be answered, or the mechanism to be figured out [1]. However, the
existence of almost tailored procedures for undertaking specific
questions made difficult the comparison of data from different
laboratories to draw a comprehensive scenario of the lineal combination of critical factors affecting digestibility and absorption of
food components. A significant effort has been made by the INFOGEST project [2], which aim was to define a consensus protocol
easy to set up in any laboratory, with experimental conditions that
should be applied to obtain a satisfactory grade of confidence in the
results, to allow their comparison between different laboratories
and to establish further improvements in the technique.
In vitro bioaccessibility of carotenoids has been a continuous
topic of interest since the onset of this century. The findings
obtained with in vivo approaches yielded a priceless legacy to conceive reliable in vitro digestion protocols, which measure the bioaccessibility of carotenoids under different experimental conditions.
In the case of carotenoids as in other lipophilic compounds, bioaccessibility is often made equal to micellarization, that is, the technique determines the quantity of ingested carotenoids incorporated
into mixed micelles and, consequently, ready for absorption. However, it should be noted that micellarization is not the single element required to measure bioaccessibility of carotenoids, but
efficiency of the cellular absorption and first-pass metabolism are
contributors to the complete bioaccessibility value. Hence, from
the sequential steps involved in the digestion and absorption of
carotenoids—release from food matrix, transfer to lipid droplets,
emulsification and micellarization, and the subsequent routes of
cellular absorption, trafficking of lipids and first-pass metabolism—
the in vitro digestion protocols are designed to measure those
factors affecting the four initial steps, while different protocols are
required to estimate the efficiency of the others. Regarding the sort
of factors that influence bioaccessibility of carotenoids, they are
grouped within food structure, food matrix and processing features, physiological issues, and genetic and host-related aspects,
which meaning has been reviewed recently [3, 4]. Again, the design
of in vitro digestion protocols does not allow ascertaining the
influence of all those factors. Thus, the impact of genetic and
host-related variations is not accessible through this technique,
while experimental conditions according to the gastrointestinal
capability of different population groups (newborns and infants,
the elderly, and patients with certain hepatobiliary disorders) are
now included in the design of in vitro digestion protocols only
recently [5, 6].
In this milieu, and although a considerable number of in vitro
digestion protocols is available, the procedures published by Garrett et al. [7] and Reboul et al. [8] contain the essential knowledge
to consistently develop the measurement of the micellarization of
carotenoids, or to be tuned with other experimental conditions, as
376
Antonio Pe ´ rez-Ga ´ lvez and Javier Fontecha
existence of almost tailored procedures for undertaking specific
questions made difficult the comparison of data from different
laboratories to draw a comprehensive scenario of the lineal combination of critical factors affecting digestibility and absorption of
food components. A significant effort has been made by the INFOGEST project [2], which aim was to define a consensus protocol
easy to set up in any laboratory, with experimental conditions that
should be applied to obtain a satisfactory grade of confidence in the
results, to allow their comparison between different laboratories
and to establish further improvements in the technique.
In vitro bioaccessibility of carotenoids has been a continuous
topic of interest since the onset of this century. The findings
obtained with in vivo approaches yielded a priceless legacy to conceive reliable in vitro digestion protocols, which measure the bioaccessibility of carotenoids under different experimental conditions.
In the case of carotenoids as in other lipophilic compounds, bioaccessibility is often made equal to micellarization, that is, the technique determines the quantity of ingested carotenoids incorporated
into mixed micelles and, consequently, ready for absorption. However, it should be noted that micellarization is not the single element required to measure bioaccessibility of carotenoids, but
efficiency of the cellular absorption and first-pass metabolism are
contributors to the complete bioaccessibility value. Hence, from
the sequential steps involved in the digestion and absorption of
carotenoids—release from food matrix, transfer to lipid droplets,
emulsification and micellarization, and the subsequent routes of
cellular absorption, trafficking of lipids and first-pass metabolism—
the in vitro digestion protocols are designed to measure those
factors affecting the four initial steps, while different protocols are
required to estimate the efficiency of the others. Regarding the sort
of factors that influence bioaccessibility of carotenoids, they are
grouped within food structure, food matrix and processing features, physiological issues, and genetic and host-related aspects,
which meaning has been reviewed recently [3, 4]. Again, the design
of in vitro digestion protocols does not allow ascertaining the
influence of all those factors. Thus, the impact of genetic and
host-related variations is not accessible through this technique,
while experimental conditions according to the gastrointestinal
capability of different population groups (newborns and infants,
the elderly, and patients with certain hepatobiliary disorders) are
now included in the design of in vitro digestion protocols only
recently [5, 6].
In this milieu, and although a considerable number of in vitro
digestion protocols is available, the procedures published by Garrett et al. [7] and Reboul et al. [8] contain the essential knowledge
to consistently develop the measurement of the micellarization of
carotenoids, or to be tuned with other experimental conditions, as
376
Antonio Pe ´ rez-Ga ´ lvez and Javier Fontecha