Viscoelastic properties and physicochemical characteristics of pressurized ostrich-meat emulsions containing gum additives

Minced-ostrich meat was blended and chopped with various proportions of gum powder in terms of carboxymethyl cellulose (CMC), locust bean gum (LBG) and xanthan gum (XAN) and other ingredients such as sodium chloride, sodium tripolyphosphate, linseed oil and ice. The mixed batters were then pressurized at 600 MPa and 50 °C for 40 min. Subsequently, their viscoelastic and physicochemical properties were assessed in terms of their dynamic oscillatory moduli, their resultant creep behavior, water-holding capacity and electrophoretic profiles. The results showed that the addition of individual gums and composite gum mixtures influenced both viscoelastic behavior and water-holding capacity of resulting pressurized ostrich-meat emulsions. The most elastic system (greatest G′ or smallest J₀ with 4.21 × 10^− 5 1/Pa) was the meat emulsion with 1% LBG added, while the least were those formed by adding 1% XAN or 0.5% XAN plus 0.5% CMC (J₀ with 10 × 10^− 5 and 20.3 × 10^− 5 1/Pa, respectively). Subsequent electrophoritic profiles and the measurement of the water-holding capacity of the materials suggested an evidence of ionic interaction between the basic ostrich-meat protein matrix and XAN or XAN plus CMC.Industrial relevanceOstrich meat emulsions containing composite gums were set by combined pressure and temperature. Subsequently, the pressurized gels were characterized by dynamic oscillatory, creep and other physicochemical measurements. In particular, the viscoelastic measuring system is a promising tool for ensuring quality of food biopolymers. Therefore, this methodology is relevant in the area of controlling quality or developing new products where difficulty exists in solubilising the samples.     

Rheology of emulsion-filled alginate microgel suspensions

Emulsion filled polysaccharide gels can be used as carrier systems of lipophilic bioactives in the food, pharmaceutical and cosmetics industry. This carrier system can exist either as bulk or discrete gel systems. In this study the rheological properties of discrete emulsion filled alginate microgel suspension was examined as a function of volume fraction (ϕ) and oil content. Fine emulsion (220 nm) was encapsulated within alginate microgels (mean size 36.2–57.8 μm) by using the impinging aerosol technique. The microgels (containing 0–77% w/w oil total solids basis) produced were estimated to have particle modulus in the range of 150–212 Pa. An increase in oil content in the microgels led to more deformable microgels due to the reduction in gel density. The deformability of microgels influenced the bulk modulus and apparent viscosity of the concentrated suspension. At the same suspension volume fraction (ϕ), suspensions with more deformable microgels exhibited a lower bulk modulus. We also showed that the Carreau and Cross models were adequate in predicting the flow behaviour of the concentrated emulsion filled microgel suspension.     

In search of confectionary fat blends stable to heat: Hydrogenated palm kernel oil stearin with sorbitan monostearate

The potential of sorbitan monostearate (SMS) addition to change the basic-crystal-structure of a confectionary fat blend (CFB) with the aim to enhance its heat resistance was investigated. The CFB used in this study was a blend of hydrogenated palm kernel oil stearin, lecithin, polyglycerol polyricinoleate (PGPR) and cocoa butter. Samples made with different proportions of SMS to CFB were prepared and the crystal structure, the melting behaviour, the crystal morphology and crystallization kinetics were studied. Heat resistance was evaluated using a temperature-variable rheological method. Powder X-ray diffraction (XRD) studies in the wide angle region (WAXS) revealed the presence of two crystalline polymorphs (α and β′) in all blends. While XRD studies in the small angle region (SAXS) revealed a shift in the CFB peak position upon addition of SMS. The presence of two polymorphic forms was confirmed by differential scanning calorimetry (DSC), while a third endotherm was evident when the amount of SMS present in the system was greater than 40%. Studies on the nucleation and crystallization kinetics showed that crystal nucleation and growth occurred in two stages: SMS appeared first followed by CFB. Iso-solid diagrams constructed from the melting profiles obtained from SFC-temperature measurements indicated monotectic solution behaviour between SMS and the CFB.The microstructure, as observed under polarized light, changed from small crystals for the CFB to needles for mixtures with 10% SMS, to spherulites for mixtures with 50% SMS, to clusters for mixtures containing between 80 and 100% SMS. Cryo-TEM showed nanoplatelet formation for the CFB and nano-blobs for SMS. The storage modulus (G′) for mixtures containing 25% SMS decreased from G′ = 1.72 10⁷ ± 4.60 10⁶ Pa at 20 °C to G′ = 3.24 10⁵ ± 2.15 10⁴ Pa at 40 °C. Thus, SMS addition to confectionery fats can provide heat resistance to the CFB.     

The protective effect of monosodium glutamate on survival of Lactobacillus rhamnosus GG and Lactobacillus rhamnosus E-97800 (E800) strains during spray-drying and storage in trehalose-containing powders

The use of trehalose as a means of preserving Lactobacillus rhamnosus GG (LGG) and L. rhamnosus E-97800 (E800) during spray-drying and the effects of incorporated monosodium glutamate (MSG) in the carrier medium on the survival rates during drying and storage were examined. E800 was more resistant to heat than LGG in 20%, w/w, trehalose; the d-values at 65 °C were 14 s and 5.1 s, respectively. An air outlet temperature of 65–70 °C was taken as optimal for the drying process, as the resultant moisture levels in trehalose containing these bacteria were 4.1% (w/w) and 3.79% (w/w) with corresponding viable counts of 3.65 × 10⁸ cfu mL^?1 and 1.80 × 10⁹ cfu mL^?1, respectively. The presence of MSG increased the final viable counts of LGG and E800 to 3.05 × 10⁹ cfu mL^?1 and 1.30 × 10⁹ cfu mL^?1, respectively. Survival of LGG and E800 remained constant at a minimum level of ～10⁸ cfu mL^?1 during storage at 25 °C in trehalose–MSG medium.     

Migration of α-tocopherol from LDPE films to corn oil and its effect on the oxidative stability

The migration of α-tocopherol (α-T) from low density polyethylene (LDPE) films, added with 20 (film A) and 40 mg g^?1 (film B) to corn oil for 12 weeks at 5, 20 and 30 °C was determined. A LDPE film added with no α-T was used as control (film C). Diffusion coefficient (D) values for the film A system were 1.4 × 10^?11, 7.1 × 10^?11 and 30.3 × 10^?11 cm² s^?1 at 5, 20 and 30 °C, respectively. Meanwhile, D values for the film B system were 1.3 × 10^?11, 9.6 × 10^?11 and 51.1 × 10^?11 cm² s^?1 at the same temperatures. The activation energy (E_a) for the diffusion of α-T was 126.5 (film A) and 105.9 kJ mol^?1 (film B). The effect of the migration of α-T on the oxidative stability of corn oil was evaluated by monitoring hexanal content by solid phase micro-extraction (SPME) and gas chromatography. The hexanal content in the oil showed that both films added with α-T resulted suitable to maintain the oxidative stability of the oil for about 16 weeks at 30 °C, compared to 12 weeks for the oil in contact with the film C.     

Effects of high intensity ultrasound and emulsifiers on crystallization behavior of coconut oil and palm olein

The objective of this research is to evaluate the crystallization behavior of coconut oil (CO) and palm olein (PO) as affected by the addition of two monoacylglycerols (MAG) emulsifiers and by the use of high intensity ultrasound (HIU). MAG with high content of palmitic, oleic, and linoleic acid (EM1) and MAG with high content of stearic acid and no unsaturated fatty acids (EM2) were used. Results show that the addition of emulsifiers did not affect crystallization kinetics of CO and similar solid fat contents (1.32 ± 0.94) (SFC) and melting enthalpies (5.90 ± 4.56) were obtained. The addition of EM1, however, significantly delayed the crystallization of PO as evidenced by a significantly lower SFC and melting enthalpy. SFC for PO was 8.56 ± 0.913 while SFC for PO + EM1 was 3.63 ± 1.38. Sonication induced the crystallization of CO samples crystallized with and without EM1 and EM2 while only induced the crystallization of PO + EM1 as measured with SFC. The induction in crystallization by HIU was also evidenced by higher enthalpy with values up to a range of 8 J/g to 11 J/g. A decrease in elasticity from 3.17 × 10⁶ to 2.52 × 10⁵ was observed in CO crystallized with emulsifiers which could be reverted by the application of HIU. Contrarily, the addition of emulsifiers increased elasticity of PO from 3.35 × 10² to 4.83 × 10⁴ and sonication did not affect these values significantly. Differences observed in elasticity values are attributed not only to the amount of solid material obtained but also to the type of microstructure of the crystalline network formed during crystallization.     

Ultrasound-assisted encapsulation of annatto seed oil: Retention and release of a bioactive compound with functional activities

This paper brings forward the encapsulation of annatto seed oil (rich in geranylgeraniol) assisted by high intensity ultrasound using gum Arabic (GA) as stabilizing agent. We studied the effects of time (min) and ultrasonication power (W) over the emulsion characteristics. After forming microparticles from the best emulsion using freeze-drying (FD) and spray-drying (SD) techniques, we evaluated particle size distribution, moisture, water activity, surface oil, entrapment efficiency, encapsulation efficiency, geranylgeraniol retention, oxidative stability and kinetic release of geranylgeraniol, a biocompound with functional activities. The combined intensification of time and ultrasonication power reduced the superficial mean diameter (D₃₂) and polydispersity (PDI) of emulsions. Drying the continuous phase of the optimized emulsion (smallest D₃₂ = 0.69 ± 0.03 μm) using FD and SD formed microparticles with different morphological characteristics, Brouckere diameter (D₄₃), particle size distribution, moisture and water activity. SD process led to microparticles with the highest oil encapsulation efficiency (85.1 ± 0.1 wt.%) as a consequence of their lowest surface oil (SO). However, GA-FD microparticles presented the highest oil entrapment efficiency (97 ± 1 wt.%). Geranylgeraniol retention (80–86 wt.%) was similar for both drying techniques. GA-FD microparticles were more stable against oxidation through accelerated test Rancimat, even though presenting higher SO. This behavior is associated with the likely phase transition on the GA-SD matrix. The difference on the kinetic release of geranylgeraniol is linked to the difference on the particles morphology and particle size distribution.     

Monitoring nisin desorption from a multi-layer polyethylene-based film coated with nisin loaded HPMC film and diffusion in agarose gel by an immunoassay (ELISA) method and a numerical modeling

Polyethylene-based films coated with nisin loaded HPMC films were put in contact with food simulants, i.e. agarose gels with 5 or 30% (w/w) fat. Nisin desorption from the multi-layer films and diffusion in agarose gels were monitored by ELISA (Enzyme Linked ImmunoSorbent Assay). The data obtained after 2 or 6 days of contact between antimicrobial films and agarose gels were employed to determine nisin mass transfer by numerical modeling following Fick's second law. The values were in the range from 0.87 × 10^? 3 m s^? 1 to 4.30 × 10^? 3 m s^? 1 and 6.5 × 10^? 11 m² s^? 1 to 3.3 × 10^? 10 m² s^? 1, for nisin apparent desorption and diffusion coefficients, respectively. The diffusion process was governed by interactions between food matrix simulant and nisin. Moreover, it was observed that the polymer in the coating did not modify plastic film initial mechanical resistance and water vapor permeability.Industrial relevanceThis paper concerns active packaging, considered as a new approach to preserve food shelf life. Active packaging is a real gain for plastic and Food industrials. The paper deals with coating as a manner to activate packaging. The impact of coating on film properties is investigated.Also, predictive models are proposed to determine antimicrobial agent desorption and diffusion during some storage conditions.     

Influence of relative humidity on carbon dioxide sorption in wheat gluten films

The influence of relative humidity (RH) on carbon dioxide sorption at 10⁵ Pa in wheat gluten films (WGF) was investigated in the range of 0–96% RH at 25 °C. The amount of water sorbed by these protein based films reached up to 60% of the dry weight at 96% RH. Carbon dioxide sorption increased with water content, ranging from 2.8 × 10⁻⁴ to 1.9 × 10⁻² mol Pa⁻¹ m⁻³ respectively at 0% and 96% RH. This behavior was tentatively explained on the grounds that sorbed water enhanced carbon dioxide accessibility to protein active sorption sites. The dependence of both the solubility and the diffusivity coefficients of CO₂ and O₂ on WGF water content explains the very good permselectivity of these films observed at high RH values (22 at 93% RH and 25 °C).     

Properties of edible sodium caseinate films and their application as food wrapping

Sodium caseinate solutions (2.5 g protein/100 g solution) containing glycerol (gly) at gly:protein ratios of 0, 0.08, 0.16, 0.24 or 0.32 w/w were dried over 48 h at 50±5% RH and 23±2 °C to form transparent flexible films of approximately 35 μm thickness. Maximum load, tensile strength and elastic modulus of films decreased and the moisture content increased significantly with increasing glycerol content. Elongation and water vapour permeability of films increased significantly only at gly:protein ratios of 0.24 and 0.32. Wrapping bread samples in the caseinate films reduced hardness during 6 h storage at ambient temperatures relative to unwrapped controls. However, the caseinate films were not as effective in this regard as synthetic polyvinyl chloride film.     

Modeling of particle size distribution of sonicated coconut milk emulsion: Effect of emulsifiers and sonication time

Coconut milk was extracted from grated coconut meat with addition of water by a hydraulic press. This milk was mixed with emulsifiers (Gum Acacia and maltodextrin) at different ratios of emulsifier to fat (4, 2.75, and 1.5) and different maltodextrin (MD) to Gum Acacia (GA) ratio (0.67, 1.085, and 1.5). The emulsion was sonicated for different time durations (0.5–3.0 min). Particle size analysis of the sonicated coconut milk emulsion revealed that the number fraction of fat globules below 2 × 10⁻⁶ m increased as the emulsifier to fat ratio increased. However, at the highest ratio of emulsifier to fat this trend reversed even at higher sonication times. Similar slump in the increasing trend of globules below 2 × 10⁻⁶ m were observed at the highest value of ratio of MD to GA (1.5) studied. Modeling of particle size distribution by Rosin–Rambler–Sperling–Bennet relation was found to be a good tool for prediction of uniformity of distribution n and statistical average globule diameter M. The n values varied between 0.981 and 1.318 where as M values lied between 2.11 × 10⁻⁶ and 4.12 × 10⁻⁶ m. Linear regression fitting of n and M values as function of ratio of emulsifier to fat, ratio of MD to GA and the sonication time resulted in a good fit with relative deviation of 3.96% and 10.77%, respectively. These linear regression equations provided a suitable model to predict the sonication time required to achieve certain degree of size reduction with a relative deviation of 2.33%.     

Comparative Studies of Ginger (Zingiber officinale) and West African Black Pepper (Piper guineense) Extracts at Different Concentrations on the Microbial Quality of Soymilk and Kunun-zaki

Extracts of two spices, namely ginger (Zingiber officinale) and black pepper (Piper guineense) were prepared in 0.4%, 1.2%, 2.4% and 3.6% concentrations. Soymilk and kunun-zaki were treated respectively with the different concentrations and stored at ambient temperature for 5 days. The microbial load and identification were determined every day of storage until samples were adjudged spoilt.On the first day, 0.4% ginger extract in soymilk and kunun-zaki had a microbial load of 7.77 × 10^6b and 5.17 × 10^6b respectively. 3.6% ginger extract in soymilk and kunun-zaki recorded 3.73 × 10^6b and 3.30 × 106 each. 0.4% black pepper extract in soymilk had 6.273 × 10^6b and recorded 4.63 × 10^6b in kunun-zaki. 3.6% black pepper extract in soymilk and kunun-zaki had a microbial load of 3.20 × 10^6d and 2.90 × 10^6c respectively. On the third day the microbial load increased for both ginger and black pepper extract. Ginger extract recorded 9.13 × 10^6b in soymilk and 5.60 × 10^6b in kunun-zaki at 0.4% concentration. Black pepper extracts recorded 7.43 × 10^6b in soymilk and 3.27 × 10^6b in kunun-zaki also at 0.4% extract. 3.6% black pepper extract recorded 4.10 × 10^6a in soymilk and 2.20 × 106c in kunun-zaki.There was linear reduction of microbial load as spice concentration increased. Black pepper recorded lower microbial load, thus having more antimicrobial activity and may be preferred to be used as natural antimicrobial preservatives to extend the shelf-life of food.     

Oats protein isolate: Thermal,rheological, surface and functional properties

Oat protein isolate (OPI) was extracted in 0.015 N NaOH and acetylated or succinylated. The thermal analysis of the isolate showed a glass transition (T_g) at 43.4 °C and ΔC_p of 0.102 J/g/°C. The positive net charge of OPI and the positive or neutral charge of the modified OPI were apparent from the free capillary zone electrophoresis (FZCE) profiles. Acetylation significantly lowered foaming and emulsifying properties of OPI, while succinylation showed the highest foaming capacity, foam stability, and emulsion stability. Acetylated OPI showed the highest surface hydrophobicity compared to the other samples, while OPI was the most soluble of all. The water holding capacity of all samples analyzed was the same except for acetylated-crosslinked (ACXL). The surface tension test confirmed that unmodified and modified OPI possessed surface activity and the equilibrium surface tensions decreased sharply with increasing protein concentration and leveled off to a constant value. The elastic modulus, G′, for the acetylated OPI suspension exhibited the highest value, while the G′ of the crosslinked (XLOPI) had the lowest. The plateau of G′, was 2961 Pa, 920 Pa, 223 Pa, 41 Pa, and 1.8 Pa for the ACOPI, ACXL, SOPI, and XL, respectively.     

Effects of flaxseed oil concentration on the performance of a soy protein isolate-based emulsion-type film

Biodegradable edible films have the potential to either replace or reduce the amount of synthetic packaging utilized by the food industry. The overall goal of this research was to investigate the effect of flax seed oil concentration (1–10%) on the mechanical, moisture barrier and swelling properties of soy protein isolate (SPI) (5.0% w/w SPI, 40% w/w glycerol) emulsion-based films. Film forming solutions showed a bimodal oil droplet distribution with peak sizes occurring at < 10 and ~ 100 μm. As the oil content increased, the size distribution shifted towards smaller droplet sizes. An equal size ratio was noted at the 5.0% oil content level. All film forming solutions were pseudoplastic in nature, where viscosity increased from 18 to 58 mPa (at 1 s^− 1) as a function of oil content (3% to 10%). Tensile strength of formed films reached a maximum at 5.35 MPa at the 5% w/w oil level, whereas tensile elongation increased from 11.3% to 22.2% with increasing oil content. Puncture strength and deformation, as well as water vapour permeability was relatively independent of the oil content. Moisture content and swelling properties of formed films were found to both decrease from 22.8% to 18.7%, and from 3114% to 1209%, respectively as the oil content was raised from 1 to 10%, and films became darker, redder and more yellow in colour as the percentage of flax seed oil increased.     

Encapsulation of Lactobacillus rhamnosus in double emulsions formulated with sweet whey as emulsifier and survival in simulated gastrointestinal conditions

Lactobacillus rhamnosus cultured in sweet whey and harvested in the late log phase was entrapped in the inner aqueous phase of a double water-in-oil-in-water emulsion using concentrated sweet whey as emulsifier. The primary and double emulsion droplets showed practically no changes in their morphology and droplet size with aging time. The viability of the entrapped L. rhamnosus in the double emulsion was compared to that of non-entrapped control cells exposed to low pH and bile salt conditions. The viability of the control cells (initial number = 6.57 ± 0.3 log cfu ml^?1) decreased significantly under low pH and bile salt conditions, and their survival was 71% and 89%, respectively. The survival of the entrapped cells (initial number = 6.74 ± 0.2 log cfu ml^?1) increased significantly under low pH and bile salt conditions, and their survival was 108% and 128%, respectively. It is concluded that the double emulsion protected L. rhamnosus against simulated gastrointestinal tract conditions.     

A risk characterization model of Salmonella Typhimurium in Irish fresh pork sausages

A second-order simulation model was built to estimate the risk of Salmonella Typhimurium associated with the consumption of Irish fresh pork sausages. To select appropriate hazard characterization models, an initial appraisal of the current dose-response models was conducted. The cooking modality of grilling was associated with a higher mean risk of infection per serving (1.399 × 10^? 6; 95% CI: 7.54 × 10^? 7–2.65 × 10^? 6) than frying (6.246 × 10^? 7, 95% CI: 2.78 × 10^? 7–1.17 × 10^? 6). When the risk was extrapolated over the consumption in a year period, the mean risk of infection increased considerably to 8.541 × 10^? 5 with an expected number of infections and illnesses of 184.3 (95% CI: 26–664) and 17 (95% CI: 2–63), respectively. Results highlighted the importance of consumer education, as scenario analysis predicted that, for the current level of Salmonella in pork sausage, decreasing the product's cold storage by approximately 8 h and cooking for an additional half minute can reduce the current risk level by ～ 50%.     

Kinetics of migration of colloidal particles in meat muscles in the absence and presence of a proteolytic enzyme to simulate non-motile bacteria penetration

In this study, migration rate and spatial distribution of colloidal particles with and without proteolytic enzymes were studied after injection in pork loin muscle cubes for 5 days at 25 °C to simulate behavior of non-motile bacteria. Samples were monitored daily by light microscopy and confocal laser scanning microscopy and particle distribution and movement analyzed by image analysis (MATLAB^®). The extent of proteolytic activity was assessed by determining the tyrosine content in muscle tissue. Results showed that particles diffused from the injection hot spot into the inner structure of the meat (1.35 ± 0.99 × 10^− 12 to 2.39 ± 2.02 × 10^− 12 m²/s). Upon addition of protease, the migration rate increased, i.e. the particle distribution became more widespread due to proteolysis of meat proteins reducing resistance to mass transfer. Results indicate that particles are able to diffuse into the densely packed fiber structure of meat muscles, which is contrary to the long held belief that such penetration may not occur in the absence of extensive proteolysis or mechanical damage of tissue.     

Physical Characterization of Wax/Oil Crystalline Networks

The objective of this research was to evaluate the physical properties of different types of wax/oil systems. Olive (OO), corn (CO), soybean (SBO), sunflower (SFO), safflower (SAFO), and canola (CAO) oils were mixed with sunflower oil wax (SFOW), paraffin wax (PW), and beeswax (BW) at different concentrations (1% to 10%). Results from this study show that the physical properties of wax/oil systems is affected not only by the concentration and type of wax used, but also by the type of oil used. In general, wax/oil systems formulated with SFOW generated crystalline networks with high enthalpies (1 to 22 J/g) and high G ′ values (2 to 6 × 10⁶ Pa) compared with the values obtained for BW and PW. SFOW crystalline networks were characterized by needle‐like crystals independently of the wax concentrations and type of oil used. BW crystalline networks, however, were characterized by different crystal morphologies (needle‐like or spherulites) depending on the wax concentration and type of oil used. PW samples were characterized by a crystalline network formed by needle‐ and platelet‐like crystals. Enthalpy values of BW and PW samples were similar (0.3 to 20 J/g), but BW samples resulted in significantly higher (P < 0.05) G ′ values in the 5% and 10% samples with values of 3.9 × 10⁶ and 6.1 × 10⁵ Pa for 10% BW and PW, respectively.     

Morphological characterization of encapsulated fish oil with β-cyclodextrin and polycaprolactone

The present study characterized the morphology of fish oil β-cyclodextrin (β-CD) complex or fish oil encapsulated with polycaprolactone (PCL) by transmission electron microscopy (TEM) observation using low or high voltage with or without phosphotungstic acid (PTA) staining. Emulsion–diffusion or self-assembly aggregation methods were used to encapsulate fish oil in PCL or β-CD. PCL spheres averaged 200 nm in diameter. However, β-CD spheres were significantly larger and dependent on host:guest mixing ratio (w:w), being approximately 300 nm and 600 nm at ratios of 10:1 and 10:10, respectively. TEM enabled the visual distinction of core and wall materials, and revealed that fish oil was encapsulated with a different structure depending on whether the self-resembling aggregation of β-CD or emulsion–diffusion method with PCL was used. Hexagonal-type β-CD aggregates were evident at a mixing ratio 10:1 between β-CD and fish oil. The hexagonal arrangement of β-CD enveloped the fish oil with a thick (100–150 nm) membrane. Incorporation of β-CD with fish oil at a 10:10 mixing ratio produced a worm-type of β-CD. It is suggested that the fish oil might be physically blended without wrapping with β-CD. For the PCL formulation, the lower voltage TEM operating condition better enabled the observation of the thin PCL layer (1–2 nm) encapsulating the fish oil. Nanosizer^® and TEM yielded comparable measurements.     

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..