Milk Protein Coatings Prevent Oxidative Browning of Apples and Potatoes

Application of Whey Protein-Based Emulsion Coating Treatment in Fresh-Cut Apple Preservation

Fresh-cut fruit requires an edible and water-resistant coating to remain fresh. This article investigated the effects of transglutaminase (TGase) and sunflower oil on the water-resistant characteristics, mechanical properties, and microstructure of a whey protein-based film. The whey protein-based emulsion coating’s preservation effect on fresh-cut apples was confirmed. According to the findings, sunflower oil (added at 1.5% w/w) could interact with β-lactoglobulin, α-lactoglobulin dimer, and β-lactoglobulin dimer to form emulsion droplets that are evenly dispersed throughout the protein film. This effect, combined with the covalent cross-linking of TGase, significantly improves the films’ microstructure, mechanical properties, and water resistance. However, too much and unevenly distributed sunflower oil (add 3% w/w) partially prevented the covalent cross-linking of TGase, reducing the elongation at the break of the composite film. In the fresh-cut apple storage experiment, the whey protein-based emulsion coating treatment significantly reduced the weight loss rate and browning index of fresh-cut apples by 26.55% and 46.39%, respectively. This was accomplished by the coating treatment significantly inhibiting the respiration rate increase, PPO and CAT activity enhancement, H2O2 production, and MDA accumulation. This research provides practical, technical, and theoretical guidance for the preservation of fresh-cut fruit.

Milk protein-based active edible packaging for food applications: An eco-friendly approach

Whey and casein proteins, in particular, have shown considerable promise in replacing fossil-based plastics in a variety of food applications, such as for O₂ susceptible foods, thereby, rendering milk proteins certainly one of the most quality-assured biopolymers in the packaging discipline. Properties like excellent gas barrier properties, proficiency to develop self-supporting films, adequate availability, and superb biodegradability have aroused great attention toward whey and other milk proteins in recent years. High thermal stability, non-toxicity, the ability to form strong inter cross-links, and micelle formation, all these attributes make it a suitable material for outstanding biodegradability. The unique structural and functional properties of milk proteins make them a suitable candidate for tailoring novel active package techniques for satisfying the needs of the food and nutraceutical industries. Milk proteins, especially whey proteins, serve as excellent carriers of various ingredients which are incorporated in films/coatings to strengthen barrier properties and enhance functional properties viz. antioxidant and antimicrobial. In this review, the latest techniques pertaining to the conceptualization of active package models/ systems using milk proteins have been discussed. Physical and other functional properties of milk protein-based active packaging systems are also reviewed. This review provides an overview of recent applications of milk protein-sourced active edible packages in the food packaging business.

Application of Whey Protein-Based Edible Films and Coatings in Food Industries: An Updated Overview

The recent surge in environmental awareness and consumer demand for stable, healthy, and safe foods has led the packaging and food sectors to focus on developing edible packaging materials to reduce waste. Edible films and coatings as a modern sustainable packaging solution offer significant potential to serve as a functional barrier between the food and environment ensuring food safety and quality. Whey protein is one of the most promising edible biopolymers in the food packaging industry that has recently gained much attention for its abundant nature, safety, and biodegradability and as an ecofriendly alternative of synthetic polymers. Whey protein isolate and whey protein concentrate are the two major forms of whey protein involved in the formation of edible films and coatings. An edible whey film is a dry, highly interacting polymer network with a three-dimensional gel-type structure. Films/coatings made from whey proteins are colorless, odorless, flexible, and transparent with outstanding mechanical and barrier properties compared with polysaccharide and other-protein polymers. They have high water vapor permeability, low tensile strength, and excellent oxygen permeability compared with other protein films. Whey protein-based films/coatings have been successfully demonstrated in certain foods as vehicles of active ingredients (antimicrobials, antioxidants, probiotics, etc.), without considerably altering the desired properties of packaging films that adds value for subsequent industrial applications. This review provides an overview of the recent advances on the formation and processing technologies of whey protein-based edible films/coatings, the incorporation of additives/active ingredients for improvement, their technological properties, and potential applications in food packaging.

Active Casein Coatings and Films for Perishable Foods: Structural Properties and Shelf-Life Extension

There is an urgent need to increase the food supplies to fulfil the demands of future generations as the population of the world is expected to grow beyond 10 billion by 2050. An essential component for ensuring global food security is to reduce food losses during the post-harvest stage. Active edible coatings and films are a promising sustainable preservation technology for shelf-life extension of food products by hindering decay kinetics of minimally processed fruits and vegetables (F&V), by restricting the mass transfer of moisture, aroma, or gases and carrying an active compound, such as an antioxidant or antimicrobial. Active protein-based coatings and films have the potential to extend the shelf-life of food products by decreasing their respiration rates, as they exhibit an excellent gas barrier and good mechanical properties as compared to other biopolymeric packaging. Among protein-based biopolymers, casein and its derivatives as packaging films have been extensively studied due to their low cost, complete biodegradability, and availability. Currently, there is no review study focusing on caseinate-based active coating and film, thus, this review aims to give insights on the composition, rheology, structure, and properties of caseinate-based formulations by critically discussing the results presented in the literature. A methodological approach was followed to obtain relevant literature to discuss the influence of additives on the shelf-life of F&V. Furthermore, changes in secondary structure of casein were observed after incorporation of bioactive compounds (i.e., phenolic acids). Likewise, there is a need to explore chemical interactions among bioactive compounds and biopolymer material by using in silico and laboratory trials as food additives have shown to influence the physicochemical properties of film and shelf-life of food products.

Apple (Malus domestica Borkh.) Cultivar 'Majda', a Naturally Non-Browning Cultivar: An Assessment of Its Qualities

Browning of apple and apple products has been a topic of numerous research and there is a great number of methods available for browning prevention. However, one of the most efficient ways, and the one most acceptable for the consumers, is the selection of a non-browning cultivar. Cultivar ‘Majda’ is a Slovenian cultivar, a cross between ‘Jonatan’ and ‘Golden Noble’. In this study, it was thoroughly examined and compared to the well-known cultivar ‘Golden Delicious’ with the aim to decipher the reason for non-browning. We have determined the content of sugars, organic acids, vitamin C, glutathione and phenolics in apple flesh, with the addition of phenolic content in apple peel and leaves. The change in color in halves and pomace was also measured and the activity of peroxidase (POX) and polyphenol oxidase (PPO) were determined. Additionally, the analyses of flesh were repeated post-storage. The most prominent results were high acidity (malic acid), low phenol content, especially hydroxycinnamic acid and flavan-3-ol content of cultivar ‘Majda’ in comparison to ‘Golden Delicious’, and no difference in PPO activity between cultivars. After the overview of the results, we believe that both low phenol content and high reduced glutathione content impact the non-browning characteristics of cultivar ‘Majda’.

Impact of Sodium Alginate Packaging Film Synthesized Using Syzygium cumini Seed Extract on Multi Drug Resistant Escherichia coli Isolated from Raw Buffalo Meat

A total of 50 Escherichia coli were isolated from buffalo meat and their antibiotic profiling was carried out. 90% E. coli isolates showed resistant to two or more classes of 21 commonly used antibiotics. Moreover, there was also variation in resistance/sensitivity behavior towards antibiotics. Highest resistance was found to be against methicillin (84%) in the isolates followed by vancomicin (70%), sulphadiazine (68%) and cefaclor (66%), whereas, resistance was less common for kanamycin (8%) and chloramphenicol (4%). ECMB1, ECMA2, ECMA8, ECMS9 and ECMA31 strains showed highest MDR pattern with presence of ^bla CTX-M, qnr S and qnr B resistant genes. ECMB1 strain was resistant to 14 antibiotics belonging to 7 different classes. Therefore, ECMB1 was selected for further studies. Sodium Alginate Film incorporated with 10, 20, and 30% ethanolic extract of Syzygium cumini (EESC) were formulated and characterized using state-of-art techniques. A dose-dependent antibacterial activity against E. coli ECMB1 was recorded by the films made from EESC (EESCF). The growth kinetics of E. coli strain ECMB1 showed 9% decrease in log CFU when it was cultured in 30% EESCF as compared to control cells after 12 h of growth. Present finding highlight the efficacy and possible use of EESCF as meat packaging film to prevent food spoilage caused by MDR bacteria.

Evaluation of the properties of whey protein films with modifications

Whey protein concentrate (WPC) has been widely studied as a biodegradable bio-based packaging material in the food industry. In this study, different whey protein films were obtained through physical, chemical, enzymatic, and composite modifications. The molecular structure, micro-morphology, mechanical properties, barrier properties, and other characteristics of the films were evaluated. The results illustrated that the thickness of WPC with composite modification increased and the transmittance decreased, but the mechanical properties and barrier properties were more prominent. The WPC film prepared by physical modification combined with transglutaminase has the best film-forming effect, the tensile strength (TS) was 5.45 MPa, the elongation at break (EAB) was 25.19%, the WVP was 5.53 g·mm/m² ·hr·kPa, and the Oxygen permeability (OP) was 1.83 meq/K, and its microstructure was and uniform. In addition, based on the the results of SDS-PAGE and Fourier transform infrared spectroscopy (FTIR), the intermolecular and intramolecular interactions of various modification methods on WPC were studied, thus contributing to analyze the properties of the film. This study provides theoretical basis and technical support for the industrial production of protein-based films.

Effects of tea polyphenols on physicochemical and antioxidative properties of whey protein coating

Effects of tea polyphenols (TP) incorporation on physicochemical and antioxidative properties of whey protein isolate (WPI) coating were studied. Two WPI coating solutions were prepared by heating WPI solutions (pH 8, 90 °C) for 30 min and then TP was incorporated. TP addition could increase the negative zeta potential of 5% solution. The surface hydrophobicity index of both solutions was increased and intrinsic fluorescence intensity decreased greatly after addition of TP. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis (2 ethylbenzothiazoline-6-sulfonate) (ABTS) radical scavenging capacities of both solutions increased with increasing TP. Compared with apple pieces coated with whey protein only, those with TP containing whey protein coatings showed lower browning index and slight changes in weight loss during 24 h storage. Data indicated that TP could influence the physicochemical properties and improve the antioxidant activity of WPI coating solutions and can be used to retard the enzymatic browning of fruit during storage.

The efficacy of edible film from Konjac glucomannan and saffron petal extract to improve shelf life of fresh-cut cucumber

The efficacy of saffron petal extract (SPE; 1%-4%) incorporated into Konjac glucomannan (KGM) edible films on the quality and shelf life of fresh-cut cucumbers was evaluated. Changes in chemical, physical, and microbial properties, antioxidant activity, and total soluble phenolic contents of sliced cucumbers during storage at 4°C for 5 days were investigated. Results showed that the addition of SPE markedly reduced the water vapor permeability features of produced films, whereas the moisture content and transparency of them increased (p < .05). All the formulated films containing 1%-4% of SPE exhibited significant antimicrobial properties against the examined pathogens (Escherichia coli, Shigella sonnei, Salmonella Typhi, Staphylococcus aureus, and Bacillus cereus) both in vitro and in vivo conditions. KGM films incorporated SPE were successful in reducing mesophilic bacteria and fungi populations so that the microbial load significantly decreased as the concentrations of SPE increased and KGM + 4% of SPE was considered as the most effective treatment in decreasing the microbial content of sliced cucumbers. Total soluble solids of the treated cucumbers were significantly increased at the end of the storage in refrigerator, compared to the control sample. Moreover, antioxidant activity (DPPH assay) and total soluble phenols in treated fruit increased with storage time, while these parameters decreased with increasing concentrations of SPE incorporated into KGM film. So according to the findings, the introduced film with KGM and SPE could be considered as an edible film and be applied to preserve the fruit and vegetables quality and extend the shelf life of sliced cucumbers.

Purification of Polyphenol Oxidase from Potato and Investigation of the Inhibitory Effects of Phenolic Acids on Enzyme Activity

Background:

Polyphenol Oxidase (PPO) belongs to the oxidoreductase enzyme family.

Methods:

Here, PPO was purified from potato using Sepharose 4B-L-tyrosine-p-aminobenzoic acid affinity chromatography. It determined the interactions between some phenolic acids and the enzyme.

Results:

The enzyme was obtained with a specific activity of 15333.33 EU/mg protein and 7.87- fold purification. It was found that phenolic acids exhibited inhibitory properties for PPO. The IC50 values of the phenolic acids were found in the range of 0.36-2.12 mM, and their Ki values were found in the range of 0.28± 0.07-1.72±0.32 mM. It was determined that all studied compounds displayed a competitive inhibition effect. Among these compounds, 3-hydroxybenzoic acid was found to be the most effective PPO inhibitor (Ki: 0.28±0.07 mM).

Conclusion:

Investigating the inhibition kinetics of the enzyme will simplify the testing of PPO inhibitor candidates.

Starch glucose coating-induced postharvest shelf-life extension of cucumber

Cucumber (Cucumis sativus L.) is a rich source of vitamins, minerals, and antioxidants. Its post-harvest deterioration leads to a limited shelf-life up to 5-7 days. To avoid such loss, the present study investigates the potential effect of starch glucose (SG) coating on the extension of its shelf-life, after harvest. 1.0, 1.5 and 2.0 µM of starch with 2.5 µM D-glucose solutions were coated over freshly harvested cucumbers and stored at refrigerated temperature (±4 °C) for 30 days. 1.5 µM starch plus 2.5 µM D-glucose displayed significantly better results as per the skin colour and sensory evaluation test. This level of SG coating extended the shelf-life of cucumbers up to 30 days with least reduction in weight loss, total soluble sugar, protein, catalase activity, peroxidase activity and increased in proline content, 2, 2-diphenyl-1-picrylhydrazyl antioxidant activities and ferrous ion chelating activities.

Antioxidant properties of Milk and dairy products: a comprehensive review of the current knowledge

Milk and dairy products are integral part of human nutrition and they are considered as the carriers of higher biological value proteins, calcium, essential fatty acids, amino acids, fat, water soluble vitamins and several bioactive compounds that are highly significant for several biochemical and physiological functions. In recent years, foods containing natural antioxidants are becoming popular all over the world as antioxidants can neutralize and scavenge the free radicals and their harmful effects, which are continuously produced in the biological body. Uncontrolled free radicals activity can lead to oxidative stresses, which have been implicated in breakdown of vital biochemical compounds such as lipids, protein, DNA which may lead to diabetes, accelerated ageing, carcinogenesis and cardiovascular diseases. Antioxidant capacity of milk and milk products is mainly due to sulfur containing amino acids, such as cysteine, phosphate, vitamins A, E, carotenoids, zinc, selenium, enzyme systems, superoxide dismutase, catalase, glutathione peroxidase, milk oligosaccharides and peptides that are produced during fermentation and cheese ripening. Antioxidant activity of milk and dairy products can be enhanced by phytochemicals supplementation while fermented dairy products have been reported contained higher antioxidant capacity as compared to the non-fermented dairy products. Literature review has shown that milk and dairy products have antioxidant capacity, however, information regarding the antioxidant capacity of milk and dairy products has not been previously compiled. This review briefly describes the nutritional and antioxidant capacity of milk and dairy products.

The impact of nitrogen gas flushing on the stability of seasonings: volatile compounds and sensory perception of cheese & onion seasoned potato crisps

The impact of natural cheese and onion seasoning on the sensory perception and shelf life stability of potato crisps was studied. This study was carried out to evaluate the impact of nitrogen (N2) gas flushing on the shelf-life stability and sensory attributes of cheese & onion seasoned potato crisps. Markers of lipid oxidation and flavour volatile compounds were evaluated in sliced, unwashed, batch fried potato crisps during accelerated storage at 45 °C for 10 weeks. Volatile flavour compounds were evaluated by headspace gas analysis using solid phase microextraction (SPME) GC-MS and correlated with sensory perception. Gas flushing significantly increases the shelf life of both unsalted and cheese & onion seasoned potato crisps in terms of the stability of volatile compounds and sensory perception. Further to this, the addition of the cheese & onion seasoning increased the shelf life of the base potato crisp; this is proposed to be explained by the antioxidant properties of milk proteins in the seasoning. Sensory evaluation indicated that the key negative sensory attributes reported were rancidity and stale attributes, which were correlated to the progression of lipid oxidation and loss of flavour over storage time irrespective of the packaging environment (with/without gas flushing).

Effects of (+)-Catechin on the Composition, Phenolic Content and Antioxidant Activity of Full-Fat Cheese during Ripening and Recovery of (+)-Catechin after Simulated In Vitro Digestion

(+)-Catechin, the representative catechin in green tea, was incorporated into a full-fat cheese (at 125-500 ppm) followed by ripening for 90 days at 8 °C and digesting for six hours. Determination of pH, proximate composition, total phenolic content (TPC) and antioxidant activity (AA) after manufacture and ripening demonstrated that the addition of (+)-catechin significantly (p ≤ 0.05) decreased the pH of both whey and curd during cheese manufacturing and ripening with no significant (p > 0.05) effect on the moisture, protein and fat contents. (+)-Catechin increased TPC, as well as AA, though the increase was not proportional with increasing the concentration of added (+)-catechin. About 57%-69% of (+)-catechin was retained in the cheese curd, whereas about 19%-39% (depending on the concentration) was recovered from the cheese digesta. Transmission electron micrographs showed that the ripened control cheese had a homogeneous pattern of milk fat globules with regular spacing entrapped in a homogenous structure of casein proteins, whereas the addition of (+)-catechin disrupted this homogenous structure. The apparent interaction between (+)-catechin and cheese fat globules was confirmed by Fourier transform infrared spectroscopy. These associations should be taken into account when incorporating antioxidants, such as (+)-catechin, to create functional dairy products, such as cheese.

Effects of fresh Aloe vera gel coating on browning alleviation of fresh cut wax apple (Syzygium samarangenese) fruit cv. Taaptimjaan

The effect of natural coating by using fresh Aloe vera (A. vera) gel alleviating browning of fresh-cut wax apple fruits cv. Taaptimjaan was investigated. The fresh-cut fruits were dipped in fresh A. vera gel at various concentrations of 0, 25, 75 or 100 % (v/v) for 2 min at 4 ± 1 °C for 6 days. Lightness (L*), whiteness index (WI), browning index (BI), total color difference (ΔE*), sensorial quality attributes, total phenolic (TP) content, antioxidant activity and polyphenol oxidase (PPO) and peroxidase (POD) activities were determined. During storage, L* and WI of the fresh-cut fruits surface decreased whilst their BI and ΔE* increased. A. vera coating maintained the L* and WI and delayed the increase in BI and ΔE*, especially at 75 % A. vera dip. The fresh-cut fruits dipped in 75 % A. vera had the lowest browning score, the highest acceptance score and delayed the increase in TP content and PPO activity. However POD activity was induced by A. vera coating. Antioxidant activity had no effect on browning incidence of the fresh-cut fruits. Consequently, A. vera gel coating could maintain quality and retarded browning of fresh-cut wax apple fruits during storage.

Preparation and Characterization of All-Biomass Soy Protein Isolate-Based Films Enhanced by Epoxy Castor Oil Acid Sodium and Hydroxypropyl Cellulose

All-biomass soy protein-based films were prepared using soy protein isolate (SPI), glycerol, hydroxypropyl cellulose (HPC) and epoxy castor oil acid sodium (ECOS). The effect of the incorporated HPC and ECOS on the properties of the SPI film was investigated. The experimental results showed that the tensile strength of the resultant films increased from 2.84 MPa (control) to 4.04 MPa and the elongation at break increased by 22.7% when the SPI was modified with 2% HPC and 10% ECOS. The increased tensile strength resulted from the reaction between the ECOS and SPI, which was confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). It was found that ECOS and HPC effectively improved the performance of SPI-based films, which can provide a new method for preparing environmentally-friendly polymer films for a number of commercial applications.

Storage stability of functional chicken meat bullets coated with composite antimicrobial biodegradable films under different packaging conditions

Storage stability of processed chicken meat bullets (CMB) packaged under different packaging conditions in supplementation with composite antimicrobial biodegradable (CAB) films impregnated with 0.5% (v/v) cinnamaldehyde, a natural antimicrobial, was evaluated. Different treatments such as aerobic (aerobic packaged product, CAB-coated product and aerobic packaging), modified atmosphere packaging (MAP; MAP 50 : 50; CO2 and N2, F-MAP; CAB-coated product and MAP) and vacuum (VAC; vacuum packaged, F-VAC; CAB-coated product and vacuum) are assessed for various physico-chemical (pH, thiobarbituric acid reactive substances number, peroxide value and free fatty acids), microbiological (standard plate count, psychrophiles, coliforms, yeast and moulds, Staphylococci sp.) and sensory quality characteristics at 7-day intervals throughout the storage period of 35 days under refrigerated (4 ± 1°C) conditions. The CMB coated with CAB films under MAP (F-MAP) conditions had significantly (P < 0.05) better value for water activity, thiobarbituric acid reactive substances number, peroxide value and free fatty acids throughout the storage in comparison to the Control (MAP). Standard plate count was significantly (P < 0.05) lower for F-MAP than all other treatments. Staphylococci sp., coliforms, Salmonellae sp., yeast and mould, and psychrophiles were completely absent in CAB-coated products throughout the storage period. All the CAB products had better (P < 0.05) sensory attributes than their respective Controls during storage. Results concluded that the CMB coated in developed CAB films have a storage life of more than 35 days under MAP conditions under refrigerated (4 ± 1°C) conditions with the acceptable physico-chemical, microbiological and sensory quality attributes.

Edible films and coatings from whey proteins: a review on formulation, and on mechanical and bioactive properties

The latest decade has witnessed joint efforts by the packaging and the food industries to reduce the amount of residues and wastes associated with food consumption. The recent increase in environmental awareness has also contributed toward development of edible packaging materials. Viable edible films and coatings have been successfully produced from whey proteins; their ability to serve other functions, viz. carrier of antimicrobials, antioxidants, or other nutraceuticals, without significantly compromising the desirable primary barrier and mechanical properties as packaging films, will add value for eventual commercial applications. These points are tackled in this review, in a critical manner. The supply of whey protein-based films and coatings, formulated to specifically address end-user needs, is also considered.