Phloridzin and other phytochemicals in apple pomace: Stability evaluation upon dehydration and storage of dried product

Green technologies for extracting plant waste functional ingredients and new food formulation: A review

Nowadays, there is a growing interest in food waste recovery by both consumers and companies. Food waste of plant origin is a source of bioactive compounds, such as phenolic acids, anthocyanins, flavonoids, phytosterols, carotenoids, and tocopherols, with well-known antioxidant, anti-glycemic, and antimicrobial properties. The use of green and sustainable technologies to recover bioactive compounds from food waste is a possible solution to valorize waste following the principles of green chemistry. Furthermore, today's consumers are more attracted, informed, and aware of the benefits associated with the consumption of functional foods, and with this in mind, the use of extracts rich in beneficial compounds obtained by green technologies from food waste can be a valid alternative to prepare functional foods. In this review, the recovery of polyphenols and fibers with green technologies from food waste for the formulation of functional foods was presented.

Green Extraction of Bioactive Compounds from Apple Pomace from the Cider Industry

The cider-making industry in Asturias generates between 9000 and 12,000 tons of apple pomace per year. This by-product, the remains of the apple pressing, and made up of peel, flesh, seeds and stems, is a valuable material, containing substantial amounts of antioxidant compounds associated with healthy properties. Polyphenols such as dihydrochalcones and quercetin glycosides, and triterpenic acids, among which ursolic acid is a major compound, are the main antioxidant families described in apple pomace. The simultaneous recovery of those families has been accomplished by low frequency ultrasound-assisted extraction. Working extraction conditions were optimised by response surface methodology (RSM): time, 5.1 min; extractant composition, 68% ethanol in water; solid/liquid ratio, 1/75 and ultrasonic wave amplitude, 90%. This procedure was further applied to analyse those components in the whole apple pomace (WAP), apple peel (AP) and apple flesh (AF). On average, dry WAP contained almost 1300 µg/g of flavonols, 1200 µg/g of dihydrochalcones and 4200 µg/g of ursolic acid. These figures increased in the apple peel to, respectively 2500, 1400 and 8500 µg/g dry matter. Two linear multivariate regression models allowed the antioxidant activity of apple by-products to be predicted on the basis of their bioactive composition. The results derived from this study confirm the potential of industrial cider apple pomace as a source of high-value bioactive compounds, and the feasibility of the ultrasound-assisted extraction technique to recover those components in a simple and efficient way.

New Strategy for Browning Prevention in Apple Pomace Processing and Toxicity Tested in a Rodent Model

Apple pomace (AP) is a byproduct of apple juice industries, which constitutes around 30% of the original fruit and rich in essential compounds like carbohydrates, phenolics, minerals, and dietary fibers. This study is focused on optimizing the combinational utilization of antibrowning agents like l-cysteine and l-ascorbic acid for the sustainable debrowning of AP with response surface methodology and assessment of its acute toxicity in female rats. In addition, the phytochemical content and antioxidant activity of treated AP were investigated and compared with the untreated control AP. The study revealed that the treated AP has higher dietary fiber (p < 0.01), protein (p < 0.0001), and phenolic content (p < 0.001) in comparison to the control AP. Moreover, the treated AP also observed with higher antioxidant activity 37% inhibition and water retention capacity (8.5 g H2O/g solid) along with the debrowning effect. Furthermore, a 4-week in vivo study is conducted to assess the toxicity of treated AP. Results indicated no discernible variations in biochemistry, morphometric, or histology between the supplementation (0.5, 1.5, and 3% AP) and control groups. Thus, adding AP rich in dietary fiber to a range of meals is deemed a safe and valuable food supplement.

Hydration and Fortification of Common Bean (Phaseolus vulgaris L.) with Grape Skin Phenolics-Effects of Ultrasound Application and Heating

Ultrasound (US)-assisted soaking combined with fortification with red grape skin (GS) phenolics was applied on two Phaseolus varieties, namely White Kidney Bean (WKB) and Cranberry Bean (CB), before heat treatment. The aims were to investigate: (a) the effect of US application on the kinetic of hydration; (b) the extent of absorption of different phenolic classes of GS into the beans and the resulting effect on antioxidant activity; (c) the effects of heat treatment on the phenolic fraction and antioxidant activity of GS extract- and water-soaked beans. US fastened the soaking step of both WKB and CB beans, which showed the sigmoidal and the downward concave shape hydration curves, respectively. Anthocyanins, flavonols, flavanol and phenolic acids levels increased with GS soaking, but US application was effective only for increasing the level of flavonols, while it favored the loss of endogenous phenolic acids and it did not affect the uptake of anthocyanins and flavanols. Heat treatment decreased the levels of most of phenolic compounds, but increased the levels of monomeric flavanols. Overall, the antioxidant activity was 40% higher in WKB and 53% higher in CB upon GS-fortification than in the control beans, despite the effects of heating. This fortification strategy could be applied for value addition of varieties low in phenolics or as a pre-treatment before intensive processing.

Macroporous resin purification of phenolics from Irish apple pomace: Chemical characterization, and cellular antioxidant and anti-inflammatory activities

Apple pomace (AP) is a highly prevalent waste product worldwide in the fruit processing sector. This study compared the chemical profile, antioxidant, and anti-inflammatory activities of crude (CE) and an extract purified using XAD-7 resin (PE). The purification process increased the total phenolic content, flavonoids, and tannins by 3.35, 40.31, and 8.87-fold, respectively. The main phenolic compounds identified in PE were phlorizin (20.54 mg/g), chlorogenic acid (10.01 mg/g), and hyperoside (2.77 mg/g). No difference was found between CE and PE in protecting human plasma against oxidation. In human erythrocytes, both CE and PE decreased the reactive oxygen species (ROS) generation and decreased lipoperoxidation. However, PE had stronger anti-inflammatory effects than CE by promoting HO-1 gene expression, suppressing NO production, and inhibiting IL-1β, IL-6, and IL-10 mRNA expression in lipopolysaccharide-challenged RAW.264.7 macrophages. Therefore, purifying apple pomace crude extract is a promising approach to boosting valuable antioxidants and anti-inflammatory phenolics.

Determination of Polyphenolic Profile of Apple Pomace (Malus domestica Golden Delicious Variety) by HPLC-MS

Apple (Malus domestica Borkh) is an appreciated source of polyphenols. Phenolic compounds are known as natural antioxidants and have a wide range of applications in different industries. Apple pomace has the potential of being an alternative source of polyphenols. To determine the polyphenolic profile of apple pomace, samples from the skin at two different stages of ripening were extracted with 80-20% EtOH-water/acetic acid 5% (S1) and 20-80% EtOH-water/acetic acid 5% (S2) in order to determine the solvent system. Ripe skins extracted with S1 showed a higher total polyphenol content or TPC (1.21 g of polyphenols per 100 g of fresh weight (FW)) than unripe apple skin, being the most effective system tested and a mean degree of polymerization of 2.47. Commercial apple pomace was extracted with S1, resulting in a TPC of 0.5615 ± 0.007 g of polyphenols per 100 g of FW. Meanwhile, the RP-HPLC-MS analysis led to the tentative identification of several polyphenolic compounds.

Assessment of the stability of compounds belonging to neglected phenolic classes and flavonoid sub-classes using reaction kinetic modeling

Phenolic compounds are known to degrade and/or undergo changes during food production and storage. Reaction kinetic modeling is generally used to define kinetic parameters of a food system and predict changes during thermal processing and storage. Data for phenolic acids and flavonoids, such as anthocyanins and flavan-3-ols, have been reviewed in detail, but the flavonoid sub-classes, dihydrochalcones and flavanones, have been mostly neglected. Other neglected phenolic classes are xanthones and benzophenones. The stability of these types of compounds is important as they are present in fruits and exposed to heat when processed into juice and jam. Other sources of the compounds are herbal teas, which are also subjected to thermal processing, either during the primary processing of the plant material, or the production of extracts for use as food ingredients. The theoretical background is given to understand the review of literature on these classes/sub-classes. Results of research on kinetic modeling are discussed in detail, while research on compound stability without the application of reaction kinetic modeling is briefly mentioned to provide context. The studies discussed included those focusing on heating during the processing and storage of model solutions, liquid foods, plant material, dried extracts, and extracts formulated with other food ingredients.

Sustainable Isolation of Bioactive Compounds and Proteins from Plant-Based Food (and Byproducts)

Plant-based food produces significantly less greenhouse gases, and due to its wealth of bioactive components and/or plant-based protein, it becomes an alternative in a sustainable food system. However, the processing and production of products from plant sources creates byproducts, which can be waste or a source of useful substances that can be reused. The waste produced during the production and processing of food is essentially nutrient- and energy-rich, and it is recognized as an excellent source of secondary raw materials that could be repurposed in the process of manufacturing and preparing food, or as feed for livestock. This review offers an overview of the sources and techniques of the sustainable isolation of bioactive substances and proteins from various sources that might represent waste in the preparation or production of food of plant origin. The aim is to uncover novel approaches to use waste and byproducts from the process of making food to provide this waste food an additional benefit, not forgetting the expectations of the end user, the consumer. For the successful isolation of bioactive ingredients and proteins from food of plant origin, it is crucial to develop more eco-friendly and efficient extraction techniques with a low CO2 footprint while considering the economic aspects.

Chemical Composition, Antioxidant Activity and Cytocompatibility of Polyphenolic Compounds Extracted from Food Industry Apple Waste: Potential in Biomedical Application

Apple pomace (AP) from the food industry is a mixture of different fractions containing bioactive polyphenolic compounds. This study provides a systematic approach toward the recovery and evaluation of the physiochemical and biological properties of polyphenolic compounds from AP. We studied subcritical water extraction (SCW) and solvent extraction with ethanol from four different AP fractions of pulp, peel, seed, core, and stem (A), peel (B), seed and core (C), and pulp and peel (D). The subcritical water method at the optimum condition resulted in total polyphenolic compounds (TPC) of 39.08 ± 1.10 mg GAE per g of AP on a dry basis compared to the ethanol extraction with TPC content of 10.78 ± 0.94 mg GAE/g db. Phloridzin, chlorogenic acid, and quercetin were the main identified polyphenolics in the AP fractions using HPLC. DPPH radical scavenging activity of fraction B and subcritical water (SW) extracts showed comparable activity to ascorbic acid while all ethanolic extracts were cytocompatible toward human fibroblast (3T3-L1) and salivary gland acinar cells (NS-SV-AC). Our results indicated that AP is a rich source of polyphenolics with the potential for biomedical applications.

Natural Polyphenol Recovery from Apple-, Cereal-, and Tomato-Processing By-Products and Related Health-Promoting Properties

Polyphenols of plant origin are a broad family of secondary metabolites that range from basic phenolic acids to more complex compounds such as stilbenes, flavonoids, and tannins, all of which have several phenol units in their structure. Considerable health benefits, such as having prebiotic potential and cardio-protective and weight control effects, have been linked to diets based on polyphenol-enriched foods and plant-based products, indicating the potential role of these substances in the prevention or treatment of numerous pathologies. The most representative phenolic compounds in apple pomace are phloridzin, chlorogenic acid, and epicatechin, with major health implications in diabetes, cancer, and cardiovascular and neurocognitive diseases. The cereal byproducts are rich in flavonoids (cyanidin 3-glucoside) and phenolic acids (ferulic acid), all with significant results in reducing the incidence of noncommunicable diseases. Quercetin, naringenin, and rutin are the predominant phenolic molecules in tomato by-products, having important antioxidant and antimicrobial activities. The present understanding of the functionality of polyphenols in health outcomes, specifically, noncommunicable illnesses, is summarized in this review, focusing on the applicability of this evidence in three extensive agrifood industries (apple, cereal, and tomato processing). Moreover, the reintegration of by-products into the food chain via functional food products and personalized nutrition (e.g., 3D food printing) is detailed, supporting a novel direction to be explored within the circular economy concept.

Cider apple pomace as a source of nutrients: Evaluation of the polyphenolic profile, antioxidant and fiber properties after drying process at different temperatures

•

Influence of cider apple pomace drying temperature was studied.

•

Temperature affected drying kinetics and antioxidant and dietary fibre properties.

•

Antioxidant properties were best preserved when drying in the range of 80–100 °C.

•

The best properties of alcohol insoluble residue were found when drying at 40–60 °C.

Apple pomace, the by-product of the cider industry, contains a high content of antioxidant compounds and dietary fiber. Drying would allow its preservation for a later use. The aim of this study was to evaluate the effect of the drying temperature on the drying kinetics, antioxidant properties and the fiber characteristics. For this, drying experiments were performed at different temperatures (40–120 °C). The increase in temperature enhanced the drying rate, as was shown by the effective diffusivity and mass transfer coefficient identified by modelling. The influence of temperature was quantified through the activation energy (38.21 kJ/mol). Regarding the retention of antioxidant properties, the best results were found at 80–100 °C while 40–60 °C was the best temperature range for the fiber characteristics. Therefore, 80 °C could be an adequate temperature for drying of cider apple pomace, as it represents a good balance between kinetics, and antioxidant and fiber properties.

New Insights into the Efficacy of Aspalathin and Other Related Phytochemicals in Type 2 Diabetes-A Review

In the pursuit of bioactive phytochemicals as a therapeutic strategy to manage metabolic risk factors for type 2 diabetes (T2D), aspalathin, C-glucosyl dihydrochalcone from rooibos (Aspalathus linearis), has received much attention, along with its C-glucosyl flavone derivatives and phlorizin, the apple O-glucosyl dihydrochalcone well-known for its antidiabetic properties. We provided context for dietary exposure by highlighting dietary sources, compound stability during processing, bioavailability and microbial biotransformation. The review covered the role of these compounds in attenuating insulin resistance and enhancing glucose metabolism, alleviating gut dysbiosis and associated oxidative stress and inflammation, and hyperuricemia associated with T2D, focusing largely on the literature of the past 5 years. A key focus of this review was on emerging targets in the management of T2D, as highlighted in the recent literature, including enhancing of the insulin receptor and insulin receptor substrate 1 signaling via protein tyrosine phosphatase inhibition, increasing glycolysis with suppression of gluconeogenesis by sirtuin modulation, and reducing renal glucose reabsorption via sodium-glucose co-transporter 2. We conclude that biotransformation in the gut is most likely responsible for enhancing therapeutic effects observed for the C-glycosyl parent compounds, including aspalathin, and that these compounds and their derivatives have the potential to regulate multiple factors associated with the development and progression of T2D.

Microwave hydrodiffusion and gravity as a sustainable alternative approach for an efficient apple pomace drying

Apple pomace valuation has been impaired by its high perishability and absence of fast drying approaches demanded by industry. This work aimed to assess the feasibility of Microwave Hydrodiffusion and Gravity (MHG) process applied for apple pomace drying using discrete delivery powers (300-900 W) and comparison with hot-air drying (40-100 °C). To dry 0.4 kg of apple pomace (81% moisture), hot-air drying required 3.6-9.9 h with estimated water evaporation flux of 1.0-3.5 mL/min. For MHG, which processed 1.2 kg, these corresponded to 1.0-2.6 h and 5.1-13.9 mL/min. Furthermore, MHG allowed water recovery containing part of apple pomace phenolic compounds and carbohydrates. The dried pomace was stable for 2 years, after which phenolic compounds and polysaccharides were still recoverable by hot water extractions. These results pave the way for MHG to be used for apple pomace and other by-products preservation, boosting their conversion into valuable co-product for valuation of its components.

Concentrate Apple Juice Industry: Aroma and Pomace Valuation as Food Ingredients

Apple concentrate juice industry generates a flavored coproduct (apple aroma) recovered in the evaporation process, which is poorly valuated due to the lack of chemical characterization and standardization. In this study, industry apple aroma was characterized, allowing for the identification of 37 compounds, the majority esters (20), alcohols (7), and aldehydes (4). The storage temperature did not affect its volatile composition. Five key compounds were selected and monitored for 10 months of storage, and also compared with other three productions of another season allowing for observation of the same Aroma Index. Apple pomace was also used to produce a hydrodistillate. Contrary to the apple aroma, apple pomace hydrodistillate was unpleasant, reflected in a different volatile composition. Although no additional aroma fraction could be obtained from this wet byproduct, when dried, apple pomace presented 15 volatile compounds with toasted, caramel, sweet, and green notes. The infusions prepared with the dried apple pomace exhibited 25 volatile compounds with a very pleasant (fruity, apple-like, citrus, and spicy notes) and intense aroma. The addition of sugar changed the volatile profile, providing a less intense flavor, with almond, caramel, and sweet notes. These results show that apple aroma and pomace are high-quality flavoring agents with high potential of valuation as food ingredients.

Mitigation effects of phlorizin immersion on acrylamide formation in fried potato strips

BACKGROUND

Several researches reported that natural polyphenols affected acrylamide formation of fried products. However, the effects of different variety of polyphenols on acrylamide formation were distinct. In this study, we isolated and purified phlorizin from apples and identified the influence of phlorizin immersion on acrylamide formation and sensory properties of fried potato strips with regard to the immersion concentration, time and temperature.

RESULTS

The acrylamide formation of fried samples decreased as the phlorizin concentration increased from 0 to 0.3 g kg^-1 , and 0.14 g kg^-1 could be selected as the suitable immersion concentration to dramatically inhibit acrylamide formation with considering the cost of industrial production. Additionally, the acrylamide formation significantly reduced from 8.71 × 10^-3 to 2.13 × 10^-3 g kg^-1 lyophilized weight (LW) with immersion time from 0 to 120 min, and 60 min could be selected to significantly reduce acrylamide formation in consideration of efficiency of the large-scale industrial processing. However, the effect of phlorizin immersion temperature on acrylamide formation of fried samples was not significant. Compared to the fried samples without immersion, the phlorizin immersion improved the color properties and the change of texture parameters was slight.

CONCLUSION

The fresh potato strips immersed in the phlorizin solution of 0.14 g kg^-1 at 40 °C for 60 min before frying could significantly decrease acrylamide formation of fried samples and retain the majority of fresh sensorial properties. The significant correlations obtained between sensory properties and acrylamide content indicated the sensory properties could be used as the indicator of acrylamide levels during industrial processing. © 2020 Society of Chemical Industry.

Apple pomace as food fortification ingredient: A systematic review and meta-analysis

The present review aimed to investigate and analyze the use of byproduct apple pomace as a fortification ingredient in different types of foods. The data obtained from English published articles found on Web of Science, Scopus, and Google Scholar in the period from 2007 to 2019 were used for making the table overview and meta-analysis of results described in those studies. The systematic review confirmed the importance of apple pomace use in the food industry due to the beneficial nutritional profile and ecological issue (waste management). The main attributes of apple pomace are high content of antioxidant compounds and dietary fibers. Dietary fibers from apple pomace significantly increased total fiber content in enriched products-meaning that the transfer of the fortification can be declared health beneficial. The conducted meta-analysis showed unambiguously the different influence of apple pomace addition according to fortified food commodity. The fortification drawbacks were noticeable in plant food products because darker and brownish color was not evaluated positively by panelists. Oppositely, color, as one of the main sensory characteristics, was beneficially affected in animal origin food. The sensory properties, including color, play an important role in product acceptance by consumers. Besides color, animal origin products fortified by apple pomace showed the most acceptable textural properties and oxidative stability.

Role of nutraceutical starch and proanthocyanidins of pigmented rice in regulating hyperglycemia: Enzyme inhibition, enhanced glucose uptake and hepatic glucose homeostasis using in vitro model

Dysregulation of glucose homeostasis result in hyperglycemia and pigmented rice, unique combination of high quality starch and phenolics has the potential in regulating it. In this study, pigmented rice was characterized in terms of nutraceutical starch (NS) and phenolic content. Further the effect of rice phenolics on carbolytic enzyme inhibition, glucose uptake, hepatic glucose homeostasis and anti-glycation ability was analyzed in vitro. The most relevant effect on enzyme inhibition (α-amylase: IC₅₀-42.34 µg/mL; α-glucosidase: IC₅₀:63.89 µg/mL), basal uptake of glucose (>39.5%) and anti-glycation ability (92%) was found in red rice (RR), than black rice (BR). The role of RR phenolics in regulating glucose homeostasis was deciphered using hepatic cell line system, which found up-regulation of glucose transporter 2 (GLUT2) and glycogen synthase 2 (GYS2); while expression of gluconeogenic genes were found down regulated. To our knowledge this study is the first report validating the role of starch-phenolic quality towards anti-hyperglycemic effect of RR.

Biocatalytic Production of a Potent Inhibitor of Adipocyte Differentiation from Phloretin Using Engineered CYP102A1

In this study, we investigated an efficient enzymatic strategy for producing potentially valuable phloretin metabolites from phlorizin, a glucoside of phloretin that is rich in apple pomace. Almond β-glucosidase efficiently removed phlorizin's glucose moiety to produce phloretin. CYP102A1 engineered by site-directed mutagenesis, domain swapping, and random mutagenesis catalyzed the highly regioselective C-hydroxylation of phloretin into 3-OH phloretin with high conversion yields. Under the optimal hydroxylation conditions of 15 g cells L^-1 and a 20 mM substrate for whole-cell biocatalysis, phloretin was regioselectively hydroxylated into 3.1 mM 3-OH phloretin each hour. Furthermore, differentiation of 3T3-L1 preadipocytes into adipocytes and lipid accumulation were dramatically inhibited by 3-OH phloretin but promoted by phloretin. Consistent with these inhibitory effects, the expression of adipogenic regulator genes was downregulated by 3-OH phloretin. We propose a platform for the sustainable production and value creation of phloretin metabolites from apple pomace capable of inhibiting adipogenesis.

Evaluation of Apple Pomace Flour Obtained Industrially by Dehydration as a Source of Biomolecules with Antioxidant, Antidiabetic and Antiobesity Effects

Apple pomace flour (APF) obtained at industrial scale level by the application of innovative technological process (dehydration (5 h, T ≤ 55 °C), grinding (300 µm)) was evaluated as a source of bioactive compounds with antioxidative, antiobesity and antidiabetic effects. Proximate composition, individual (HPLC–DAD–MS/MS) and total phenols (TPC) as well as flavonoids content (TFC), antioxidant (AO) activity (DPPH, ABTS, HPMC), water and oil holding capacity (WHC and OHC) of APFs obtained from apple pomace from mixed and individual apple cultivars grown conventionally and organically were compared. The effect of APF supplementation on the glycaemic status and glucose tolerance (oral glucose tolerance test (OGTT)) of C57BL/6J mice exposed to high-fat and sucrose diet was examined. High K content (4.2–6.4 g/kg), dietary fibres (35–45 g/100 g), TPC (4.6–8.1 mg GAE/g), TFC (18.6–34.6 mg QE/g), high water and oil holding capacity (4.7–6.4 and 1.3–1.6 g/g) were observed in the APFs. Content of major phenols (phlorizin, chlorogenic acid, quercetin), TPC and TFC correlated highly with prominent AO activity. APF supplementation lowered the increase of body weight gain and blood glucose, and improved glucose tolerance significantly. Health-promoting biomolecules, AO activity, functional properties and prevention of diet-driven glucose metabolism disorders pave the way to APF exploitation in human nutrition.

Bioactives From Agri-Food Wastes: Present Insights and Future Challenges

Sustainable utilization of agri-food wastes and by-products for producing value-added products (for cosmetic, pharmaceutical or food industrial applications) provides an opportunity for earning additional income for the dependent industrial sector. Besides, effective valorisation of wastes/by-products can efficiently help in reducing environmental stress by decreasing unwarranted pollution. The major focus of this review is to provide comprehensive information on valorisation of agri-food wastes and by-products with focus laid on bioactive compounds and bioactivity. The review covers the bioactives identified from wastes and by-products of plants (fruits, exotic fruits, vegetables and seeds), animals (dairy and meat) and marine (fish, shellfish seaweeds) resources. Further, insights on the present status and future challenges of sustainably utilizing agri-food wastes/by-products for value addition will be highlighted.

Effect of temperature, oxygen and light on the degradation of β-carotene, lutein and α-tocopherol in spray-dried spinach juice powder during storage

The aim of this study was to evaluate the interaction between packaging parameters (transmission of light and oxygen) and storage temperatures (4, 20, 40 °C) on nutrient retention of Spinach (Spinacia oleracea) juice, spray-dried in the absence of an added encapsulant. β-Carotene was more susceptible to degradation compared with lutein and α-tocopherol. Under our experimental conditions, it was observed that excluding low fluorescent light intensity and air by vacuum packaging at 20 °C did not seem to improve nutrient retention loss over time (p > 0.05). The rate of β-carotene, lutein and α-tocopherol loss displayed first order reaction kinetic with low activation energy of 0.665, 2.650 and 13.893 kJ/mol for vacuum, and 1.089, 4.923 and 14.142 kJ/mol for non-vacuum, respectively. The reaction kinetics and half-life for β-carotene, lutein and α-tocopherol at 4 °C and non-vacuumed were 2.2 × 10^-2, 1.2 × 10^-2, and 0.8 × 10^-2 day^-1, and 32.08, 58.25 and 85.37 day, respectively.

A comprehensive analysis of the composition, health benefits, and safety of apple pomace

Apple processing results in peel, stem, seeds, and pulp being left as a waste product known as apple pomace. This review comprehensively assessed apple pomace composition for nutritional value and bioactive substances and evaluated potential health benefits and safety. Apple pomace is a rich source of health-benefitting nutrients, including minerals, dietary fiber, antioxidants, and ursolic acid, which suggests it has potential use as a dietary supplement, functional food, and/or food additive. Preclinical studies have found apple pomace and its isolated extracts improved lipid metabolism, antioxidant status, and gastrointestinal function and had a positive effect on metabolic disorders (eg, hyperglycemia, insulin resistance, etc.). Safety studies have shown apple pomace to be a safe livestock feed additive and to have pesticide concentrations within safety thresholds established for human consumption. Commercial development of apple pomace for human consumption requires more research focusing on standardized methods of nutrient reporting, mechanistic studies, and human clinical trials.

Valorization of Apple Pomace by Extraction of Valuable Compounds

Apple pomace is a promising source of carbohydrates, proteins, amino acids, fatty acids, phenolic compounds, vitamins, and other compounds with a vast range of food applications. This review focuses on the valorization of apple pomace towards the recovery of the main compounds, namely pectin and polyphenols. Applications, advantages, and drawbacks of conventional extraction (acidic medium under high temperatures) compared with novel extraction technologies are presented. The comparison is based on an extensive literature review of research on extraction of valuable compounds from plant matrixes, particularly apple pomace. Novel extraction techniques involving enzymes, electric field, ultrasound, microwave heating, pressurized liquid, and super/subcritical fluid are also discussed. These techniques offer several advantages, including shorter extraction time, increased yield, reduction-or suppression-of solvents, and minimization of the environmental impact. This paper may help researchers and food industry professionals on the scaling-up and optimization of eco-friendly extractions of pectin and phenolic compounds.

Apple phenolics as inhibitors of the carbonylation pathway during in vitro metal-catalyzed oxidation of myofibrillar proteins

The effect of apple phenolics on the oxidative damage caused to myofibrillar proteins by an in vitro metal-catalyzed oxidation system was investigated. Three pure phenolic compounds (chlorogenic acid, (-)-epicatechin and phloridzin) and an apple peel extract were added to myofibrillar proteins in three concentrations (50, 100 and 200μM), and a blank treatment was included as a control. All suspensions were subjected to Fe(3+)/H2O2 oxidation at 37°C during 10days, and protein oxidation was evaluated as carbonylation (α-amino adipic and γ-glutamic semialdehydes) and Schiff base cross-links. Significant inhibition by apple phenolics was found as compared to the control treatment, with (-)-epicatechin being the most efficient antioxidant and phloridzin showing the weakest antioxidant effect. The higher concentrations of apple extract showed effective antioxidant activity against protein oxidation in myofibrillar proteins, emphasizing the potential of apple by-products as natural inhibitors of protein oxidation in meat products.

Apple phenolics as nutraceuticals: assessment, analysis and application

Humankind is presently engulfed by convenience quench, modern life style and urbanized diet system leading to progression in array of health disorders. The past decade confronted cardiometabolic disorder (21.8 %), lower respiratory and chronic obstructive lung disease (12.5 %) as the major causes of death world over. In anticipation, scientific communities' have demonstrated the role of healthy diets, especially those rich in fruits and vegetables, for management of such health related issues. These horticultural  crops are considered as a good source of polyphenols such as dihydrochalcones, flavanols, flavonols, anthocyanins and phenolic acids. The present article reviews the efforts made to assess the potential of apple phenolic compounds present in fresh fruits, leaves, bark and pomace as dietary polyphenols. Considering the positive impact of such phytochemicals on human health, various nutraceuticals, dietary supplements and phenolic-rich food products are presently available on market shelves. On analytical front, improved instrumentation based on liquid chromatography (HPLC, UPLC, LC/MS/MS) have made the assessment of phenolics more rapid and reliable. Thus, owing to the emergent interest in natural compounds, it is pertinent to discuss the latest significant research findings on therapeutic aspects along with probable metabolic mechanisms of dietary polyphenols found in apples and their implications on human health.

Acute anti-hyperglycaemic effects of an unripe apple preparation containing phlorizin in healthy volunteers: a preliminary study

BACKGROUND

The health-promoting properties of apples are directly related to the biologically active compounds that they contain, such as polyphenols. The objective of this study was to prepare a low-sugar, fibre- and phlorizin-enriched powder from unripe apples and to gain insight regarding its anti-hyperglycaemic activity in healthy volunteers.

RESULTS

The unripe apples (Malus domestica Borkh.) were collected 30 days after the full bloom day; blanched and pressed to obtain apple pomace which was then processed with a food cutter, oven-dried and milled to prepare apple powder. The concentrations of total sugars, water-soluble pectin and phlorizin in the apple preparation were 153.44 ± 2.46, 27.73 ± 0.51 and 12.61 ± 0.15 g kg(-1), respectively. Acute ingestion of the apple preparation improved glucose metabolism in the oral glucose tolerance test (OGTT) in six healthy volunteers by reducing the postprandial glucose response at 15 to 30 min by approximately two-fold (P < 0.05) and by increasing urinary glucose excretion during the 2- to 4-h interval of the OGTT by five-fold (P < 0.05).

CONCLUSION

The results obtained indicate that the dried and powdered pomace of unripe apples can be used as a health-promoting natural product for the reduction of postprandial glycaemia and to improve the health of patients with diabetes.

Impingement drying for preparing dried apple pomace flour and its fortification in bakery and meat products

This study aimed to evaluate impingement drying (ID) as a rapid drying method to dry wet apple pomace (WAP) and to investigate the fortification of dried apple pomace flour (APF) or WAP in bakery and meat products. ID at ~110 °C reduced the moisture content of apple pomace from 80 % (wet basis) to 4.5 % within 3 h, compared with 24 h to 2.2 % using 40 °C forced-air drying and ~60 h to 2.3 % using freeze drying. Furthermore, ID enhanced the extractable phenolic compounds, allowing for a 58 % increase in total phenolic content (TPC) compared with wet pomace, a 110 % and 83 % higher than TPC in forced-air dried and freeze dried samples, respectively. The 15-20 % APF-fortified cookies were found to be ~44-59 % softer, ~30 % more chewy, and ~14 % moister than those of the control. WAP-fortified meat products had significantly higher dietary fiber content (0.7-1.8 % vs. 0.1-0.2 % in control) and radical scavenging activity than that of the control. These results suggest that impingement drying is a fast and effective method for preparing dried APF with highly retained bioactive compounds, and apple pomace fortified products maintained or even had improved quality.