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The impact of freezing and toasting on the glycaemic response of white bread

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To investigate the impact of freezing and toasting on the glycaemic response of white bread. Ten healthy subjects (three male, seven female), aged 22-59 years, recruited from Oxford Brookes University and the local community. A homemade white bread and a commercial white bread were administered following four different storage and preparation conditions: (1) fresh; (2) frozen and defrosted; (3) toasted; (4) toasted following freezing and defrosting. They were administered randomized repeated measures design. Incremental blood glucose, peak glucose response, 2 h incremental area under the glucose response curve (IAUC). The different storage and preparation conditions resulted in lower blood glucose IAUC values compared to both types of fresh white bread. In particular, compared to the fresh homemade bread (IAUC 259 mmol min/l), IAUC was significantly lower when the bread was frozen and defrosted (179 mmol min/l, P<0.05), toasted (193 mmol min/l, P<0.01) and toasted following freezing and defrosting (157 mmol min/l, P<0.01). Similarly, compared to the fresh commercial white bread (253 mmol min/l), IAUC was significantly lower when the bread was toasted (183 mmol min/l, P<0.01) and frozen, defrosted and toasted (187 mmol min/l, P<0.01). All three procedures investigated, freezing and defrosting, toasting from fresh, and toasting following freezing and defrosting, favourably altered the glucose response of the breads. This is the first study known to the authors to show reductions in glycaemic response as a result of changes in storage conditions and the preparation of white bread before consumption. In addition, the study highlights a need to define and maintain storage conditions of white bread if used as a reference food in the determination of the glycaemic index of foods.
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ORIGINAL ARTICLE
The impact of freezing and toasting on the
glycaemic response of white bread
P Burton and HJ Lightowler
Nutrition and Food Science Group, School of Life Sciences, Oxford Brookes University, Oxford, UK
Objective: To investigate the impact of freezing and toasting on the glycaemic response of white bread.
Subjects/methods: Ten healthy subjects (three male, seven female), aged 22–59 years, recruited from Oxford Brookes
University and the local community. A homemade white bread and a commercial white bread were administered following four
different storage and preparation conditions: (1) fresh; (2) frozen and defrosted; (3) toasted; (4) toasted following freezing and
defrosting. They were administered randomized repeated measures design. Incremental blood glucose, peak glucose response,
2 h incremental area under the glucose response curve (IAUC).
Results: The different storage and preparation conditions resulted in lower blood glucose IAUC values compared to both types
of fresh white bread. In particular, compared to the fresh homemade bread (IAUC 259 mmol min/l), IAUC was significantly lower
when the bread was frozen and defrosted (179 mmol min/l, Po0.05), toasted (193 mmol min/l, Po0.01) and toasted following
freezing and defrosting (157 mmol min/l, Po0.01). Similarly, compared to the fresh commercial white bread (253 mmolmin/l),
IAUC was significantly lower when the bread was toasted (183 mmol min/l, Po0.01) and frozen, defrosted and toasted
(187 mmol min/l, Po0.01).
Conclusions: All three procedures investigated, freezing and defrosting, toasting from fresh and toasting following freezing and
defrosting, favourably altered the glucose response of the breads. This is the first study known to the authors to show reductions
in glycaemic response as a result of changes in storage conditions and the preparation of white bread before consumption. In
addition, the study highlights a need to define and maintain storage conditions of white bread if used as a reference food in the
determination of the glycaemic index of foods.
European Journal of Clinical Nutrition (2008) 62, 594599; doi:10.1038/sj.ejcn.1602746; published online 4 April 2007
Keywords: glycaemic response; bread; food storage; food preparation; blood glucose
Introduction
The glycaemic index (GI), first introduced in 1981 (Jenkins
et al., 1981), is a classification of the blood glucose raising
potential of carbohydrate foods. It is defined as the
incremental area under the blood glucose curve (IAUC) of
a 50 g available carbohydrate portion of a test food expressed
as a percentage of the response to 50 g available carbohydrate
of a reference food taken by the same subject, on a different
day (FAO/WHO, 1998).
Recent data support the preventive potential of a low-GI
diet against the development of type 2 diabetes and
cardiovascular disease (Salmeron et al., 1997a, 1997b; Frost
et al., 1999). There is also an interest in the potential of low-
GI diets in body weight management, with studies showing
that low-GI foods, or lowering the GI of a food, may reduce
hunger and result in a lower energy intake (Ludwig, 2000;
Warren et al., 2003).
As consumer interest in GI has grown in recent years, a
major challenge for the food industry is to develop and
produce foods of low glycaemic response. In the UK, bread
forms the most important staple amongst starch foods and is
one of the largest sectors in the food industry, producing
almost 12 million loaves and packs every day (Federation of
Bakers, 2005). Moreover, white bread sales represent over
70% of all bread sales in the UK. In 2004–2005, the
household consumption of white bread was almost 400 g
per person per week compared to 120 and 45 g per person per
Received 3 July 2006; revised 14 February 2007; accepted 19 February 2007;
published online 4 April 2007
Correspondence: Dr H Lightowler, Nutrition and Food Science Group, School
of Biological and Molecular Sciences, Oxford Brookes University, Gipsy Lane
Campus, Headington, Oxford OX3 0BP, UK.
E-mail: hlightowler@brookes.ac.uk
Contributors: PB planned and designed the study and was responsible for the
collection of data and writing the manuscript. HJL advised on the study design
and contributed to the preparation of the manuscript.
European Journal of Clinical Nutrition (2008) 62, 594–599
&
2008 Nature Publishing Group All rights reserved 0954-3007/08 $
30.00
www.nature.com/ejcn
week for wholemeal and brown bread, respectively (Depart-
ment for Environment, Food and Rural Affairs, 2006).
In the UK, the baking industry predominantly uses the
Chorleywood Bread Process (CBP), which is responsible for
over 80% of bread produced. The CBP, developed in 1961, is
a mechanical dough development process involving inten-
sive mixing, the use of oxidants, a short fermentation process
and the use of a pan for baking. In addition, the process has
an important impact in the UK as it enables the use of low-
protein home-produced wheat (Belderok, 2000). However, the
result of developments in the bread-making process is a
highly favoured, but medium- to high-GI white bread.
In the UK, an increase in time pressure in family life has
meant that infrequent, bulk shopping and freezing are
widespread. Consequently, the consumption of bread that
has been defrosted following freezing is commonplace. In
addition, consumption of bread in the form of toast, mainly
at breakfast, is also customary.
Although some food processes, for example gelatinization,
may lead to high-GI foods (Granfeldt et al., 2000), some food
manufacturing and handling may have an effect on the
degree of starch retrogradation, involving a rearrangement
or realignment of initially heated starch molecules (Berry,
1986; Lang and Vitapole, 2004). Moreover, retrograded
starch has been shown to reduce glycaemic response and
there is evidence of this happening under conditions of
cooling (Larsen et al., 2000; Frei et al., 2003). Retrogradation
is greater where the degree of gelatinization is more
complete, facilitated by higher temperature and greater
water availability or with greater mixing, for example in
the formation of bread dough. Furthermore, it has also been
shown that overall starch recrystallization reaches a max-
imum at around 41C and below this temperature further
starch recrystallization is minimal (Lang and Vitapole, 2004;
Goesaert et al., 2005). Importantly, the process of freezing
and defrosting bread will involve bread passing through this
point of maximal recrystallization and retrogradation twice,
once while cooling and again during defrosting.
Relatively small differences in the glycaemic response of
regularly consumed starch foods have shown beneficial
effects on health, including reduced cardiovascular disease
risk and glycaemic control (Frost et al., 1998; Brand-Miller et al.,
2003). Thus, investigations into ways of reducing the glycaemic
response to white bread are of important application. In the
light of the above, the aim of the present study was to
determine whether the glycaemic response of white bread could
be changed by everyday storage and preparation conditions
such as procedures of freezing, defrosting and toasting.
Subjects and methods
Subjects
Ten healthy subjects (three male and seven female) were
recruited to participate in the study. Subjects were staff and
students from Oxford Brookes University and from the wider
community. To participate, subjects were required to be
between 18 and 59 years of age, with a body mass index
(BMI) o30 kg/m
2
. Interested subjects were asked to complete
a health screening questionnaire to check against ill health,
including clinically abnormal glucose metabolism (fasting
blood glucose 46.1 mmol/l) and any medical conditions or
medications that might affect glucose regulation, gastric
emptying, body weight, appetite or energy expenditure.
Anthropometric measurements were made in the fasting
state, using standardized methods, on the morning of the
first test. Height was recorded to the nearest centimetre
using a stadiometer (Seca Ltd, UK), with subjects standing
erect and without shoes. Body weight was recorded to the
nearest 0.1 kg using the Tanita BC-418 MA (Tanita UK Ltd),
with subjects wearing light clothing and no shoes. BMI was
calculated using the standard formula weight (kg)/height
(m)
2
. Characteristics of the subjects are shown in Table 1.
Ethical approval for the study was obtained from the
University Research and Ethics Committee at Oxford
Brookes University. Subjects were given full details of the
study protocol and the opportunity to ask questions. All
subjects gave written informed consent before participation.
Study protocol
The method used to measure glycaemic response and to
calculate the GI value was in line with procedures recom-
mended by the FAO/WHO (1998). In addition, on the day
preceding a test, subjects were asked to restrict their intake of
alcohol and caffeine-containing drinks and to refrain from
intense physical activity (e.g., long periods at the gym,
excessive swimming, running, aerobics). To minimize the
possible influence of the second meal effect, subjects were
asked to refrain from eating an extra-large evening meal or
have an unusually high or low food intake throughout the
day preceding a test (Wolever, 1990). Where possible,
subjects ate a similar meal type on the evening before
testing; however subjects were asked to avoid consuming
pulses for this meal to avoid the effects of colonic fermenta-
tion on postprandial glycaemic (Macintosh et al., 2003). All
foods were tested in subjects after a 12 h overnight fast.
Test breads were administered to subjects in a randomized,
repeated measures design, with each subject acting as his/her
own control. Subjects travelled to the laboratory by car or
public transport and rested for 10 min before the test
commenced. Test breads were consumed first thing in the
Table 1 Characteristics of study population
Mean7s.d.
Age (years) 45.4714.3
Height (m) 1.7370.97
Weight (kg) 71.3710.1
BMI (kg/m
2
) 23.972.1
Abbreviations: BMI, body mass index; s.d., standard deviation.
Glycaemic response of white bread
P Burton et al
595
European Journal of Clinical Nutrition
morning (i.e., as breakfasts) and were compared with a
reference food (glucose) and were tested in equivalent
amounts (50 g) of available carbohydrate. Available carbo-
hydrate was estimated according to the FAO/WHO procedure
(total carbohydrate minus dietary fibre), using calculated data
of macronutrient content (Table 2). Thus, in this context,
dietary fibre was defined as unavailable carbohydrate.
As blood glucose responses vary within subjects from
day to day, the reference food (glucose) was tested 3 times
in each subject. Thus, subjects tested each test bread once
and the reference food 3 times in random order on
separate days, with at least a one-day gap between measure-
ments to minimize carry over effects. All test breads and the
reference food were served with 200 ml water. A further
200 ml water was given during the subsequent 2 h. Subjects
were asked to eat the test breakfast within a 10–12 min
period to reduce the influence of chewing on particle size
(Hoebler et al. 1998).
Test breads
Two white breads, one homemade bread prepared using a
standard home bread-making machine (Breadman Pro,
Russell Hobbs, Manchester, UK) and one commercially
available bread (Hovis Classic, British Bakeries Ltd, UK),
were tested for glycaemic response. The homemade white
bread was made from 500 g white wheat flour (Carr’s white
strong bread flour; a high-protein wheat that does not
contain enzymes, improvers or bleach), 8 g NaCl, 6 g sugar,
287 ml water, 6 g butter, 7 g skimmed milk powder and 8 g
dehydrated yeast without additives (Fermipan, DSM Bakery
Ingredients, Holland). Details of the macronutrient, dietary
fibre and sodium content of the two test breads are given in
Table 2. Parallel investigations of homemade and commer-
cial breads allowed investigation of any modulation, for
example by additives, in commercial breads not found in the
homemade bread.
Both breads were tested following four different storage
and preparation conditions: (1) fresh; (2) frozen and
defrosted; (3) fresh and toasted; (4) toasted following
freezing and defrosting. Fresh bread was tested on the
morning following baking or purchase. Frozen bread was
defrosted overnight at room temperature before consump-
tion the following morning. Breads were frozen between 2
and 7 days; it has been suggested that further retrogradation
during freezing following temperature reduction to the
frozen state does not occur (Gray and Bemiller, 2003). Bread
was toasted on the morning following baking or purchase
and, where applicable, following defrosting overnight at
room temperature. For the duration of the study, a toaster
was standardized to medium setting, ensuring consistent
moderate toasting.
Blood glucose measurements
Finger-prick blood samples were taken for capillary blood
glucose analysis. Recent reports suggest that capillary blood
sampling is preferred for reliable GI testing (FAO/WHO,
1998; Wolever and Mehling, 2003). To establish blood
glucose stability at the start of the blood glucose response
curve, fasting blood samples were taken at 5 and 0 min
before consumption of the food and the baseline value taken
as a mean of these two values. The reference food/test bread
was consumed immediately after this and further blood
samples were taken at 15, 30, 45, 60, 90 and 120 min after
starting to eat.
Blood was obtained by finger prick using the Glucolet 2
multi-patient lancing system (Bayer HealthCare, Newbury,
UK). Where necessary, before a finger prick, subjects were
encouraged to warm their hand under running warm water
to increase blood flow. Fingers were not squeezed to extract
blood from the fingertip as this may dilute with plasma.
Blood glucose was measured using Ascensia Contour auto-
matic blood glucose meters (Bayer HealthCare). The blood
glucose meters were calibrated daily using control solutions
from the manufacturer and were also regularly calibrated
against a clinical dry chemistry analyser (Reflotron Plus,
Roche, Welwyn Garden City, UK) and the HemoCue Glucose
201 þanalyser (HemoCue Ltd, Dronfield, UK). Using the
Bland–Altman analyses, there was a very strong correlation
(r¼0.980, Po0.001) and good agreement (mean difference
0.2 mmol, 95% CI 0.3 to 0.2, limits of agreement 0.80
and 0.32) between blood glucose measurements for a
random selection of 140 blood samples simultaneously
measured using the Ascensia Contour and the HemoCue
Glucose 201 þanalyser.
Statistical analysis
Statistical analysis was performed using the Statistical
Package for the Social Sciences (SPSS version 11.0. 1,
Chicago, IL, USA). Data are presented as means and standard
deviations. Before statistical analysis, the normality of the
data was tested using the Shapiro–Wilk statistic. The
Pearson’s correlation coefficient and the method of Bland
and Altman (1986) were used to examine the correlation and
agreement between the automatic analyser and the Hemo-
Cue Glucose 201 þanalyser. Levels of intra-individual
variation of the three reference (glucose) tests were
assessed by determining the coefficient of variation
(CV% ¼100 standard deviation/mean). Repeated measures
analysis of variance, with Bonferroni’s correction, was used
Table 2 Nutritional composition (per 100 g) of test breads, using
manufacturers’ data
Test bread Available
carbohydrate
a
Protein Fat Dietary fibre
b
Sodium
Homemade bread 43.9 8.6 1.7 1.9 0.6
Commercial bread 40.5 9.2 4.5 3.1 0.4
a
Calculated according to FAO/WHO (1998).
b
AOAC International methodology.
Glycaemic response of white bread
P Burton et al
596
European Journal of Clinical Nutrition
to compare glycaemic response between test breads stored
and processed in different ways. Statistical significance was
set at Po0.05.
Results
The mean intra-individual variation in glycaemic response
to the three reference tests in the subjects was 28% CV. This
value is consistent with previously reported data in normal
subjects (Wolever, 2006).
Figure 1 shows the incremental blood glucose response
curves for the homemade white bread. There was no overall
effect of storage and preparation on the peak rise in blood
glucose response (P¼0.64) in the homemade bread.
Table 3 shows the IAUC across the different storage and
preparation conditions for the homemade white bread.
Significant differences in IAUC (F ¼10.503, Po0.001) were
seen. Compared to the fresh homemade bread, IAUC was
significantly lower for homemade frozen and defrosted bread
(P¼0.010), homemade fresh toasted bread (P¼0.007) and
homemade bread that had been toasted following freezing
and defrosting (P¼0.001).
Figure 2 shows the incremental blood glucose response
curves for the commercial white bread. Peak rise in blood
glucose was significantly different across the storage and
preparation conditions (F ¼7.425, P¼0.001). Peak rise in
blood glucose for commercial fresh toasted bread and
commercial bread that had been toasted following freezing
and defrosting was significantly lower than fresh commercial
bread (P¼0.024 and P¼0.018, respectively) and commercial
bread that had been frozen and defrosted (P¼0.020 and
P¼0.006, respectively).
There were significant differences in IAUC (F ¼6.105,
P¼0.003) between the storage and preparation conditions
for the commercial bread (Table 3). IAUC values for fresh
toasted bread and bread that had been frozen, defrosted and
toasted were significantly lower than for fresh bread
(P¼0.001 and P¼0.026, respectively). The IAUC value for
fresh toasted bread was also significantly lower compared to
bread that had been frozen and defrosted (P¼0.046).
Discussion
The current study investigated the impact of storage
conditions and food preparation on the glycaemic response
to white bread. This is the first study known to the authors to
show reductions in glycaemic response as a result of changes
in storage conditions and the preparation of white bread
before consumption. All three procedures investigated, that
is freezing and defrosting, toasting from fresh and toasting
following freezing and defrosting, led to a reduced glycaemic
response and reduction in IAUC values.
The influence of food processing and cooking on glycae-
mic response is well documented (Brand et al., 1985; Bjorck
et al., 1994). Treatments incorporating the generation of
forces such as shearing, compression and extreme heat
treatment increase gelatinization, which results in the
breakdown of the starch granule. Thus, many processing
conditions lead to an increased susceptibility of the starch
Figure 1 Blood glucose response curve for homemade bread:
Glucose (*); fresh (J); frozen, defrosted (K); fresh, toasted (&);
frozen, defrosted, toasted ().
Table 3 IAUC (mmol min/l) for homemade bread and commercial
white bread with different storage and preparation conditions
Test food Homemade bread Commercial bread
(mean7s.d.) (mean7s.d.)
Glucose 2917100
a
2917100
a
Fresh 2597103
a
2537106
a,b
Frozen, defrosted 179774
b
217799
b,c
Fresh, toasted 193779
b
183796
d
Frozen, defrosted, toasted 157785
c
187795
c,d
Abbreviation: IAUC, incremental area under the glucose response curve; s.d.,
standard deviation.
Values in the same column with different letters are significantly different,
Po0.05.
Figure 2 Blood glucose response curve for commercial white
bread: Glucose (*); fresh (J); frozen, defrosted (K); fresh, toasted
(&); frozen, defrosted, toasted ().
Glycaemic response of white bread
P Burton et al
597
European Journal of Clinical Nutrition
granule to enzymatic salivary and pancreatic amylases
following consumption, resulting in greater availability of
glucose for absorption and increased glycaemic response.
Examples of such treatments are flour milling, intensive
mixing in bread dough formation, as in the CBP, and bread
baking, which may explain the relatively highGI value of
white bread.
Retrograded starch constitutes RS3, a form of resistant
starch, and there is evidence of the formation of RS3 during
the processes of cooling and freezing (Hoebler et al., 1999;
Goesaert et al., 2005). There has been an increasing interest
in resistant starch in recent years and positive health benefits
have been demonstrated, mediated through effects on colonic
fermentation and on both postprandial glucose and lipid
metabolism (Robertson et al., 2003; Higgins et al., 2004).
An important difference in the constituents of the home-
made and commercial white breads in this study was the
presence of dough conditioners and improvers. These
ingredients are widely used in commercial bread and are
designed to optimize dough formation and quality, reduce
staling rate and maintain water retention during baking
(Goesaert et al., 2005). However, water content and activity
within the dough facilitates the retrogradation process.
Moreover, amylopectin retrogradation, together with moist-
ure transfer between bread components, may be reduced
by the use of dough improvers (Baik et al., 2003). This may
explain smaller reductions in glycaemic response within the
commercial bread, compared to changes within the home-
made bread.
The implications of this study are twofold. First, it is
suggested that simple household methods, such as freezing,
defrosting and toasting, may alter the glycaemic response to
white bread, thus white bread need not always be a highGI
food. There still remains a preference for white bread in the
UK (Department for Environment, Food and Rural Affairs,
2006), therefore the current study will be informative to
consumers in terms of optimal storage and preparation of
white bread to favourably alter glycaemic response. Second,
this study highlights a need to reconsider the use of white
bread as a reference food in GI methodology. Although GI
values determined using white bread as a reference food can
be converted to GI values based on glucose (Wolever, 2006),
the findings from the current study suggest that if bread is
unintentionally treated differently each time it is used as a
reference food, reproducibility and comparisons of the GI of
foods between different studies will be difficult.
Variability of glycaemic response has been a major
criticism of the GI concept. This variability may be owing
to a host of factors, acting independently or together. In this
study, conscientious efforts were made to maximize standar-
dizing of possible factors, to reduce intra- and inter-
individual variability, including a 12 h fast before testing,
restriction of exercise, alcohol and caffeine consumption the
day before a test and time spent chewing the test food.
A limitation of this study was the indirect estimation of
available carbohydrate content of the bread samples. It is
recommended that future studies include such measure-
ments, including resistant and retrograded starch (Englyst
et al., 1992; McCleary and Monaghan, 2002), both before
and after storage and preparation conditions. In addition,
other methods have been proposed to classify the glycaemic
impact of foods based on total carbohydrate rather than
available carbohydrate, such as relative glycaemic effect
(Brouns et al., 2005). However, further research is needed on
the use of alternative indices to measure the glycaemic
response of foods.
In conclusion, this is the first study known to the authors
to show reductions in glycaemic response following different
storage and preparation conditions of white bread and
highlights the need to define and maintain storage condi-
tions of food products when the glycaemic response of foods
is determined. Relatively small differences in the glycaemic
response of regularly consumed starch foods have been
shown previously to have beneficial effects on health (Frost
et al., 1998; Brand-Miller et al., 2003). Thus, considering the
high consumption of white bread, the identification of ways
to reduce the glycaemic response of white bread and other
foods is important in the prevention and management of
chronic disease.
Acknowledgements
Sponsorship: This study was supported by a Biotechnology
and Biological Sciences Research Council studentship.
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Glycaemic response of white bread
P Burton et al
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European Journal of Clinical Nutrition
... When compared to food containing only readily digestible starch, the rate of digestion of RS-containing foods in the small intestine is substantially slower. As a result, consumption of such food leads to a sustained and lower level of glucose release [45]. This It has been reported that the extended lack of dietary fiber can lead to irreversible changes in the gut microbiota composition and elicit gut dysbiosis, even impairing gut inflammatory mediators, thereby inducing several bowel diseases [44]. ...
... When compared to food containing only readily digestible starch, the rate of digestion of RS-containing foods in the small intestine is substantially slower. As a result, consumption of such food leads to a sustained and lower level of glucose release [45]. This effect is reflected by the GI, a ranking system that organizes different food products based on the glycemic response to food consumption [45]. ...
... As a result, consumption of such food leads to a sustained and lower level of glucose release [45]. This effect is reflected by the GI, a ranking system that organizes different food products based on the glycemic response to food consumption [45]. Researchers discovered a decrease in starch digestibility in treated food compared to untreated food after producing retrogradation in test meals [46]. ...
Article
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Resistant starch (RS) is the starch fraction that eludes digestion in the small intestine. RS is classified into five subtypes (RS1–RS5), some of which occur naturally in plant-derived foods, whereas the others may be produced by several processing conditions. The different RS subtypes are widely found in processed foods, but their physiological effects depend on their structural characteristics. In the present study, foods, nutrition and biochemistry are summarized in order to assess the type and content of RS in foods belonging to the Mediterranean Diet (MeD). Then, the benefits of RS consumption on health are discussed, focusing on their capability to enhance glycemic control. RS enters the large bowel intestine, where it is fermented by the microbiome leading to the synthesis of short-chain fatty acids as major end products, which in turn have systemic health effects besides the in situ one. It is hoped that this review will help to understand the pros of RS consumption as an ingredient of MeD food. Consequently, new future research directions could be explored for developing advanced dietary strategies to prevent non-communicable diseases, including colon cancer.
... mmol x min/L) (Robert et al., 2008). However, in a study that investigated the glycemic response of white bread (Burton and Lightowler, 2006), the iAUC of glucose (279 mmol x min/L) was comparatively nearer to the that in the present study. Meanwhile, the iAUC values of HM30 (105.2 mmol x min/L) and control CSB (186.1 mmol x min/L) were significantly lower (p ¼ 0.001, p < 0.05) than that of the glucose and were lower than that reported for white CSB (Lau et al., 2015;Liu et al., 2017). ...
... When HM was added, the development of gluten network was reduced and resulted in lower specific volume than control CSB (Li et al., 2020). According to Burton and Lightowler (2006), lower specific volume reduced the glycemic response and GI value of white bread; therefore, denser, and more compact CSB slowed down the rate of gastric emptying (Borczak et al., 2018). Moreover, the reduced gelatinization in the reduced volume of HM30 produced higher amount of resistant starch compared with that in control CSB (Haini et al., 2021). ...
Article
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The incorporation of resistant starch (RS) in food has gained importance to be a good replacement for digestible carbohydrate. This study examined the effect of compositing RS (high-amylose maize starch (HM)) as wheat flour substitute (30%) in Chinese steamed bun (CSB) formulation on postprandial glycemic response in healthy human subject. In this single-blind and cross-over experimental trial, a total of 15 female participants (mean age=31.5±3.9) were randomly assigned to receive CSB containing 30% HM (HM30) or control CSB (without HM) with their blood glucose were recorded throughout the test. The blood glucose concentrations recorded for HM30 were significantly lower than control CSB at 15 minutes (6.03 vs. 7.04 mmol/L, p=0.041), 30 minutes (6.93 vs. 7.76mmol/L, p=0.021), 45 minutes (6.21 vs. 7.55 mmol/L, p=0.032), 60 minutes (5.68 vs. 6.26 mmol/L, p=0.038), and 90 minutes (5.08 vs. 5.73 mmol/L, p=0.022). The 2-h postprandial glucose was significantly lower in HM30 (iAUC=105.2 mmol x min/L) than the control (186.1 mmol x min/L). The low GI property of HM30 (GI=39.11±5.6) did not cause sudden rapid increase in blood glucose concentration as observed in medium-GI control CSB (GI=69.18±9.8). This study suggests that adding 30g of HM decreased the glycemic index of CSB in healthy female adult.
... Non-significant difference in GI score of crackers was recorded with respect to WCF whereas GL of crackers was found to be significantly lower than both WCF and BF. During the baking process, starch gets gelatinized and when the freshly baked foods are chilled, starch recrystallization take place which leads to more organized form of starch chains where amylose and amylopectin form double helical linkages (Burton and Lightowler, 2007;Dewettinck et al., 2008). Freezing before and after baking causes reduction in GI score due to recrystallization of starch thereby decreasing its bioavailability (Nayak et al., 2014) which justifies the low GL (13.45) of crackers than WCF and BF (Table III). ...
... Freezing before and after baking causes reduction in GI score due to recrystallization of starch thereby decreasing its bioavailability (Nayak et al., 2014) which justifies the low GL (13.45) of crackers than WCF and BF (Table III). Formation of resistant starch in baked foods during freezing has been justified as another reason for lowering of GI by many researchers (Nehir, 1999;Raben et al., 1994;Carreira et al., 2004;Burton and Lightowler, 2007;Borczak et al., 2008). ...
Article
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Purpose The purpose of the present study was to develop low Glycemic Index (GI) crackers from water chestnut flour (WCF) and barley flour (BF). Design/methodology/approach Five blends were prepared by mixing WCF with BF in the proportion of 100:0, 70:30, 50:50, 30:70 and 0:100, respectively. The baking process as well as ingredients were modified for the production of low GI crackers. Findings BF incorporation had significant ( p < 0.05) effect on physical characteristics, organoleptic attributes and glycemic response of crackers. The resistant starch content of final product was found to be higher than WCF and BF. The research confirmed that replacement of 30 percent WCF with BF is feasible for development of low GI crackers with desired sensory attributes. The inference drawn from storage studies was that the developed crackers can be stored safely (with an overall acceptability score of greater than three on a 5-point scale) in metallized polyethylene up to 35 days under refrigerated conditions and 28 days under ambient conditions. Research limitations/implications Although low GI crackers were developed successfully from WCF and BF in the present study. However, detailed storage studies of such crackers can be done in future so as to perform the tests of type-intensity and temporal dominance of sensation. Also, in view of their low GI, these crops need to be evaluated in future for development of other bakery products like bread, cake, muffins, etc. Practical implications Water chestnut and barley despite having good nutritional profile and low GI are still considered as underutilized crops. In the present study, these crops were explored for development of low GI crackers especially for people suffering from diabetes. The outcome of this study will open up a new window in the baking sector to develop low GI crackers viz-a-viz will add value to these crops which will help to provide remunerative returns to those who are directly or indirectly involved in trade of these underutilized crops. Originality/value This was the first reported innovative attempt to develop low GI crackers from WCF and BF. For development of crackers having desired sensory characteristics, it was found feasible to blend WCF and BF in the ratio of 70:30.
... Previous research suggested that changing the matrix of foods could impact GI and SI (Fardet, 2015), and two starchy foods with similar nutrient content but distinct matrices were shown to exhibit different satiety and glycemic responses (Holt & Miller, 1994). Food form, texture (hardness, porosity), starch structure, water activity, particle size, and more generally food processing have all been demonstrated to influence the GI of starchy foods (Burton & Lightowler, 2008 ;Fardet, 2015;Pascua et al., 2013). The majority of these non-nutrient variables can be processed and modified at home using simple methods (Eleazu, 2016). ...
Article
Background and objectives: The impact of food structure on postprandial physiological responses has received sustained attention in recent years. Changes in the glycemic response and satiety score to commonly consumed starchy foods may have a positive impact on health. However, no data on Ethiopian staple foods has been reported. This study aimed at investigating the effects of structural changes in injera (stale and fresh with similar macronutrient content) on glycemic and satiety responses in ten healthy subjects during two hours in a randomized cross-over design. Findings: With increasing hardness, stale injera had a marked higher satiety index (iAUC = 407 ±14; p = 0.001) than fresh injera (iAUC = 333 ± 18). Besides, stale injera had a slightly, but not significant, lower glycemic index (GI) than fresh injera (stale, 35.9 ± 3.6; fresh, 40.2 ±3.0). Conclusions: Injera staling increased satiety but not glycemic response, and may provide a simple means for improving its health potential. Significance and Novelty: The effect of injera staling on satiety/glycemic responses has never been studied before. Injera is a staple food in Ethiopia, eaten several times a day. Therefore, stale injera may help reducing food intake of subsequent unhealthy foods through increased satiety.
... Loaves were baked at 230 °C for 40 min. After cooling, loaves were cut into slices and subjected to in vitro digestion within a few hours to avoid any alteration of the digestibility due to storage conditions (e.g., starch retrogradation due to freezing) [35]. ...
Article
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Tritordeum results from the crossbreeding of a wild barley (Hordeum chilense) species with durum wheat (Triticum turgidum spp. turgidum). This hexaploid crop exhibits agronomic and rheological characteristics like soft wheat, resulting in an innovative raw material to produce baked goods. We applied a gel-based proteomic approach on refined flours to evaluate protein expression differences among two widespread tritordeum cultivars (Aucan and Bulel) taking as the reference semolina and flour derived from a durum and a soft wheat cvs, respectively. The products of in vitro digestion of model breads were analyzed to compare bio-accessibility of nutrients and mapping tritordeum bread resistant peptides. Significant differences among the protein profiles of the four flours were highlighted by electrophoresis. The amino acid bio-accessibility and the reducing sugars of tritordeum and wheat breads were comparable. Tritordeum cvs had about 15% higher alpha-amino nitrogen released at the end of the duodenal simulated digestion than soft wheat (p < 0.05). Bulel tritordeum flour, bread and digested bread had about 55% less R5-epitopes compared to the soft wheat. Differences in protein expression found between the two tritordeum cvs reflected in diverse digestion products and allergenic and celiacogenic potential of the duodenal peptides. Proteomic studies of a larger number of tritordeum cvs may be successful in selecting those with good agronomical performances and nutritional advantages.
... Compared with whole-grain wheat, the dietary fiber content of brown rice is also much lower and only slightly higher than that of refined white rice (Table 1). Similarly, whole-grain wheat breads and refined-wheat breads both have higher GI values of around 75 that are further affected by storage and toasting (Burton & Lightowler, 2008), whereas wholegrain spaghetti and refined-grain spaghetti have very similar but lower GI values of around 48 (Atkinson et al., 2008;Ludwig et al., 2018). For both food categories switching from the refined-grain to the whole-grain option will deliver more dietary fiber and nutrients associated with the bran and germ and improve the quality of the diet by this measure, but it would not affect the GI of the diet and so this component of diet quality would be unaffected. ...
Article
Full-text available
Grains are important sources of carbohydrates in global dietary patterns. The majority of these carbohydrates, especially in refined‐grain products, are digestible. Most carbohydrate digestion takes place in the small intestine where monosaccharides (predominantly glucose) are absorbed, delivering energy to the body. However, a considerable part of the carbohydrates, especially in whole grains, is indigestible dietary fibers. These impact gut motility and transit and are useful substrates for the gut microbiota affecting its composition and quality. For the most part, the profile of digestible and indigestible carbohydrates and their complexity determine the nutritional quality of carbohydrates. Whole grains are more complex than refined grains and are promoted as part of a healthy and sustainable diet mainly because the contribution of indigestible carbohydrates, and their co‐passenger nutrients, is significantly higher. Higher consumption of whole grain is recommended because it is associated with lower incidence of, and mortality from, CVD, type 2 diabetes, and some cancers. This may be due in part to effects on the gut microbiota. Although processing of cereals during milling and food manufacturing is necessary to make them edible, it also offers the opportunity to still further improve the nutritional quality of whole‐grain flours and foods made from them. Changing the composition and availability of grain carbohydrates and phytochemicals during processing may positively affect the gut microbiota and improve health.
... Regarding the effect of regularly consuming toasted food towards the incidence of NCD, there was no specific study provided online. A study towards ten healthy subjects showed that toasted bread compared to fresh commercial white bread had lower IAUC values (glycemic index) [33], which is better to be consumed by DM patients. The toasting process, which is a non-enzymatic browning reactions, could generate antioxidant activity similar to the baking process [34]. ...
Article
Full-text available
Lifestyle is one of the underlying risk factor of non-communicable disease (NCD). Dietary habit and exercise pattern are two indicators of lifestyle. Elderly are prone to NCD due to increased age which being independent risk factor. This study aimed to analyze and compare the lifestyle profile of elderly living with NCD between Bangkok and Surabaya, in term of dietary habit and exercise pattern, and to determine the best predictor of sedentary lifestyle among this population. This cross-sectional study involved 100 and 96 elderly with HT and/or DM in communities of Bangkok and Surabaya respectively (n=196). Self-developed instrument was used in data collection (r=0.178–0.715, Chronbach Alpha=0.644). Mann-Whitney U and regression tests were used in data analysis (α<0.05). There was a significant difference of lifestyle in elderly living with NCD between Bangkok and Surabaya (p=0.008), especially in term of eat variety food (p=0.002), oily food (p=0.015), and curry with coconut milk (p=0.026). Eat vegetable and fruit could not predict dietary habit in elderly living with NCD (p=0.064). Eat fermented food was came up as the best predictor of lifestyle (p=0.000). It was accounted for 52.1% variance in lifestyle score in this population.
Article
Background Glycemic index (GI) value is an important factor determining the postprandial glycemic response of available carbohydrate in our daily foods. Ideally, it should be determined by feeding foods to healthy human, while this is not always ethically, technically and financially possible especially with a large number of testing foods. Thus, many in vitro and animal models have been developed to predict GI values in human. Scope and approach In this review, the definition of GI related concepts is introduced, followed by reviewing the advantages and limitations of current in vitro and animal models in predicting food GI values. The animal models are especially focused. Key findings and conclusions Generally, in vitro digestion models appear to be reliable estimates of food GI values. However, due to difficulties in standardizing in vitro experimental conditions among different laboratories, many correlation equations have been proposed to predict GI values. This is potentially confusing for the food industry in order to develop food products with low GI values. Animal models are more physiologically relevant to human subjects over in vitro digestion models. However, it may involve ethical issues when applying animal models solely for the GI prediction purpose. In addition, there is currently the lack of correlation analysis between predicted GI values from animal models with those from human studies to support that animal models are reliable indicators of food GI values. The information summarized could help developing an optimal method for a high throughput screening of carbohydrate ingredients for low GI values.
Article
Background: It was suggested that low salivary-amylase activity (SAA) and cooling or stir-frying cooked starch decreases its digestibility and glycemic index. Objective: We determined the effects of SAA, cooling, and single-nucleotide polymorphisms (SNPs) in the salivary amylase (AMY1), pancreatic amylase (AMY2A, AMY2B), maltase-glucoamylase (MGAM), and sucrase-isomaltase (SI) genes on starch digestibility and glycemic index of cooked polished rice. Methods: Healthy subjects [pilot, n = 12; main, n = 20 with low-SAA (<50 U/mL), and n = 20 with high-SAA (>105 U/mL)] consumed test meals containing 25 g (pilot) or 50 g (main) available carbohydrate at a contract research organization using open-label (pilot) or assessor-blinded (main), randomized, crossover, Latin-square designs (trial registration: NCT03667963). Pilot-trial test meals were dextrose, freshly cooked polished rice, cooked rice cooled overnight, stir-fried hot rice, or stir-fried cold rice. Main-trial test meals were dextrose, dextrose plus 10 g lactulose, plain hot rice, or plain cold rice. In both trials, blood glucose was measured fasting and at intervals over 2 h. In the main trial, breath hydrogen was measured fasting and hourly for 6 h to estimate in vivo starch digestibility. Data were analyzed by repeated-measures ANOVA for the main effects of temperature and stir-frying (pilot trial) or the main effects of SAA and temperature (main trial) and their interactions. Effects of 24 single nucleotide polymorphisms (SNPs) were assessed separately. Means were considered to be equivalent if the 95% CI of the differences were within ±20% of the comparator mean for glucose response/glycemic index or ±7% for digestibility. Results: Pilot: neither temperature nor stir-frying significantly affected glucose incremental AUC (primary endpoint, n = 12). Main: mean ± SEM glycemic index (primary endpoint, n = 40) was equivalent for low-SAA compared with high-SAA (73 ± 3 vs. 75 ± 4) and cold rice compared with hot rice (75 ± 3 vs. 70 ± 3). Estimated starch digestibility (n = 39) was equivalent for low-SAA compared with high-SAA (95% ± 1% vs. 92% ± 1%) and hot rice compared with cold rice (94% ± 1% vs. 93% ± 1%). No meaningful associations were observed between genotypes and starch digestibility or glycemic index for any of the SNPs. Conclusions: The results do not support the hypotheses that low-SAA, cooling, and common genetic variations in starch-digesting enzymes affect the glycemic index or in vivo carbohydrate digestibility of cooked polished rice. This trial was registered at clinicaltrials.gov as NCT03667963.
Article
In this study, we aimed to formulate low glycemic index gluten-free cookies from high amylose rice flour by modifying baking conditions and ingredient composition. Baking temperature, baking time, and concentration of carboxymethyl cellulose were varied between 170 and 190 °C, 12–25 min, and 0.2–1%, respectively, using central composite rotatable design. Among the physical quality attributes, spread ratio and hardness of cookies increased predominantly with the increase in baking temperature. Resistant starch content and overall acceptability of cookies increased prominently, whereas predicted glycemic index and glycemic load decreased with the increase in the concentration of carboxymethyl cellulose. Design expert predicted baking temperature of 185 °C, baking time of 22 min, and 0.8% concentration of carboxymethyl cellulose as desirable conditions for the development of gluten-free low-glycemic index cookies from rice flour. Dietary fiber content of developed cookies was recorded as 4.66%. In-vitro starch digestibility results confirmed that resistant starch increased from 2.85% in rice flour to 7.20% in cookies, whereas predicted glycemic index and glycemic load decreased from 50.12 to 30.07 in rice flour to 44.60 to 17.51 in cookies, respectively. Overall acceptability of cookies was recorded as 8.90 on a 9-point hedonic scale.
Article
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Objective: To examine prospectively the relationship between glycemic diets, low fiber intake, and risk of non-insulin-dependent diabetes mellitus. Design: Cohort study. Setting: In 1986, a total of 65173 US women 40 to 65 years of age and free from diagnosed cardiovascular disease, cancer, and diabetes completed a detailed dietary questionnaire from which we calculated usual intake of total and specific sources of dietary fiber, dietary glycemic index, and glycemic load. Main outcome measure: Non-insulin-dependent diabetes mellitus. Results: During 6 years of follow-up, 915 incident cases of diabetes were documented. The dietary glycemic index was positively associated with risk of diabetes after adjustment for age, body mass index, smoking, physical activity, family history of diabetes, alcohol and cereal fiber intake, and total energy intake. Comparing the highest with the lowest quintile, the relative risk (RR) of diabetes was 1.37 (95% confidence interval [CI], 1.09-1.71, P trend=.005). The glycemic load (an indicator of a global dietary insulin demand) was also positively associated with diabetes (RR= 1.47; 95% CI, 1.16-1.86, P trend=.003). Cereal fiber intake was inversely associated with risk of diabetes when comparing the extreme quintiles (RR=0.72, 95% CI, 0.58-0.90, P trend=.001). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of diabetes (RR=2.50, 95% CI, 1.14-5.51) when compared with a low glycemic load and high cereal fiber intake. Conclusions: Our results support the hypothesis that diets with a high glycemic load and a low cereal fiber content increase risk of diabetes in women. Further, they suggest that grains should be consumed in a minimally refined form to reduce the incidence of diabetes.
Article
Full-text available
Differences in glycemic responses to various starchy foods are related to differences in the rate of starch digestion and absorption. In this study, the importance of the degree of gelatinization and the product thickness for postprandial glycemic and insulinemic responses to rolled oats and barley were studied in healthy subjects (5 men and 5 women). Thick (1.0 mm) rolled oats were made from raw or preheated (roasted or steamed) kernels. In addition, thin (0.5 mm) rolled oats were made from roasted or roasted and steamed (processed under conditions simulating commercial production) oat kernels. Finally, steamed rolled barley kernels (0.5 or 1.0 mm) were prepared. All thin flakes elicited high glucose and insulin responses [glycemic index (GI), 88-118; insulinemic index (II), 84-102], not significantly different from white wheat bread (P > 0.05). In contrast, all varieties of thick oat flakes gave significantly lower metabolic responses (GI, 70-78; II, 58-77) than the reference bread (P < 0.05). Thick barley flakes, however, gave high glucose and insulin responses (GI, 94; II, 84), probably because the botanical structure underwent move destruction than the corresponding oat flakes. We conclude that minimal processing of oat and barley flakes had a relatively minor effect on GI features compared with the more extensive commercial processing. One exception was thick oat flakes, which in contrast to the corresponding barley flakes, had a low GI.
Article
The glycaemic index (GI) is a measure of the ability of a food to raise blood sugar. Written by one of the co-inventors of the term, this is a clear and balanced review of current knowledge on this controversial concept. The book explores all the key issues of the definition of the GI, how to measure the GI of a food, how to apply GI information to meals and diets, the reasons why foods have different GI values and the impact of altering a diet GI on health and disease. The book highlights the benefits and the problems surrounding the GI concept, whilst encouraging readers to think critically about the issues involved.
Article
The glycemic index was proposed in 1981 as an alternative system for classifying carbohydrate-containing food. Since then, several hundred scientific articles and numerous popular diet books have been published on the topic. However, the clinical significance of the glycemic index remains the subject of debate. The purpose of this review is to examine the physiological effects of the glycemic index and the relevance of these effects in preventing and treating obesity, diabetes, and cardiovascular disease.
Article
Objective. —To examine prospectively the relationship between glycemic diets, low fiber intake, and risk of non—insulin-dependent diabetes mellitus.Desing. —Cohort study.Setting. —In 1986, a total of 65173 US women 40 to 65 years of age and free from diagnosed cardiovascular disease, cancer, and diabetes completed a detailed dietary questionnaire from which we calculated usual intake of total and specific sources of dietary fiber, dietary glycemic index, and glycemic load.Main Outcome Measure. —Non—insulin-dependent diabetes mellitus.Results. —During 6 years of follow-up, 915 incident cases of diabetes were documented. The dietary glycemic index was positively associated with risk of diabetes after adjustment for age, body mass index, smoking, physical activity, family history of diabetes, alcohol and cereal fiber intake, and total energy intake. Comparing the highest with the lowest quintile, the relative risk (RR) of diabetes was 1.37 (95% confidence interval [CI], 1.09-1.71, Ptrend=.005). The glycemic load (an indicator of a global dietary insulin demand) was also positively associated with diabetes (RR=1.47; 95% CI, 1.16-1.86, Ptrend=.003). Cereal fiber intake was inversely associated with risk of diabetes when comparing the extreme quintiles (RR=0.72,95% CI, 0.58-0.90, Ptrend=.001). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of diabetes (RR=2.50, 95% CI, 1.14-5.51) when compared with a low glycemic load and high cereal fiber intake.Conclusions. —Our results support the hypothesis that diets with a high glycemic load and a low cereal fiber content increase risk of diabetes in women. Further, they suggest that grains should be consumed in a minimally refined form to reduce the incidence of diabetes.
Article
The molecular basis of staling is examined by reviewing what is known about the components of wheat flour, factors that affect staling rate, and the various mechanisms that have been proposed. The conclusion reached is that bread staling is a complex phenomenon in which multiple mechanisms operate. Polymer crystallizations with the formation of supermolecular structures are certainly involved. The most plausible hypothesis is that retrogradation of amylopectin occurs, and because water molecules are incorporated into the crystallites, the distribution of water is shifted from gluten to starch/amylopectin, thereby changing the nature of the gluten network. The role of additives may be to change the nature of starch protein molecules, to function as plasticizers, and/or to retard the redistribution of water between components. Nothing more definite can be concluded at this time.
Article
The vast majority of bread is traditionally produced from wheat flour. Apart from its major constituent starch, wheat flour also contains many other types of substances of which the gluten, the non-starch polysaccharides as well as the lipids are the most important in terms of their impact on the processability of the raw material and in terms of the quality of the final products. We here provide the basics on the processability and quality determining wheat flour constituents and present common concepts on their fate during the breadmaking process as well as on approaches targeted to influence their functionality.
Article
Heat-processed foods can contain appreciable amounts of resistant starch (RS) that has the ability to survive prolonged incubation with a-amylase and other amylolytic enzymes. The occurrence of RS has important implications for dietary fibre (DF) determination and, possibly, for human bowel physiology also. Studies using cereal and potato starches have identified three key factors that influence yields of RS after heat-processing, i.e. amylose content, processing temperature and water content. The highest yields of RS (20–34% of total dry weight) were obtained from amylomaize starches, either raw or processed, and from amylopectin starches (32–46% RS) after incubation with α-(1→6)-debranching enzyme (pullulanase) followed by heat-processing. In contrast, the lowest yields of RS (0⁗2–4⁗md2%) were obtained from intact (i.e. non-debranched) amylopectin starches, with or without heat-processing. Yields of RS from wheat starch were affected primarily by processing temperature, reaching levels of about 9% in a single cycle of autoc1aving at 134°C with excess water and subsequent cooling (cf. levels of less than 1% in uncooked wheat starch) and higher levels still (about 15%) after five repeated cycles of autoclaving and cooling. A similar increase in yields of RS was seen in dilute (1%) starch suspensions that were subjected to repeated cycles of heating to 100°C, followed by cooling and storage. The time of storage after gelatinisation was only important in these dilute systems: levels of RS in freshly prepared concentrated starch gels (typically 57–67% H2O) or in white bread did not alter significantly on storage.