Journal on Processing and Energy in Agriculture 17 (2013) 4 141

Biblid: 1821-4487 (2013) 17; 4; p 141-145 Original Scientific Paper UDK: 582.681.71 Originalni naučni rad

SQUEEZING ENERGY REQUIREMENT FOR PUMPKIN (Cucurbita pepo) KERNEL DEFORMATION

POTREBNA ENERGIJA GNJEČENJA ZA DEFORMACIJU SEMENA BUNDEVE (Cucurbita pepo)

Ljiljana BABIĆ, Milivoj RADOJČIN, Mirko BABIĆ, Ivan PAVKOV, Jan TURAN University of Novi Sad, Faculty of Agriculture, Тrg Dositeja Obradovića 8, 2100 Novi Sad, Serbia

e-mail: ljbab@polj.uns.ac.rs

ABSTRACT

Pumpkin seed and pulp has been used because of edible and medicinal values from ancient times as a source of quality oil and protein. Oil is consisting of saturated and unsaturated fatty acids. The mayor kernel composition of saturated fatty acids is palmitic and stearic acid (19.3% of the total) the rest of 80.7% are unsaturated fatty acids like oleic (C18:1), linoleic (C18:2) linolenic (C18:3), palmitic and gadoleic acids (Gohari Ardabili et al, 2011). The production of pumpkin crude oil is done by the help of equipment which squeeze the seeds by pressing using a screw press, actually this is the perform of external force. The slow loading compression test was done in order to gather information about intensity of force which raptures the single kernel of Gleisdorf ex-press F1. The tests were conducted so that it was possible to identify the influence of seed moisture content and loading rates onto hybrid compressive behaviour. The range of kernel moisture content were 6.0%, 19.8%, 24.0% and 30.5%, and loading rates were 10 mm/min; 30 mm/min and 50 mm/min. The curve of rapture force versus kernel moisture content, express the decreasing tendency of force for loading rate of 10 and 50 mm/min as the moisture content increasing. Maximum value of force (491.6 N) was recorded an low moisture content (6.0% w.b.). The rapture forces had highest values of 493.51 N (loading rate 50 mm/min) and 488.37 N (load-ing rate 30 mm/min) when moisture content was 19.8% w.b. The values of single kernel deformation were recorded at same moisture content for loading rate of 30 mm/min and 50 mm/min. The highest values of squeezing forces for tested range of kernel moisture content were observed during loading range of 10 mm/min. Specially, at kernel moisture content of 19.8% this force was 2.9 times larger compare to loading rate of 30 mm/min, or 1.7 times compare to loading rate of 50 mm/min.

Key words: pumpkin kernel, compression behaviour, moisture content, loading rate.

REZIME Seme bundeve kao i pulpa se koriste još od davnina od strane ljudi zbog njihovih jestivih i medicinskih svojstava. Ulje koje se do-

bija iz semena se satoji iz zasićenih i nezasićenih masnih kiselina. Najvažnije nezasićene masne kiseline čine palmolinska i stearinska kiselina (19,3%), a ostatak od 80,7% sačinjavaju oleinska (C18:1), oleinska (C18:2) linolinska (C18:3 i C18:3) i gadolinka (Gohari Ardabili et al, 2011). Ceđenje sirovog ulja bundeve se uglavnom radi pomoću presa koje gnječe seme, što znači da je u pitanju pri-mena neka spoljne sile. Ta spoljna sila je sila razaranja semena prilikom pritisnog testa. Zbog toga je obavljen planski eksperiment naprezanja semena jednog hibrida bundeve na pritisak, kako bi se došlo do rezultata o njihovim intenzitetima. Materijal je bilo seme F1 hibrida Gleisdorf express (Saatzucht Gleisdorf GmbH, Austrija), proizvedeno u Institutu za ratarstvo i povrtarstvo, Novi Sad. Testovi su opbavljeni tako da je beležena sila razaranja ovog semena pri četiri vrednosti vlažnosti zrna i pri tri vrednosti brzine kretanja pokretne glave instrumenta. Vrednosti vlažnosti semena su bile 6,0%, 19,8%, 24,0% i 30,5%, a brzine kretanja glave su bile 10 mm/min; 30 mm/min i 50 mm/min. Rezultati merenja su prikazani grafički, te se uočava padajući trend promene sile razaranja od vlažnosti semena samo pri kretanju glave od 10 mm/min. Maksimalna vrednost sile pri ovoj brzini kretanja glave instrumenta je 491,6 N pri brzini kretanja glave od 10 mm/min i vlažnosti zrna od 6.0%. Najveći intenzitet sile je zabeležen kao 493,51 N pri brzini kretanja od 50 mm/min i 488,37 N pri brtini kretanja od 30 mm/min, i to pri vrednosti vlažnosti uzorka od 19,8% računato u odnosu na vlažnu bazu. Pri istoj vrednosti vlažnosti semena uočene su slične vrednosti deformacije semena pri brzini kretanja glave od 30 mm/min i 50 mm/min. Poređenjem triju krivih deformacije semena i sile gnječenja pri vrednosti vlažnosti zrna od 19,8% konstatuje se da je ona kod brzine kretanja glave instrumenta od 10 mm/min bila 2,9 puta veća u poređenju sa brzinom kretanja od 30 mm/min; i 1,7 puta veća od sile koja je zabeležena pri brzini kretanja glave od 50 mm/min.

Ključne reči: bundeva, pritisno opterećenje, vlažnost zrna, brzina kretanja glave instrumenta.

INTRODUCTION Pumpkin kernel has been used because of its edible and me-

dicinal value from ancient times. This plant originated in the Americas, where it was cultivated over 7000 years ago (Milani et al, 2007; Gohari Ardabili et al, 2011). At nowadays the pro-duction of pumpkin is wide spread in continental and sub conti-nental climate all over the planet; it is a worm season crop. The production regions in Europe are Middle and South-East part of continent. Harvesting is in autumn, mostly manually and thresh-ing is done by hand in order to separate the pulp or flesh from fruits. The orange colour pulp is traditionally used in human diet within the countries of Balkan Peninsula, as the main component for rolled pie preparation, or it is oven roasted. It is also valuable source for feed mixture preparation. The industrial utilization of pulp is primarily in juice beverages prepare, like juice blends or

thick fruit and vegetable drinks. The fruits of pumpkin are cov-ered by hull or not (hull less). The fruits are washed, dried and roasted, so directly consumed as snack food. Such a many centu-ries habit of people to use pumpkin flesh and fruits as food and feed recline on its healing power, which was actually based on human tradition. The intensive studying of chemical and physi-cal properties of such a plant happened in the second half of last century, in order to confirm previous statements scientifically. It was proved that healing capabilities of pumpkin kernel is based on its chemical composition.

Pumpkin becomes an increasing significance as a source of quality edible oil and protein. According to Alfawaz (2004) the kernel contained a high percentage of crude protein (39.25%), crude oil (27.83%), total ash (4.59%), crude fibre (16.84%) and carbohydrate (11.48%). Those results confirmed the data pre-viously reported by Lazos in the year 1986. The amount of

Babić, Ljiljana et al. / Squeezing Energy Requirement for Pumpkin (Cucurbita pepo) Kernel Deformation

142 Journal on Processing and Energy in Agriculture 17 (2013) 4

whole pumpkin seed oil and other ingredients varies mostly af-fected by species and varieties. Chemical analyzes published by Gohari Ardabili and others (2011) informed about 41.59% of crude oil for one no name pumpkin variety. The amount of ker-nel crude protein ranged from 28.78% to 35.52% valued for four different pumpkin varieties (Jafari et al, 2012, Dimić, et al, 2008), as well as the crude oil (36.9%-47.78%). Oil is consisting of saturated and unsaturated fatty acids. The mayor kernel com-position of saturated fatty acids is palmitic and stearic acid, to-gether with others the total is 19.3%, the rest of 80.7% are unsa-turated fatty acids like oleic (C18:1), linoleic (C18:2) linolenic (C18:3), palmitic and gadoleic acids (Gohari Ardabili et al, 2011).

Crude oil and protein from pumpkin seed and pulp has pharmacological activities. The methanolic seeds extract have antibacterial effect against Bacillus subtilis, Staphylococcus au-reus, Escherichia coli and Klebsiella pneumonia isolates (Abd El-Aziz and Abd El-Kalek, 2011), as well as antifungal activity against Rhodotorula rubra and Candida albicans. The authors reported about antimicrobial activity of crude protein extracted from pumpkin (seeds, rinds and pulp). Prepared extract works very well against Staphyococcus aureus, Bacillus subtilis, Peni-cillium chrysogenum, Aspergillus flavus and Aspergillus niger. The seed of pumpkin has also anti-diabetic, anti-inflammation, anticancer, anti-bladder stone and antioxidant activities. The im-portant health benefit of crude oil is emphasizing in preventing the growth and reduces the size of the prostate (Caili et al, 2006). The pumpkin pulp is a good source of minerals. One hundred grams of pulp contains 212 mg of potassium, 32 mg of phosphorus, 0.48 mg of iron, 2 mg of sodium, 21 mg of magne-sium, 21 mg of calcium, 0.29 mg of zinc, 0.157 mg of manga-nese and 0.102 mg of copper (www.botanical-online.com). The carotenoids in pumpkin pulp are converted unto vitamin A in human body. The properties of carotenoids are wide; among them is ability to inhibit the development of prostate cancer and to prevent eye diseases like cataracts, in a way to disable the negative action of free radicals from degradation of the retina. Coumarins and lycopene are also anti-oxidants component in the pulp of pumpkin, which reduce cholesterol in the blood, as well as vitamin C. Vitamin C along with carotenes helps to maintains good health of the circulatory apparatus and preventing the ap-pearance of atherosclerosis or plaque deposits in the arteries. Pumpkin seeds, pumpkin seed extracts, and pumpkin seed oil have long been valued for their healing properties. The link be-tween incorporated seeds and crude oil in diet and diseases treatment have been identified and marked as food constituents who could promote the health to the mankind, therefore the pumpkin pulp and fruits are actually the functional food. Ac-cording to European Commission, Food, Agriculture & Fisheries & Biotechnology (2000) the working definition of functional food as a food with beneficially affects one or more target func-tion in the body beyond adequate nutritional effects in a way that is relevant to either an improved the state of the health and well-being and/or reduction the risk of disease. The production of pumpkin crude oil is done by the help of equipment which squeeze or press the fruits; this is an external force acting pro-duced by different press design. Therefore an objective of this study is to identify the compressive behaviour of one hulless pumpkin variety. The effect of kernel’s moisture content and compressive loading rate onto secant modulus of elasticity will be evaluated, as representative parameter of material’s response on external force perform.

MATERIAL AND METHOD An oily hulless pumpkin hybrids Gleisdorf express F1 hybrid

was tested on compression loading behaviour. The kernels were delivered from the Institute of Field and vegetable Crops, Novi

Sad, although this hybrid origin from Saatzucht Gleisdorf GmbH, Austria. The chemical composition of Gleisdorf express F1 cold pressed oil was reported by Rabrenvić and Dimić (2011). One of the conclusions indicates that the amount of squalens in this oil is high (788.3 mg/100 g). The squalens is recognized as organic material with positive benefit in some cancer treatment, therefore besides nutrition and biological va-lidity has a medical purpose. Approximately 5 kg of each pump-kin hybrids seed in plastic bags were delivered to the laboratory of Faculty of Agriculture. The kernels were manually cleaned and culled to remove all foreign matter and broken kernels. The sample was divided into four groups that were adjusted to differ-ent moisture contents for compression loading testing. The ker-nels were kept in sealed plastic bags and stored in a refrigerator at 40C. Before each compression test, the necessary amount of sample was removed from the refrigerator and allowed to equili-brate to room temperature. Moisture content was determined by the oven method and expressed as w (%) on wet basis.

The stress-strain uniaxial compression test shows the re-sponse of biomaterials to an externally applied force that de-forms the body of the material, causing changes in dimension, shape, or volume. This test provides important information about elastic and plastic behaviour. Stress is the external force F (N) upon the unit specimen cross-sectional area, Ao (m2). An impor-tant aspect of this is not necessarily the quantity of force but its application on the unit of cross-section area. For this reason, all specimens have regular shape such as a cylinder or a cube. Ac-cording to the straining action, stress is identified as compres-sive, tensile, or shearing and is referred to using the Greek letter σ. The unit of stress is (N/m2); its equation (Đorđević, 1999) is:

σ = F/Ao (1)

Biomaterials under compression change in length. The ratio between displacement δ (mm) and initial specimen length Lo (mm) is strain ε (m/m); its equation is:

ε = δ/Lo = (L-Lo)/Lo (2)

where L is final length after compressing, therefore the dis-placement is δ = (L-Lo). Strain is an internal reaction of elemen-tary biomaterial particles that is induced by an external force. The stress-strain diagram is a graphical representation of simul-taneous values of force and head displacement recorded during testing. Stress and strain are in linear correlation; the slope of the straight line portion of this correlation is called the modulus of elasticity (E or Young’s modulus).

E = σ/ε or σ = E ε (3)

The unit of Young’s modulus is (N/m2). This expression which describes the relationship between stress and deformation is well known as Hook’s law. On the test graphical presentation the point that represents the maximum stress that can be applied without resulting in permanent deformation when specimen is unloaded is marked as proportional limit, followed by elastic limit or bio yield point. The ultimate strength point represents the external force that is sufficient to cause kernel cracking or squeezing. From an engineering point of view, information about the val-

ues of yield point and ultimate strength point forces F (N) and head displacements D (mm) for those forces are interesting and relevant. For this reason, the kernel stress-strain compression tests in this study were conducted using whole kernels. In such a case, it is possible to calculate the secant modulus of elasticity, Es (N/ mm), which represents the slope of the secant drawn from the origin to bio yield point, as well as to the ultimate strength point on the force-head displacement curve (Mohsenin, 1980).

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CONCLUS

Moisture contensity on itspression test of

urbita pepo) Ke

cessing and En

orce secant moe contents and

ce of secant mdiferent kern

s follow: 53 R2=0.842475 R2=0.61558 R2=0.9886

ce of ultimate skernel moistur

rat

rapture force vasing tendency s the moisture1.6 N) was reapture forces hmm/min) and

oisture contentthe realtionshipor loading rate rgy or ultimate50 mm/min ofggestion is thatues of kernel me case of largeme difficulties

SION

ent of biomates mechnanicaf pumpkin hul

ernel Deforma

nergy in Agricu

odulus of elastidiferent loadin

modulus of elasnel moisture c

4 for loading r5 for loading r6 for loading r

strength forcesre contents andtes

versus kernel of force for le content increecorded at lowhad highest vad 488.37 N t was 19.8% wp for ultimateof 30 mm/min

e strength forcf loading ratest crude oil pro

moisture contene quantity of ros in the storage

erials have an al propertiesless seed allow

tion

ulture 17 (201

icity versus kerng rates

sticity for ultimontents and th

rate of 50 mm/rate of 30 mm/rate of 10 mm/

s secant moduld diferent loadi

moisture contloading rate ofeasing. Maxim

w moisture conalues of 493.5(loading rate

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Babić, Ljiljana et al. / Squeezing Energy Requirement for Pumpkin (Cucurbita pepo) Kernel Deformation

Journal on Processing and Energy in Agriculture 17 (2013) 4 145

values of its resistance behaviour to some external force. The tested parameters show the existing of relations between loading rates, kernel moisture contents and force onto kernel deformation.

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Received: 18.02.2013. Accepted:05.05.2013.