Michael C. Bowyer

Preharvest and postharvest treatments are widely used to maintain citrus fruit quality during extended cold storage. This study evaluated the effects of pre- and postharvest applications of salicylic acid (SA) and oxalic acid (OA), applied separately and in combination, on the quality of ‘Lane Late’ navel oranges and ‘Summerina’ mandarins at harvest and stored at 1 °C for 10 weeks followed by 1 week at 20 °C. Fruit quality attributes, including weight loss, fungal decay, firmness, total soluble solids (TSS), titratable acidity (TA), electrolyte leakage, and biochemical markers, were assessed. Overall, treatments had limited and inconsistent effects on most quality parameters, with no significant differences observed in chilling injury, respiration rate, ethylene production, ethanol content, vitamin C content, malondialdehyde content, or colour. At harvest, oranges subjected to preharvest OA treatments had lower TSS and TA, while peel antioxidant capacity (AOC) was lower for oranges treated with preharvest SA or OA. After storage, postharvest SA reduced calyx stem-end rot by 30% in mandarins. Electrolyte leakage was reduced by preharvest SA in oranges and postharvest OA in mandarins, indicating improved membrane stability. No consistent synergistic effects were observed for combined treatments, and responses varied between cultivars, highlighting the importance of cultivar-specific optimisation. These findings indicate that SA and OA provide limited but targeted benefits under extended cold storage conditions.

The Illawarra plum (IP) is native to Australia and has been used as a bush food for centuries. With rich phytochemicals and natural pigments, IP has the potential to be an added ingredient to improve the physicochemical properties of food, including yoghurt. This study prepared dried IP powders through vacuum drying (VD) and freeze drying (FD), produced extracts from these dried powders, and fortified them into Greek-style set yoghurt. The changes in colour, pH, titratable acidity (TA), syneresis, total soluble solids (TS), and phytochemicals were measured throughout a chilled storage period of 28 days. The results showed that FD and FD extract could provide a stable, distinct pink colour to yoghurt. IP powders and their extracts improved TS content and, thus, the consistency of yoghurt. Compared to the control, VD, FD, and FD extract of IP did not significantly affect the level of acidity or syneresis after 28 days of chilled storage. Yoghurt fortified with FD and FD extract had the greatest level of phenolics, anthocyanins, and radical scavenging antioxidant activities. This study revealed that IP powders and their extracts can positively improve the physicochemical properties of Greek-style set yoghurt. FD powder is recommended over its extract to fortify this yoghurt, as it can be cost-effectively prepared by freeze drying and then grinding the fresh fruit into powder. Future studies are needed to evaluate other variables in yoghurt preparation, including the concentration of IP and strains of yoghurt culture. Further, the consumer perception of sensory quality and acceptability of yoghurt fortified with FD IP powder should be investigated.

The effectiveness of lemon myrtle (LM) (Backhousia citriodora) essential oil (EO) was investigated to combat Penicillium digitatum by in vitro agar diffusion and vapour assay and in artificially infected oranges. The main constituent of LM EO was revealed as citral when analysed in gas chromatography–mass spectrometry. Pure citral was also included in the experiment for comparison. The in vitro fungal growth was significantly inhibited by LM EO at 1, 2, 3, 4 and 5 μL per disc while complete growth inhibition by both the pure citral and LM EO occurred at 4 and 5 μL per disc. Inoculated fruits treated by dipping in 1000 μL L⁻¹ LM EO solutions for 5, 10, 15, 30 and 120 s showed significantly lower fungal wounds compared to control. While longer dipping times led to some rind injuries, fruits with a 5 and 10 s dip were found free from any injury. The evaluation after dipping and storage confirmed that the fruits maintained the sensory attributes and were not compromised by the incorporation of the essential oil. The results of this study indicate that LM EO can be a promising alternative to synthetic fungicides for preserving the quality of citrus fruits during storage.

This study examined the efficacy of essential oil (EO) obtained from the Australian native plants, lemon myrtle (Backhousia citriodora) (LM) to inhibit Penicillium digitatum by in vitro agar diffusion and vapor assay, and in inoculated oranges. Gas chromatograph/mass spectrometry analysis revealed the main constituent of LM EO as citral. Pure citral was also included in the experiment for com-parison. LM EO at 1, 2, 3, 4 and 5 µL disc-1 in the in vitro tests significantly inhibited fungal growth compared to the non-treated control. Moreover, LM EO at 4 and 5 µL disc-1 in both the assays completely inhibited fungal growth similar to its main component of citral. Inoculated oranges dipped in 1000 μL L-1 LM EO solutions for 5, 10, 15 and 30 sec showed significantly lower fungal wounds compared to control. While higher dipping times generated slight rind injury, a 5 and 10 sec dip did not cause any injury to the fruit rind. The quality assessments and sensory evaluations also revealed that the addition of LM EO did not adversely affect the quality and taste of the oranges. These findings suggest LM EO as an alternative to synthetic fungicides to inhibit wastage in citrus during storage.

Molecularly imprinted polymers (MIPs) for benzylpiperazine (BZP, 1), an illicit designer drug, were developed by using both self-assembly and semi-covalent approaches. From an array of potential functional monomers (FMs) and using a combination of pre-synthetic interaction studies (by molecular modelling and NMR analysis) and binding assays, the highest performing self-assembly 1-MIPs were confirmed to result from methacrylic acid (7) as FM, ethylene glycol dimethacrylate (EGDMA) or trimethylolpropane trimethacrylate (TRIM) as crosslinkers and chloroform as the porogen and rebinding solvent at template (T): FM ratios of 1:1 and 1:2, giving imprinting factors (IF) 3 to 7. The semi-covalent 1-MIPs were designed using benzylpiperazine (4-vinylphenyl) carbamate (16) as the template–monomer adduct in combination with either EDGMA or TRIM. Our comparative analysis showed the semi-covalent polymers to have a stronger affinity for 1 (significantly lower K_d values and higher IFs) and faster uptake than the self-assembly systems. Both approaches have comparable cross-reactivity: marginal to low against cocaine (17) and morphine (18) and high against ephedrine (19) and phenylpiperazine (20). They also have comparable selectivity: highly selective towards 1 against 17, moderate against 18 and non-selective against 19. EGDMA-based self-assembly MIPs displayed a greater imprinting effect (higher IFs and NIP-to-MIP K_d ratios) than TRIM-based MIPs, while the TRIM-based semi-covalent MIP outperformed its EGDMA-based equivalent. By virtue of its modest selectivity against the test illicit drugs, 1-MIPs could potentially be used as a dummy MIP for the broad-based capture and enrichment of illicit drug blends for subsequent laboratory analysis.

The function of free amino acids in protein synthesis, as a source of energy and unique roles in catabolism have been well studied in plant development but their function in postharvest fruit and vegetables has received little attention. This study evaluated 11 amino acids—arginine, alanine, aspartic acid, glutamic acid, glycine, ornithine, phenylalanine, serine, tyrosine, tryptophan and valine—on the development of senescence of broccoli. Broccoli florets were dipped in 5 mM solution of amino acids, then stored at 10 °C in air containing 0.1 µL L⁻¹ ethylene. Senescence was assessed by green life, ethylene production, respiration rate and ion leakage. Green life was increased by all the amino acids except valine. Similarly, ethylene production and ion leakage were decreased by all the amino acids except valine, while respiration rate was reduced by all amino acids. It is speculated that the early reduction in ethylene production could be the mechanism by which the amino acids delayed senescence. The beneficial effect of naturally occurring amino acids in inhibiting senescence has potential commercial relevance, as the amino acids have Generally Recognised As Safe (GRAS) status which should assist gain regulatory approval, and gain acceptance by consumers wary of synthetic chemicals on foods.

Catharanthus roseus (C. roseus) is an important medicinal plant distributed in many countries. It has attracted increasing attention due to it being shown to possess a range of phytochemicals with various biological activities such as antioxidant, antibacterial, antifungal, antidiabetic and anticancer properties. Remarkably, vinblastine and vincristine isolated from this plant were the first plant-derived anticancer agents deployed for clinical use. Recently, new isolated indole alkaloids from this plant including catharoseumine, 14′,15′-didehydrocyclovinblastine, 17-deacetoxycyclovinblastine and 17-deacetoxyvinamidine effectively inhibited human cancer cell lines in vitro. Moreover, vindoline, vindolidine, vindolicine and vindolinine isolated from C. roseus leaf exhibited in vitro antidiabetic property. These findings strongly indicate that this plant is still a promising source of bioactive compounds, which should be further investigated. This paper provides an overview of the traditional use and phytochemical profiles of C. roseus, and summarises updated techniques of the preparation of dried material, extraction and isolation of bioactive compounds from this plant. In addition, purported health benefits of the extracts and bioactive compounds derived from this plant were also addressed to support their potential as therapeutic agents.

The effect of UV-C irradiation on antifungal properties of orange essential oil (EO) against Penicillium digitatum in inoculated Navel oranges was examined. The UV-C irradiation of orange EO resulted in a 20% loss of the major constituent, limonene, and the generation of three hydroperoxide oxidation products, (2S,4R)-p-mentha-6,8-diene-2-hydroperoxide,(1S,4R)-p-mentha-2,8-diene-1-hydroperoxide, and (1R,4R)-p-mentha-2,8-diene-1-hydroperoxide. The P. digitatum growth in oranges dipped in non-irradiated orange EO at 1000–4000 µL L⁻¹ was not significantly different to control the fruit. Dipping in UV-C treated orange EO inhibited the growth of P. digitatum with 4000 µL L⁻¹ having the greatest effect. No phytotoxic injury to the rind was observed at any concentration. Citral, as a known antifungal chemical, was included for comparison. The non-irradiated citral (1000 µL L⁻¹) was more effective than irradiated orange EO, but elicited rind phytotoxicity. The irradiated citral was less effective in inhibiting P. digitatum growth with the loss of citral, but not hydroperoxide formation. These results suggest UV-C irradiated orange EO as a potential alternative to synthetic fungicides to inhibit P. digitatum decay. The source of orange EO could be waste flavedo generated by the orange juice processing industry.

Helicteres hirsuta Lour. (H. hirsuta) has been traditionally used as a folk medicine for treating a range of common diseases. It has been used in furuncle treatment, pain relief, dysentery, measles, flu, antimalaria and antiobesity treatments in some Asian countries, revealing that this plant material contains important bioactive compounds which are linked with health benefits and/or can act as therapeutic agents. Hence, many attempts have been made to isolate and identify the key bioactive compounds present in H. hirsuta and conduct in vitro tests to investigate their biological activities. We recently revealed that H. hirsuta leaf has a high total phenolic content (TPC: 192.6 mg gallic acid equivalents (GAE)/g) and total flavonoid content (TFC: 215.2 mg catechin equivalents (CE)/g). The stem of H. hirsuta also had high contents of TPC and TFC (212.6 mg GAE/g and 280.1 mg CE/g, respectively). The results also revealed that phenolic compounds from this plant had a strong positive correlation with antioxidant capacity including DPPH, ABTS radical scavenging activity and ferric reducing antioxidant power (R² range of 0.78 and 0.99), which are known to link with diverse bioactivities including antioxidant, antimicrobial, anticancer, antiobesity and antidiabetic effects. Additionally, H. hirsuta leaf and stem were found to contain high levels of saponins (808.0 and 347.5 mg escin equivalents/g, respectively), that were determined using colorimetric assay. Several individual compounds have been identified in the extracts of H. hirsuta, including rutin, methyl caffeate, 5,8-dihydroxy-7,4-dimethoxyflavone, isoscutellarein 4-methyl ether 8-O--d-glucopyranoside, 4,4-sulfinylbis(2(tert-butyl)-5-methylphenol), 7-O-methylisoscutellarein, 7,4-di-O-methylisoscutellarein, six lignans (pinoresinol, medioresinol, syringaresinol, boehmenan, boehmenan H and trans-dihydrodiconiferyl alcohol), betulinic acid, 3-O-trans-caffeoylbetulinic acid, 3-benzoylbetulinic acid, betulinic acid methyl ester, lupeol, 3β-O-acetylbetulinic acid, simiarenol, stigmasterol and β-sitosterol. The derived extracts and isolated compounds from this plant have been shown to inhibit the growth of various cancer cell lines in vitro and offer a promising source of active compounds against other health problems including obesity, diabetes and malaria. Further studies on the mechanisms of bioactive compounds from this plant are suggested to elucidate their mechanisms of action for health benefits. In addition, more in vivo tests associated with clinical trials are also needed to validate and confirm their effects for further development of nutraceutical and pharmaceutical products from this plant material.

Tuckeroo (Cupaniopsis anacardioides) is an Australian native tree, possessing high level bioactivity and antioxidant activity. To prevent deterioration of active constituents, appropriate drying practices must be determined. This study comparatively evaluates the impact of a range of drying methods including freeze-, microwave-, vacuum-, hot air- and sun-drying on the physical, phytochemical and antioxidant characteristics of Tuckeroo fruit. Experimental results showed that the five drying methods had significant impact on the physicochemical properties and antioxidant activity of the fruits. Of the drying methods assessed, freeze drying best preserved Tuckeroo activity, recording higher total phenolic content (TPC) (81.88 mg gallic acid equivalent (GAE)/g), total flavonoids (TFC) (107.71 mg catechin equivalent (CAE)/g), proanthocyanidins (TPro) (83.86 mg CAE/g) and exhibited the strongest antioxidant capacity. However, vacuum drying at 65 kPa, 100 °C for 5 h is recommended for drying Tuckeroo fruits for further processing in a large scale as it also retained high levels of TPC, TFC and TPro (58 mg GAE/g, 91 mg CAE/g and 74 mg CAE/g, respectively).