Variability within intramuscular fat content of pigs as measured by gravimetry, FTIR and NMR spectroscopy

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ELSEVIER

.

Geers,a

C,” c

aLaboratory for Agricultural urlCingsResearch,KU. Leuven,“Biomedical NMR Unit, KU. Leuven & ‘SeghersHybrid, Buggenhout,Belgium (Received 16 March 1994;revised version received3 June 1994;accepted22 July 1994)

In order to determine in vivo intramuscular fat content of pigs’ biceps femoris, three methods were compared. Gravimetry and FTIR spectroscop}? after totalfat extraction from a biopsy (about 400 mg skeletal muscle tissue) ectroscopy after imaging and volume of interest

tissue.

Increasingly, consumersdeman ever, an intramuscular fat c

373

R. Geerset al. does not influence intramuscular fat content (Lundstrom, 1990), since a low correlation seemsto exist betweenboth parameters(Duniec et al., 1961; arriss et al., 1990). Therefore, pig breedersput more and more emphasison t content as a selection parameter for meat quality (Kanis 85 enier et al., 1992).This meansthe needfor a cost-effectiveand accurate method to quantify intramuscular fat in VI’VO, since repeatedmeasurements within time and s e are necessaryon the same animal intended for breeding(Glodek, 1984). wever, such a procedure is not possiblewhen samplesof about 3 g haveto be taken from the living animal as is the casefor carcass evaluation. igs havean intramuscular fat content of about 2 g per 100g fresh muscletiss very low to quantify exactly on small tissuevolumes(e.g. biopsiesof herefore, the in vivo measurementscurrently available are only for total body fat content, and being collected with the following technology. A promising method is the application of ultrasonic waves through a body section, with measurementof speed(Fursey et al., 1991),spectral characteristics aker et al., 1992) and image analysis of ultrasonic images (Liu et al.,

genetic

combination with

of this sturdywas to co

s~e~tros~o~y)and in vitro

Pig fat content variability and measurement

375

using the ISIS localization technique(Ordidge et al., 1986).These in viva N measurementswere performed in a 30cm bore (m al body weight of 25 kg), 4-7 T horizontal magnet equippedwith a specspectrometer( Karlsruhe, Germany). Proton signalsfrom the m. biceps femoris of the anaesthetized pi.gletswere acquired with a 5 cm diameter coaxial tran surfacecoil positioned horizontally over the hind leg of the piglets 1993).The result of the measurementis a number (a) representingthe proportion of (CH& protons vs protons from water presentin the definedvolume of interest as selectedby an imaging procedure. In order to transform that a-value to a quantity of fat per kg muscletissue,the following calculationwas made. Basedon gas chromatography analysisof fat extracts from nine referenceb concluded that 1 mol triglyceride was equivalent to 914 g, or 64-3 protons. The water content was found to be 0-785 f O*Ol1 1wat scleweight. This yielded a musclewater proton concentration of 87-2 f 1.22 Hence, the amount of triglyceride (g) per kg fresh muscleweight equalsa x 914 x (8792/64*3)g. Only the triglycerideswere taken into account becauseof the NMR invisibility of th brane bound phospholipids( etz et al., 1992).To check the results from spectroscopy,a biopsy was ken from five other the samebreed,sincethe original pigs piglets(m. bicepsfemoris) originating fr became too large for measurements. t was extracted from those biopsies according to Folch et al. (1957), and t ceridesand phospholipidswere determined accordingto De Schrijver & Vermeulen(1991). The aim of the researchwas (1) to find a calibration line betweenin vitro and in uivo measurements,(2) to test the repeatability of results collected at the same body site, (3) to compare results from different volumeswithin the samemuscle, and (4) to compare inter-individual resu!tsfrom 18 and 100kg live wei the same breed, and kept within the sameenvironmental conditions. latter, after slaughtering,a musclesampleof was taken from the intramuscular fat content was cJorsimuscle without damaging the carcass. determined by ravimetry as describedabove.

able 1 shows the in vitro (extracted from a few mm3 tissue)and in vivo (volume of 4 cm3 tissue)resultsof the intramuscularfat content measure volume of the m. bicepsfemoris of 18 kg piglets. paring these results with a one w~4yanalysis resultswere lower (P < 0.05) than the others. be explainedby the fact that phospholipidswere indeednot

of the Intramuscular iglets(g per 100g wet

eanValuesand St etry

.-

. Geerset al.

376

2 Values and Standard Deviations (SD) of Total Intramuscular Fat, Triglycerides and holipids After Folch Extraction and Iatroscan Analysis (five piglets) (g/100 g wet weight)

Total fat Triglycerides Phospholipids

oefficient of Variation

Mean

SD

la97 O-72 l-20

O-33 O-18 0*21

- -----

--

Mean

-Samevolume ifferent volume -v---p

edted N

rd Deviation, S (n = number of animals)

5.5 14

-

. .

SD

n

2.7 10

5 4

-

hip between in vitro and in vivo scularfat per 100g , r2 = 04, P < ration line atas19 measurementson e same muscle). was the hetero to the mean valuesof different pi within the sameenvironmentalcondi within the kmgissimuschxsimuscleof 100

Pig fat content variability and measurement

377

estimation of the phospholipid content, i.e. 0.69 vs 1~20(measured).The sum of triglyceride and phospholipid content was lower than total fat, since only the former two fractions were measured.In the caseof an intramuscular fat content of l-97 g/100 g fresh tissue, 1.20g phospholipidsmeans61% of the total fat connt. This is higher than that observedon 100kg pigs (40%) (LeseizneurGandemer, 1991).As a function of age, the triglyceride/phospholipidproportion seemsto increase,which is alsoillustrated by the higherallometric coefficient of triglycerideson the total carcassweight of sheep@road & Davies, 1981).The mean error on the estimate of the ultimate calibration line is 19%, which may be explainedby (1) the measuringerror within eachmethod, and (2) the fact that in vitro measurementson a few mm3 are not completely representativefor in vivo measurementson 4 cc of tissue.Thesefindings illustrate the well-known heterogeneity of intramuscular fat content, and proportion of triglycerid ratio, within a muscle(Davies ryor, 1977;Gispert et al., 1990; 1991).Thus the application of e tissuevolumescombinedwit of carrying out repeatableand multiple measurementson sameanimal without damaging or killing it (Table 3), make in vivo *I3 N spectroscopyand scular fat content imaging a better tool than taking biopsiesto study intr above 1.1-l 5 g per 100g fresh tissue.Furth on a large number of pigs is necessaryto im;prove the accuracy and y of the method in field conditions. In view of reducing labour cost, it would be worthwhile to look for a ring site being representativefor the whole lean musclevolume. etry of the body composition would be an advantage in this quality parameters, which can be measured with N and glycolytic potential (Geerset al., 19926). breeding work and animal nutrition studies, the in vivo will allow repeatedmusclequality evaluationas a function of a environmental factors, such as feedcomposition and environment

technic ct 106)

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