Application of an Experimental Design to the Detection of Foreign Substances in Milk

Abstract

NIRA was used in order to study interactions between temperature (T) and soluble substances and to detect solutes added to milk. A two-level factorial design was planned to estimate the effects of the main factors and of the most interesting interactions on spectral data. Water (W), NaCl (N), reconstituted skim milk powder (P) and W with N were alternately added to milk. The plan was repeated on eight different milks. The interactions studied were W × N, W × T, N × T, P × T, W × N × T. The values assigned to the experimental design model were 1 and —1 for active and non-active factors, respectively. This model and the corresponding analysis of variance were assessed independently at each wavelength, making it possible to plot results versus wavelengths as a spectrum. Thus, absorbance (predicted variable) was considered as the response to experimental design variations (predictors). Principal Component Analysis (PCA) was applied to the overall data collection to identify the main variation factors. The ability of principal components to predict the presence of foreign substances was assessed by Principal Component Regression. Several PCRs were calculated on two sub-collections (HIGH and LOW temperature), obtained from the overall collection (TOTAL), in order to assess whether recording spectra at two temperatures was useful to predict the presence of foreign substances. PCA on the overall data collection identified T as the most important factor affecting the total spectra variation; N and P groups were also separated according to the third and the fourth principal components. The parameters of the analysis of variance confirmed that the main factors N, P and T and the T interactions were more significant. T and N induced a shift of water absorption bands around 1450 and 1940 nm. There was no prediction improvement in recording milk spectra at two temperatures. PCA on the LOW sub-collection identified W and P according to the first factor and N according to the second one.

Keywords

Experimental design temperature milk additions Analysis of Variance Multidimensional analysis

Get full access to this article

View all access options for this article.

References

FIL-IDF Bulletin , Measurement of Extraneous Water by the Freezing Point Test, Document 154 (1983).

Politi

, in Chimica del Latte e dei Latticini, Ed. by Centro Sperimentale del Latte, Milan, p.197 (1958).

Resmini

Pellegrino

Masotti

Tirelli

and Prati

, Scienza e Tecnica Latt.-cas. 43, 169–186 (1992).

Luck

W.A.P.

, in The Hydrogen Bond—Recent Development in Theory and Experiments, Ed. by Schuster

North-Holland, Amsterdam, pp. 1403–1408 (1976).

Luck

W.A.P.

, in Structure of Water and Aqueous Solutions, Ed. by Luck

W.A.P.

Verlag Chemie, Weinheim, pp. 221–245, 247–284 (1974).

Takoaka

, NIR news 3(5), 4 (1992).

Giangiacomo

and Galliena

, in Proc. 3rd Int. Conf. on NIRS, Brussels, 1990, Vol. II, Ed. by Biston

and Bartiaux-Thill

Agricultural Research Centre, Gembloux, p. 477 (1991).

Box

G.E.P.

and Draper

N.R.

, Empirical Model-Building and Response Surfaces. John Wiley & Sons, Chichester and New York, p. 105–142 (1990).

Tomassone

Lesquoy

and Millier

, La Régression—Nouveaux Regards sur une Ancienne Méthode Statistique. INRA and Masson, Paris (1983).

10.

Mark

, in Handbook of Near-Infrared Analysis, Ed. by Burns

D.A.

and Ciurczak

E.W.

Marcel Dekker, New York and Basel, p. 129–158 (1989).

11.

Bertrand

and Scotter

C.N.G.

, Appl. Spectrosc. 46, 1420–1425 (1992).

12.

Dagnelie

, Analyse Statistique A Plusieurs Variables. Les Presses Agronomiques de Gembloux, p. 313 (1975).

13.

Iwamoto

Uozumi

and Nishinari

, “Preliminary Investigation of the State of Water in Food by Near Infrared Spectroscopy”, in International NIR/NIT Conference, Budapest, 1986. Hungarian Academy of Science, Budapest, p. 1 (1986).

14.

Stark

and Luchter

, “Overview of Near-Infrared Spectroscopy”, in Proc. 3rd Int. Conf. on NIRS, Brussels, Belgium, 1990. Documented. by KES Analysis, New York (1990), p. v-15.

15.

Lin

and Brown

C.W.

, Appl. Spectrosc. 46, 1809–1815 (1992).

16.

Osborne

B.G.

and Fearn

, Near Infrared Spectroscopy in Food Analysis. Longman Scientific and Technical, New York (1986).

17.

Nathier-Dufour

Bertrand

Courcoux

Devaux

M.F.

Robert

, “Application of Factorial Design and Analysis of Variance for the Study of Near Infrared Spectra of Animal Feed Mixtures”, in 3éme Journées Européennes Agro-industrie et Méthods Statistiques, Montpellier, France, 30 November–1 December 1992. Association pour la Statistique et ses Utilisations, p. 148–151 (1992).