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-β-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-β-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.

This study describes the impact of utilising different strains of lactic acid bacteria (LAB) for the fermentation of papaya puree and their effect on the quality parameters and bioaccessibility of phenolic compounds during simulated in vitro gastrointestinal digestion. Papaya was processed into puree; pasteurised and fermented at 37 °C for 2 days; and stored for 7 days at 4 °C using LAB strains Lactiplantibacillus plantarum 75 (L75*D2; L75*D7), Weissella cibaria64 (W64*D2; W64*D7) and Leuconostoc pseudomesenteroides 56 (L56*D2; L56*D7), respectively. Non-fermented samples at 0 (PPD0), 2 (PPD2) and 7 days (PPD7) served as controls. pH was reduced with fermentation and was lowest in L56*D2 (3.03) and L75*D2 (3.16) after storage. The colour change (ΔE) increased with the fermentation and storage of purees; L75*D7 showed the highest ΔE (13.8), and its sourness reduced with storage. The fermentation by W64*D7 and L75*D7 increased the % recovery of chlorogenic, vanillic, syringic, ellagic, ferulic acids, catechin, epicatechin and quercetin in the intestinal fraction compared to the L56*D7 and PPD7. Fermentation by W64*D7 and L75*D7 significantly improved the antioxidant capacity of the dialysed fraction compared to the L56*D7 or PPD7. L56*D7-fermented papaya puree showed the highest inhibitory effect of α-glucosidase activity followed by L75*D7. L75*D7 had a significantly higher survival rate. LAB fermentation affected the bioacessibilities of phenolics and was strain dependent. This study recommends the use of Lpb. plantarum 75 for fermenting papaya puree.

Natal plum (Carissa macrocarpa) contains anthocyanins, cyanidin 3-O-β-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.

Due to spoilage microflora and browning, minimally processed fresh-cut fruits have a short shelf life, and over the years, studies have shown the potential of using edible coatings to extend the shelf life and improve the safety of fresh-cut fruits. Recently, there has been a rise in research on the incorporation of probiotics in edible coatings due to the bespoke health and biopreservation benefits they impart. Therefore, in this study, lactobacillus strains (Lactiplantibacillus plantarum 75 and Bifidobacterium longum) were incorporated into a xanthan edible coating to enhance color retention, sensory properties, antioxidant retention (ascorbic acid, carotenoids, total phenols), and antioxidant activity (FRAP antioxidant power, ABTS scavenger activity) of fresh-cut cantaloupes and honeydew cucumis melo L. melons during cold storage at 5 C and 85% RH for five days. The edible coating was prepared by mixing 0.5% xanthan gum, 1% glycerol, and 2% citric acid solution with L. plantarum 75 (LAB 75) and Bifidobacterium longum bacteria separately, and the final lab count for each strain was made to be 8.0 log CFU/mL. Stable probiotic coatings with ζ-potential of between −39.7 and −51.4 mV and a PdI of 1 were developed, and the incorporation of the probiotic bacteria into the coating was justified using FTIR analysis. The probiotic coatings showed a typical pseudoplastic behavior, in which the viscosity curves fall as the shear rate increases. Thermal stability analysis showed a continuous and multi-step weight reduction in this work, illustrating how the edible coating components interact. The survival of both Lactobacillus strains was recorded on day 5. Both freshly cut melons coated with xanthan and loaded with Lactobacillus strains retained a sufficient quantity of probiotics at the end of storage, while L. plantarum 75 (7 log CFU/g for cantaloupe and 8 log CFU/g for honeydew) retained the highest viability compared to B. longum (6 log CFU/g for cantaloupe and 7 log CFU/g for honeydew). In comparison to the coated and uncoated control samples, the inclusion of L. plantarum 75 in xanthan coatings significantly retained the color properties, pigments (total chlorophyll and carotenoids), ascorbic acid, total phenols, and antioxidant activity (FRAP, DPPH, and ABTS). The overall acceptability of fresh cuts of cantaloupe and honeydew melons coated with xanthan gum loaded with L. plantarum 75 was higher than that of other treatments. Thus, xanthan gum loaded with L. plantarum 75 coating is most suitable for reducing postharvest losses in fresh cuts of honeydew melons and cantaloupe, which will help preserve antioxidant and bioactive properties. The xanthan gum loaded with L. plantarum 75 coatings exhibited the highest preservation impact; therefore, it can be recommended for the fresh-cut industry.