4. Valorization of Fruits and Vegetable Waste into Valuable Applications
In parallel with the food waste reduction strategies, recovery and revaluing of crop wastes have been actively conducted. The valorization of crop wastes are discussed in detail in the subsections below.
4.1. Antioxidant
The food sector is becoming increasingly influential in the outcome of novel biomaterials featuring antioxidant characteristics as it has the advantage of enhancing the shelf life of food products
[50]. Compounds that are rich in polyphenols, such as phenolic acids and flavonoids, have been reported to have excellent antioxidant capacity
[51], as those compounds can scavenge the reactive oxygen species (ROS) present in the food products
[52]. Recently, Rangaraj et al.
[53] developed an active gelatin film incorporated with date fruit syrup waste extract (DSWE) as an antioxidant additive for food storage studies. The active gelatin/DSWE blend films show a high release profile of the active phenolic compounds and higher antioxidant capacity in an aqueous food medium when compared to lipid-based food stimulants. Venturi et al.
[54] used potato peels, which contain bioactive compounds and have higher antioxidant power to enhance the qualitative parameters of fresh-cut apples. During storage, a substantial anti-browning effect and a slowing of the softening of fruits were identified. The observed results indicate that potato extracts are suitable as antioxidant supplements for fresh-cut fruits, hence minimizing the usage of hazardous chemicals. Kurek et al.
[52][55] created a chitosan and pectin film mixed with blackcurrant pomace powder to reduce the losses of food production, and this film is focused on food coating and wrappers. Based on the research, the antioxidant activity of the film was increased 30-fold. This film is suitable to be used as active or intelligent packaging films for antioxidant activity of fresh produce.
Kam et al.
[56] utilized durian leaf extract in gelatin-based film for antioxidant activity enhancement of biodegradable film as active packaging. This research revealed that gelatin-based film with added 0.5% crude extract of durian leaf has 17.6 times higher DPPH scavenging activity than the negative control sample. Gelatin film with 0.5% durian leaf extract reduced the oxidation of palm oil at a rate that was three times lower. Deshmukh et al.
[57] also employed guar gum/carboxymethyl cellulose incorporated with litchi shell waste extract (GCH/LSE) for antioxidant active packaging. According to the results obtained by the researchers, GCH/LSE 20% shows the highest antioxidant activity, which is 91.52%. Active GCH/LSE films are good at maintaining roasted peanuts’ oxidative stability. The GCH/LSE films were proven to be effective antioxidant packaging for foods with a high lipid content. Orqueda et al.
[58] tested an active edible film using red chilto (
Solanum betaceum) peel and seed to reduce the oxidation of salmon filets during storage. Based on the experiment conducted, samples collected from chilto peel had the highest concentration of phenolic compounds. Antioxidant pectin-based film can be found in
S. betaceum fruit peel, and it successfully shows remarkable antioxidant properties that protect the salmon filets.
Ribeiro et al.
[59] created pectin–phenolic antioxidant films from mango peels for food packaging applications. Result shows that film with aqueous or methanolic extracts provides higher antioxidant activity based on the inhibition of the DPPH radical. The extracts, on the other hand, increased elongation and the water vapor barrier and also provided films with a greater antioxidant capacity, making them promising materials as active food packaging/coating, particularly for food products susceptible to lipid oxidation, such as edible nuts, fruits, and breakfast cereals. Merino et al.
[60] developed a highly antioxidant bioplastic film from avocado peels and seeds. The findings suggest that combining hydrolysis, plasticization, and pectin blending is critical for obtaining materials with competitive mechanical properties, biodegradability, excellent oxygen barrier properties, high antioxidant activity, optical clarity, and component migration suitable for food contact applications. The created materials, which stand out for their antioxidant activity, natural composition, and ecologically safe technique of creation, thereby constitute an appropriate and sustainable alternative to conventional nonbiodegradable plastic food packaging materials. A new active coating was developed using
Cucumis metuliferus (CM) fruit-extract-loaded acetate cellulose coating for antioxidant active packaging
[61]. To assess the total phenolic components and antioxidant activity of CM, the extraction procedure was initially optimized. Release studies of CM from the cellulose acetate layer to a fatty food simulant verified the antioxidant efficiency of bilayer packaging.
Gaikwad et al.
[13] created a biocomposite film made of polyvinyl alcohol and apple pomace that possesses antioxidant qualities and may be used in active food packaging applications for the storage of soybean oil. They discovered that the inclusion of apple pomace into PVA films increased the overall phenolic content and the antioxidant capabilities of the films in delaying lipid oxidation. Meanwhile, Matta et al.
[62] created an active edible film of methylcellulose (MC) containing extracts of green apple (
Granny Smith) skin by incorporating ethanolic extracts of freeze-dried apple skin (EEFD) and aqueous extracts of apple skin (AES). The results indicate that including extract of green apple skin into MC films increases the films’ overall phenolic contents and antioxidant capabilities. The potential for developing these films into functional packaging materials for food to ensure quality and safety and broaden the shelf life of packaged foods is therefore significant, and it represents an attractive alternative to the conventional packaging materials in terms of food safety and shelf life extension. Similarly, Han and Song
[63] conducted a study on the antioxidant properties of mandarin (
Citrus unshiu) peel pectin films comprising sage (
Salvia officinalis) leaf extract for environmentally and biodegradable food packaging in which the biopolymer films were made from pectin derived from mandarin peel, a waste of fruit processing. Antioxidant activity of the film increased as the amount of sage leaf extract increased, which indirectly proved the antioxidant properties of sage leaf extract.
Furthermore, Saberi et al.
[14] utilized pea starch and guar gum (PSGG) to produce food packaging that was incorporated with natural antioxidants comprising of epigallocatechin gallate (EGCG), blueberry ash (BBA) fruit extract, macadamia (MAC) peel extract, and banana (BAN) peel extract. The findings showed that EGCG-PSGG films had the most antioxidant power, followed by BBA-PSGG, MAC-PSGG, and BAN-PSGG films, at all concentrations (0.75–3 mg mL
−1) when measured using DPPH radical scavenging ability assay, cupric reducing antioxidant (CUPRAC), and ferric reducing activity power (FRAP). Inclusion of natural additives has been demonstrated to improve the moisture barrier of the films. Shahbazi
[64] combined ethanolic red grape seed extract and
Ziziphora clinopodioides essential oil into chitosan and gelatin films to enhance the antibacterial, antioxidant, physical, and mechanical properties of the chitosan (Ch) and gelatin (Ge) films. The two most important chemicals in the ZEO are carvacrol and thymol, which provide antibacterial and antioxidant properties for ZEO. In addition, mango peel extract (MPE) has revealed its robust free-radical-scavenging capabilities and was combined with fish gelatin films to improve the physical, barrier, mechanical, and antioxidant capabilities of the developed film
[65].
Interestingly, Melo et al.
[66] integrated three chemical fractions derived from mango kernels to create active films: mango kernel starch (MKS) as a matrix, mango kernel fat (MKF), and phenolic extract (MKPE). MKPE was added to give the films active qualities such as primarily antioxidant and UV absorber. The active films are especially appealing for use as bags, pouches, or coatings for oxidizable foods. Additionally, Moghadam et al.
[67] created edible antioxidant films using mung bean protein and pomegranate peel. The current study effectively enhanced mung bean protein-based edible films with varying amounts of pomegranate peel as a natural bioactive chemical to develop an antibacterial and antioxidant packaging system. Pomegranate peel, a low-cost by-product of the food industry, has the potential to improve the bio-functional qualities of mung bean protein film. Rodsamran and Sothornvit
[68] developed a pectin fraction from pineapple peel to serve as biopolymer films. As expected, TPC and antioxidant activity against DPPH and ABTS radicals in pectin films rose significantly when the PPS to water ratio increased in both stimulation media. The results demonstrated that the whole pineapple peel pectin extract solution (PPS) can be used as a natural plasticizer to produce pectin films with enhanced film properties, particularly in terms of the water vapor barrier and antioxidant properties, and that this research has the potential to become an effective active film or coating for food applications.
Additionally, Vargas-Torrico et al.
[69] created gelatin/carboxymethylcellulose active films with Hass avocado peel extract as berry preservation packaging. According to their findings, avocado extract gave active films antifungal and antioxidant properties and altered the physicochemical characteristics of active films. Talón et al.
[70] created edible films with a polyphenol from thyme extract (TE) as an antioxidant incorporated into chitosan and starch matrix. Inclusion of TE in the polymer matrix has been shown to improve the mechanical properties of the film as well as providing great antioxidant capacity. The findings also suggested that these antioxidant films may be used for coating applications to extend the shelf life of items susceptible to oxidative processes. Moreover, Urbina et al.
[71] employed 100% apple-waste-derived multicomponent films as antioxidants in developing an active packaging. The researcher creates nano papers (NPs) with higher hydrophobicity and antioxidant activity from bacterial cellulose. PHA coatings with varying concentrations of apple extract (e) with antioxidant activity were also applied to the nano papers (NP/PHA-e). The integration of apple extract in the PHA coating supplied free radical scavenging capability to the films since the extracts retained their antioxidant potential after the films were processed. Kurek et al.
[11] examined blueberry and red grape skin extract incorporated with chitosan (CS) and carboxymethyl cellulose (CMC) as an antioxidant film. The result showed that blueberry and red grape skin pomace extracts gives a great antioxidant activity.
4.2. Antimicrobial
As a result of recent worldwide food-borne microbial outbreaks, researchers have been looking for novel approaches to preventing microbial growth in food without compromising its flavor, texture, or safety. Use of antimicrobial packaging is one strategy that gives consumers more peace of mind about the quality and security of their food. Therefore, the use of polymers or antimicrobial agents to create barrier-enhanced or active packaging materials is a promising strategy for preventing the growth and dissemination of microorganisms in food. Recently, Ali et al.
[16] employed pomegranate peel particles (PGP) mixed with starch as antimicrobial films which can also be used as food grade packaging material. PGP suppressed the development of both gram-positive (
S. aureus) and gram-negative (
Salmonella) bacteria. The research showed that created films displayed good antibacterial properties against both
S. aureus and
Salmonella. It was observed that as the concentration of PGP increased, so did the inhibition zone of the films against the targeted bacteria. PGP was significantly more effective against
S. aureus than it was against
Salmonella. Comparably, Hanani et al.
[72] investigated fish gelatin films’ antibacterial characteristics as active packaging using pomegranate (
Punica granatum L.) peel powder (PPP). Inclusion of PPP increased the physicochemical properties of the films as well as providing antibacterial capabilities. One of the most sensitive bacteria to the active film was determined to be
Staphylococcus aureus (
S. aureus), followed by
Listeria monocytogenes (
L. monocytogenes) as well as
Escherichia coli (
E. coli). For
S. aureus, the most significant inhibitory zone (7.00 mm) was detected surrounding the film containing 5% PPP. These findings indicate that fish gelatin incorporating PPP has tremendous potential as a compelling film with antibacterial capabilities and can help maintain food quality and extend shelf life. Saleem and Saeed
[73] studied the orange (
Citrus sinensis L.), yellow lemon (
Citrus limonia Osbeck), and banana (
Musa acuminata) peel extracts as wide-range natural antimicrobial agents for agrowaste minimization. This study discovered that gram-negative bacteria are more sensitive to the extracts, with
Klebsiella pneumoniae (gram-negative) bacteria exhibiting the highest sensitivity to the yellow lemon peel extract and the largest zone of inhibition.
Jodhani and Nataraj
[74] utilized aloe vera gel and lemon peel extract to maintain the shelf life of banana (
Musa spp.). The antifungal properties of lemon peel extract have been successfully tested on
Colletotrichum musae, a decay-causing pathogen in bananas. The coating extended the shelf life of bananas up to 9 days without any disease incident. The combination effect on aloe vera and lemon peel essential oil effectively reduced quality losses of bananas without the use of chemical preservatives and hazardous fungicides. Meydanju et al.
[75] developed a biodegradable film from lemon peel powder combined with xanthan gum (XG) and TiO
2–Ag nanoparticles to inhibit the growth of
Escherichia coli and
Staphylococcus aureus. The synergistic effect of XG/TiO
2-Ag and lemon peel powder has been reported to increase the growth of inhibition zone diameter. Additionally, Alparslan and Baygar
[76] utilized orange (
Citrus sinensis [L.]
Osbeck) peel and combined it with chitosan films to monitor and evaluate the shelf life of deepwater pink shrimp. The antimicrobial properties of the combined film were tested on
Bacillus subtilis,
Staphylococcus aureus,
Escherichia coli,
Pseudomonas aeruginosa, and
Candida albicans. The combination of chitosan film and OPEO (CH+OPEO) was effective in extending the shelf life of fresh shrimp to 15 days, whereas the only chitosan-coated (CH) group had a shelf life of 10 days, and the uncoated samples (control) only had a shelf life of 7 days.
Furthermore, Agdar et al.
[77] evaluated the effectiveness of the salep gum coating containing orange peel essential oil in inhibiting the microbial growth on fish filets stored in refrigerated temperature for 16 days. The combined film prevented the growth of total aerobic mesophilic, coliforms, psychrophilic, and lactic acid bacteria. Additionally, the shelf life of fish filets was extended to 12 days when coated with salep gum containing 0.5% orange peel essential oil. Ramli et al.
[78] observed the antibacterial activity of durian (
Durio zibethinus) seed and peel extracts for effective shelf life enhancement of preserved meat. In terms of antibacterial characteristics, studies indicate that seeds have promising antimicrobial properties against
E. coli,
P. vulgaris,
S. marcescens, and
S. aureus and greater inhibitory zone size than peeling. Mayeli et al.
[79] innovated a coating layer enriched with zein and sour orange peel extract to act as an antibacterial coating for refrigerated fish. The developed coating reduced the number of
Enterobacteriaceae,
Pseudomonas spp., and psychrotrophic bacteria during the storage period. The combined effect of the coating layers extended fish freshness by an average of 12 days. Shukor et al.
[80] innovated antimicrobial packaging films using jackfruit peel waste for the shelf life of cherry tomatoes. The samples were tested for 7 days and the antimicrobial activity was done using
Escherichia coli and
Staphylococcus aureus. Based on the results gained, both
Escherichia coli and
Staphylococcus aureus were inhibited by films containing 10 wt% thymol. The application of these active films to actual food demonstrated that cherry tomato samples exhibited a considerable reduction in fungus growth.
4.3. Antibrowning
The browning reaction, caused by an enzyme, is a serious issue with fresh produce. It alters the food’s quality in an unfavorable way, shortens its shelf life, and decreases its value on the market. Chemicals, especially sulfites, can inhibit enzymes responsible for browning. Reports indicate, however, that it poses health risks to consumers. Recently, Thivya et al.
[81] discovered a new alternative to prevent the browning of fresh-cut apples and potatoes by proposing an active packaging composed of sodium alginate (SA) and carboxymethyl (CMC) along with shallot onion waste extract (SOWEs). Shallot onion waste extracts were reported to have an antibrowning effect due to their high content of polyphenols and antioxidant activity. The incorporation of SOWEs in SA/CMC active packaging has successfully inhibited the enzymatic reaction of polyphenol oxidase that is responsible for enzymatic browning in fruits and vegetables. Similarly, Tinello et al.
[82] inactivated polyphenol oxidase enzyme using juices and distillates extracted from different onion varieties (white, yellow, and red) and inner layers of Borettana onion wastes. The inhibitory action of the extracted anti-browning agents was tested on commercial mushroom tyrosinase. The studies not only inhibited browning action but also extended the shelf life and improved the sensory properties of the food products. Interestingly, Liang et al.
[83] successfully inhibited browning action in fresh-cut asparagus lettuce using extractable condensed tannins (ECTs) extracted from durian shells. The inhibitory action is predominant due to the presence of B-type procyanidins, propelargonidins and prodelphinidins, as well as a low degree of 3-O-galloylation, which are potent compounds that inhibit tyrosinase activity in fruits and vegetables.
Furthermore, Jirasuteeruk and Theerakulkait
[84] investigated the anti-browning properties of mango peel extract from different varieties of mangoes. It was reported that mango extract from the Chok-Anan cultivar showed to have greater inhibition action compared to the Nam-Dok-Mai and Kaew cultivars. Chok-Anan mangoes exhibited high phenolics content and therefore inhibited polyphenol oxidase to a greater extent than the other two cultivars. Faiq and Theerakulkait
[85] also reported that papaya peel crude extract has high bioactive phenolic compounds and hence has successfully inhibited browning reaction in potatoes, apples, and bananas. Martínez-Hernández et al.
[86] produced an antibrowning agent from tomato skin which has a very high lycopene content. Fresh-cut apples were dipped in the lycopene microspheres, which successfully controlled the browning reaction after 9 days at 5 °C. Tinello et al.
[87] utilized the juices from unripe grapes to serve as antibrowning and antioxidant agents to dried “Golden Delicious” apple slices. The appearance of the treated apple slices showed good results, demonstrating that the antibrowning agent of unripe grape juices effectively inhibited polyphenol oxidase activity.
4.4. Adsorbents
There is an alarming level of contamination in the aqueous medium, atmosphere, and geosphere due to the large number of toxic and poisonous chemicals released into our environment by various industries. Heavy metal pollution of the aqueous medium is a growing environmental crisis. Particularly problematic in treating industrial wastewater are toxic metals like zinc, mercury, lead, chromium, cadmium, nickel, and copper. Most of them cause cancer and are not biodegradable; they also form aggregates in living organisms. In order to safely remove pollutants and metallic elements from industrial effluents and wastewater, considerable in-depth industrial research has been conducted. As a result, several forms of fruit waste could be utilized to absorb or eliminate hazardous compounds, such as pesticides, heavy metals, and dyes.
Hussain et al.
[88] study the flavonoids, total phenolics, and antioxidant properties of agricultural wastes and their capacity to eliminate pesticide waste using banana peels. Banana peels contain chlorophyll, hemicellulose, pectin, cellulose, and other low-molecular-weight compounds with higher antioxidant activity and phenolic content. At a concentration of 9 g, banana peels successfully decreased diazinon by 63.86%, while parathion was lowered by 50.34%. This study shows that agricultural wastes effectively remove diazinon from water, and their usage is environmentally friendly. Maia et al.
[89] created activated carbon using banana peel waste using NaOH and pyrolysis to remove methylene blue. The results revealed that the activated carbon derived from banana peel waste has a vast surface area, which is required to remove blue methylene. The maximum dye removal efficiency was 99.8% when the MB starting concentration was 25 mg/L, the sorbent was 0.03 g, and the contact duration was 60 min. Banana-peel-activated carbon coated with Al
2O
3-Chitosan was developed. Ramutshatsha-Makhwedzha et al.
[90] tested this study for the adsorption removal process of cadmium and lead from wastewater and found it to be successful. The BPAC composite was proven reusable until the third cycle of adsorption–desorption (% Re > 80). Based on the data obtained, the produced material could remove Cd
2+ and Pb
2+ up to 99.9% of the time.
Wang et al.
[91] investigated activated carbon generated using tangerine seed waste for high-performance carbamate pesticide adsorption of plants and water. A novel activated carbon produced from waste tangerine seed was effectively synthesized in this work. Batch adsorption investigations revealed that the pseudo-second-order kinetic model and the Langmuir isotherm model predicted TSAC adsorption behavior well. Bendiocarb, metolcarb, isoprocarb, pirimicarb, carbaryl, and methiocarb have adsorption capacities of 7.97, 9.11, 13.95, 39.37, 44.64, and 93.46 mg/g, respectively. Furthermore, this adsorption mechanism was both spontaneous and exothermic. Gnanasekaran et al.
[92] used orange peel extract with 3D ZnO/SnO
2 for the removal of chlorophenol effluent. The research found that the existing various (Zn
2+, Sn
4+, and Sn
2+) states aided in postponing the transmission of electron–hole recombination to achieve photocatalytic chlorophenol degradation. In this study, a green 3D composite system is used to absorb the chlorophenol by 77.5% through photocatalysis. Aminu and Oladepo
[93] created orange-peel-mediated synthesis of silver nanoparticles for the detection of mercury (II) ions. Their results found that the golden-brown AgNPs colloid solution turned colorless when applied to water. AgNPs show good sensitivity and selectivity for the colorimetric detection of mercury (II) ions with the limit of detection og 1.24 × 10
−6 mol/L.
Hassan et al.
[94] also used date pits for the removal of organophosphorus pesticide from water. Three types of date pits were used as adsorbents, including roasted date pits, activated date pits, and nanoactivated date pits. The observation shows that nanoactivated date pits have high removal percentage and removal capacity of profenofos from aqueous solution compared to roasted date pits and activated date pits. Mohammad and El-Sayed
[95] created activated carbon peach stones for the removal of imidacloprid. The researcher used two types of activated carbon (PSAC 300 and PSAC 500). The result shows that both PSAC 300 and PSAC 500 were able to remove imidacloprid, with about 80% and 99% removal efficiencies, respectively. Overall, PSAC 500 exhibited the maximum adsorption capacity of 39.37 mg/g. Al-Ghouti and Sweleh
[96] employed activated carbon (ACOS) from black and green olive stones to remove methylene blue (MB) in water successfully. It was also discovered that black activated carbon olive stones had the most significant N%, H%, and C% prior to adsorption. Furthermore, the highest absorption of methylene blue occurred at the optimal pH value of 10. Methylene blue adsorption capacities were 714 mg g
−1 and 769 mg g
−1 for black and green activated carbon olive stones, respectively.
Batool et al.
[97] removed organochlorine pesticides (OCPs) using a zerovalent iron (Fe
0) supported on biochar nanocomposite (Fe
0-BRtP) from
Nephelium lappaceum (Rambutan) fruit peel waste. The experiment found that Fe
0-BRtP combined the advantages of adsorption and dechlorination of OCPs in aqueous solution and up to 96–99% removal was obtained within 120 min. The removal efficiency of regenerated Fe
0-BRtP was 89–92% after being reused five times. This Fe
0-BRtP nanocomposite could be used as a green and low-cost prospective material for adsorption and reduction of OCPs in aquatic environments. Shakoor and Nasar
[98] used citrus limetta peel waste as a methylene blue dye adsorbent. Langmuir adsorption isotherm was found to be the best fit for the data. The maximum adsorption capacity for a monolayer coverage was found to be 227.3 mg/g. The results show that CLP is a very effective, low-cost method of removing dyes from wastewater. Salama
[99] investigated cellulose grafted with soy protein isolate (SPI) to remove organic dyes from wastewater. This method exhibited adsorption capacity up to 454 mg/g. The efficiency of MB removal was 95% after four adsorption-desorption cycles. This method is a new sustainable, cost-effective, and reusable hybrid material which can successfully adsorb dyes in wastewater. Goksu and Tanaydin
[100] devised a technique for removing crystal violet (CV) color that uses almond shells as an effective adsorbent, and according to the findings of this study, almond shells are effective adsorbents for extracting crystal violet (CV) from aqueous solutions. On almond shells, the excellent adsorption capacity was reported to be 1.075 mg g
−1. According to the results of the adsorption experiment, almond shells might be utilized to effectively remove CV in aqueous solutions.
4.5. Indicator in Packaging
Petrochemical-derived synthetic pigments have been widely employed in a variety of food items. However, these colors negatively impact human health, making it necessary for the scientific community to search for safer, natural, and eco-friendly pigments. Recently, the pigments industry has expanded fast due to its numerous applications in food. As a result, it requires sustainable pigments manufacturing from renewable bio-resources. The valorization of vegetal wastes can fulfill the needs of natural pigment production at the industrial scale for food, medicinal, and cosmeceutical uses. Natural colors, such as anthocyanins, betalains, carotenoids, and chlorophylls, are abundant in these wastes
[101].
Figure 1 below shows the source of natural pigments.
Figure 1. Natural source of pigments.
4.6. Enzymes
In the industrial sector, enzymes play a crucial role in reducing chemical loads, eliminating toxic substances, and reducing pollution
[102]. Industrial enzymes currently have a market value of USD 5.9 billion, with a projected market value of USD 8.7 billion in 2026 and a compound annual growth rate of 6.5%
[103]. A wide range of enzymes are commonly used in the industry, including lipases, carbohydrases, proteases, and polymerases
[104]. Most of the waste produced by the food industry is lignocellulosic, which contains enzymes that are essential raw materials for production and processing
[105]. As an example, bromelain, which is extracted from pineapple peel, can improve food digestion
[106] and soften beef meat
[107] and can be transformed into value-added products.
Previously, Hussain et al.
[108] extracted bromelain from pineapple core using the maceration extraction method. A maceration of chicken breast meat with 100% core extract shows an 86% reduction in hardness and pH decreases from 5.87 to 4.99. Meanwhile, Singh et al.
[109] analyzed the effect of bromelain enzyme extracted from four different pineapple wastes—peel, stem, core, and crown—on tenderizing chicken and beef meat. Rizqiati et al.
[110] investigated the effect of drying on cayenne pineapple crown enzyme characteristics—including protein content, activity units, and specific activity—in terms of moisture content, yield, and characteristics. The results obtained showed that the optimal drying temperature was 55 °C because it had the highest moisture content, protein content, and enzyme characteristics as well as the longest immersion duration for the best texture of meat. Lipases have been applied as food additives in the modification of taste in the food industry
[111]. Recently, Okino-Delgado et al.
[112] examined different varieties and fractions of orange wastes as sources of lipases. Among the fruit varieties studied, bagasse, peel, and frit lipases showed optimal pH values between 6.0 and 8.0 and optimal temperatures between 30 °C and 60 °C. Next, Tambun et al.
[113] successfully produced fatty acids directly from avocado seeds by activating the lipase enzyme. The highest fatty acid content found was 11.67%. Furthermore, there is an enzyme called papain present in the bark, leaves, and fruit of the papaya plant
[114].
Papain is extracted from fruit and stem latex can be utilized as a primary ingredient in brewing and winemaking
[115]. Singla et al.
[32] previously investigated the effects of microwave treatment and enzyme addition on ultrasound-assisted extraction (UAE) of bioactive compounds and antioxidant activity from papaya peels. Extracts prepared using UAE extraction were found to have antioxidant activity, indicating that they are useful for preparing plant extracts that contain antioxidants. Phothiwicha et al.
[116] evaluated the bioactivity of papain extracted from Chaya and papaya stalks on beef meat. The texture and mastication of beef samples marinated with papain had a softer texture and were easier to chew after the marination. Amylases can therefore be used in a variety of industries, such as food, fermentation, and pharmaceuticals
[117]. At present, Abdullah et al.
[118] produced a safe sweetener in the form of glucose syrup using alpha amylase extracted from mango seed core, which can be used as an alternative to artificial sweeteners through enzymatic reactions. In a study which tested the amylase production ability of
Bacillus subtilis K-18 (KX881940) by hydrolyzing potato peels as carbon sources, Mohtaq et al.
[119] found that the bacterium can produce amylase as a result of starch hydrolysis.