Ohmic heating as a promising technique for extraction of herbal essential oils: Understanding mechanisms, recent findings, and associated challenges

Clove Essential Oil: Chemical Profile, Biological Activities, Encapsulation Strategies, and Food Applications

Plants have proven to be important sources for discovering new compounds that are useful in the treatment of various diseases due to their phytoconstituents. Clove (Syzygium aromaticum L.), an aromatic plant widely cultivated around the world, has been traditionally used for food preservation and medicinal purposes. In particular, clove essential oil (CEO) has attracted attention for containing various bioactive compounds, such as phenolics (eugenol and eugenol acetate), terpenes (β-caryophyllene and α-humulene), and hydrocarbons. These constituents have found applications in cosmetics, food, and medicine industries due to their bioactivity. Pharmacologically, CEO has been tested against a variety of parasites and pathogenic microorganisms, demonstrating antibacterial and antifungal properties. Additionally, many studies have also demonstrated the analgesic, antioxidant, anticancer, antiseptic, and anti-inflammatory effects of this essential oil. However, CEO could degrade for different reasons, impacting its quality and bioactivity. To address this challenge, encapsulation is viewed as a promising strategy that could prolong the shelf life of CEO, improving its physicochemical stability and application in various areas. This review examines the phytochemical composition and biological activities of CEO and its constituents, as well as extraction methods to obtain it. Moreover, encapsulation strategies for CEO and numerous applications in different food fields are also highlighted.

Inactivation effects and mechanism of ohmic heating on Bacillus cereus

The inactivation effects and mechanism of ohmic heating (OH) on Bacillus cereus ATCC 11778 were investigated in this study, conventional heating (CH) was also carried out and served as control. All OH treatments (10 V/cm 50 Hz, 10 V/cm 500 Hz, 5 V/cm 50 Hz and 5 V/cm 500 Hz) could achieve a comparable inactivation effect with CH, while OH treatments significantly shortened the processing time. OH treated cells exhibited significantly higher leakage of metal ions (Mg²⁺ and K⁺) and biomacromolecules (nucleic acids and proteins) than those treated with CH when bacterial suspensions were heated to the same temperature. Moreover, OH treatment caused more damage on membrane structure, greatly decreased the cell membrane potential and endogenous enzyme activity than that of CH. The results of this study indicated that OH is more efficient in the inactivation of bacteria.

Co-encapsulation of Pimpinella anisum and Coriandrum sativum essential oils based synergistic formulation through binary mixture: Physico-chemical characterization, appraisal of antifungal mechanism of action, and application as natural food preservative

The present study aimed to co-encapsulate binary synergistic formulation of Pimpinella anisum and Coriandrum sativum (PC) essential oils (0.75:0.25) into chitosan nanoemulsion (Nm-PC) with effective inhibition against fungal proliferation, aflatoxin B₁ (AFB₁) secretion, and lipid peroxidation in stored rice. Physico-chemical characterization of Nm-PC by SEM, FTIR, and XRD confirmed successful encompassment of PC inside the chitosan nanomatrix with efficient interaction by functional groups and reduction in crystallinity. Nm-PC showed superior antifungal, antiaflatoxigenic, and antioxidant activities over unencapsulated PC. Reduction in ergosterol biosynthesis and enhanced leakage of Ca²⁺, K⁺, Mg²⁺ ions and 260, 280 nm absorbing materials by Nm-PC fumigation confirmed irreversible damage of plasma membrane in toxigenic Aspergillus flavus cells. Significant diminution of methylglyoxal in A. flavus cells by Nm-PC fumigation illustrated biochemical mechanism for antiaflatoxigenic activity, suggesting future exploitation for development of aflatoxin resistant rice varieties through green transgenic technology. In silico findings indicated specific stereo-spatial interaction of anethole and linalool with Nor-1 protein, validating molecular mechanism for AFB₁ inhibition. In addition, in situ investigation revealed effective protection of stored rice against fungal occurrence, AFB₁ biosynthesis, and lipid peroxidation without affecting organoleptic attributes. Moreover, mammalian non-toxicity of chitosan entrapped PC synergistic nanoformulation could provide exciting potential for application as eco-smart safe nano-green food preservative.

Aqueous Extraction of Curcuminoids from Curcuma longa: Effect of Cell Disintegration Pre-treatment and Extraction Condition

Cell structure modification techniques have the potential to improve curcuminoid recovery in Curcuma longa. In this study, different pre-treatments such as high hydrostatic pressure (HPP, high pressure processing), ultrasound (US), pulsed electric field (PEF), and ohmic heating (OH) were used on dried C. longa before aqueous extraction at pH 2.0, 5.0, and 8.0. The released curcuminoids, cell disintegration index (Zp), particle size distribution (PSD), and color (CIE L*, a*, b*) were used to evaluate the different pre-treatment impacts on plant structure and extract properties. In untreated turmeric, the highest amount of released curcuminoids (3.89 mg/g dry matter) was obtained after extraction for 30 min at 95° in the aqueous phase. After pre-treatments, the acidic conditions showed a considerable improvement in curcuminoid recovery; PEF, HPP, and OH improved the curcuminoid recovery by 3.39-, 3.13-, and 1.24-fold, respectively; while US did not lead to an increased release of curcuminoids compared to the untreated material. The highest curcuminoid recovery (with PEF and extraction at pH 5.0) was 6.6% w/w of the total curcuminoids. The non-thermal pre-treatments have less impact on the extract’s color compared to the extraction pH, with alkaline conditions reducing the lightness of the extract.

Ohmic Heating in the Food Industry: Developments in Concepts and Applications during 2013–2020

Various technologies have been evaluated as alternatives to conventional heating for pasteurization and sterilization of foods. Ohmic heating of food products, achieved by passage of an alternating current through food, has emerged as a potential technology with comparable performance and several advantages. Ohmic heating works faster and consumes less energy compared to conventional heating. Key characteristics of ohmic heating are homogeneity of heating, shorter heating time, low energy consumption, and improved product quality and food safety. Energy consumption of ohmic heating was measured as 4.6–5.3 times lower than traditional heating. Many food processes, including pasteurization, roasting, boiling, cooking, drying, sterilization, peeling, microbiological inhibition, and recovery of polyphenol and antioxidants have employed ohmic heating. Herein, we review the theoretical basis for ohmic treatment of food and the interaction of ohmic technology with food ingredients. Recent work in the last seven years on the effect of ohmic heating on food sensory properties, bioactive compound levels, microbial inactivation, and physico-chemical changes are summarized as a convenient reference for researchers and food scientists and engineers.

Tangerine, banana and pomegranate peels valorisation for sustainable environment: A review

Over the last decade the world has been generating a high quantity of tangerine peel waste (TPW), pomegranate peel waste (PPW) and banana peel waste (BPW). These peels have several economic benefits but there is mismanagement or inappropriate valorisation that could present risks to environment and public health. In the current review, we discussed the use of TPW, PPW and BPW directly for animal feed, soil fertilization, specific compost production and bio-adsorbent. We also discussed the valorisation of these peels for manufacturing the value-added products including enzymes, essential oil and other products that can be used in human food, in medical and cosmetic industry. Additionally, recent studies concerning the valorisation of these peels by biorefinery for bioethanol, biogas and biohydrogen production have been discussed. In the same context some other recent studies about valorisation of microorganisms isolated from these peels for medical, agronomic and industrial interests have been also discussed.

Pilot-scale ohmic heating-assisted extraction of wheat bran bioactive compounds: Effects of the extract on corn oil stability

Recent studies introduced ohmic heating-assisted extraction (OHAE) as a promising emerging technology at laboratory-scales. The objectives of the present study were, first, to investigate the applicability of OHAE at pilot-scale for extraction of bioactive compounds from wheat bran immersed in a polar solvent (salted water containing 0.1% NaCl) at the electric field strengths (EFS) of 4.28, 7.90, and 15.71 V/cm and, second, to evaluate the effects of the wheat extracts on the corn oil stability during 30 days of storage at 45 °C. The results showed that OHAE saved 63% of energy consumption compared with the conventional extraction method. Also, the scaled-up OHAE unit yielded extracts with high quantities of bioactive compounds (110-460 ppm total phenolics) and higher antioxidant activities (antioxidant effectiveness of 56-84%) than those of the extract obtained through the conventional extraction method, i.e., 95 ppm total phenolics with antioxidant effectiveness of 51%. Increasing the EFS increased total phenolics and antioxidant effectiveness of extracts. The incorporation of 250 ppm of the extract obtained at the highest EFS effectively postponed the oxidation of corn oil during one month of storage (peroxide value of 7 vs. 19 meq/kg compared with the control sample) and extended the half-life of oil from 11 to 26 days. Besides, mathematical models proposed in this study well-predicted the oxidation stability of the oil samples mixed with the extract.

Recent nano-, micro- and macrotechnological applications of ultrasonication in food-based systems

There is a neoteric and rising demand for nutritional and functional foods which behooves food processors to adopt processing techniques with optimal conservation of bioactive components in foods and with minimal pernicious impacts on the environment. Ultrasonication, a mechanochemical technique has proven to be an efficacious panacea to these concerns. In this review, an analytic exploration of recent researches and designs regarding ultrasound methodology and equipment on diverse food systems, technological scales, procedural parameters and outcomes of such experimentations optimally scrutinized. The relative effects of ultrasonication on food formulations, components and attributes such as nanoemulsions, nanocapsules, proteins, micronutrients, sensory and mechanical characteristics are evaluatively delineated. In food systems where ultrasonication was employed, it was found to have a remarkable effect on one or more quality parameters. This review is a supplementation to the pedagogical awareness to scholars on the suitability of ultrasonication for research procedures, and a call to industrial food brands on the adoption of this technique for the development of foods with optimally sustained nutrient profiles.