Introduction

Antimicrobial packaging is an idea in active packaging that successfully infuses antimicrobial chemicals into the food packaging film material and eradicates pathogenic bacteria that harm food goods, extending the shelf life by a significant margin. The lack of interest in preservative addition and the fact that the rate of antimicrobials diffusion from packaging may be controlled are the driving forces for the interest in antimicrobial films or coatings [36]. Food packaging innovations that may shield food from the environment and serve as carriers of active chemicals include films and coatings produced from biodegradable and edible materials [3]. As an alternative to extending the shelf life and guaranteeing the safety of various foods, traditional and natural antimicrobials and other active chemicals have been integrated into edible films and coatings [25]. It has been demonstrated that using antimicrobial compounds in food packaging to reduce microbial load and target particular microorganisms results in high-quality and safe products. According to [5], improper handling and storage methods result in the loss of almost two-thirds of the food produced. This circumstance emphasizes the need to create innovative environmentally friendly solutions to reduce food waste by lengthening the shelf life of food goods as well as by discovering environment friendly ways to reuse food byproducts and waste streams [9]. In order to contribute to the circular economy concept by lowering food waste generation and preventing the unnecessary use of chemicals as additives into packaging, active packaging has emerged as a potential approach.

Aloe Vera (Aloe barbadensis) is a species of succulent plant in the Aloe genus. It is a large plant with short stems that holds water in its leaves. It is regarded as an invasive species in many parts of the world. It is a well-known medicinal herb with antibacterial and antioxidant effects. Aloe Vera (AV) gel extract has a long history of being used in food packaging [23]. These characteristics are a result of AV’s high concentration of special polysaccharides (such glucomannan and acemannan), phenolic compounds (like flavonoids and anthraquinones), organic acids, and vitamins (B1, B2, etc.) [20]. For extending the shelf life of several perishable food items, Aloe Vera gel films or coatings are particularly successful Aloe Vera gel can be combined with conventional biopolymers (proteins and polysaccharides) and lipids (emulsions) to modify the transparency, smoothness, stiffness, elasticity, water vapor permeability, and bio-functionality of films and coatings. A functional additive called AV has recently been employed in edible matrices to preserve several fruits’ postharvest qualities, including those of the mango, tomato, strawberry, and blueberry. Additionally, edible films based on alginate and AV have shown the additive's ability to create uniform films with good transparency for usage in a variety of industries (Jorge et al. 2020).

The Liliaceae family includes garlic (Allium sativum) [4]. It is consumed all around the world because of its culinary worth and medicinal qualities (Paula et al. 2022). Since the beginning of time, it has been utilized as medicine to treat a variety of human ailments [18]. It has a great flavor and a strong smell, making it a favorite component in cooking. Each clove of garlic has between 10 and 20 segments. The peel of a full garlic bulb makes up about 24% of its weight. About 800 g/kg of cloves and 250 g/kg of outer and inner husks are produced per bulb of garlic. As a result, residues made from garlic by-products could be a great biological resource that is effective and safe for the environment [14]. Allicin, an organosulfur molecule found in garlic, is well known for its antibacterial properties.

As agricultural trash, garlic peel is often disposed of in landfills or burned. Incinerating waste results in the emission of a variety of air pollutants including particulate matter, greenhouse gases, volatile organic compounds, etc. [28]. Vitamins A, C, and E as well as a variety of antioxidants are abundant in garlic peel. The presence of organosulfurs and different aliphatic sulfurides gives the peels antibacterial action. Allicin and ajoene are the two main antibacterial organosulfur chemicals found in garlic [17]. Allicin is the major compound that contributes to antimicrobial activity [31]. All of these factors combine to make garlic peel a fantastic byproduct. Simple methods can be used to extract the peel from garlic. According to Fortunata et al. [6], ethanolic extraction of garlic peel extract revealed good retention of antioxidant and antibacterial components.

Materials and Methods

Materials

Garlic peel, Aloe Vera leaf, Ethanol, Distilled water, Folin–Ciocalteu reagent (0.1 N). Na2CO3 (0.05% w/v), NaNO2 (1.5% w/v), AlCl3 (3% w/v), NaOH (1 N).

Preparation of Aloe Vera Gel Extract

Aloe Vera gel was prepared by removing the leaf base and spines. 2 cm of the white part of the leaf base, 5–6 cm of the leaf top and the sharp spines along the margins were removed [2]. The pulp was manually separated from the inner fillet. This pulp was subjected to a grinding process and was further centrifuged at 5000 rpm for 30 min to remove the suspended solids [21]. The colorless supernatant was filtrated under vacuum, freeze-dried and stored at − 4 °C.

Preparation of Garlic Peel Extract

Garlic peels (GP) were collected from the garlic processing centre. The collected GP was dried using two different ways, sun dried for 6 days and oven dried at 60 °C for 4 h. Dried GP was then powdered using a blender. GP powder was stored for further use [10]. For aqueous extraction, the extraction was done with an ultrasonicator [16] with ultrasonic power 1800 W and frequency range 20–25 kHz, samples of 1-g fine GP powder were mixed with distilled water at ratios of 1:15, 1:20, and 1:25 (w/v) and extraction temperatures of 30 °C, 35 °C, and 40 °C for 20, 30, and 40 min.

Characterization of the Extracts

Total Phenolic Compounds

The evaluation of total phenolic compounds was conducted using the approach described by Ochoa et al. [24]. In a nutshell, 1 mL of extract was combined with 1 mL of 0.1 N Folin-Ciocalteu reagent. After the mixture had stood for 3 min, 1 mL of a Na2CO3 solution (0.05% w/v) was added. The mixture was incubated for one hour in a dark area at room temperature. A UV–Vis spectrophotometer was used to measure the absorbance at 765 nm while using distilled water as a reference. Using a Gallic acid standard curve, the results were reported as milligrams of gallic acid equivalents (GAE) per gram of dry sample (dm).

Total Flavonoids

The analysis of total flavonoids (TF) was conducted using the approach suggested by Carlos et al. (2016). The mixture was then combined with 1 mL of NaNO2 (1.5% w/v) and allowed to stand for 5 min. 0.5 mL of NaOH (1 N) and 1 mL of AlCl3 (3% w/v) were added and stirred for 1 min. A UV–Vis spectrophotometer was used to read the absorbance at 415 nm after the combination had been incubated for 1 min while using distilled water as a blank. Using a quercetin standard curve, results were represented as mg of quercetin per g of sample.

Antioxidant Activity

A variety of extract concentrations were combined with 1 mL of 0.004% DPPH solution and left to stand for 30 min at room temperature in the dark. In order to test antioxidant capacity, a UV–Vis spectrophotometer was used at 517 nm.The following equation was used to calculate the inhibition ratio (%) [40].

The inhibition ratio (%) was obtained from the following equation

$${\text{Inhibition ratio }}\left( \% \right) \, = \, \left( {{\text{A1 }} - {\text{ A2}}} \right) \, \times { 1}00/{\text{A1}},$$

where A1 is the absorbance of the addition of ethanol instead of testing sample and A2 is the absorbance of testing sample solution.

Antimicrobial Activity of the Extracts

The antibacterial activity of the extracts were evaluated using the agar diffusion method [26]. Gram positive and Gram negative common bacterial strains associated with food spoiling in refrigerators, S. aureus and E. coli, were employed [13]. On Muller Hinton agar plates, 0.1 mL of inoculums containing roughly 105 CFU mL 1 of the examined bacteria was applied. After 24 h of incubation at 37 °C, the inhibition zone’s diameter (mm) surrounding the film disc (1.0 cm2) was measured. Tetracycline served as the control. Each sample was tested three times.

Preparation of Gelatin Film

Gelatin (8 wt%) [8] was dispersed in distilled water at 35 °C and placed in a magnetic stirrer at 1000 rpm for 20 mins. Glycerol (30 wt%) was added and dispersed for 10 min under the same conditions. Varying concentration with varying ratios of extracts were added and stirred for 10 mins. Finally the mixture was dried in petri dishes in a climate chamber [30]. Gelatin Film with Antimicrobial Agent (AM) concentration 1%, 2%, 3% with varying AM ratios (Garlic peel extract: Aloe Vera gel extract) of 1:1, 1:2, 2:1 were prepared.

Characterization of Edible Film

Visual Appearance and Thickness

The thickness of films were measured using a Micrometer. Each film sample was measured at five random positions. Colour of the film was determined by using a colorimeter [29]. Gloss was measured by shining a known amount of light at a surface at a specific angle and measuring the amount of reflected light [39]. A gloss meter was used to find the gloss of the edible film.

Mechanical Properties

Utilizing a tensile stress testing machine with a cross head speed of 10 mm/min, the tensile properties of the edible films, including tensile strength (TS) and percent elongation at break (Eb), were assessed [41]. Dimension of the specimens were 8 cm length and 2 cm width, 3 distinct blends with various extract concentrations in gelatin were examined.

Barrier Properties

Water vapor permeability (WVP) was determined by using the WVTR tester (Water vapor transmission rate tester). Oxygen transmission rate (OTR) tests were carried out with an OTR analyzer [24]. WVTR and OTR rates were determined from the graphs obtained.

Antimicrobial Activity

The antibacterial activity of the produced films was evaluated using the agar diffusion method [26]. Gram positive and Gram negative common bacterial strains associated with food spoiling in refrigerators, S. aureus and E. coli were employed. On Muller Hinton agar plates, 0.1 mL of inoculums containing roughly 105 CFU mL-1 of the examined bacteria was applied. After 24 h of incubation at 37 °C, the inhibition zone's diameter (mm) around the film disc’s (1 1 cm2) surface area was measured. Gelatin served as the control. Each sample was tested three times.

Results and Discussion

Extraction of Garlic Peel

Ultrasound extraction gives maximum yield with very fine garlic peel powder [19]. The yield percentage was 82.23%.

Characterization of Extracts

Total Phenolic Compounds and Total Flavonoids

The TPC value for Aloe Aera gel extract was found to be 30.15 μg GAE/ml. where as total phenolic compound value for garlic peel extract was found to be 32.47 μg GAE/ml. The total flavonoids of GPE was found to be higher than Aloe Vera extract. Total flavonoid content of GPE was 18.13 μg of quercetin/mL and it was 0.503 μg of Catechin/mL for Aloe Vera extract. According to various writers, a number of factors, including variety, pre- and post-harvest treatment, and storage, can alter the bioactive components of different fruits and other crops. The most crucial factors are extraction condition and quantification [12] (Figs. 1, 2, Table 1).

Fig. 1
figure 1

Standard calibration curve of Gallic acid (A) Aloe Vera extract (B) GPE

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Fig. 2
figure 2

Standard curve of quercetin (A) Aloe Vera extract (B) GPE

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Table 1 TPC and Total flavonoids of GPE and Aloe Vera gel extracts
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Antioxidant Activity of Extracts

IC 50 value obtained from the graph were 768.26 µg/ml of garlic peel extract and 498.63 µg/ml of Aloe Vera gel extract. The phenolic chemicals in garlic peel, particularly the phenyl propanoids, may be strongly associated with this antioxidant effect had already been discovered and investigated [11]. According to the results of the experiments, the antioxidant activity appears to be inversely related to the total phenolic compound [15]. As shown in Table 2, the Radical Scavenging Activity is connected to the capacity to scavenge DPPH radicals, was used to express the antioxidant activity of the Aloe Vera powder.The IC50 value is a parameter used to measure the antioxidant activity of test samples. It is calculated as the concentration of antioxidants needed to decrease the initial DPPH concentration by 50%. Thus, the lower IC50 value the higher antioxidant activity (Fig. 3, Tables 2, 3).

Table 2 Antioxidant activity of Aloe Vera
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Fig. 3
figure 3

Inhibition %- DPPH assay A AV extract and B GPE

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Table 3 Antioxidant activity of GPE
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Antimicrobial activity of extracts

Highest inhibition zones for S. aureus and E. coli were detected for antimicrobial agents with ratio (1:1). Given the high TPC and antioxidant activity values obtained in this study, it is possible that the presence of polyphenols and other antioxidants in AV and GPE were responsible for this antibacterial activity. Allicin present in garlic peel extract would be the key element in antibacterial activity, On the other hand, the acemannan present in AV had been reported to be also responsible for antibacterial activity [22].

From Table 4 Inhibition zone obtained was maximum for GPE: AV in the ratio 1:1. Maximum inhibition zone for S. aureus was 13 mm for both 1:1 and 2:1 ratios of GPE:AV and for E. coli was found to be 20 mm in well diffusion method.

Table 4 Antimicrobial activity of GPE:AV extracts
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Characterization of Edible Film

Visual Appearance, Thickness

The majority of the films displayed good visual transparency and uniformity, which are desirable qualities for applications involving food packaging. Average thickness value for the films was found to be 0.255 mm. Gelatin film thickness values were not significantly different, indicating that the inclusion of AV and GPE did not significantly alter the film forming process (Sui et al., 2017). Gelatin thickness values were not significantly different, indicating that the inclusion of AV and GPE did not significantly alter the film forming process [27].

Mechanical Properties-Tensile Strength

Tensile stress for Edible gelatin film 1%, 2%, and 3% of antimicrobial agents with varying ratios of 1:1, 2:1, and 1:2 were analyzed using a tensile stress tester [41]. From Table 5, it is found that the highest elongation percentage of 186.61 was obtained for film with AM agent 2% (2:1) while the Maximum force 14.629 Mpa was withstand by the film with AM agent 3% (2:1). From the overall results, it can be concluded that the tensile strength has improved with addition of antimicrobial agents. And thus the stretchability of the film is increased by increasing its suitability to become sausage casing.

Table 5 Mechanical and barrier properties of AM film
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Barrier Properties

Water vapor permeability (WVP) was determined by using the WVTR tester (Water vapor transmission rate tester). Oxygen transmission rate (OTR) tests were carried out with an OTR analyzer [24]. Gelatin is hydrophilic in nature, due to the presence of polar amino acids and large number of hydroxyl groups (-OH). Addition of Antimicrobial agents has slightly increased the WVTR of the film but addition of AM agents increased Oxygen transfer ratios of the films, but the changes are influenced by the ratios or concentrations of antimicrobial agent. From Table 5, the highest water vapor transmission ratio was found in gelatin film with antimicrobial agent 3% (2:1) and the lowest water vapor transmission ratio was found in control gelatin film. The highest Oxygen transmission ratio was obtained for gelatin film with antimicrobial agent 3% (1:2) and the lowest oxygen transmission ratio was obtained for control gelatin film.

Antimicrobial Activity of Gelatin Films

In interaction with the two strains of bacteria under study, Edible gelatin films’ antibacterial efficacy varied noticeably. Highest inhibition zones for S. aureus and E. coli were detected for gelatin film with AM agent 3% (1:1), respectively, as opposed to the control gelatin film, which did not manifest any inhibitory zone as would be expected [1]. Given the high TPC and antioxidant activity values obtained in this study, it is possible that the presence of polyphenols and other antioxidants in AV and GPE were responsible for this antibacterial activity. Allicin present in garlic peel extract would be the key element in antibacterial activity, On the other hand, the acemannan present in AV had been reported to be also responsible for antibacterial activity [22]. These antioxidants have the ability to produce the precipitation of cell membrane proteins or have non-specific interactions with them [33] (Fig. 4).

Fig. 4
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Antimicrobial activity of film against A S. aureus and B E. coli

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From Table 6, the inhibition zone obtained was maximum for AM film with 3% (1:1) Am agent concentration. Maximum inhibition zone for S. aureus was 15 mm and for E. coli was found to be 17 mm in well diffusion method.

Table 6 Antimicrobial activity of AM films
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Conclusion

The extraction and analysis of Aloe Vera gel and garlic peel was successfully performed to obtain active edible films with antimicrobial properties against S. aureus and E. coli. Analysis of GP and AV shown that GPE and AV were effective antioxidants and have antimicrobial properties against S. aureus and E. coli. So these two extracts can be used as antimicrobial agent in the gelatin based edible films and it can be used for the extension of shelf-life of different food products. In conclusion, this project underlines the optimization of extraction and analysis of AV inner gel and garlic peel extract, development of gelatin based edible antimicrobial films and characterization of the edible film. The main motive of the study was reducing the use of synthetic additives and contributing to the circular economy concept by reducing food wastes.