Inﬂuence of impregnation solution viscosity and osmolarity
on solute uptake during vacuum impregnation of apple cubes
(var. Granny Smith)
, Pascal Degraeve
, Claude Noe
Lyon 1, Laboratoire de Recherche en Ge
nie Industriel Alimentaire (EA no. 3733), IUT A – De
partement de Ge
Technopole Alimentec – rue Henri de Boissieu, F-01060 Bourg en Bresse cedex 9, France
de Bourgogne, Equipe Eau – Mole
cules actives – Macromole
cules – Activite
s (EA no. 581), ENSBANA,
1 Esplanade Erasme, F-21000 Dijon, France
Received 26 February 2007; received in revised form 25 October 2007; accepted 28 October 2007
Available online 1 November 2007
Vacuum-assisted impregnation of pectinmethylesterase (PME) solution has been recognized as an eﬃcient pretreatment to improve
the ﬁrmness of heat-treated fruit. In order to improve the control of solute infusion into fruit pieces, the eﬀect of the osmolarity and
viscosity of vacuum impregnation solution on solute penetration and distribution was studied in 1.5 cm apple cubes, using model
PME-based solutions containing sodium chloride and/or sodium alginate. While vacuum impregnation of either a viscous hypotonic
or a non-viscous hypertonic solution infused solutes homogeneously into fruit pieces, the penetration of viscous hypertonic solutions
was much lower, and PME or chloride infusion was limited primarily to the superﬁcial zone of apple cubes. Similar penetration was
observed with a highly concentrated sucrose solution. These ﬁndings may result from a synergistic combination of negative osmotic
and friction eﬀects during liquid ﬂow into fruit pores.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Osmolarity; Viscosity; Mass transfer; Vacuum impregnation; Fruit; Pectinmethylesterase
Vacuum impregnation technology can be used to eﬀec-
tively incorporate solutes into porous, solid food matrices
containing air, such as fruits and vegetables. This method
involves holding food under vacuum to enhance air extrac-
tion from pores, then, immersing it in the desired solution.
As a result of capillary forces, a limited amount of liquid
penetrates the porous space adjacent to the liquid–solid
interface; the bulk of liquid penetration, however, occurs
following vacuum release. Vacuum impregnation (VI) tech-
nology, therefore, allows an impregnation solution to
replace a portion of the air initially contained in the porous
structure of food, as a result of the positive pressure diﬀer-
ential that develops when atmospheric pressure conditions
are restored. The hydrodynamic mechanism (HDM)
enhancing liquid penetration has been precisely described
and modelled (Fito, 1994; Fito et al., 1996). It is may be
aﬀected by deformation and relaxation of the food matrix
due to pressure changes.
Vacuum impregnation has been used as an alternative to
impregnation under atmospheric pressure to increase eﬃ-
ciency and save time. In previous studies (Degraeve et al.,
2003; Guillemin et al., 2006), this technology was used to
successfully incorporate exogenous pectinmethylesterase
and calcium ions into the porous structure of strawberry
halves and apple cubes. These solutes were shown to act
synergistically to increase the ﬁrmness of fruit tissues.
Pectinmethylesterase (PME, E.C. 18.104.22.168) catalyzes the
0260-8774/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
Corresponding author. Tel.: +33 474472140; fax: +33 474455253.
E-mail address: email@example.com (P. Degraeve).
Available online at www.sciencedirect.com
Journal of Food Engineering 86 (2008) 475–483