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Transforming liquid smoke to powder form can provide convenience for use and storage. Liquid smoke was prepared by fast pyrolysis technology using a fluidised bed and converted to smoke powder by spray-drying or freeze-drying processes. Both drying processes effectively retained the bioactive compounds in the powder encapsulates with retention efficiencies up to 80%. The bioactive capacities were approximately two times higher than liquid smoke. Spray-drying did not induce thermal damage to the bioactive compounds, and the dominant compounds were retained in the powders. Gas chromatography–mass spectrometry and principal component analysis indicated that the chemical composition was not significantly changed after both drying methods, but small molecular carbonyls, furans and phenols were partially lost. The spray-dried particles had a spherical shape, while freeze-dried particles had irregular shapes because of different powder preparation methods. The particle size of spray-dried powders was in the range of 6.3 to 6.9 µm, while the value for freeze-dried powders was decreased from 580.4 to 134.7 µm by increasing the maltodextrin concentration. The freeze-dried powders performed better in terms of flowability and cohesiveness because of their relatively high density and large particle size. This study revealed that both encapsulation methods could efficiently prepare smoke powder. Spray-drying process would be suitable for large-scale production, while freeze-drying could be used to optimize the encapsulation efficiency of bioactive compounds.

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BACKGROUND Subcritical water kānuka leaf extracts contain high levels of polyphenols. However, whether these extracts can serve as natural antimicrobial and chemopreventive agents is still a question. This study aimed to evaluate the antibacterial and antiproliferative efficacy of SWE kanuka leaf extracts. Subcritical water extraction (SWE) was used to obtain natural extracts from kānuka leaves potentially rich in biologically active compounds. The antibacterial and antiproliferative capacities were assessed by broth microdilution assay and MTT‐assay, respectively. The assessed properties were compared to extraction from ethanol extraction (EE). Results The screening results for antibacterial properties demonstrated that subcritical water kānuka leaf extracts were active against Escherichia coli (minimum conc. 0.8 mg/mL) and Staphylococcus aureus (minimum conc. 3.8 mg/mL). These extracts also exerted dose‐dependent antiproliferative effects on the viability of cancerous human cervical cell lines (Hep‐2 and RD cells) and mouse cell lines (L cells). The extraction temperature had significantly affected the extract's activities by enhancing neoformed compounds with beneficial effects. CONCLUSIONS Subcritical water extracts of kānuka demonstrated a better efficacy against bacterial growth and malignant cells viability in comparison to extracts obtained using conventional ethanol extraction. This SWE kānuka leaf product could be used in a range of applications where antimicrobial and antiproliferative properties are required. Further studies are needed to examine the mechanism and markers of these properties. © 2020 Society of Chemical Industry

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Liquid smoke food flavouring is an alternative to traditional food smoking. Ageing treatment of liquid smoke can remove tar to improve a consistent sensory experience but traditionally takes months by storage. This study proposed a thermal treatment approach to accelerate the ageing process. Liquid smoke samples from kānuka and hickory woodchips were prepared by fast pyrolysis. The obtained liquid smoke samples were subjected to ageing by storing them at ambient temperature for 18 months. Accelerated ageing of liquid smoke was carried out by heat treatment at 80 °C for 24 and 48 h. Tar formed during the ageing process, with a yield ranging from 2.2 to 4.1 wt.%. Both ageing treatments resulted in decreases in bioactive content and their activities in terms of total phenolic content (TPC), total flavonoid content (TFC), ferric reducing antioxidant power assay (FRAP) and 2,2-diphenyl-1-picrylhydrazyl scavenging activity (DPPH). Chemical composition and principal component analyses indicated that liquid smoke chemical compositions were influenced by wood type and ageing conditions. It was found that thermal treatment at 80 °C for 24 h was sufficient to age liquid smoke.