Instant Controlled Pressure Drop (DIC) was evaluated as a texturing pre-treatment for the extraction of

Native to different Romanian areas, northern Europe, the Mediterranean region, and Central Asia, Camelina (

Furthermore, thanks to its high oil content, with about 0.40 g oil/g db (dry matter basis), which is 0.67 g oil/g ddb (dry-dry matter basis: this means a mass basis of raw material rid of water and oil), and its healthy oil properties, with up to 90% of unsaturated fatty acid, camelina seeds have seen an increased interest from different industries (Budin

Camelina seed vegetable oil is extracted by cold mechanical pressing, by solvent extraction, or by a combination of both methods. In fact, combinations of both methods are most often used for economic reasons since the pressing process leaves a significant amount of residual oil in the oilcakes and meal, which can be extracted by solvent extraction (Gunstone,

Mechanical pressing and solvent extraction are the most commonly applied industrial techniques for camelina oil recovery, although they present some drawbacks such as low yields, long extraction periods, toxicological risks, excessive solvent residues and high costs (Belayneh

DIC technology is based on thermo-hydro-mechanical processing induced by subjecting a product to a rapid transition from high-steam pressure to a vacuum, triggering an instant autovaporization of a quantity of material water, a fast cooling and a well-controlled expansion of the product. The change in the structural characteristics of the product is generally revealed through the expansion rates of the product, which depend on the operating conditions. Various studies have shown that the most influential DIC operating parameters are saturated steam pressure, which is strictly correlated with temperature, and processing time (Mounir and Allaf,

On the other hand, previous studies on numerous crops (Allaf

Therefore, the goal of this study was to enhance the oil extraction of

Camelina seeds (

Camelina moisture content was determined by the ISO 6540:2010 gravimetric method (ISO,

Study protocol of oil extraction from

To define ASE suitable conditions for camelina, preliminary tests based on the study of Kraujalis _{ASE;} seeds); ddb concerns material which excludes both water and oil contents.

DM was performed with extraction batches of 2 g of grain powder with 20 ml of n-Hexane. To assure a good contact between the phases, the entire extraction operation was conducted under magnetic stirring at 400 rpm. The extraction was carried out at ambient temperature (25 °C), in triplicate. To evaluate the extraction performance, oil yield was determined at different interval times (0, 15, 30, 45, 60, 90, 120, 150, 180, 240, 300, 360, 420, 480 and 1440 min). To measure the oil contents, the extracts were filtered with 0.2 μm PTFE filters (Sartorius Stedim Biotech GmbH/Germany), and the mixtures (hexane/oil solutions) were separated under vacuum by nitrogen flow (Liebisch Mini evaporator, Germany). The extracted oil was dried until constant weight. Oil extraction yield (Y_{DM;} seeds) was calculated as shown in

_{pressing 1}), and it was expressed as g oil/kg of dried seeds (ddb):

To measure the total residual oil contents of the meals, the ASE method was applied by using 10 g of meal powder (Y_{ASE;} meals), and the recovered oils were stored at 4 °C for further analysis. To establish the extraction kinetics of camelina pressed meals, the DM method was applied as described previously (Y_{DM;} meals).

^{-1}) triggers an autovaporization of volatile molecules which induces a cooling and texturing effect (Allaf and Allaf,

A) DIC treatment cycle: pressure evolution vs time and B) Schematic diagram of DIC equipment: (1) DIC Reactor, (2) Vacuum tank, (3) Vacuum pump, V1-V7-valves, S1 and S2- saturated steam injection, W1- cooling water.

DIC texturing pre-treatment was carried on 300 g of camelina seeds, and selected DIC processing parameters were saturated steam pressure (from 0.2 to 0.7 MPa) and treatment time (from 20 to 120 s). The DIC equipment was composed of three main elements: i) the processing vessel (1), where samples were treated; ii) the vacuum system, which consists of a vacuum tank (2) with a volume 130 times greater than the processing reactor, and an adequate vacuum pump (3) and iii) the pneumatic valve (V2) with a large diameter (more than 200 mm). To ensure an abrupt/instant connection between the vacuum tank and the processing reactor, V2 was opened in a very short time (less than 0.2 s).

To determine the impact of the DIC treatment on the oil extraction yield and quality, treated samples were submitted to both extraction methods: a) Solvent Extraction (ASE and DM) and b) Pressing Extraction. Untreated raw material was used as a control (RM), and in both cases oil yields were expressed in g oil/kg ddb.

Through previous preliminary studies, saturated steam pressure (P) and process heating time (t) were identified as the most important independent variables in the DIC treatment of camelina seeds (n=2). Then to determine the impact of these independent variables, a five-level central composite rotatable design was employed. The studied design included 2^{n}=2^{2}=4 (-1/-1; -1/+1; +1/-1 and +1/+1) factorial trials, 2*n=2*2=4 (-α/0; + α/0; 0/-α and 0/+α) star trials; and five repetitions of the central point (0,0). The total trials were 13. The value of α (axial distance) depending on the number (n) of operating parameters was calculated as

Coded and real levels of independent variables used in the experimental design

Independent Variables | Coded level |
||||
---|---|---|---|---|---|

-α | -1 | 0 | +1 | +α | |

Saturated Steam pressure (MPa) | 0.2 | 0.27 | 0.45 | 0.63 | 0.7 |

Saturated Steam Temperature (°C) | 120.2 | 129.9 | 147.9 | 160.7 | 164.9 |

Processing time (s) | 20 | 35 | 70 | 105 | 120 |

The experiments were run randomly to minimize the effects of unexpected variability in the observed responses due to extraneous factors.

To identify the significant differences of the effects between independent variables, the analysis of variance (ANOVA) was performed (p < 0.05). Moreover, a second-order polynomial function was employed to relate each response variable (Y) to the operating parameters (χ) as shown in

Where Y is the response, _{0}
_{i}
_{ii}
_{ij}
_{i} and _{j} are the independent variables of DIC,

The significance and the adequacy of the model were interpreted by estimating the lack of correspondence, R^{2} and Fisher test value (F-value). The Pareto chart was used to determine the effects that were statistically significant with a p-value of 0.05. Response surface methodology (RSM) was used to analyze the experimental design results and optimize the treatment parameters through a multi-criteria procedure. Experimental results were statistically analyzed by Statgraphics Centurion Software (MANUGISTICS Inc., Rockville, USA).

The moisture content of raw camelina seeds was 5.5 ±0.2 g H_{2}O/100 g db %. After DIC treatment, among the 13 experimental points, the results varied between 4.9 to 6.0 ±0.02 g H_{2}O/100 g db.

The averages oil yields of treated and non-treated

Oil yields from camelina seeds and pressing-meals

Run no | DIC_{1; 4; 7; 10; 13} |
DIC_{2} |
DIC_{3} |
DIC_{5} |
DIC_{6} |
DIC_{8} |
DIC_{9} |
DIC_{11} |
DIC_{12} |
RM | |
---|---|---|---|---|---|---|---|---|---|---|---|

0.45 | 0.70 | 0.45 | 0.63 | 0.63 | 0.27 | 0.27 | 0.20 | 0.45 | - | ||

70 | 70 | 120 | 105 | 35 | 35 | 105 | 70 | 20 | - | ||

_{ASE;seeds} |
588.0±6.0 | 603.0 | 610.4 | 615.9 | 570.0 | 569.4 | 571.4 | 573.9 | 575.3 | 555.50± 4.00 | |

_{2h-DM;seeds} |
451.0±1.0 | 455.8 | 442.6 | 462.8 | 453.6 | 439.9 | 439.5 | 446.5 | 441.0 | 284.80±0.05 | |

_{pressing} |
(g oil/kg ddb) | 475.0±1.0 | 484.7 | 485.5 | 490.9 | 463.3 | 449.8 | 481.7 | 472.1 | 451.8 | 444.70± 4.00 |

_{ASE;meals} |
131.8±0.2 | 133.3 | 132.4 | 133.4 | 133.0 | 131.0 | 131.2 | 130.7 | 131.7 | 110.00±0.25 | |

_{2h-DM;meals} |
113.0±4.0 | 114.1 | 113.8 | 115.8 | 114.5 | 111.4 | 112.5 | 111.9 | 113.6 | 51.60±0.27 |

Y_{ASE; seeds}: Accelerated solvent extractionoil yield faraom camelina seeds assisted by DIC

Y_{2h-DM;seeds}: Dynamic Maceration 2h oil yield from camelina seeds assisted by DIC

Y_{pressing}: Pressing extraction 1 oil yield from camelina seeds assisted by DIC

Y_{ASE;meals}: Accelerated Solvent Extraction oil yield from camelina meals assisted by DIC

Y_{2h-DM;meals}: Dynamic Maceration 2h oil yield from camelina meals assisted by DIC

Furthermore, to evaluate the impact of DIC parameters on ASE oil yield, the Analysis of Variance (ANOVA) and the response surface methodology (RSM) were applied.

Analysis of Variance (ANOVA) of the camelina oil yields from the different studied extraction methods

Source | Sum of Squares | Degree of freedom | Mean Square | F-Ratio | P-Value |
---|---|---|---|---|---|

Oil seeds extraction assisted by DIC texturing pre-treatment | |||||

1. Analysis of variance of Accelerated Solvent Extraction oil yield from camelina seeds assisted by DIC (Y_{ASE; seeds}) |
|||||

A: Pressure | 9.32118 | 1 | 9.32118 | 13.59 | |

B: Time | 11.9513 | 1 | 11.9513 | 17.43 | |

AA | 0.0843607 | 1 | 0.0843607 | 0.12 | 0.7361 |

AB | 4.84 | 1 | 4.84 | 7.06 | |

BB | 0.769668 | 1 | 0.769668 | 1.12 | 0.3246 |

Total error | 4.80019 | 7 | 0.685741 | ||

Total (corr.) | 31.7138 | 12 | |||

2. Analysis of variance of Dynamic Maceration 2 h oil yield from camelina seeds assisted by DIC (Y_{2h-DM; seeds}) |
|||||

A: Pressure | 3.14405 | 1 | 3.14405 | 22.92 | |

B: Time | 0.152975 | 1 | 0.152975 | 1.12 | 0.3260 |

AA | 0.0384822 | 1 | 0.0384822 | 0.28 | 0.6127 |

AB | 0.2304 | 1 | 0.2304 | 1.68 | 0.2361 |

BB | 1.0751 | 1 | 1.0751 | 7.84 | |

Total error | 0.960233 | 7 | 0.137176 | ||

Total (corr.) | 5.67451 | 12 | |||

3. Analysis of variance of pressing extraction oil yield of camelina seeds assisted by DIC (Y_{pressing}) |
|||||

A: Pressure | 2.05225 | 1 | 2.05225 | 38.79 | |

B: Time | 14.3538 | 1 | 14.3538 | 271.29 | |

AA | 0.092801 | 1 | 0.092801 | 1.75 | 0.2270 |

AB | 0.046225 | 1 | 0.046225 | 0.87 | 0.3811 |

BB | 0.96265 | 1 | 0.96265 | 18.19 | |

Total error | 0.370361 | 7 | 0.0529087 | ||

Total (corr.) | 17.9757 | 12 | |||

4. Analysis of variance of Accelerated Solvent Extraction oil yield from camelina meals assisted by DIC (Y_{ASE; meals}) |
|||||

A: Pressure | 0.077558 | 1 | 0.077558 | 195.65 | |

B: Time | 0.0037471 | 1 | 0.0037471 | 9.45 | |

AA | 0.00126782 | 1 | 0.00126782 | 3.20 | 0.1169 |

AB | 0.0001 | 1 | 0.0001 | 0.25 | 0.6309 |

BB | 0.00238088 | 1 | 0.00238088 | 6.01 | |

Total error | 0.00277491 | 7 | 0.000396416 | ||

Total (corr.) | 0.0874308 | 12 | |||

5. Analysis of variance of Dynamic Maceration 2 h oil yield from camelina meals assisted by DIC (Y_{2h-DM; meals}) |
|||||

A: Pressure | 0.11308 | 1 | 0.11308 | 30.21 | |

B: Time | 0.00899735 | 1 | 0.00899735 | 2.40 | 0.1650 |

AA | 0.00668517 | 1 | 0.00668517 | 1.79 | 0.2232 |

AB | 0.0001 | 1 | 0.0001 | 0.03 | 0.8748 |

BB | 0.0303029 | 1 | 0.0303029 | 8.10 | |

Total error | 0.0262023 | 7 | 0.00374318 | ||

Total (corr.) | 0.182231 | 12 |

Effect of DIC parameters on the solvent extraction yields from camelina seed powder: A) Standardized Pareto Chart of ASE _{seeds}; B) Estimated Response Surface of ASE _{seeds}; C) Standardized Pareto Chart of DM_{2hseeds} and D) Estimated Response Surface of DM_{2hseeds.} ASE: Accelerated Solvent Extraction and DM_{2h}: Dynamic Maceration 2 h.

By expressing the “P” in MPa and “t” in s, the statistical analysis allowed to obtain a regression model for the ASE oil yield (Y_{ASE seeds}), with R^{2} of 89.8%:

To optimize (maximize) the ASE oil yield of seeds, the optimal conditions for DIC treatment for this response were P =0.7 MPa and t = 120 s (638.49 g of oil/100 g dry-dry basis).

For RM, the average oil content obtained after 2, 8 and 24 h of DM were 284.8, 405.2 and 550.0 g oil/kg ddb, respectively. In the case of DIC-treated seeds, after 1, 2 and 8h of DM yields were 407.8, 462.8 and 520 g oil/kg ddb, respectively. All these results corresponded to experimental point DIC 5 (P: 0.63 MPa and t: 105 s). In the specific case of DM after 2h (DM_{2h}), DIC-treated seeds varied from 439.5 to 462.8 g oil/kg ddb. At this extraction time (2 h), in any of the selected DIC-treatment conditions, the oil yield kinetics of camelina seeds were always better than that of untreated samples.

Extraction kinetics by dynamic maceration (DM) of camelina oil from RM and DIC-treated seeds (A) and meals (B).

To evaluate the impact of DIC parameters on DM_{2h} oil yield, the ANOVA and the RSM were applied. _{2h} oil yield of camelina seeds. The results showed that under the selected domain values, the pressure (P) and the quadratic effect of the time (t^{2}) had a significant effect on the oil yield. The higher the pressure, the higher the DM_{2h} oil yield.

_{2h} oil yield (DM_{2h; seeds}), with R^{2} of 83%:

P: Saturated steam pressure in MPa

t: Thermal treatment time in s

To optimize (maximize) the DM_{2h} oil yield of seeds, the optimal conditions for DIC treatment for this response were P =0.7 MPa and t = 91 s (462.68 g of oil/100 g dry-dry basis).

The average camelina seed oil pressing yield (Y_{pressing}) from RM was 444.7 g oil/kg ddb. And in the case of DIC-treated seeds Y_{pressing} values varied from 449.8 to 490.9 g oil/kg ddb. The highest oil yield value for the DIC samples corresponded to experimental point DIC 5 (P: 0.63 MPa and t: 105 s) and the lowest to DIC 8 (P: 0.27 MPa and t: 35 s).

The ANOVA and the RSM allowed to evaluate the effect of DIC parameters on oil Y_{pressing} and the results showed that under the selected domain values, the pressure (P), time (t) and quadratic effect of this factor (t^{2}) had a significant effect on the pressing oil yield. The higher the pressure and the time, the higher the oil Y_{pressing}. _{pressing} of camelina seeds.

Effect of DIC parameters on the oil Y_{pressing} from camelina seeds: A) Standardized Pareto Chart; B) Estimated Response Surface.

_{pressing}, with R^{2} of 97%:

P: Saturated steam pressure in MPa

t: Thermal treatment time in s

To optimize (maximize) the oil Y_{pressing} of seeds, the optimal conditions for DIC treatment for this response were P =0.7 MPa and t = 120 s (493.59 g of oil/100 g dry-dry basis).

To determine the performance of pressing extraction, the residual oil yields of the meals were determined through ASE (Y_{ASE; meals}). The average oil meal content for RM was 110 g oil/kg ddb, while for DIC-treated samples, yields varied from 130.7 to 133.4 g oil/kg ddb. The highest oil yield value for DIC samples corresponded to experimental point DIC 5 (P: 0.63 MPa and t: 105 s) and the lowest to DIC 11 (P: 0.20 MPa and t: 70 s).

To evaluate the effect of DIC parameters on Y_{ASE; meals,} the ANOVA and the RSM were applied. The results showed that under the selected domain values, the pressure (P), the time (t) and the quadratic effect of this factor (t^{2}) had a significant positive effect on the pressing oil yield. The higher the pressure and the time, the higher the oil Y_{ASE; meals}. _{ASE; meals}.

Effect of DIC parameters on the oil yield solvent extraction from camelina meals: A) Standardized Pareto Chart of ASE _{meals}; B) Estimated Response Surface of ASE _{meals}; C) Standardized Pareto Chart of DM_{2hmeals} and D) Estimated Response Surface of DM_{2hmeals}
_{2h}: Dynamic Maceration 2h.

_{ASE; meals}, with R^{2} of 96.8%:

P: Saturated steam pressure in MPa

t: Thermal treatment time in s

To optimize (maximize) the oil Y_{pressing} of seeds, the optimal conditions of DIC treatment for this response were P =0.7 MPa and t = 120 s (134.15 g of oil/100 g dry-dry basis).

The average oil contents obtained after 2, 8 and 24 h of dynamic maceration of untreated camelina meals were 51.6, 63.5 and 110 g oil/kg ddb, respectively. In the case of DIC-treated meals, the best performance was shown by DIC 5 (0.63 MPa and 105 s). For this treatment, after 1, 2 and 8 h of DM, oil extraction oil yields were 91.3, 115.8 and 130 g oil/kg ddb, respectively. As it can be observed in

To evaluate the effect of DIC parameters on the oil yield of meals after 2h of DM (DM_{2h; meals}), the ANOVA and the RSM was applied. The results showed that under the selected domain values, the pressure (P) and the quadratic effect of the time (t^{2}) had a significant positive effect on the pressing oil yield. The higher the pressure and the time, the higher the DM_{2h; meals} oil yield_{s}. _{2h; meals}.

_{2h; meals}, with R^{2} of 85.6%:

P: Saturated steam pressure in MPa

t: Thermal treatment time in s

To maximize the of Y_{DM2h} of meals, the optimal conditions of DIC treatment were P =0.7 MPa and t = 120 s (121.02 g of oil/100 g dry-dry basis).

Thanks to its environmental adaptability, its satisfactory seed yields, and its multiple oil applications (i.e, biofuels, oleochemical compounds, animal feed, and food applications),

Then, to make the extraction of camelina oil more affordable, it is therefore important to redefine industrial methods that allow for recovering the largest amount of this oil in the shortest time. In this study, DIC texturing pre-treatment was applied to camelina seeds before mechanical pressing and solvent extraction, and the results showed that this technology systematically enhanced the oil extraction (

Camelina oil solvent extraction was studied through ASE and DM, the first one aimed to determine the total oil content of seeds and meals, and the second one to study the different transfer mechanisms during oil solvent extraction. In the case of ASE of seed oil, DIC treatment allowed to extract 10.8% (615.9 g oil/kg ddb) more than RM samples, which means that through ASE it was not feasible to obtain the total oil amount from the seeds. In fact, DIC treatment allowed the seeds to attain higher porosity which triggered the rupture of the oil-containing glands. Moreover, in

In the specific case of 2h of DM of seeds, DIC 5 presented 1.6 times (462.8 g oil/kg ddb) better oil yield than RM (284.8 g oil/kg ddb); which meant that thanks to the DIC treatment more than 80% of the total RM seed oil (555.5 g oil/kg ddb) could be obtained after 2 h of DM extraction. Furthermore, in both cases, ASE and DM, it was observed that the higher the pressure of the DIC treatment, the higher the improvement in the seed oil yield; the optimum experimental pressure value was 0.63 MPa.

Due to the fact that conventional solvent extraction methods represent 80% of the total processing time, 90% of the required energy, and more than 99% of the solvent used for the whole analysis procedure, pressing extraction has become an interesting solvent-free extraction technique to study and to ameliorate (Chemat

Though pressing extraction allowed for obtaining good oil yields, at best there was around 20% of seed oil that remained in meals. For this reason, in order to attain total oil recovery, industries apply a second solvent extraction step (Uitterhaegen and Evon,

When comparing the performance of the different studied extraction methods, it can be concluded that by coupling DIC treatment (P: 0.63 MPa and t: 105 s) to pressing extraction followed by the DM of meals for 2 h it was possible to reach 606.7 g oil/kg ddb of oil yield, which meant that thanks to the DIC treatment it was possible to obtain 9.21% more than the initial total oil content recovered by ASE of camelina RM seeds (555.5 oil/kg ddb of oil yield). Moreover, by comparing these results to RM oil yield after pressing coupled to DM for 2 h (496.3 g oil/kg ddb), we could highlight an improvement of 22% in the final oil yield as a result of the DIC pre-treatment.

DIC is a convenient texturing pre-treatment to increase the oil yield from seeds, to reduce the oil extraction time, to ensure the final oil quality, to valorized pressing meals, and to increase the industrial processing capacities. Moreover, one of the main advantages of the DIC process is its ease of use at industrial level. In fact, the obtained optimal laboratory parameters could be scaled up without any problem. DIC reactors are currently operating at laboratory, pilot, and industrial scales. Nowadays, different DIC reactors are operating worldwide, e.g., in France, Spain, Italy, Mexico, Malaysia, and China.

This study was supported by Mrs. Nathalie Horn from sanCtum méditerranée (Les-Combes, 30250 JUNAS; France), which provided the camelina seeds. Additional support and laboratory facilities were made available by Abcar DIC Process (La Rochelle, France). It provided the DIC unit, and the engineering know-how.

_{2}extraction of