Influence of heating conditions in continuous-flow microwave or tubular heat exchange systems on the vitamin B1 and B2 content of milk

Free access article

Issue		Lait Volume 80, Number 6, November-December 2000


Page(s)		601 - 608
DOI		http://dx.doi.org/10.1051/lait:2000147

DOI: 10.1051/lait:2000147

Lait 80 (2000) 601-608

Influence of heating conditions in continuous-flow microwave or tubular heat exchange systems on the vitamin B₁ and B₂ content of milk

Isabel Sierra - Concepción Vidal-Valverde

Instituto de Fermentaciones Industriales (CSIC), Juan de la Cierva 3, 28006 Madrid, Spain

(Received 17 January 2000; accepted 10 May 2000)

Abstract:

The effect of continuous-flow microwave heating of milk on the stability of vitamins B₁ and B₂ was determined by ion-pair reverse-phase high-performance liquid chromatography. Results were compared with those obtained using a conventional process having the same heating, holding and cooling phases. When milk was heated in a continuous microwave heating system, at 90 $^\circ$ C without a holding phase, no vitamin B₁ and vitamin B₂ losses were observed. However, when the holding time was raised to 30 s or 60 s, while the content of vitamin B₂ was not modified, the content of vitamin B₁ was lowered (3% and 5%, respectively). Analogous results were obtained when the milk was submitted to a similar heating process using a conventional system. These results indicate that continuous-flow microwave heating of milk at high temperature does not offer any advantage with respect to the vitamin B₁ and B₂ retention compared with a conventional heating process having the same heating, holding and cooling times.

Keywords: vitamin B₁ / vitamin B₂ / milk / microwave heating

Résumé:

Étude de l'effet des différentes conditions de chauffage dans un micro-ondes à flux continu et dans des systèmes tubulaires d'échange de chaleur sur la teneur en vitamines B₁ et B₂ du lait. L'effet du chauffage dans un micro-ondes à flux continu sur la stabilité des vitamines B₁ et B₂ du lait a été déterminé par HPLC en phase reverse. Il a été comparé aux résultats obtenus par la méthode conventionnelle avec les mêmes phases de chauffage, maintien à température et refroidissement. Le chauffage du lait dans un micro-ondes à flux continu à une température de 90 $^\circ$ C et sans maintien à température ne conduit pas à des pertes en vitamines B₁ et B₂. Par contre, si le temps de maintien à température est de 30 ou 60 s, la teneur en vitamine B₂ est maintenue tandis que celle en vitamine B₁ est diminuée (3 % et 5 % respectivement). Des résultats similaires ont été obtenus en utilisant la méthode conventionnelle. Cette étude met en évidence que le chauffage du lait dans un micro-ondes à flux continu n'offre aucun avantage sur la conservation des vitamines B₁ et B₂ en comparaison à la méthode conventionnelle utilisant les mêmes phases de chauffage, maintien à température et refroidissement.

Mots clé : vitamine B₁ / vitamine B₂ / lait / chauffage par micro-ondes

Correspondence and reprints: Concepción Vidal-Valverde
Tel.: (34) 91 5622900; fax: (34) 91 5644853; e-mail: ificv12@ifi.csic.es

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