Implementation of the supercritical carbon dioxide technology in oil palm fresh fruits bunch sterilization: A review

Effect of Green Food Processing Technology on the Enzyme Activity in Spelt Flour

In this research, a new approach to enzyme inactivation in flour was presented by supercritical technology, considered a sustainable technology with lower energy consumption compared to other technologies that use ultra-high temperature processing. Total protein concentration and the activity of enzymes α-amylase, lipase, peroxidase, polyphenol oxidase, and protease were determined in flour pre-treated with scCO₂. During the study, it was observed that the activity of enzymes such as lipase and polyphenol oxidase, was significantly reduced under certain conditions of scCO₂ treatment, while the enzymes α-amylase and protease show better stability. In particular, polyphenol oxidase was effectively inactivated below the 60% of preserved activity at 200 bar and 3 h, whereas α-amylase under the same conditions retained its activity. Additionally, the moisture content of the scCO₂-treated spelt flour was reduced by 5%, and the fat content was reduced by 58%, while the quality of scCO₂-treated flour was maintained. In this regard, the sustainable scCO₂ process could be a valuable tool for controlling the enzymatic activity of spelt flour since the use of scCO₂ technology has a positive effect on the quality of flour, which was verified by the baking performance of spelt flour with the baked spelt bread as an indicator of quality.

Application of sonodynamic technology and sonosensitizers in food sterilization: a review of developments, trends and challenges

Food safety and food waste have always been hot topics of discussion in recent years. However, the infection of human pathogenic bacteria and the waste of food resources caused by microbial-contaminated food remains common. Although traditional sterilization technology has been very mature, it causes changes in food flavor and excessive energy consumption to a certain extent. Moreover, the widespread bacterial resistance has also sounded a warning for researchers and finding a new alternative to antibiotics is urgently needed. The application of sonodynamic sterilization technology in medical treatment has aroused the interest of researchers. It provides ideas for new food sterilization technology. As a new non-thermal sterilization technology, sonodynamic sterilization technology has strong penetration, safety, less residue and by-products, and will less change the quality of the food itself. Therefore, sonodynamic sterilization technology has great potential applied in food sterilization technology. This review describes the concept of sonodynamic sterilization technology, the sterilization mechanism of sonodynamic sterilization and the inactivation mechanism of various pathogens, the classification and application of sonosensitizers, and the ultrasonic technology in sonodynamic sterilization in the application over the recent years. It provides a scientific reference for the application of sonodynamic sterilization technology in the field of food sterilization.

Advanced Treatment of Palm Oil Mill Effluent Using Thermally Activated Persulfate Oxidation

Advanced treatment of biologically processed palm oil mill effluent (BIOTPOME), which possesses a potential danger to the water sources is required to meet the Malaysian discharge standard, as BIOTPOME contains high level of chemical oxygen demand (COD), suspended solids and oil and grease even after going through conventional treatment process. The significant but insufficient treatment efficiency of ponding system in Malaysia urged an alternative method to treat the recalcitrant organic compounds. Thus, post-treatment of BIOTPOME using oxidation by thermally activated persulfate process was proposed to solve this issue. In order to maximize the removal of COD and color, the central composite design (CCD) module of the response surface approach was used to optimize the interactions of the process variables temperature, S2O82−/COD ratio, and reaction time. In order to identify the significant terms of interacting process factors, CCD performed a batch study from which statistical models of responses were created. All models were confirmed by analysis of variance (ANOVA) showing significances with Prob > F less than 0.1. The optimal performance was obtained at the temperature of 67.4 °C, S2O82−/COD ratio of 9.8 and reaction time of 120 min, rendering COD removal of 85.65% and color removal of 85.74%. The total cost for the treatment process was RM0.94 per liter.

Supercritical CO2 Extract from Microalga Tetradesmus obliquus: The Effect of High-Pressure Pre-Treatment

High-pressure pre-treatment followed by supercritical carbon dioxide (ScCO₂) extraction (300 bar, 40 °C) was applied for the attainment of the lipophilic fraction of microalga Tetradesmus obliquus. The chemical profile of supercritical extracts of T. obliquus was analyzed by ultra-high-performance liquid chromatography-high-resolution mass spectrometry with electrospray ionization (UHPLC-ESI-HRMS). Moreover, the impact of ScCO₂ on the microbiological and metal profile of the biomass was monitored. The application of the pre-treatment increased the extraction yield approximately three-fold compared to the control. In the obtained extracts (control and pre-treated extracts), the identified components belonged to triacylglyceroles, fatty acid derivatives, diacylglycerophosphocholines and diacylglycerophosphoserines, pigments, terpenes, and steroids. Triacylglycerols (65%) were the most dominant group of compounds in the control extract. The pre-treatment decreased the percentage of triacylglycerols to 2%, while the abundance of fatty acid derivatives was significantly increased (82%). In addition, the pre-treatment led to an increase in the percentages of carotenoids, terpenoids, and steroids. Furthermore, it was determined that ScCO₂ extraction reduced the number of microorganisms in the biomass. Considering its microbiological and metal profiles, the biomass after ScCO₂ can potentially be used as a safe and important source of organic compounds.

Biosorption of Cr(VI) Using Cellulose Nanocrystals Isolated from the Waterless Pulping of Waste Cotton Cloths with Supercritical CO2: Isothermal, Kinetics, and Thermodynamics Studies

In the present study, supercritical carbon dioxide (scCO₂) was utilized as a waterless pulping for the isolation of cellulose nanocrystals (CNCs) from waste cotton cloths (WCCs). The isolation of CNCs from the scCO₂-treated WCCs’ fiber was carried out using sulphuric acid hydrolysis. The morphological and physicochemical properties analyses showed that the CNCs isolated from the WCCs had a rod-like structure, porous surface, were crystalline, and had a length of 100.03 ± 1.15 nm and a width of 7.92 ± 0.53 nm. Moreover, CNCs isolated from WCCs had a large specific surface area and a negative surface area with uniform nano-size particles. The CNCs isolated from WCCs were utilized as an adsorbent for the hexavalent chromium [Cr(VI)] removal from aqueous solution with varying parameters, such as treatment time, adsorbent doses, pH, and temperature. It was found that the CNCs isolated from the WCCs were a bio-sorbent for the Cr(VI) removal. The maximum Cr(VI) removal was determined to be 96.97% at pH 2, 1.5 g/L of adsorbent doses, the temperature of 60 °C, and the treatment time of 30 min. The adsorption behavior of CNCs for Cr(VI) removal was determined using isothermal, kinetics, and thermodynamics properties analyses. The findings of the present study revealed that CNCs isolated from the WCCs could be utilized as a bio-sorbent for Cr(VI) removal.

Influence of the Degumming Process Parameters on the Formation of Glyceryl Esters and 3-MCPDE in Refined Palm Oil: Optimization and Palm Oil Quality Analyses

The presence of glyceryl esters (GE) and 3-monochloropropane-1,2-diol esters (3-MCPDE) in refined, bleached, and deodorized (RBD) palm oil is severely concerning to the palm oil consumer. In the present study, the influence of the phosphoric acid degumming process on the formation of GE and 3-MCDE and in the RBD palm oil was determined with varying the acid dose (0.03-0.06 wt%), temperature (70-100 °C), and reaction time (15-45 min). The experimental conditions of the acid degumming process were designed following the central composite design of experiments, and they were optimized using Response Surface Methodology (RSM) based on the minimal formation of GE and 3-MCDE in the RBD palm oil. The optimal experimental conditions of the acid degumming process were a reaction time of 30 min, phosphoric acid concentration of 0.06 wt%, and temperature of 90 °C. Under these experimental conditions, the minimal GE and 3-MCDE formation in RBD palm oil were determined to be 0.61 mg/kg and 0.59 mg/kg; respectively. Several analytical methods were employed to determine RBD palm oil quality, including color, phosphorus, free fatty acids (FFAs), peroxide values, and fatty acid properties. It was found that the phosphoric acid degumming of CPO effectively removed the phosphorus and hydroperoxide content without conceding the quality of palm oil.

Influence of Fresh Palm Fruit Sterilization in the Production of Carotenoid-Rich Virgin Palm Oil

Palm oil is known to be rich in carotenoids and other phytonutrients. However, the carotenoids and phytonutrients degrade due to high heat sterilization of oil palm fruits. The present study was conducted to produce carotenoid-rich virgin palm oil (VPO) using cold-press extraction. Herein, the influence of sterilization of oil palm fresh fruits in the production of cold-pressed VPO was determined with varying sterilization temperatures, times, and amounts of palm fruits in sterilization. The experimental sterilization conditions were optimized using response surface methodology (RSM) based on the maximum VPO yield and minimum FFAs in cold-pressed VPO. The optimal sterilization experimental conditions of oil palm fruits were determined to be a sterilization temperature of 62 °C, a time of 90 min, and an amount of oil palm fruits of 8 kg. Under these experimental conditions, the maximum cold-pressed VPO yield and the minimal content of free fatty acids (FFAs) obtained were 27.94 wt.% and 1.32 wt.%, respectively. Several analytic methods were employed to determine cold-pressed VPO quality and fatty acids compositions and compared with the crude palm oil. It was found that cold-pressed VPO contains higher carotenoids (708 mg/g) and unsaturated fatty acids compared with the carotenoid (343 mg/g) and fatty acid compositions in CPO. The findings of the present study reveal that the sterilization temperature potentially influences the carotenoid and nutrient contents in VPO; therefore, the optimization of the sterilization conditions is crucial to producing carotenoid- and phytonutrient-rich VPO.

Exogenous ethylene application on postharvest oil palm fruit bunches improves crude palm oil quality

Quality and food safety are of paramount importance to the palm oil industry. In this work, we investigated the practicability of ethylene gas exogenous application on post-harvested oil palm fruit bunches to improve the crude palm oil (CPO) quality. The bunches were first exposed to ethylene gas for 24 hr to induce abscission of palm fruits from bunches. The detached fruits were then subjected to heat treatment, mechanical extraction, clarification and drying to produce CPO. Critical quality parameters of CPO produced, that is free fatty acid, deterioration of the bleachability index and triacylglycerol showed improvement with ethylene gas treatment. Contaminant content that is phosphorus, chloride, iron, and copper also showed a reduction in the CPO derived from ethylene-treated bunches. These findings corresponded with low levels of contaminants such as 3-monochloropropane-1,2-diol esters and glycidyl esters in refined oil. The implementation strategy and practicability of this method is herein proposed and discussed. Ethylene application not only improves the CPO quality, but could potentially enhance the process sustainability of palm oil mills.

Palm oil supply chain factors impacting chlorinated precursors of 3-MCPD esters

Chlorinated compounds such as sphingolipid-based organochlorine compounds are precursors for the formation of 3-monochlororopanediol (3-MCPD) esters in palm oil. This study evaluates the effects of several factors within the palm oil supply chain on the levels of sphingolipid-based organochlorine, which in turn may influence the formation of 3-MCPD esters during refining. These factors include application of inorganic chlorinated fertiliser in the oil palm plantation, bruising and degradation of oil palm fruits after harvest, recycling of steriliser condensate as water for dilution of crude oil during oil palm milling, water washing of palm oil and different refining conditions. It was observed that bruised and degraded oil palm fruits showed higher content of sphingolipid-based organochlorine than control. In addition, recycling steriliser condensate during milling resulted in elevated content of sphingolipid-based organochlorine in palm oil. However, the content of sphingolipid-based organochlorine compounds was reduced by neutralisation, degumming and bleaching steps during refining. Although water washing of crude palm oils (CPO) prior to refining did not reduce the content of sphingolipid-based organochlorine, it did reduce the formation of 3-MCPD esters through the removal of water-soluble chlorinated compounds. It was found that the use of inorganic chlorinated fertiliser in plantations did not increase the content of chlorinated compounds in oil palm fruits and extracted oil, and hence chlorinated fertiliser does not seem to play a role in the formation of 3-MCPD esters in palm oil. Overall, this study concluded that lack of freshness and damage to the fruits during transport to mills, combined with water and oil recycling in mills are the major contributors of chlorinated precursor for 3-MCPD esters formation in palm oil.

Combination of supercritical CO2 and high-power ultrasound for the inactivation of fungal and bacterial spores in lipid emulsions

For the first time, this study addresses the intensification of supercritical carbon dioxide (SC-CO2) treatments using high-power ultrasound (HPU) for the inactivation of fungal (Aspergillus niger) and bacterial (Clostridium butyricum) spores in oil-in-water emulsions. The inactivation kinetics were analyzed at different pressures (100, 350 and 550 bar) and temperatures (50, 60, 70, 80, 85 °C), depending on the microorganism, and compared to the conventional thermal treatment. The inactivation kinetics were satisfactorily described using the Weibull model. Experimental results showed that SC-CO2 enhanced the inactivation level of both spores when compared to thermal treatments. Bacterial spores (C.butyricum) were found to be more resistant to SC-CO2 + HPU, than fungal (A.niger) ones, as also observed in the thermal and SC-CO2 treatments. The application of HPU intensified the SC-CO2 inactivation of C.butyricum spores, e.g. shortening the total inactivation time from 10 to 3 min at 85 °C. However, HPU did not affect the SC-CO2 inactivation of A.niger spores. The study into the effect of a combined SC-CO2 + HPU treatment has to be necessarily extended to other fungal and bacterial spores, and future studies should elucidate the impact of HPU application on the emulsion's stability.

Treatment of Palm Oil Refinery Effluent Using Tannin as a Polymeric Coagulant: Isotherm, Kinetics, and Thermodynamics Analyses

The refining of the crude palm oil (CPO) generates the palm oil refinery effluent (PORE). The presence of high contents of biochemical oxygen demand (BOD), chemical oxygen demand (COD), turbidity, and suspended solids (SS) in PORE encourages the determination of an effective treatment process to minimize the environmental pollution and preserve aquatic life. In the present study, a biodegradable natural polymer, namely tannin, was utilized as a coagulant to treat PORE. The coagulation experiment was conducted using a jar test apparatus. The tannin coagulation efficiency was evaluated based on the BOD, COD, turbidity, and SS removal from PORE by varying the tannin dose (50-300 mg/L), pH (pH 4-10), treatment time (15-90 min), and sedimentation time (15-90 min). It was found that the maximum removal of BOD, COD, turbidity, and SS was 97.62%, 88.89%, 93.01%, and 90.21%, respectively, at pH 6, a tannin dose of 200 mg/L, 60 min of coagulation time, and 60 min of sedimentation time. Analyses of isotherm models revealed that the Freundlich isotherm model was well fitted with the coagulation study. Kinetics studies show that the pseudo-second-order kinetics model was the well-fitted kinetics model for the BOD, COD, turbidity, and SS removal from PORE using tannin as a polymeric coagulant. The determination of thermodynamics parameters analyses revealed that BOD, COD, turbidity, and SS removal from PORE was spontaneous, exothermic, and chemical in nature. The finding of the present study shows that tannin as a natural polymeric coagulant would be utilized in PORE treatment to avoid toxic sludge generation.

The role of silica-containing agro-industrial waste as reinforcement on physicochemical and thermal properties of polymer composites

This study was conducted to determine the influence of the oil palm boiler ash (OPBA) reinforcement on the microstructural, physical, mechanical and thermal properties of epoxy polymer composites. The chemical composition analysis of OPBA revealed that it contains about 55 wt.% of SiO₂ along with other metallic oxides and elements. The surface morphology of OPBA showed angular and irregular shapes with porous structures. The influence of OPBA as a reinforcement in epoxy composite was studied with varying filler loadings (10–50 wt.%) and different particle sizes (50–150 μm). The result showed that the incorporation of OPBA in composites has improved the physical, mechanical and thermal properties of the epoxy matrix. The highest physical and mechanical properties of fabricated composites were attained with 30 wt.% loading and size of 50 μm. Also, thermal stability and the percentage of char residue of the composite increased with increasing filler loading. Furthermore, the contact angle of OPBA reinforced epoxy composites increased with the increase of filler loading. The lowest value of the contact angle was obtained at 30 wt.% of filler loading with the OPBA particle size of 50 μm. The finding of this study reveals that the OPBA has the potential to be used as reinforcement or filler as well as an alternative of silica-based inorganic fillers used in the enhancement of mechanical, physical and thermal properties of the epoxy polymer composite.

A new era for sterilization based on supercritical CO2 technology

The increasing complexity in morphology and composition of modern biomedical materials (e.g., soft and hard biological tissues, synthetic and natural-based scaffolds, technical textiles) and the high sensitivity to the processing environment requires the development of innovative but benign technologies for processing and treatment. This scenario is particularly applicable where current conventional techniques (steam/dry heat, ethylene oxide, and gamma irradiation) may not be able to preserve the functionality and integrity of the treated material. Sterilization using supercritical carbon dioxide emerges as a green and sustainable technology able to reach the sterility levels required by regulation without altering the original properties of even highly sensitive materials. In this review article, an updated survey of experimental protocols based on supercritical sterilization and of the efficacy results sorted by microbial strains and treated materials was carried out. The application of the supercritical sterilization process in materials used for biomedical, pharmaceutical, and food applications is assessed. The opportunity of supercritical sterilization of not only replace the above mentioned conventional techniques, but also of reach unmet needs for sterilization in highly sensitive materials (e.g., single-use medical devices, the next-generation biomaterials, and medical devices and graft tissues) is herein unveiled.

Some Advances in Supercritical Fluid Extraction for Fuels, Bio-Materials and Purification

Supercritical fluids are used for the extraction of desired ingredients from natural materials, but also for the removal of undesired and harmful ingredients. In this paper, the pertinent physical and chemical properties of supercritical water, methanol, ethanol, carbon dioxide, and their mixtures are provided. The methodologies used with supercritical fluid extraction are briefly dealt with. Advances in the application of supercritical extraction to fuels, the gaining of antioxidants and other useful items from biomass, the removal of undesired ingredients or contaminants, and the preparation of nanosized particles of drugs are described.