Differences in the composition of phenolic compounds, carotenoids, and volatiles between juice and pomace of four citrus fruits from Southern Italy

Selected fruit pomaces: Nutritional profile, health benefits, and applications in functional foods and feeds

The utmost objective of every nation is to achieve zero hunger and ensure the health and well-being of its population. However, in impoverished nations, particularly in rural areas, such issues persist on a daily basis. Currently, there is a growing demand for fruit consumption due to their potential health benefits. Surprisingly, their most prevalent by-product is pomace, which is produced in millions of tonnes and is usually discarded as waste after processing or consumption. Even food produced with these kinds of raw resources can contribute to the objective of eradicating world hunger. Owing to these advantages, scientists have begun evaluating the nutritional content of various fruit pomace varieties as well as the chemical composition in different bioactive constituents, which have significant health benefits and can be used to formulate a variety of food products with notable nutraceutical and functional potential. So, the purpose of this review is to understand the existing familiarity of nutritional and phytochemical composition of selected fruit pomaces, those derived from pineapple, orange, grape, apple, and tomato. Furthermore, this article covers pre-clinical and clinical investigations conducted on the selected fruit pomace extracts and/or powder forms and its incorporation into food products and animal feed. Adding fruit pomaces reduces the glycemic index, increases the fibre content and total polyphenolic contents, and reduces the cooking loss, etc. In animal feeds, incorporating fruit pomaces improves the antioxidant enzyme activities, humoral immune system, and growth performance and reduces methane emission.

Comprehensive Update on Carotenoid Colorants from Plants and Microalgae: Challenges and Advances from Research Laboratories to Industry

The substitution of synthetic food dyes with natural colorants continues to be assiduously pursued. The current list of natural carotenoid colorants consists of plant-derived annatto (bixin and norbixin), paprika (capsanthin and capsorubin), saffron (crocin), tomato and gac fruit lycopene, marigold lutein, and red palm oil (α- and β-carotene), along with microalgal Dunaliella β-carotene and Haematococcus astaxanthin and fungal Blakeslea trispora β-carotene and lycopene. Potential microalgal sources are being sought, especially in relation to lutein, for which commercial plant sources are lacking. Research efforts, manifested in numerous reviews and research papers published in the last decade, have been directed to green extraction, microencapsulation/nanoencapsulation, and valorization of processing by-products. Extraction is shifting from conventional extraction with organic solvents to supercritical CO2 extraction and different types of assisted extraction. Initially intended for the stabilization of the highly degradable carotenoids, additional benefits of encapsulation have been demonstrated, especially the improvement of carotenoid solubility and bioavailability. Instead of searching for new higher plant sources, enormous effort has been directed to the utilization of by-products of the fruit and vegetable processing industry, with the application of biorefinery and circular economy concepts. Amidst enormous research activities, however, the gap between research and industrial implementation remains wide.

Changes in, and correlation analysis of, volatile compounds, key enzymes, and fatty acids in lemon juice vesicles during freeze drying and hot-air drying

BACKGROUND

Lemon juice vesicles are distinguished by their unique and abundant volatile flavor compounds, which can undergo complex changes during drying. In this study, integrated freeze drying (IFD), conventional freeze drying (CFD), and hot-air drying (AD) were used to dry lemon juice vesicles to investigate the changes in, and correlations among volatile compounds, fatty acids, and key enzyme activity during the drying process.

RESULTS

Twenty-two volatile compounds were detected during the drying processes. Compared with fresh samples, seven compounds were lost in the dried samples after IFD, seven after CFS, and six after AD, and the loss rates of the total content of volatile compounds in the dried samples were 82.73% in CFD, more than 71.22% in IFD, and more than 28.78% in AD. In total, 1.015 mg/g of seven fatty acids were detected in the fresh samples; the content loss rates of total fatty acids after drying were 67.68% in AD, more than 53.00% in CFD, and more than 36.95% in IFD, respectively. During the three drying processes, IFD retained relatively higher enzyme activity in the samples.

CONCLUSION

Many positive and negative correlations (P < 0.05) were observed among the key enzyme effects, fatty acids, and volatile compounds, showing close associations. The current work provides information that is important for the selection of suitable drying techniques for lemon juice vesicles and suggests how to control their flavor during the drying process. © 2023 Society of Chemical Industry.

Bergamot juice powder with high bioactive properties: Spray-drying for the preservation of antioxidant activity and ultrasound-assisted extraction for enhanced phenolic compound extraction

The spray-drying process yielded functional bergamot juice powder with high antioxidant activity, phenolic content, and vitamin C content. Optimal drying conditions were determined as 10% maltodextrin concentration, 146.02°C inlet temperature, and 39.99% pump rate, preserving powder's bioactive properties. Under these drying conditions, bergamot juice powder exhibited an antioxidant activity of 62.2% DPPH scavenging activity, a total phenolic content of 3862.1 ppm, and a vitamin C content of 1385.9 ppm. The bergamot juice powder, with a water activity of 0.2, bulk density of 0.4 g/mL, tapped density of 0.5 g/mL, porosity of 89.6%, hygroscopicity of 8.6%, and cohesiveness of 37.2%, is highly suitable for further processing. High-pressure liquid chromatography analysis revealed the presence of major phenolic compounds in both fresh bergamot juice and spray-dried powder, although their concentrations were lower in the powder form. The major phenolics identified in the fruit juice were naringin (197.5 ppm), eriocitrin (105.9 ppm), neoeriocitrin (53.4 ppm), neohesperidin (68.8 ppm), and naringenin (119.8 ppm). However, in the powder form, the bitterness-associated compounds, naringin and neohesperidin, exhibited a significant reduction of 85.0% and 90.3%, respectively. Compared to dimethyl sulfoxide (48.4%), ethanol (37.9%), and distilled water (17.3%), ultrasound-assisted extraction with acetone solvent demonstrated the highest efficiency (61.7%) in obtaining phenolic compounds from bergamot juice powder. In conclusion, spray-drying is an effective method for obtaining functional bergamot juice powder, and ultrasound-assisted extraction can further enhance phenolic compound extraction efficiency. These findings have potential applications in the food, cosmetics, and pharmaceutical industries, with opportunities for further research in functional foods or nutraceuticals. PRACTICAL APPLICATION: Spray-drying yields functional bergamot juice powder with high bioactive properties. Optimal drying conditions can be applied in industrial settings. Ultrasound-assisted extraction enhances phenolic compound extraction efficiency. Potential applications in food, cosmetics, and pharmaceutical industries.

Research advances in citrus polyphenols: green extraction technologies, gut homeostasis regulation, and nano-targeted delivery system application

Citrus polyphenols can modulate gut microbiota and such bi-directional interaction that can yield metabolites such as short-chain fatty acids (SCFAs) to aid in gut homeostasis. Such interaction provides citrus polyphenols with powerful prebiotic potential, contributing to guts' health status and metabolic regulation. Citrus polyphenols encompass unique polymethoxy flavonoids imparting non-polar nature that improve their bioactivities and ability to penetrate the blood-brain barrier. Green extraction technology targeting recovery of these polyphenols has received increasing attention due to its advantages of high extraction yield, short extraction time, low solvent consumption, and environmental friendliness. However, the low bioavailability of citrus polyphenols limits their applications in extraction from citrus by-products. Meanwhile, nano-encapsulation technology may serve as a promising approach to improve citrus polyphenols' bioavailability. As citrus polyphenols encompass multiple hydroxyl groups, they are potential to interact with bio-macromolecules such as proteins and polysaccharides in nano-encapsulated systems that can improve their bioavailability. This multifaceted review provides a research basis for the green and efficient extraction techniques of citrus polyphenols, as well as integrated mechanisms for its anti-inflammation, alleviating metabolic syndrome, and regulating gut homeostasis, which is more capitalized upon using nano-delivery systems as discussed in that review to maximize their health and food applications.

Quantitative metabolomic analysis reveals the fractionation of active compounds during lemon fruit juicing

In this study, metabolomic analysis was employed to investigate the separation (fractionation) of active compounds into lemon juice (LJ) and lemon pomace (LP) during lemon juicing. A total of 968 metabolites were identified, and 438 differentially abundant metabolites (DAMs) were screened out between LJ and LP, suggesting significant metabolite fractionation during juicing. The "flavonoids", "phenolic acids", and "saccharides and alcohols" were mainly retained in the LP, while the fractionation of major "organic acids" was differentiated. Seven of the 12 potential bitter metabolites were more abundant in the LP and two were more abundant in the LJ, suggesting that LP would be more bitter. L-Ascorbic acid, thiamine, and acitretin were significantly lost during juicing, while riboflavin was newly dissolved during juicing. The antioxidant capacity of LP was significantly higher than that of LJ, which was closely related to the higher abundance of phenolic acid metabolites in LP. These findings suggtested that promoting the release of flavonoids and phenolic acids from LP is a potential strategy to improve the quality of LJ. Results also provides important information and reference for developing high-value products by using LP.

Enrichment of Cookies with Fruits and Their By-Products: Chemical Composition, Antioxidant Properties, and Sensory Changes

Cookies made from wheat have become increasingly popular as a snack due to their various advantages, such as their convenience as a ready-to-eat and easily storable food item, wide availability in different types, and affordability. Especially in recent years, there has been a trend towards enriching food with fruit additives, which increase the health-promoting properties of the products. The aim of this study was to examine current trends in fortifying cookies with fruits and their byproducts, with a particular focus on the changes in chemical composition, antioxidant properties, and sensory attributes. As indicated by the results of studies, the incorporation of powdered fruits and fruit byproducts into cookies helps to increase their fiber and mineral content. Most importantly, it significantly enhances the nutraceutical potential of the products by adding phenolic compounds with high antioxidant capacity. Enriching shortbread cookies is a challenge for both researchers and producers because the type of fruit additive and level of substitution can diversely affect sensory attributes of cookies such as color, texture, flavor, and taste, which have an impact on consumer acceptability.

By-Products of Fruit and Vegetables: Antioxidant Properties of Extractable and Non-Extractable Phenolic Compounds

Non-extractable phenolic compounds (NEPs), or bound phenolic compounds, represent a crucial component of polyphenols. They are an essential fraction that remains in the residual matrix after the extraction of extractable phenolic compounds (EPs), making them a valuable resource for numerous applications. These compounds encompass a diverse range of phenolic compounds, ranging from low molecular weight phenolic to high polymeric polyphenols attached to other macro molecules, e.g., cell walls and proteins. Their status as natural, green antioxidants have been well established, with numerous studies showcasing their anti-inflammatory, anti-aging, anti-cancer, and hypoglycemic activities. These properties make them a highly desirable alternative to synthetic antioxidants. Fruit and vegetable (F&Veg) wastes, e.g., peels, pomace, and seeds, generated during the harvest, transport, and processing of F&Vegs, are abundant in NEPs and EPs. This review delves into the various types, contents, structures, and antioxidant activities of NEPs and EPs in F&Veg wastes. The relationship between the structure of these compounds and their antioxidant activity is explored in detail, highlighting the importance of structure-activity relationships in the field of natural antioxidants. Their potential applications ranging from functional food and beverage products to nutraceutical and cosmetic products. A glimpse into their bright future as a valuable resource for a greener, healthier, and more sustainable future, and calling for researchers, industrialists, and policymakers to explore their full potential, are elaborated.

Role and mechanism of fruit waste polyphenols in diabetes management

Among various diseases in humans, diabetes is one of the most complicated disorders resulting either from the malfunctioning of β cells, causing a poor discharge of insulin from them, or poor functioning of the liberated insulin. A wide array of chemical compounds so-called secondary metabolites are present in plants. These phytochemicals are produced as by-products of metabolism and play a key role in plant protection. However, in humans, they offer several beneficial functions. Polyphenols are an important class of phytochemicals and apart from fruits, they are also found in their major wastes mainly including the peel, pomace, and seed. The current review is aimed to focus on the potential sources, distribution, and extraction/isolation of polyphenols from major fruit wastes along with highlighting their medicinal and therapeutic benefits, especially in the management of diabetes.

Extraction and purification of α-pinene; a comprehensive review

Extensive use of α-pinene in cosmetics, and medicine, especially for its antioxidant/antibacterial, and anti-cancer properties, and also as a flavoring agent, has made it a versatile product. α-Pinene (one of the two pinene isomers) is the most abundant terpene in nature. When extracting α-pinene from plants and, to a lesser extent, fruits, given that its purity is essential, purification methods should also be used as described in this study. Also, an attempt has been made to describe the extraction techniques of α-pinene, carried out by conventional and novel methods. Some disadvantages of conventional methods (such as hydrodistillation or solvent extraction) are being time consuming, low capacity per batch and being labor intensive and the requirement of trained operators. Most novel methods, such as supercritical fluid extraction and microwave-assisted extraction, can reduce the extraction time, cost, and energy compared to conventional methods, and, in fact, the extraction and preservation efficiency of α-pinene in these methods is higher than conventional methods. Although the above-mentioned extraction methods are effective, they still require rather long extraction times. In fact, advanced methods such as green and solvent-free ultrasonic-microwave-assisted extraction are much more efficient than microwave-assisted extraction and ultrasound-assisted extraction because the extraction efficiency and separation of α-pinene in these methods are higher; furthermore, no solvent consumption and maximum extraction efficiency are some crucial advantages of these techniques. However, the application of some novel methods, such as ultrasound-assisted extraction, in industry scale is still problematic because of their intricate design data.

The recovery from agro-industrial wastes provides different profiles of anti-inflammatory polyphenols for tailored applications

Food and agro-industrial processing produce a great amount of side-stream and waste materials that are excellent sources of functional bioactive molecules such as phenolic compounds that recover them can be beneficial not only for food sustainability but also to human for many industrial applications such as flavor compounds and therapeutic applications such as antimicrobial and anti-inflammatory. The treatments and extraction techniques have major effects on the recovery of bioactive compounds. Along with the conventional extraction methods, numerous innovative techniques have been evolved and have been optimized to facilitate bioactive extraction more efficiently and sustainably. In this work, we have summarized the state-of-the-art technological approaches concerning novel extraction methods applied for five most produced crops in Italy; Grape Pomace (GP), Tomato Pomace (TP), Olive Pomace (OP), Citrus Pomace (CP), and Spent Coffee Grounds (SCG), presenting the extraction yield and the main class of phenolic classes, with the focus on their biological activity as an anti-inflammatory in vitro and in vivo studies via describing their molecular mechanism of action.

Dynamic Changes in Volatile Flavor Compounds, Amino Acids, Organic Acids, and Soluble Sugars in Lemon Juice Vesicles during Freeze-Drying and Hot-Air Drying

Lemon juice vesicles have abundant flavor components that can undergo complex changes during drying. Three drying methods, including integrated freeze-drying (IFD), conventional freeze-drying (CFD), and hot-air drying (AD), were studied to determine their effects on the dynamic changes in the flavor compounds in lemon juice vesicles. Compared with the fresh samples, the final dried samples that underwent IFD, CFD, and AD lost seven, seven, and six volatile flavor compounds and three, four, and five amino acids, respectively; the order of the loss ratios with respect to the volatile compound content was: 82.73% in CFD > 71.22% in IFD > 28.78% in AD. AD resulted in the highest total amino acid content (10.83 ± 0.20 mg/g), which was 1.39 and 5.54 mg/g higher than that of IFD and CFD, respectively; CFD resulted in the highest total organic acid content (45.94 ± 0.34 mg/g), which was 8.01 and 7.87 mg/g higher than that of IFD and AD, respectively; and AD contributed to the highest total soluble sugars (17.12 ± 0.20 mg/g), which was 1.24 and 1.49 mg/g higher than that of IFD and CFD, respectively. A correlation analysis demonstrated that most of the amino acids and the soluble sugars were closely related to the profiles of the volatile compounds in the lemon juice vesicles during drying.

Hesperetin (citrus peel flavonoid aglycone) encapsulation using pea protein-high methoxyl pectin electrostatic complexes: complex optimization and biological activity

BACKGROUND

Orange pomace polyphenols have potential for use as nutraceutical ingredients in functional foods and beverages. However, owing to their low water solubility and bioaccessibility, they are not being utilized to their full potential. The goal of this research is to assess the impact of encapsulation on hesperetin (HT - a model orange polyphenol) water solubility, antioxidant activity, and in vitro bioaccessibility.

RESULTS

In this study, a citrus flavonoid aglycone, HT, was encapsulated within water-dispersible colloidal complexes (d = 350 ± 8 nm) formed by electrostatic attraction of pea protein isolate and high-methoxyl pectin at a mixing ratio of 1:1 (v/v) and pH 4. The maximum amount of HT that could be dispersed in water was much higher for the encapsulated form (99 ± 7 μg mL^-1 ) than the non-encapsulated form (<10 μg mL^-1 ). The radical scavenging activity of the encapsulated HT (>90%, pH 4) was much higher than the non-encapsulated form (<15% at pH 4 or 7). The in vitro bioaccessibility of encapsulated HT (27 ± 7%) was also much higher than the non-encapsulated form (<7%).

CONCLUSION

These results suggest that a well-designed, biopolymer-based delivery system may improve the effective incorporation of HT, and potentially other orange pomace polyphenols, into food and beverage products. This could provide an additional high-value use for orange juicing by-products while introducing a new nutraceutical product to the food and beverage industry. © 2022 Society of Chemical Industry.

Fruit Juice Industry Wastes as a Source of Bioactives

Food processing sustainability, as well as waste minimization, are key concerns for the modern food industry. A significant amount of waste is generated by the fruit juice industry each year. In addition to the economic losses caused by the removal of these wastes, its impact on the environment is undeniable. Therefore, researchers have focused on recovering the bioactive components from fruit juice processing, in which a great number of phytochemicals still exist in the agro-industrial wastes, to help minimize the waste burden as well as provide new sources of bioactive compounds, which are believed to be protective agents against certain diseases such as cardiovascular diseases, cancer, and diabetes. Although these wastes contain non-negligible amounts of bioactive compounds, information on the utilization of these byproducts in functional ingredient/food production and their impact on the sensory quality of food products is still scarce. In this regard, this review summarizes the most recent literature on bioactive compounds present in the wastes of apple, citrus fruits, berries, stoned fruits, melons, and tropical fruit juices, together with their extraction techniques and valorization approaches. Besides, on the one hand, examples of different current food applications with the use of these wastes are provided. On the other hand, the challenges with respect to economic, sensory, and safety issues are also discussed.

Determination of Bioactive Components in Mandarin Fruits: A Review

During the last decade, there has been a continuous rise in the consumption of fresh easy-to-peel mandarins. However, the majority of the knowledge comes from other citrus fruit, like orange, while there are relatively few studies about mandarins and no comprehensive research on literature data about them. One of the most important steps in the analytical process is sample preparation. Its value is evident in analyzing the samples with complex matrices, such as in mandarin fruit. In addition, mandarin contains hundreds to thousands of various compounds and metabolites, some of them present in extremely low concentrations, that interfere with the detection of one another. Hence, mandarin samples are commonly pretreated by extraction to facilitate analysis of bioactive compounds, improve accuracy and quantification levels. There is an abundance of extraction techniques available, depending on the group of compounds of interest. Finally, modern analytical techniques, have been applied to cope with numerous bioactive compounds in mandarins. Considering all the above, this review aims to (i) list the most valuable procedures of sample preparation, (ii) highlight the most important techniques for extraction of bioactive compounds from mandarin fruit, and (iii) summarize current trends in the identification and determination of bioactive compounds in mandarin.

Organic Acid-Catalyzed Subcritical Water Hydrolysis of Immature Citrus unshiu Pomace

Immature Citrus unshiu pomace (ICUP) was hydrolyzed under organic acid-catalyzed, subcritical water (SW) conditions to produce flavonoid monoglucosides (hesperetin-7-O-glycoside and prunin) and aglycons (hesperetin and naringenin) with high biological activities. The results of single-factor experiments showed that with 8 h of hydrolysis and an increasing citric acid concentration, the yield of flavonoid monoglucosides (hesperetin-7-O-glycoside and prunin) increased from 0 to 7% citric acid. Afterward, the hesperetin-7-O-glycoside yield remained constant (from 7 to 19% citric acid) while the pruning yield decreased with 19% of citric acid, whereas the aglycon yield increased continuously. In response surface methodology analysis, a citric acid concentration and hydrolysis duration of 13.34% and 7.94 h were predicted to produce the highest monoglucoside yield of 15.41 mg/g, while 18.48% citric acid and a 9.65 h hydrolysis duration produced the highest aglycon yield of 10.00 mg/g. The inhibitory activities of the SW hydrolysates against pancreatic lipase (PL) and xanthine oxidase (XO) were greatly affected by citric acid concentration and hydrolysis duration, respectively. PL and α-glucosidase inhibition rates of 88.2% and 62.7%, respectively, were achieved with 18.48% citric acid and an 8 h hydrolysis duration, compared to 72.8% for XO with 16% citric acid and 12 h of hydrolysis. This study confirms the potential of citric acid-catalyzed SW hydrolysis of ICUP for producing flavonoid monoglucosides and aglycons with enhanced enzyme inhibitory activities.

Recent advances in valorization of citrus fruits processing waste: a way forward towards environmental sustainability

Citrus fruits are well known for their medicinal and therapeutic potential due to the presence of immense bioactive components. With the enormous consumption of citrus juice, citrus processing industries are focused on the production of juice but at the same time, a large amount of waste is produced mainly in the form of peel, seeds, pomace, and wastewater. This waste left after processing leads to environmental pollution and health-related hazards. However, it could be exploited for the recovery of essential oils, pectin, nutraceuticals, macro and micronutrients, ethanol, and biofuel generation. In view of the importance and health benefits of bioactive compounds found in citrus waste, the present review summarizes the recent work done on the citrus fruit waste valorization for recovery of value-added compounds leading to zero wastage. Therefore, instead of calling it waste, these could be a good resource of significant valuable components, in this way encouraging the zero-waste theory.

Encapsulation and delivery of bioactive citrus pomace polyphenols: a review

Citrus pomace consists of the peel, pulp, and membrane tissues remaining after juice expression. Globally, around one million tons of citrus pomace are generated annually, which contains a variety of bioactive constituents that could be used as value-added functional ingredients in foods. However, the polyphenols in citrus pomace are not currently being utilized to their full potential, even though they can be used as nutraceuticals in functional foods and beverages. Citrus phenolics face significant roadblocks to their successful incorporation into these products. In particular, they have poor water solubility, chemical stability, and bioavailability. This review describes the diverse range of colloidal systems that have been developed to encapsulate and deliver citrus phenolics. Examples of the application of these systems for the encapsulation, protection, and delivery of polyphenols from citrus pomace are given. The use of colloidal delivery systems has been shown to improve the stability, dispersibility, and bioaccessibility of encapsulated polyphenols from citrus pomace. The selection of an appropriate delivery system determines the handling, storage, shelf life, encapsulation efficiency, dispersibility, and gastrointestinal fate of the citrus polyphenols. Furthermore, the purity, solubility, and chemical structure of the polyphenols are key factors in delivery system selection.