Influence of roasting conditions on the acrylamide content and the color of roasted almonds.

The influence of roasting conditions on the acrylamide content and on the color of roasted almonds of 3 cultivars was investigated. The temperature inside the almond kernel, the water content, the color, and the acrylamide content were determined at different roasting temperatures and times. The formation of acrylamide started only when the kernel temperature had exceeded approximately 130 degrees C. The activation energy for the acrylamide formation during the roasting of almonds was 123 kJ x mol(-1). The color as measured by the degree of brightness correlated well with the acrylamide content as acrylamide content increased with increasing darkness. Therefore, control of roasting temperature presents the critical factor for limiting the acrylamide concentration in the final product. At constant roasting conditions, almonds with higher initial moisture content contained less acrylamide after roasting, which is probably due to the influence of moisture on the development product temperature during roasting.

Occurrence of acrylamide in selected foods and mitigation options.

Acrylamide reduction in certain food products is an important issue for both the food industry and academic research institutions. The present paper summarises past and current research on the occurrence and reduction of acrylamide in potatoes, bakery products, almonds, olives and dried fruit. In potatoes, the control of reducing sugars, process temperature and moisture is imperative to limit acrylamide formation. In bakery products, free asparagine and the type of baking agent largely determine acrylamide formation and present the starting points for reduction. The application of asparaginase is promising in this respect because it acts only on the key precursor, asparagine, whereby the product character remains unchanged. The baking agent NH4HCO3 promotes acrylamide formation in sweet bakery but its replacement by NaHCO3 effectively decreases acrylamide concentrations. Temperature and free asparagine are the key factors for acrylamide formation in roasted almonds. Olives and dried fruit may contain acrylamide and large amounts of acrylamide can be formed upon heating these products, a phenomenon which needs further investigation.

Fermentation of resistant starches: influence of in vitro models on colon carcinogenesis.

Resistant starch type 2 (RS2) and type 3 (RS3) containing preparations were digested using a batch (a) and a dynamic in vitro model (b). Furthermore, in vivo obtained indigestible fractions from ileostomy patients were used (c). Subsequently these samples were fermented with human feces with a batch and a dynamic in vitro method. The fermentation supernatants were used to treat CACO2 cells. Cytotoxicity, anti-genotoxicity against hydrogen peroxide (comet assay) and the effect on barrier function measured by trans-epithelial electrical resistance were determined. Dynamically fermented samples led to high cytotoxic activity, probably due to additional compounds added during in vitro fermentation. As a consequence only batch fermented samples were investigated further. Batch fermentation of RS resulted in an anti-genotoxic activity ranging from 9-30% decrease in DNA damage for all the samples, except for RS2-b. It is assumed that the changes in RS2 structures due to dynamic digestion resulted in a different fermentation profile not leading to any anti-genotoxic effect. Additionally, in vitro batch fermentation of RS caused an improvement in integrity across the intestinal barrier by approximately 22% for all the samples. We have demonstrated that batch in vitro fermentation of RS2 and RS3 preparations differently pre-digested are capable of inhibiting the initiation and promotion stage in colon carcinogenesis in vitro.

Physiological and metabolic properties of a digestion-resistant maltodextrin, classified as type 3 retrograded resistant starch.

UNLABELLED: There is a growing interest in highly fermentable dietary fibers having the potential to reduce risks of disease through the production of short-chain fatty acids (SCFA). Recently a digestion-resistant retrograded maltodextrin (RRM), classified as type 3 resistant starch was developed. Systematic work to determine its molecular and physiological properties was carried out to determine (1) the fraction resistant to digestion in vitro and in vivo, (2) its postconsumption effect on blood glucose in healthy volunteers, and (3) its in vitro fermentation pattern, at different ages, by use of pooled fresh human fecal inoculum. RESULTS: The digestion resistant fraction obtained in vivo from ileostomy patients (59.4%) is similar to that obtained by the AOAC method for measuring retrograded resistant starch (59.7%). The relative glycemic response after consumption of 50 g of RRM was 58.5% compared to glucose set as 100%. When exposed to colonic microbiota, in vitro obtained indigestible fractions behave similarly to those obtained in vivo in ileostomy patients. Fermentation of RRM and production of butyric acid is negligible during the first months of life but develops subsequently during weaning. In adults, RRM fermentation results in a high yield of SCFA, with butyrate representing 21-31 mol % of total SCFA. The high yield of SCFA during colonic fermentation, observed from weaning age on, as well as the potential to help reduce glycemic load may be of benefit to a number of health-related functions in the host. Further study on clear clinical end points is warranted.

Investigations on the promoting effect of ammonium hydrogencarbonate on the formation of acrylamide in model systems.

NH4HCO3 is known to promote acrylamide formation in sweet bakery products. This effect was investigated with respect to sugar fragmentation and formation of acrylamide from asparagine and sugar fragments in model systems under mild conditions. The presence of NH4HCO3 led to increases in acrylamide and alpha-dicarbonyls from glucose and fructose, respectively. As compared to glucose or fructose, sugar fragments such as glyoxal, hydroxyethanal, and glyceraldehyde formed much higher amounts of acrylamide in reaction with asparagine. The enhancing effect of NH4HCO3 is explained by (1) the action of NH3 as base in the retro-aldol reactions leading to sugar fragments, (2) facilitated retro-aldol-type reactions of imines in their protonated forms leading to sugar fragments, and (3) oxidation of the enaminols whereby glyoxal and other reactive sugar fragments are formed. These alpha-dicarbonyl and alpha-hydroxy carbonyl compounds may play a key role in acrylamide formation, especially under mild conditions.

In vitro fermentability of differently digested resistant starch preparations.

The in vitro fermentability of two resistant starch preparations type 2 (RS2) and type 3 (RS3) was investigated using human colonic microbiota. Prior to the fermentation experiments, samples were digested using two in vitro models, a batch (ba) and a dynamic (dy), as well as an in vivo method (il) for RS3. Digestion residues were fermented in vitro using a simple batch model lasting 24 h and a more sophisticated dynamic model enduring 72 h. During batch fermentation, metabolite productions and starch degradation rates were similar for RS2 and RS3 but higher for dy- compared to ba-digested samples. RS3il led to the lowest fermentability. Furthermore, increased butyrate ratios were observed for all preparations. The varying RS preparations behaved similarly in the dynamic fermentation but showed high SDs. Moreover, the fermentability was slow during the first 24 h, indicating that the microbiota needed an adaptation period to ferment RS. Propionate ratios increased at the expense of butyrate with exception for RS2dy showing an increase in acetate only. Differences in fermentability observed between the dynamic model, allowing a closer simulation of the in vivo behavior, and the batch model, recommended for screening purposes, could be due to the varying microbiota used.

Human faecal microbiota develops the ability to degrade type 3 resistant starch during weaning.

BACKGROUND: Colonisation of the human colon starts immediately after birth. Bacterial composition is substantially influenced by the type of feeding. During weaning, microbiota diversifies considerably to finally approach the composition of that of adults. The aim of this study was to investigate the ability of colonic microbiota obtained from different age groups to ferment resistant starch (RS). METHODS: Faecal samples of breast-fed and formula-fed infants, infants at weaning, adults and elderly subjects were used as inocula. Fermentation experiments were performed by applying a standardised in vitro batch method. Fermentability was established by measuring both metabolite production and substrate degradation. An RS type 3 (RS-3) was used as substrate; its behaviour was compared with that of lactulose (positive control), whereas inoculum without substrate was used as negative control. RESULTS: Overall fermentation patterns clearly showed that the human microbiota of all age groups is able to degrade lactulose. In contrast, RS-3 was found resistant to the attack by microbiota of both breast-fed and formula-fed infants. Bacteria collected from infants at weaning were able to degrade RS-3 completely, but slower compared with adults. With increasing age, RS-3 fermentation was observed to be slightly retarded again. CONCLUSIONS: Human faecal microbiota of all age groups is able to ferment lactulose in vitro quickly and completely. The ability to degrade RS-3, however, is only established during weaning. Whether fermentation-related production of short-chain fatty acids from RS-3 and concurrent modifications of the microbiota can result in potential health benefits to the host at this stage of life needs to be elucidated.

Digestibility of resistant starch containing preparations using two in vitro models.

BACKGROUND: Resistant starch (RS) is known for potential health benefits in the human colon. To investigate these positive effects it is important to be able to predict the amount, and the structure of starch reaching the large intestine. AIM OF THE STUDY: The aim of this study was to compare two different in vitro models simulating the digestibility of two RS containing preparations. METHODS: The substrates, high amylose maize (HAM) containing RS type 2, and retrograded long chain tapioca maltodextrins (RTmd) containing RS type 3 were in vitro digested using a batch and a dynamic model, respectively. Both preparations were characterized before and after digestion by using X-Ray and DSC, and by measuring their total starch, RS and protein contents. RESULTS: Using both digestion models, 60-61 g/100 g of RTmd turned out to be indigestible, which is very well in accordance with 59 g/100 g found in vivo after feeding RTmd to ileostomy patients. In contrast, dynamic and batch in vitro digestion experiments using HAM as a substrate led to 58 g/100 g and 66 g/100 g RS recovery. The degradability of HAM is more affected by differences in experimental parameters compared to RTmd. The main variations between the two in vitro digestion methods are the enzyme preparations used, incubation times and mechanical stress exerted on the substrate. However, for both preparations dynamically digested fractions led to lower amounts of analytically RS and a lower crystallinity. CONCLUSIONS: The two in vitro digestion methods used attacked the starch molecules differently, which influenced starch digestibility of HAM but not of RTmd.

Influence of thermal processing conditions on acrylamide generation and browning in a potato model system.

Fried potato products such as French fries and chips may contain substantial amounts of acrylamide. Numerous efforts are undertaken to minimize the acrylamide content of these products while sensory properties such as color and flavor have to be respected as well. An optimization of the frying process can be achieved if the basic kinetic data of the browning and acrylamide formation are known. Therefore, heating experiments with potato powder were performed under controlled conditions (moisture, temperature, and time). Browning and acrylamide content both increased with heating time at all temperatures and moisture contents tested. The moisture content had a strong influence on the activation energy of browning and acrylamide formation. The activation energy strongly increased at moisture contents below 20%. At higher moisture contents, it was very similar for both parameters. At low moisture contents, the activation energy of acrylamide formation was larger as compared to the one for browning. This explains why the end of the frying process is very critical. Therefore, a lower temperature toward the end of frying reduces the acrylamide content of the product while color development is still good.

Authentication of the botanical and geographical origin of honey by front-face fluorescence spectroscopy.

Front-face fluorescence spectroscopy, directly applied on honey samples, was used for the authentication of 11 unifloral and polyfloral honey types (n = 371 samples) previously classified using traditional methods such as chemical, pollen, and sensory analysis. Excitation spectra (220-400 nm) were recorded with the emission measured at 420 nm. In addition, emission spectra were recorded between 290 and 500 nm (excitation at 270 nm) as well as between 330 and 550 nm (excitation at 310 nm). A total of four different spectral data sets were considered for data analysis. Chemometric evaluation of the spectra included principal component analysis and linear discriminant analysis; the error rates of the discriminant models were calculated by using Bayes' theorem. They ranged from <0.1% (polyfloral and chestnut honeys) to 9.9% (fir honeydew honey) by using single spectral data sets and from <0.1% (metcalfa honeydew, polyfloral, and chestnut honeys) to 7.5% (lime honey) by combining two data sets. This study indicates that front-face fluorescence spectroscopy is a promising technique for the authentication of the botanical origin of honey and may also be useful for the determination of the geographical origin within the same unifloral honey type.

Authentication of the botanical origin of honey by near-infrared spectroscopy.

Fourier transform near-infrared spectroscopy (FT-NIR) was evaluated for the authentication of eight unifloral and polyfloral honey types (n = 364 samples) previously classified using traditional methods such as chemical, pollen, and sensory analysis. Chemometric evaluation of the spectra was carried out by applying principal component analysis and linear discriminant analysis. The corresponding error rates were calculated according to Bayes' theorem. NIR spectroscopy enabled a reliable discrimination of acacia, chestnut, and fir honeydew honey from the other unifloral and polyfloral honey types studied. The error rates ranged from <0.1 to 6.3% depending on the honey type. NIR proved also to be useful for the classification of blossom and honeydew honeys. The results demonstrate that near-infrared spectrometry is a valuable, rapid, and nondestructive tool for the authentication of the above-mentioned honeys, but not for all varieties studied.

Authentication of the botanical and geographical origin of honey by mid-infrared spectroscopy.

The potential of Fourier transform mid-infrared spectroscopy (FT-MIR) using an attenuated total reflectance (ATR) cell was evaluated for the authentication of 11 unifloral (acacia, alpine rose, chestnut, dandelion, heather, lime, rape, fir honeydew, metcalfa honeydew, oak honeydew) and polyfloral honey types (n = 411 samples) previously classified with traditional methods such as chemical, pollen, and sensory analysis. Chemometric evaluation of the spectra was carried out by applying principal component analysis and linear discriminant analysis, the error rates of the discriminant models being calculated by using Bayes' theorem. The error rates ranged from <0.1% (polyfloral and heather honeys as well as honeydew honeys from metcalfa, oak, and fir) to 8.3% (alpine rose honey) in both jackknife classification and validation, depending on the honey type considered. This study indicates that ATR-MIR spectroscopy is a valuable tool for the authentication of the botanical origin and quality control and may also be useful for the determination of the geographical origin of honey.

Human gut microbiota does not ferment erythritol.

Erythritol, a naturally occurring polyol, is gaining attention as a bulk sweetener for human nutrition. Industrially, it is produced from glucose by fermentation. From various studies it is known to be non-cariogenic. Moreover, it is rapidly absorbed in the small intestine and quantitatively excreted in the urine. Only about 10 % enters the colon. Earlier in vitro experiments showed that erythritol remained unfermented for a fermentation period of 12 h. In order to investigate whether fresh human intestinal microbiota is able to adapt its enzyme activities to erythritol, a 24 h lasting fermentation was carried out under well-standardised in vitro conditions. For comparison maltitol, lactulose and blank (faecal inoculum only) were incubated as well. Fermentation patterns were established by following total gas production, hydrogen accumulation, changes in pH value, SCFA production and substrate degradation. Taking all fermentation parameters into account, erythritol turned out to be completely resistant to bacterial attack within 24 h, thus excluding an adaptation within that period. Since under in vivo conditions more easily fermentable substrates enter the colon continuously, it seems very unlikely that erythritol will be fermented in vivo.

Acrylamide in roasted almonds and hazelnuts.

The influences of composition and roasting conditions on acrylamide formation in almonds and hazelnuts were investigated. Eighteen samples of almonds originating from the U.S. and Europe were analyzed for sugars and free amino acids, and acrylamide formed during roasting was determined. Asparagine was the main free amino acid in raw almonds and correlated with the acrylamide content of dark roasted almonds. Roasting temperature was another key factor and had a very strong influence on acrylamide formation. Almonds of European origin contained significantly less free asparagine and formed significantly less acrylamide during roasting as compared to the almonds from the U.S. Roasted hazelnuts contained very little acrylamide because of the low content of free asparagine in the raw nut. Reducing sugars, although being consumed much faster than free amino acids in both types of nuts, were not decisive for the extent of acrylamide formation during roasting.

Authentication of the botanical origin of honey by front-face fluorescence spectroscopy. A preliminary study.

The potential of front-face fluorescence spectroscopy for the authentication of unifloral and polyfloral honey types (n = 57 samples) previously classified using traditional methods such as chemical, pollen, and sensory analysis was evaluated. Emission spectra were recorded between 280 and 480 nm (excit: 250 nm), 305 and 500 nm (excit: 290 nm), and 380 and 600 nm (excit: 373 nm) directly on honey samples. In addition, excitation spectra (290-440 nm) were recorded with the emission measured at 450 nm. A total of four different spectral data sets were considered for data analysis. After normalization of the spectra, chemometric evaluation of the spectral data was carried out using principal component analysis (PCA) and linear discriminant analysis (LDA). The rate of correct classification ranged from 36% to 100% by using single spectral data sets (250, 290, 373, 450 nm) and from 73% to 100% by combining these four data sets. For alpine polyfloral honey and the unifloral varieties investigated (acacia, alpine rose, honeydew, chestnut, and rape), correct classification ranged from 96% to 100%. This preliminary study indicates that front-face fluorescence spectroscopy is a promising technique for the authentication of the botanical origin of honey. It is nondestructive, rapid, easy to use, and inexpensive. The use of additional excitation wavelengths between 320 and 440 nm could increase the correct classification of the less characteristic fluorescent varieties.

Factors influencing acrylamide formation in gingerbread.

The influence of ingredients, additives, and process conditions on the acrylamide formation in gingerbread was investigated. The sources for reducing sugars and free asparagine were identified and the effect of different baking agents on the acrylamide formation was evaluated. Ammonium hydrogencarbonate strongly enhanced the acrylamide formation, but its N-atom was not incorporated into acrylamide, nor did acrylic acid form acrylamide in gingerbread. Acrylamide concentration and browning intensity increased both with baking time and correlated with each other. The use of sodium hydrogencarbonate as baking agent reduced the acrylamide concentration by more than 60%. Free asparagine was a limiting factor for acrylamide formation, but the acrylamide content could also be lowered by replacing reducing sugars with sucrose or by adding moderate amounts of organic acids. A significant reduction of the acrylamide content in gingerbread can be achieved by using sodium hydrogencarbonate as baking agent, minimizing free asparagine, and avoiding prolonged baking.

Acrylamide in gingerbread: critical factors for formation and possible ways for reduction.

The influence of ingredients, additives, and process conditions on acrylamide formation in gingerbread was investigated. The sources for reducing sugars and free asparagine were identified, and the effect of different baking agents on acrylamide formation was evaluated. Ammonium hydrogencarbonate strongly enhanced acrylamide formation, but its N atom was not incorporated into acrylamide, nor did acrylic acid form acrylamide in gingerbread. Acrylamide concentration and browning intensity both increased with baking time and correlated with each other. The use of sodium hydrogencarbonate as baking agent reduced the acrylamide concentration by >60%. Free asparagine was a limiting factor for acrylamide formation, but the acrylamide content could also be lowered by replacing reducing sugars with sucrose or by adding organic acids. It is concluded that a significant reduction of acrylamide in gingerbread can be achieved by using sodium hydrogencarbonate as baking agent, minimizing free asparagine, and avoiding prolonged baking.

Potential of acrylamide formation, sugars, and free asparagine in potatoes: a comparison of cultivars and farming systems.

Glucose, fructose, sucrose, free asparagine, and free glutamine were analyzed in 74 potato samples from 17 potato cultivars grown in 2002 at various locations in Switzerland and different farming systems. The potential of these potatoes for acrylamide formation was measured with a standardized heat treatment. These potentials correlated well with the product of the concentrations of reducing sugars and asparagine. Glucose and fructose were found to determine acrylamide formation. The cultivars showed large differences in their potential of acrylamide formation which was primarily related to their sugar contents. Agricultural practice neither influenced sugars and free asparagine nor the potential of acrylamide formation. It is concluded that acrylamide contents in potato products can be substantially reduced primarily by selecting cultivars with low concentrations of reducing sugars.

Aroma compounds formed from 3-methyl-2,4-nonanedione under photooxidative conditions.

The behavior of the prominent aroma compound 3-methyl-2,4-nonanedione under photooxidative conditions was investigated in a model experiment. The four well-known aroma compounds 2,3-butanedione, 2,3-octanedione, acetic acid, and caproic acid were identified. The main oxidation product was 3-hydroxy-3-methyl-2,4-nonanedione, an aroma compound with the odor description of rubbery, earthy, and plastic-like (GC-O). Its structure has been tentatively assigned based on mass (GC-MS) and vapor phase infrared spectra (GC-IR). The formal formation pathways are discussed for these compounds, and other origins described in the literature are presented.

Quality assessment of strawberries (Fragaria species).

Several cultivars of strawberries (Fragaria sp.), grown under different conditions, were analyzed by both sensory and instrumental methods. The overall appreciation, as expressed by consumers, was mainly reflected by attributes such as sweetness and aroma. No strong correlation was obtained with odor, acidity, juiciness, or firmness. The sensory quality of strawberries can be assessed with a good level of confidence by measuring the total sugar level ( degrees Brix) and the total amount of volatile compounds. Sorting out samples using the score obtained with a hedonic test (called the "hedonic classification method") allowed the correlation between consumers' appreciation and instrumental data to be considerably strengthened. On the basis of the results obtained, a quality model was proposed. Quantitative GC-FID analyses were performed to determine the major aroma components of strawberries. Methyl butanoate, ethyl butanoate, methyl hexanoate, cis-3-hexenyl acetate, and linalool were identified as the most important compounds for the taste and aroma of strawberries.