) who found that the decrease in titratable acidity of Gooseberry fruits coated with calcium chloride demonstrates maturity development. They also noticed that the TA was decreased as storage time increased for all the tested samples. So, the application of AV film and coating support the postharvest life of Physalis fruits and prolong the shelf life due to a higher fruits content of acid. Therefore, Valero1 and Serrano (2013) reported that mature fruits do not taste acidic because of the large amounts of accumulated sugars and the decrease of total acidity that usually occur during ripening.

Figure 3
Effect of Aloe vera gel film and coating on pH of Physalis fruit during storage at 5±1°C for 30 days.
Means followed by different letters are significantly different (P<0.05%).

Maturity index
Maturity index showed significant change during cold storage between control and other treatments meanwhile, no differences were observed between film and coating of AV gel (Fig 4). The obtained results were shown a higher maturity index of near 12 for control sample at the end of the storage period ( Effect of Aloe vera gel film and coating on maturity index of Physalis fruit during storage at 5±1°C for 30 days. Means followed by different letters are significantly different (P<0.05%).

CONCLUSIONS
The results of this study showed that the AV gel solution is suitable for producing an edible film and coating with good physical characteristics. Also, the current study showed the ability of Aloe Vera gel edible film and coating for prolonging the shelf life and maintain of the quality parameter of Physalis fruits. Edible film and coating showed a decreasing in fungal decay % comparing to control fruits. Moreover, Aloe Vera gel film and coating conserve the regarding of the physicochemical parameters for30 days of storage at 5°C which, significantly reduced weight loss, firmness and retarded the changes on the color of physalis fruits.