Oil composition,mineral nutrient and fatty acid distribution in the lipid classes of underutilized oils of Trilepisium madagascariense and Antiaris africana from Nigeria

Trilepisium madagascariense (TM) and Antiaris africana (AA) are two underutilized plants from Nigeria. They have been subjected to standard analytical techniques in order to evaluate the proximate composition, physico-chemical properties, mineral nutrient, fatty acid composition and distribution in the lipid classes of the seeds and seed oils. The carbohydrate composition of these seeds are high; TM is 62.73 ± 0.30% and AA is 53.97 ± 0.50%. Iodine value of TM was found to be 46.10 ± 0.70 mg iodine/g while that of AA was 88.24 ± 0.50 mg iodine/g. The mineral composition of the seeds and the oils varied with K having the highest concentration in the seed and Na the highest concentration in the oils. Linoleic acid is the dominant fatty acid in the oil of AA with the highest composition in the neutral lipids while palmitic acid is the dominant fatty acid in oil of TM. Vitamin E, Gamma-Sitosterol, α and β-Amyrin, Lupeol, Stigmast-4-en-3-one, and hydrocarbons were isolated from these oils. The results of the proximate, mineral nutrient compositions, chemical characterization and fatty acid distribution of these seeds and seed oils shows their possibility as potential resources.     

Evolution of potential and free furfural compounds in milk-based infant formula during storage

HPLC-DAD was used to monitor the evolution of potential and free furfural compounds (5-hydroxymethyl-2-furaldehyde, HMF; 2-furaldehyde, F; 2-furyl methyl ketone, FMC; and 5-methyl-2-furaldehyde, MF) over the shelf life of two types of infant powder formula: one supplemented with long-chain polyunsaturated fatty acids (LC-PUFA) in the form of microencapsulated fish oil (MFO), the other not supplemented with LC-PUFA. Following production, the formulae were stored at 25 and 37 °C. The initial furfural content in the supplemented formula was as follows: potential HMF (485.88 μg/100 g), potential F (167.13 μg/100 g), and free HMF (58.23 μg/100 g), while free F was not detected. In the unsupplemented formula, the following values were recorded: potential HMF (515.85 μg/100 g), potential F (170.29 μg/100 g), free HMF (84.92 μg/100 g), and free F (1.19 μg/100 g). In general, increased furfural content was observed during storage, an increase more pronounced in formula stored at 37 °C. Hardly any differences in furfural evolution during storage were observed between supplemented and unsupplemented infant formulae. The results suggest that the uses of MFO material for supplement formula not affected furfural formation. Neither FMC nor MF was formed in the formulae studied.     

Mitigation of acrylamide and hydroxymethyl furfural in instant coffee by yeast fermentation

Acrylamide being known as carcinogenic and hydroxymethyl furfural (HMF) being known as cytotoxic compounds are heat induced process contaminants found in instant coffee. Today's instant coffee production method involves roasting of coffee beans, grinding, flavor and aroma separation, extraction, concentration, and drying steps. During roasting, acrylamide and HMF are formed in varying amounts depending upon the degree of heat treatment as a result of the Maillard reaction. This study was conducted in order to reduce the concentrations of acrylamide and HMF in instant coffee. Instant coffee (20%, w/v) was mixed with sucrose (0–10, w/v) and baker's yeast (Saccharomyces cerevisiae, 1–2%, w/v) in a tightly closed glass vessel. The mixture was fermented at 30 °C for 48 h. The kinetics of acrylamide and HMF degradation was investigated. HMF and acrylamide contents were reduced exponentially at varying rates, depending upon fermentation medium and time. After 24 h, HMF concentration was decreased by 61.2%, 75.7%, 93.6% and 99.2% in the fermentation media containing none, 1%, 5%, and 10% of sucrose, respectively. After 48 h, acrylamide concentration was decreased by about 70%. These results revealed that yeast fermentation is promising for the mitigation of HMF and acrylamide in instant coffee.     

Oil content and fatty acid composition of some underutilized legumes from Nigeria

Three underutilized legumes from Nigeria, Brachystegia eurycoma, Tamarindus indica and Mucuna flagellipes, have been subjected to standard analytical techniques in order to evaluate proximate composition, physicochemical properties and contents of nutritional valuable elements and fatty acids of the seeds and oils. The proximate analysis indicated that the oil content was 5.87 ± 0.30, 7.20 ± 0.45 and 3.77 ± 0.21 g/100 g for B. eurycoma, T. indica and M. flagellipes, respectively. The seeds are rich in protein and carbohydrate, the protein content ranging from 11.82 ± 0.25 g/100 g–24.94 ± 0.18 g/100 g dry matter. These compare favourably with high protein animal sources like oyster, beef, pork and marine fishes. The iodine value of two of the oils place them in the non-drying group of oils, while the composition of all the oils compare well with those of rape seed, sesame, sunflower and groundnut seed oils. This suggests their use as edible oils.Analyses of the oils for fatty acids indicate that the oils contain linoleic acid which is one of the three essential fatty acids. The dominant fatty acids however are linoleic, palmitic, oleic and stearic acids with oleic acid having the highest percentage 24.13–31.50%. Eight nutritional valuable minerals were determined in the seed flours. The seeds are rich in potassium 52.1 mg/100 g–131 mg/100 g. They also contain significant concentration of iron 4.55 mg/100 g–8.20 mg/100 g.     

Factors affecting the rheological properties of a structured cellular solid used as a fat mimetic

The effects of water content, monoglyceride chain length and concentration, oil type, and the addition of oil-phase and water-phase additives on the elastic modulus and yield stress of a structured oil in water were evaluated. The goal was to increase the elastic modulus of the original emulsion from 8.42 × 10³ ± 11.3 Pa to 1.55 × 10⁶ ± 2.1 × 10⁵ Pa, and the yield stress from 112 ± 2.31 Pa to 835 ± 227 Pa. The addition of wax at greater than 10% (w/w), the use of palm oil or the gelation of the liquid oil phase with 5–7.5% rice bran wax, the use of C-18 saturated monoglyceride at 6%(w/w), and 4% (w/w) for C-22 saturated monoglyceride molecules were effective modifications capable of improving the mechanical behavior of the emulsion so that it can be used as a zero trans and reduced saturated fat laminating shortening substitute for puff pastry products.     

HPLC-MSn identification and quantification of phenolic compounds in hazelnut kernels,oil and bagasse pellets

The paper reports the phenolic content of kernels, bagasse pellets (residue of oil pressing) and oils from five different cultivars and a mix of cultivars. Phenolic compounds were identified by high-performance liquid chromatography coupled with mass spectrometry. Two compounds, glansreginin A and glansreginin B, were detected for the first time in hazelnuts. The main polyphenolic subclass comprised of mono- and oligomeric flavan 3-ols, which accounted between 34.2 and 58.3% in hazelnut kernels and between 36.7 and 48.6% in pellets of the total phenolics detected. In hazelnut oils four compounds have been detected, their content levels ranged from 0.97 to 0.01 μg g^− 1. Total phenolic content ranged from 491.2 to 1700.4 mg GAE kg^− 1 in kernels, from 848.4 to 1148.5 mg GAE kg^− 1 in pellets and only from 0.14 to 0.25 mg GAE g^− 1 in oils. The percentage of radical scavenging activity ranged from 60.0 to 96.4% for kernels, 63.0 to 73.2% for pellets and from 17.7 to 29.9% for oil. The study provides clear evidence on high phenolic contents and similarly high antioxidant potential of hazelnut kernels and bagasse pellets. The latter could be used as ingredients in cooking and baking or even for production of plant-based pharmaceuticals.     

Effect of Moisture Content,Nut Size and Hot-Oil Roasting Time on the Whole Kernel “Out-Turn” of Cashew Nuts (Anacardium occidentale) During Shelling

The effect of moisture content (MC), nut size and roasting time (RT) on the whole kernel out-turn (WKO) of cashew nuts during shelling was investigated in this study. Cashew nuts were graded into three sizes: small (18 – 22 mm), medium (23 – 25 mm) and large nuts (26 – 35 mm). About 3 kg of nuts from each grade was conditioned with water at 25°C to five moisture levels of 8.34, 11.80, 12.57, 15.40 and 16.84% (wb). The nuts were subjected to roasting in hot cashew nut shell liquid at a temperature range between 180 and 190°C for 0.75, 1.00, 1.25, and 1.50 min. The nuts were then shelled using a hand-operated shelling machine. The results showed that pre-shelling treatment of cashew nuts enhanced WKO. The single effect of MC, roasting time (RT) or nut size distribution is not enough for estimating WKO; it is rather by an interaction of these parameters. The average WKO of raw nuts was characteristically below 50% at all combinations of MC and RT. Pre-treatment by roasting was found to improve WKO considerably. The highest values were 96.96, 99.63 and 100% for large, medium and small-sized nuts at MC*RT of 16.84%*1 min, 16.84%*1 min and 15.4%*1.5 min respectively. As RT and MC increased, WKO increased within the experimental range.     

Chemical composition and potential of some underutilized tropical biomass. I: fluted pumpkin (telfairia occidentalis)

The seeds of Telfairia occidentalis have been subjected to standard chemical analysis to evaluate their properties. Proximate analysis indicated a low moisture content (6.30 ± 0.50%). The ash content was slightly higher than the range recommended for compounding of animal feed (3.44 ± 0.06%). The carbohydrate content was low (16.5 ± 0.12%). Starch, however, constituted the dominant carbohydrate (62.5 ± 0.48), while three sugars, glucose, fructose and sucrose were detected in the seed. The crude protein in the seed was high (16.0 ± 0.03%), a value which compared favourably with high protein seeds and nuts. In all, 16 amino acids were detected in the protein. Glutamic acid showed the highest concentration (16.4 g 100 g⁻¹), while lysine showed the lowest (2.6 g 100 g⁻¹). The brown oil extracted from the seed (yield 48.6 ± 0.94) had the following physicochemical properties; acid value, 3.05 ± 0.80 g, saponification value 166 ± 1.34 mg/KOH g⁻¹, free fatty acids, 0.3 g and peroxide value 3.02 ± 0.07 mg Eq kg⁻¹. The iodine value (80.1 ± 0.10)g 100 g⁻¹ indicated a preponderance of unsaturated fatty acid. Four fatty acids were detected whilst unsaturated acids constituted 61.3 g. Triglyceride was the dominant lipid species while hydrocarbons, waxes, sterols and sterol esters and higher alcohols, were detected in the unsaponifable matter. Results of nutritionally valuable mineral elements indicated that potassium occurred at the highest concentration.     

A DSC determination of phase transitions and liquid fraction in fish oils and mixtures of triacylglycerides

The thermal phase transitions of 18 pure triacylglycerides (TAGs) and four fish oils were investigated using differential scanning calorimetry (DSC) and modulated DSC (MDSC) in the temperature range from − 150 to 80 °C. The dependence between the heat of fusions and the melting temperatures was determined for pure TAGs, and a regression equation was obtained. A liquid fraction in TAG mixtures and fish oils was determined by the partial integration of melting peaks enhanced by the regression equation. The method was considered to be beneficial for fish oils, because several pure TAGs did not show crystallization. These “unfreezable” TAGs were composited by polyunsaturated fatty acids with three or more double bonds. They showed a glass transition in the temperature range between − 113.9 and − 105.6 °C. The fish oils melted in the range between − 92.6 and 23 °C. The heat of melting was measured to be between 31.5 and 41.8 J g^− 1. The oils had a significant share of liquid fraction (between 40.0 and 58.0%) at temperatures down to − 110.0 °C when the glass transition appeared.     

Transglutaminase-induced caseinate gelation for the microencapsulation of probiotic cells

A novel method for the encapsulation of probiotic cells in foodgrade casein microcapsules was developed. The process is based on a transglutaminase-catalysed gelation of casein suspensions containing probiotic cells. Water insoluble, spherical capsules with a volume-based median diameter of 165 ± 23 μm resulted from the process. Encapsulation yields of 70 ± 15% and 93 ± 22% were achieved for Lactobacillus paracasei ssp. paracasei F19 and Bifidobacterium lactis Bb12, respectively. Analysis of living cell numbers after incubation of free and encapsulated probiotics in simulated gastric juice without pepsin at pH 2.5 and pH 3.6 (37 °C, 90 min) showed a protective effect due to microencapsulation under all conditions tested. The study indicates that transglutaminase-induced caseinate gelation can be applied to the microencapsulation of probiotics. Furthermore, it could be shown that an entrapment in a dense casein matrix can protect these microorganisms from damage due to pH-levels similar to those in the human stomach.     

Rapid evaluation of frying oil degradation using ultrasonic technology

The quality of frying oils covering a wide range of oil degradation and degree of unsaturation was analyzed using ultrasonic techniques. Ultrasonic velocity and attenuation decreased with temperature, and the average velocity temperature coefficients were −3.59 and −3.51 m s⁻¹ °C⁻¹ for monounsaturated (MUO) and polyunsaturated (PUO) oils, respectively. Velocity was linearly related to viscosity, showing higher values for PUO than for MUO. Velocity was also related to the percentage of polar compounds (R² = 0.77 and 0.86 for PUO and MUO, respectively) and polymers (R² = 0.86 for PUO and MUO together). The use of velocity and viscosity in a single prediction model allowed to classify 97.5% of the samples correctly, according to the 25% polar compounds limit. Therefore, ultrasonic techniques can be used to characterize thermal degradation of oils when subjected to different frying conditions, which could be useful for frying operators or inspection services.     

Production of sophorolipids by the yeast Candida bombicola using simple and low cost fermentative media

In the present study, low cost media based on sugarcane molasses and three different oils, viz. soybean oil, sunflower oil or olive oil, were evaluated for the production of sophorolipids (SLs) from the yeast Candida bombicola in batch shake flasks. At the end of 5 days fermentation period, medium containing only molasses and soybean oil gave a maximum SLs yield of 23.25 ± 1.07 g/l compared to other media containing sugarcane molasses and either sunflower oil or olive oil. Moreover, the obtained yield was comparable to that obtained using a conventional synthetic medium having yeast extract, urea, soybean oil and glucose. Emulsification activity and stability of the produced SLs using different oils, and the effect of pH and temperature on the same were also studied. And these properties of the biosurfactant indicated good potential of the cheaply produced SLs in the pretreatment of high fats and oils containing food industry wastewaters.     

Composition and stability of olive oil following partial crystallization

Extra virgin olive oils were separated into two fractions, one being liquid at 4 °C and one solid. Each of the oils and their associated fractions underwent analysis for fatty acid composition, analysis of the total antioxidant activity and stability towards oxidation when heated at 150 °C. The solid fraction contained greater amounts of saturated fatty acids, although analysis of the fatty acids on position 2, obtained via a pancreatic lipase treatment, showed similar total levels of unsaturated fatty acids for all fractions. Analysis of the antioxidant components showed that there was a higher proportion associated with the liquid fractions. This trend, in combination with the results of the heating trials of the oils and associated fractions, indicated that the liquid fraction was not more susceptible to oxidation. Hence it is possible to fractionate olive oil to give fractions with onset of melting differing by some 10 °C without compromising stability towards oxidation.     

Gas assisted mechanical expression (GAME) as a promising technology for oil and phenolic compound recovery from tiger nuts

The aim of this work was to investigate the potential of gas assisted mechanical expression (GAME) process as an innovative technology for oil extraction and polyphenol recovery from tiger nuts. GAME process was first studied by varying the supercritical carbon dioxide (SC-CO₂) and the mechanical expression (ME) pressures (10–30 MPa), then was compared to separate processes applied alone, using either SC-CO₂ or ME. The results showed that the better conditions for GAME were found using 20 MPa for SC-CO₂ and 30 MPa for ME. Under these conditions, 50% of oil was released from tiger nuts after 10 min extraction, compared to only 10% and 20% when using SC-CO₂ and ME separately at 20 and 30 MPa pressures, respectively. In addition to the faster extraction of oil using GAME process, the obtained results showed that this oil contains higher amount of polyphenols than that obtained using either SC-CO₂ or ME. These molecules were extracted and identified using ultra performance liquid chromatography–high resolution mass spectrometry (UPLC–HRMS). Polyphenol profiles showed that GAME process led to the maximum polyphenol's recovery with 57 compounds, followed by SC-CO₂ with 48 compounds, and ME process with only 27 compounds, concurring with the trends observed for total phenolic compounds. Although non-significant differences were observed in oil recovery after applying GAME or SC-CO₂ alone, scanning electron microscopy (SEM) images revealed that GAME had a higher impact on cell structure, which can facilitate the release of important valuable compounds. All of these results pave the way towards the industrialization of GAME process as an innovative and alternative technology for enhanced oil extraction, thus replacing the conventional processes.Industrial relevanceThe increasing need in application of more efficient extraction processes in full correspondence with green extraction concept has led to deeper interest in new non-conventional methods that can reduce the extraction time, process temperature and consumption of toxic solvents (i.e. hexane). For instance, gas assisted mechanical expression (GAME) technology may constitute a useful tool for food industry as it allows to improve oil recovery and the amount of bioactive compounds (polyphenols) from tiger nuts, compared to supercritical fluid extraction and conventional methodologies (mechanical expression and hexane extraction) thus avoiding the use of toxic solvents.     

Quantitative evaluation of sanguinarine as an index of argemone oil adulteration in edible mustard oil by high performance thin layer chromatography

A simple analytical procedure based on HPTLC method was developed for the detection of argemone oil adulteration in edible mustard oil using sanguinarine as an index of argemone oil adulteration (measured as % adulteration). The methodology required no elaborate extraction procedure. The quantitation was achieved by densitometric scanning of the chromatogram in fluorescence/reflectance mode. Dihydrosanguinarine concentration was determined after its conversion to sanguinarine by UV (366 nm) irradiation, for a period of 15 min. The limit of detection (LOD) of sanguinarine in argemone oil was estimated as 1 ng per 6 mm band with a signal-to-noise ratio of 3:1 and limit of quantitation in the samples was estimated as 3 ng per 6 mm band with a signal-to-noise ratio of 10:1. The total content of sanguinarine (sanguinarine + dihydrosanguinarine) in argemone oil samples were in the range of 4.84–5.79 mg/ml of oil. Standard sanguinarine was spiked to edible mustard oil at two levels (50 and 100 μg/ml) and recoveries were found to be 79% and 82%, respectively. A linear regression plot (y = 40.44 (±0.014)x − 5.81 (±0.078)) was generated between the percent adulteration of argemone oil in edible mustard oil and the concentration of sanguinarine in the edible mustard oil spiked with various levels of argemone oil (1–30%). Analyzing the adulterated edible mustard oil samples collected from the area, wherein an outbreak of epidemic dropsy was reported in the recent past, validated this linear regression plot. The percent adulteration in these samples was found to be in the range of 1.22–8.77%. Food and forensic laboratories can use this method routinely in order to assess the adulteration of edible oils by argemone oil and in poisoning cases due to argemone oil toxicity.     

Acrylamide and 5-hydroxymethylfurfural formation during baking of biscuits: NaCl and temperature–time profile effects and kinetics

The present study aimed to investigate the effect of recipe and temperature–time on the formation of acrylamide and 5-hydroxymethylfurfural (HMF) during biscuit baking. Baking experiments were performed with biscuits of two different recipes, with and without NaCl, at 180 °C, 190 °C and 200 °C. Acrylamide and HMF reached highest concentrations at 200 °C for both recipes. The presence of NaCl in the biscuit formulation lowered acrylamide concentrations at 180 °C and 190 °C but not at 200 °C, and led to higher concentrations of HMF at all the tested temperatures. Sucrose hydrolysis was a key step in acrylamide and HMF formation during biscuit baking, even though a significant amount of acrylamide already had formed before the onset of sucrose hydrolysis. A lag phase was observed before sucrose hydrolysis occurred, which might depend on the melting of crystalline sucrose occurring at approximately 180 °C.A mathematical model based on the chemical reaction pathways was developed for the recipe with NaCl baked at 200 °C. The model described the chemical evolution during the last part of biscuit baking, and accurately predicted acrylamide and HMF content at the end of baking. The model showed the significant contribution of the reducing sugars to the formation of both acrylamide and HMF. The model could not be extended to the entire baking period because it was not possible to incorporate the lag phase observed before sucrose hydrolysis. The results reported in this study confirm that the kinetics of acrylamide and HMF formation in real food and dry systems may depend on the physical state of their precursors.     

Advances in batch culture fermented Coriolus versicolor medicinal mushroom for the production of antibacterial compounds

Bioactive compounds obtained from Coriolus versicolor (Trametes versicolor (L.: Fr) Lloyd, 1920.) mushrooms cultivated in a stirred-tank bioreactor were tested to determine their antimicrobial potential. Extracellular polysaccharides were isolated from the fermentation broth by ethanol precipitation. A methanol extract was prepared from mycelium. The cultivation conditions applied during the fermentation process provided for significant biomass 6.63 ± 0.31 g dry weight L^− 1 and yield of extracellular polysaccharides (EPS) (0.74 ± 0.12 g L^− 1). Microscopic analyses revealed that the mycelium grew predominately in the form of fluffy pellets. The methanol extract demonstrated very good activity against all the tested Gram-positive bacteria. Bacillus spizizeni and Staphylococcus epidermidis were the most sensitive strains (minimum inhibitory concentration (MIC) < 0.3125 mg mL^− 1). Among the Gram-negative bacteria, Yersinia enterocolitica had the lowest MIC value, 5 mg mL^− 1. Microbicidal activity of mycelia methanol extract was established in seven out of ten tested Gram-negative bacteria strains with minimum bactericidal concentration (MBC) values ranged from 20 to 40 mg mL^− 1. Enterococcus faecalis and Staphylococcus aureus showed higher sensitivity to the extracellular polysaccharides (MIC values 2.5 mg mL^− 1). FTIR analysis revealed a more complex chemical composition of the methanol extract compared to EPS, which might explain the better antibacterial activity of the methanol extract.Our results suggested that the submerged cultivation of Coriolus versicolor followed by ethanol precipitation of EPS and the methanol extraction of mycelia can be a promising process to obtain biological active compounds with significant antimicrobial activity.Industrial RelevanceMushrooms contain a large number of chemicals with potential use as antimicrobial compounds.One of the biggest challenges for providing biologically active compounds from mushrooms is short-term process standardization with a low risk for contamination. Submerged culture cultivation is the best choice for providing antimicrobial compounds from mushrooms. The submerged culture method represents an effective and energy-efficient means to produce novel antibacterial compound from mushrooms. Antibacterial activity testing revealed that methanol extract and isolated exopolysaccharides exhibited strong antibacterial activity, especially against Gram-positive bacteria.     

Phospholipids determination in vegetable oil by thin-layer chromatography and imaging densitometry

A rapid reliable method was developed to measure vegetable oil phospholipid content by thin-layer chromatography–imaging densitometry. Phospholipid samples were obtained from crude soybean oil by water degumming and then analyzed and quantified by thin-layer chromatography and imaging densitometry. Phosphatidyl choline (PC), phosphatidyl ethanolamine (PE) and phosphatidyl inositol (PI) standard curves were generated. The total phospholipid content of the oil was 1.12–1.26%, of which 27.1 ± 1.86% was PC, 22.7 ± 0.45% was PE, while PI accounted for 17.2 ± 0.85% of the total. A high correlation coefficient of 0.985 was found for reproducibility of pixel area (OD*mm) at a constant concentration of standard phospholipid. Regression analysis of the pixel area vs the phospholipid (PC, PE, and PI) weights (μg) generated R² greater than 0.983. Thin-layer chromatography–imaging densitometry proved a useful tool for rapid determination and quantification of the major phospholipids in soybean oil.     

Modelling of 5-hydroxymethylfurfural photo-degradation by UV irradiation. Influence of temperature and pH

The main aims of this study were (a) to prove that the UV irradiation of juices prevents the formation of 5-hydroxymethylfurfural (HMF), (b) to know the influence of temperature and pH on the UV photo-degradation of the HMF when it is unfortunately present in the juice (for example, after a previous thermal treatment or after a long storage period) and (c) to model this photo-degradation, proposing a reaction mechanism related to the power absorbed by the solution that depends on the HMF concentration.For these purposes a mid-pressure mercury lamp with emission wavelengths between 250 and 740 nm was used.Firstly, nectarine juice was irradiated to be sure that HMF was not synthesised. Then, aqueous solutions of 100 mg·L^− 1 HMF at pH 3, 4 and 5 were irradiated at 12, 25, 35 and 45 °C for 120 min. Aliquots were analysed to measure their HMF contents and absorption spectra.The photo-degradation data fitted well to both zero-order and pseudo-first-order kinetic models and the constant values were similar. The increases in both temperature and pH enhanced the photo-degradation, the optimal conditions inside the ranges studied being 45 °C and pH = 5, when a reduction of 60% of the initial content of HMF was reached.The spectral radiant power absorbed by the whole solution and the incident spectral radiant power reaching any depth of the reactor were evaluated taking into account the linear spherical emission model and using the Simpson integration method. Its dependence on the HMF concentration was also studied. A three stage degradation mechanism was proposed, matching both the zero-order and pseudo-first-order kinetic models previously obtained.     

Methyl ketone production from copra oil by Penicillium roqueforti spores

Bioconversion of copra oil by two strains of Penicillium roqueforti spores was studied in the presence or absence of exogenous lipase. Without exogenous lipase action, methyl ketone productivities were weak: 33 ± 1.9 to 61 ± 2.4 μmol g⁻¹ of oil, respectively, for strains 1 and 2. This formation results from the bioconversion of free fatty acids present in copra oil and appears strain-dependent. The major ketone was 2-undecanone, reflecting the high concentration of dodecanoic acid in the substrate. After lipolysis of copra oil by a Candida cylindracea lipase, a large increase of methyl ketone productivities (912 ± 13 and 1935 ± 26 μmol g⁻¹ of oil, respectively) is noticed with 2-heptanone predominating. This observation could result from the selectivity of the lipase used in the bioconversion process, or from the preferential oxidation due to spore specificity. When the reaction time was increased, the amount of methyl ketones decreased and other volatile compounds were formed..