In Vitro Release of Anthocyanins from Microencapsulated Natal Plum (Carissa macrocarpa) Phenolic Extract in Alginate/Psyllium Mucilage Beads.

Natal plum (Carissa macrocarpa) contains anthocyanins, cyanidin 3-O-ß-sambubioside (Cy-3-Sa), and cyanidin 3-O-glucoside (Cy-3-G) that possess great bioactive properties. During in vitro gastrointestinal digestion, Cy-3-Sa and Cy-3-G are highly sensitive to pH changes and have low bioaccessibility rates of 7.9% and 22%, respectively. This study aimed to therefore use microencapsulation techniques to improve the bioaccessibility of Cy-3-Sa and Cy-3-G. The crude anthocyanin-rich extract was extracted from freeze-dried Natal plum fruit using ultrasonic-assisted ethanol extraction. The anthocyanin-rich extract was encapsulated using the ionic gelation method. Four distinct carrier agents, namely sodium alginate, pectin, xanthan gum and psyllium mucilage were used to form the wall materials. Encapsulation efficiency was highest for alginate/psyllium mucilage beads (93.67%), while alginate showed the least efficiency (86.80%). Scanning Electron Microscopy revealed a cracked and porous structure for the Natal plum extract and a continuous smooth structure for all the beads. Fourier transform infrared spectroscopy showed peaks at 3300 and 1610 cm-1, confirming the presence of polyphenols and polysaccharides in all beads. Thermal stability was higher for the alginate/psyllium mucilage beads and the observed thermal transitions were due to the bonds formed between the polymers and the polyphenols. Alginate beads combined with xanthan gum, pectin, and psyllium mucilage showed a prolonged release of anthocyanins compared to alginate in vitro alone. The highest anthocyanin bioaccessibility was obtained from alginate/psyllium mucilage beads (85.42 ± 1.03%). The results showed the effectiveness of alginate/psyllium mucilage beads in improving stability and in vitro anthocyanin release.

Antioxidant Activities of Co-Encapsulated Natal Plum (Carissa macrocarpa) Juice Inoculated with Ltp. plantarum 75 in Different Biopolymeric Matrices after In Vitro Digestion.

Biopolymeric systems that co-encapsulate probiotics and bioactive compounds ensure timely delivery in the gastrointestinal tract. Cyanidin 3-sambubioside is the dominant anthocyanin in Natal plum (Carissa macrocarpa). This study aims at the co-encapsulation of Natal plum (Carissa macrocarpa) juice inoculated with Lactiplantibacillus plantarum 75 (Ltp. plantarum 75) by freeze-drying using pea protein isolate, maltodextrin, and psyllium mucilage and evaluating their release in vitro. An encapsulation efficiency of >85% was noted in lactic acid bacteria (LAB) survival and anthocyanin content. Freeze-drying produced pinkish-red powder, rich in polyphenols and LAB (>6 Log CFU mL−1) after 14 days of storage. Natal plum juice + maltodextrin + pea protein isolate + psyllium mucilage + Ltp. plantarum 75 (NMPeaPsyB) showed the highest LAB population (6.74 Log CFU mL−1) with a survival rate of 81.9%. After digestion, NMPeaPsyB and NMPeaPsy had the highest LAB survival (>50%) at 67.5% and 67.5 ± 0.75%, respectively, and the highest bioaccessibility of cyanidin 3-sambubioside in Natal plum juice than the other co-encapsulation with other biopolymers. NMPeaPsy and NMPeaPsyB showed phenolic stability in the gastric phase and controlled release in the intestinal simulated phase. The antioxidant activities had strong correlations with cyanidin 3-sambubioside. The results confirmed that microencapsulation is important for improving stability and allowing for the development of functional foods.

Influence of different rootstocks on quality and volatile constituents of cantaloupe and honeydew melons (Cucumis melo. L) grown in high tunnels.

Two rootstock crosses of sweet melon and watermelon (Cucurbita moschata × Cucurbita maxima hybrids), 'Kickstart' and 'Carnivor', grafted onto four melon cultivars (cantaloups; 'Majestic', 'Hunter', 'Honeygoal' and 'Honeyval') were evaluated for quality, phytonutrient composition and volatile compounds in the 2020 and 2021 growing season at two harvests. Grafted fruits showed higher SSC/TA ratio, and antioxidant scavenging activity. Grafted 'Majestic/Carnivor' and 'Honeyval/ Carnivor' melons significantly increased the ascorbic acid content than the controls. 'Majestic/Carnivor' melons showed the highest ß- carotene and lutein than the controls. PLS-DA score plots discriminated the grafted cantaloupes and honeydew melons from controls based on the concentration of volatile compounds. Hexyl acetate and hexadecane respectively discriminated the grafted cantaloups and honeydew melons from ungrafted fruits. 'Carnivor' rootstocks showed higher expression of volatiles in the grafted cantaloupes and honeydew melons in the heat map. Panellists preferred Majestic/Carnivor' and 'Honeyval/ Carnivor' melons.

Changes in Functional Compounds, Volatiles, and Antioxidant Properties of Culinary Herb Coriander Leaves (Coriandrum sativum) Stored Under Red and Blue LED Light for Different Storage Times.

This study evaluated the influence of red (630-640 nm) and blue (450 nm) light-emitting diodes (LED) lights on the changes in antioxidant constituents, activity, volatile compounds, and overall acceptability of Coriander leaves (Coriandrum sativum) during post-harvest storage. Coriander leaves are harvested at commercial maturity, packed in polyethylene terephthalate punnets, and exposed for 2 h to the red LED or blue LED lights separately during storage at 5°C and 85% RH up to 9 days. Coriander leaves exposed to the white light (2 h) and continuous darkness served as controls. Samples were removed from cold storage at 3, 6, and 9 days to determine the antioxidant constituents, their activity, retention of volatile compounds, and overall acceptance. Coriander leaves exposed to red and blue LED lights for 2 h showed a commercially allowable mass loss of up to 9 days compared to the other treatments. Compared to those exposed to red LED light (2 h) and the control, leaves exposed to blue LED light for 2 h and stored for 3-9 days showed a reduction in colour change (ΔE). The ß-carotene content significantly peaked at 44.55% on day 6 in coriander leaves exposed to the red LED light. However, leaves exposed to blue and red LED light showed an increase in total phenolic content by 9.34 and 6.39% on day 9, respectively. Exposure to blue LED lights increased the antioxidant activities (DPPH, ABTS, and FRAP), quercetin content, and the concentration of typical coriander aroma, 2-tridecenal, 2-dodecenal, (E), and Z-9-19 hexadecenal on day 9. Coriander leaves exposed to blue LED light (2 h) and stored up to day 9 scored a higher acceptance level by the panellists. Thus, blue light LED treatment during post-harvest storage can be recommended to retain the antioxidant property of coriander leaves.

Comparison of Caffeoylquinic Acids and Functional Properties of Domestic Sweet Potato (Ipomoea batatas (L.) Lam.) Storage Roots with Established Overseas Varieties.

Root samples of sweet potato varieties originating from South Africa ('Ndou', 'Bophelo', 'Monate', and 'Blesbok'), the USA ('Beauregard'), and Peru ('199062.1') were analyzed using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC/QTOF/MS) and chemometrics to characterize and compare the locally developed varieties with well-known established overseas varieties. The highest total phenol content was detected in 'Bophelo', followed by 'Beauregard' and Peruvian variety '199062.1'. The Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) model classified the storage roots of six sweet potato varieties into two clusters. In the OPLS-DA scatter plot, one cluster, which included Peruvian variety '199062.1', was separated from the others. L-tryptophan and 3-caffeoylquinic acid (CQA) showed variable importance in projection (VIP) scores greater than 1.5. Based on the OPLS-DA-S-plot, L-tryptophan separated the other varieties from Peruvian variety '199062.1'. Peruvian variety '199062.1' contained higher concentrations of CQA (1,3-diCQA, 1,4-diCQA, 3,5-diCQA, 4,5-diCQA, 3-CQA, and 5-CQA) and 5-hydroxy-6-methoxycoumarin 7-glucoside than other varieties. Among all sweet potato varieties analyzed, Peruvian variety '199062.1' showed the highest ferric reducing antioxidant power (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free radical scavenging activity, and [2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate)] scavenging activity. Among the local sweet potato varieties, 'Bophelo' has the greatest potential for commercialization as it is the richest source of CQA.

Influence of Lactic Acid Bacterium Strains on Changes in Quality, Functional Compounds and Volatile Compounds of Mango Juice from Different Cultivars during Fermentation.

The effects of lactic acid fermentation using Lactiplantibacillus plantarum 75 (L75), Leuconostoc pseudomesenteroides 56 (L56) and its combination (L56 + 75) on the quality, bioactive and volatile compounds of mango juices (MJ) from three cultivars ('Peach', 'Sabre' and 'Tommy Atkins') were investigated. Fermented and unfermented MJ were evaluated for LAB growth, physicochemical parameters, volatile compounds, antioxidants activities (DPPH, ABTS, FRAP methods), total phenolic content (TPC) and sensory properties. The unfermented juices served as a control. Twenty-four-hour fermentation was ideal for MJ based on LAB growth profiles. Generally, titratable acidity, TPC, FRAP, DPPH and ABTS scavenging activities significantly increased with fermentation by the L75 strain and were highest in the L75-fermented 'Sabre' MJ, while L75-fermented 'Peach' MJ had higher ABTS activity (p < 0.05). In contrast, the L56 strain enhanced ß-carotene retention, with improved colour properties in L56-fermented 'Peach' MJ. Fermentation with L75 in 'Sabre' and 'Peach' MJ aided the synthesis of new volatile compounds (alcohols, esters, ketones and aldehydes). A PLS-DA scatter plot showed two clusters separating the 'Peach' and 'Sabre' mango juice fermented with L75 from the rest. Based on the variable importance of the projection value (VIP) scores, pentadecane, 8-hexyl and butyl isobutyrate were shown as marker candidates to distinguish 'Peach' and 'Sabre' MJ fermented with L75 from the other treatments, whereas ethyl octanoate and isobutyl acetate differentiated the 'Sabre' MJ fermented with L75 from the other treatments. 'Sabre' and 'Peach' MJ fermented with L75 and L56 could provide antioxidants, meeting the recommended daily requirements for ascorbic acid and carotenoids in adults and teenagers. Hence, lactic acid fermentation of these local cultivars is a way to benefit consumers.

Metabolomic and chemometric profiles of ten southern African indigenous fruits.

Using UPLC-QTOF/MS, metabolites were identified in 10 indigenous fruits from South Africa. Metabolomic-chemometric analysis showed chlorogenic acid scored highest for the discrimination of three different fruit clusters. Heat maps showed patterns and groupings based on the metabolite concentrations. The highest concentrations of quercetin 3-O-α-l-arabinopyranoside (401.09 mg/kg), delphinidin 3-galactoside (57.80 mg/kg), procyanidin B-type dimer (527.07 mg/kg) and epicatechin (1349.46 mg/kg), was in Englerophytum magalismontanum (Transvaal milkplum). Syzygium cordatum (Water berry) had the highest concentrations of quercetin 3-galactoside and methyl gallate 3-O-beta-d-glucopyranoside, Ficus capensis (Cape fig) the most 3-CQA and 5-CQA, and Parinari curatellifolia (Mobola plum) had the highest FRAP (9.5 mmol TEAC/g) and DPPH (14.2 IC50 µg/mL) scavenging activities. When compared to eight other indigenous fruits, Ximenia caffra (Sour plum), and Landolphia kirkii (Sand apricot vine), showed the highest inhibition of carbohydrate hydrolysing enzymes. Correlation analysis identified candidates responsible for each biological activity in these fruits, proving their utility as functional ingredients.

Co-Ingestion of Natal Plums (Carissa macrocarpa) and Marula Nuts (Sclerocarya birrea) in a Snack Bar and Its Effect on Phenolic Compounds and Bioactivities.

This study investigated the effect of co-ingesting Natal plums (Carissa macrocarpa) and Marula nuts (Sclerocarya birrea) on the bioaccessibility and uptake of anthocyanins, antioxidant capacity, and the ability to inhibit α-glucosidase. A Natal plum-Marula nut bar was made by mixing the raw nuts and the fruit pulp in a ratio 1:1 (v/v). The cyanidin-3-O-sambubioside (Cy-3-Sa) and cyanidin-3-O-glucoside content (Cy-3-G) were quantified using the ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS). Inclusion of Natal plum in the Marula nut bar increased the Cy-3-Sa, Cy-3-G content, antioxidants capacity and α-glucosidase inhibition compared to ingesting Marula nut separately at the internal phase. Adding Natal plum to the Marula nut bar increased bioaccessibility of Cy-3-Sa, Cy-3-G, quercetin, coumaric acid, syringic acid and ferulic acid to 80.2% and 71.9%, 98.7%, 95.2%, 51.9% and 89.3%, respectively, compared to ingesting the Natal plum fruit or nut separately.

An Evaluation of Phenolic Compounds, Carotenoids, and Antioxidant Properties in Leaves of South African Cultivars, Peruvian 199062.1 and USA's Beauregard.

In this study, leaves of sweet potato cultivars from South Africa ("Ndou," "Bophelo," "Monate," and "Blesbok"), "Beauregard," a sweet potato cultivar from the USA, and a Peruvian cultivar "199062. 1" were analyzed using UPLC/QTOF/MS and chemometrics, with the aim of characterizing the locally developed sweet potato cultivars and comparing them with already well-known established varieties on the market. A set of 13 phenolic compounds was identified. A partial least squares discriminant analysis, a hierarchical cluster analysis, and variables importance in projection were used to successfully distinguish sweet potato varieties based on their distinct metabolites. Caffeic acid enabled to distinguish Cluster 1 leaves of varieties ("Beauregard" and "Ndou") from Cluster 2 ("199062.1," "Bophelo," "Monate," and "Blesbok"). The leaves of "Bophelo" contained the highest concentrations of rutin, quercetin 3-O-galactoside, 3-caffeoylquinic acid (3-CQA), (5-CQA), 1,3 dicaffeoylquinic acid (1,3-diCQA), 1,4-diCQA, and 3,5-diCQA. Furthermore, Bophelo leaves showed the highest antioxidant activities (FRAP 19.69 mM TEACg-1 and IC50 values of (3.51 and 3.43 mg ml-1) for DPPH and ABTS, respectively, compared to the other varieties. Leaves of "Blesbok" contained the highest levels of ß-carotene (10.27 mg kg-1) and zeaxanthin (5.02 mg kg-1) on a dry weight basis compared to all other varieties. This study demonstrated that the leaves of local cultivars "Bophelo" and "Blesbok" have the potential to become functional ingredients for food processing.

Cooking African Pumpkin Leaves (Momordicabalsamina L.) by Stir-Frying Improved Bioactivity and Bioaccessibility of Metabolites-Metabolomic and Chemometric Approaches.

The leaves of African pumpkins (Momordica balsamina L.) are a commonly consumed traditional vegetable. They are a good source of polyphenolic antioxidants and carotenoids, which are, however, affected by cooking or digestion. We investigated the effect of household cooking methods (stir-frying or boiling) on the changes in bioactive metabolites, antioxidant capacity, release and accessibility of ß-carotene and also inhibition of inhibitory activity against α-amylase and α-glucosidase enzymes during in vitro digestion of African pumpkin leaves compared to the raw leaves. Compared to boiled or raw leaves, stir-frying improved the availability of bioactive metabolites at the gastrointestinal phase. Quercetin 3-galactoside and rhamnetin 3-O-glucoside (marker compounds) discriminated the stir-fried leaves from raw leaves and boiled leaves after digestion. Stir-frying improved the release and accessibility of ß-carotene and enhanced the antioxidant activities compared to boiling. Dialysable fractions of stir-fried leaves exhibited the greatest inhibitory activity against α-amylase and α-glucosidase enzymes compared to the raw and boiled leaves, as well as acarbose. Stir-frying, therefore, is recommended for use in household cooking to benefit consumers by increasing the intake of phenolics and ß-carotene.

Effect of Freeze Drying and Simulated Gastrointestinal Digestion on Phenolic Metabolites and Antioxidant Property of the Natal Plum (Carissa macrocarpa).

Natal plums (Carissa macrocarpa) are a natural source of bioactive compounds, particularly anthocyanins, and can be consumed as a snack. This study characterized the impact of freeze drying and in vitro gastrointestinal digestion on the phenolic profile, antioxidant capacity, and α-glucosidase activity of the Natal plum (Carissa macrocarpa). The phenolic compounds were quantified using high performance liquid chromatography coupled to a diode-array detector HPLC-DAD and an ultra-performance liquid chromatograph (UPLC) with a Waters Acquity photodiode array detector (PDA) coupled to a Synapt G2 quadrupole time-of-flight (QTOF) mass spectrometer. Cyanidin-3-O-ß-sambubioside (Cy-3-Sa) and cyanidin-3-O-glucoside (Cy-3-G) were the dominant anthocyanins in the fresh and freeze-dried Natal plum powder. Freeze drying did not affect the concentrations of both cyanidin compounds compared to the fresh fruit. Both cyanidin compounds, ellagic acid, catechin, epicatechin syringic acid, caffeic acid, luteolin, and quercetin O-glycoside from the ingested freeze-dried Natal plum powder was quite stable in the gastric phase compared to the small intestinal phase. Cyanidin-3-O-ß-sambubioside from the ingested Natal plum powder showed bioaccessibility of 32.2% compared to cyanidin-3-O-glucoside (16.3%). The degradation of anthocyanins increased the bioaccessibility of gallic acid, protocatechuic acid, coumaric acid, and ferulic acid significantly, in the small intestinal digesta. The ferric reducing antioxidant power (FRAP), 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) activities, and inhibitory effect of α-glucosidase activity decreased in the small intestinal phase. Indigenous fruits or freeze-dried powders with Cy-3-Sa can be a better source of anthocyanin than Cy-3-G due to higher bioaccessibility in the small intestinal phase.

Enrichment of Mango Fruit Leathers with Natal Plum (Carissa macrocarpa) Improves Their Phytochemical Content and Antioxidant Properties.

Natal plum fruit (Carissa macrocarpa) is indigenous to South Africa and a rich source of cyanidin derivatives. Indigenous fruits play a major role in food diversification and sustaining food security in the Southern African region. Agro-processing of indigenous are practiced adopted by the rural African communities in order to reduce the postharvest wastage of fruit commodities. In the current study, Natal plum was added to mango pulp at different ratios (mango and Natal plum (5:1, 3:1, 2:1)) to develop a healthy-functional snack (fruit leather). The effects of added Natal plum on the availability of antioxidant constituents and in vitro antioxidant properties of a mango-based fruit leather were evaluated by comparing with mango fruit leather. Fruit leather containing mango and Natal plum (2:1) retained the highest content of cyanidin-3-O-glucoside chloride, cyanidin- 3-O-ß-sambubioside, epicatechin, apigenin, kaempferol, luteolin, quercetin-3-O-rhamnosyl glucoside, catechin, quinic, and chlorogenic acids, and in vitro antioxidant activity. Proximate analysis showed that 100 g of fruit leather (2:1) contained 63.51 g carbohydrate, 40.85 g total sugar, 0.36 g fat, and 269.88 cal. Therefore, enrichment of mango fruit leather with Natal plum (2:1) increases its phytochemical content and dietary phytochemical intake, especially for school children and adolescents.

Laccase-mediated crosslinking of gluten-free amadumbe flour improves rheological properties.

The absence of gluten in gluten-free flours presents a challenge to their application in baking. Enzymatic modification of the protein and polysaccharides may result in a network that mimics gluten. In the current study, the effects of laccase on the rheological properties of amadumbe dough were investigated. Thiol and total phenolic contents of dough decreased by up to 28% and 93%, respectively, as laccase activity was increased (0-3 U/g flour). Both G' and G″ of laccase-treated dough increased significantly due to laccase-catalysed cross-linking of proteins and polysaccharides esterified with phenolics, as demonstrated by relevant model reactions. Tan δ decreased with increase in laccase activity indicating an increase in the elastic character of the dough. The improvement in dough viscoelasticity may enable the retention of adequate carbon dioxide during proofing and production of more acceptable gluten-free bread.

Composition, thermal and rheological properties of polysaccharides from amadumbe (Colocasia esculenta) and cactus (Opuntia spp.).

The extensive application of hydrocolloids in the food industry, coupled with their short supply and shortcomings, has led to the ongoing search for alternative sources. In this study, the compositional, rheological and thermal properties of amadumbe and cactus mucilages were investigated. The mucilages had a similar qualitative composition of monosaccharides and amino acids, except for the absence of rhamnose in amadumbe mucilage. Fractionation of amadumbe and cactus mucilages on an anion-exchange column yielded four and three fractions, respectively. The fractions eluting with protein showed no ß-elimination, suggesting stronger glycosylation bonds such as those in arabinogalactan proteins (AGPs). There was no evidence of thermal depolymerisation of the mucilages up to 195 °C. Cactus mucilage showed a pseudoplastic flow behaviour whilst amadumbe mucilage showed a Newtonian flow behaviour at up to 5% (w/v) concentrations. Amadumbe mucilage may be a potential emulsifier, whilst cactus mucilage can potentially be used as a thickening or emulsifying agent.