Optimization of combined microwave-hot air roasting of malt based on energy consumption and neo-formed contaminants content.

UNLABELLED: To produce specialty malt, malts were roasted by combined microwave-hot air at various specific microwave powers (SP = 2.5 to 3 W/g), microwave heating times (t(mw) = 3.3 to 3.5 min), oven temperatures (T(oven) = 180 to 220 degrees C), and oven heating times (t(oven) = 60 to 150 min). The response variables, color, energy consumption by microwave (E(mw)) and oven (E(oven)), total energy consumption (E(tot)), quantity of neo-formed contaminants (NFCs), which include hydroxymethylfurfural, furfural, furan, and acrylamide were determined. Response surface methodology (RSM) was performed to analyze and predict the optimum conditions for the specialty malt. Production using combined microwave-hot air roasting process based on minimum energy consumption and level of NFCs. At 95% confident level, SP, T(oven), and t(oven) were the most influencing effects with regard to E(tot), whereas t(mw) did not affect E(tot). T(oven) and t(oven) significantly affected malt color. Only T(oven) significantly influenced the NFCs content. The optimum parameters were: SP = 2.68 W/g for 3.44 min, T(oven) = 206 degrees C for 136 min for coffee malt, SP = 2.5 W/g for 3.48 min, T(oven) = 214 degrees C for 136 min for chocolate malt, and SP = 2.5 W/g for 3.48 min, T(oven) = 211 degrees C for 150 min for black malt. Comparing with conventional process, combined microwave-hot air reduced E(tot) by approximately 40%, 26%, and 26% for coffee, chocolate, and black malts, respectively, and reduced HMF, furfural, furan, and acrylamide contents by 40%, 18%, 23%, and 95%, respectively, for black malt. PRACTICAL APPLICATION: An important goal for research institutions and the brewery industry is to produce colored malt by combining microwave and hot air roasting, while saving energy, getting desirable color, and avoiding the formation of carcinogenic and toxic neo-formed contaminants (NFCs). Therefore, one objective of this study was to compare energy consumption and content of NFCs during roasting of malt by hot air-only and combined microwave-hot air processes as well as to determine the effect of specific power, microwave processing time, oven temperature, and oven processing time during combined microwave-hot air roasting. Another objective was to predict the optimum conditions for the production of coffee, chocolate, and black malts.

The health and technological implications of a better control of neoformed contaminants by the food industry.

The recent discovery of the presence of variable amounts of the carcinogenic compound acrylamide in a wide range of severely heat-treated food products, such as fried potatoes, biscuits, bread and coffee or malt, as a result of the heat process, has induced an important research in the area of the Maillard reaction in food. The interaction between a specific food composition and the heat process applied results in the development of complex oxidation and glycation reactions, which give rise to a mixture of flavoured compounds and possible neoformed contaminants (NFC). Recommendations by the European Commission aim at monitoring the content of major NFC, such as acrylamide and furan, in a list of food products commercialized in Europe. On the other hand, the Commission for European Normalization (CEN) has created recently a new workgroup (WG13) responsible for normalization of analytical method for NFC assessment. The European collective research ICARE was carried out to identify the possible health consequences of the ingestion of heat-treated products, characterize the reaction kinetics leading to NFC and evaluate some mitigation procedures proposed by the CIAA toolbox, and finally develop a simple, rapid and non destructive control method based on fluorescence acquisition on the crushed food products and chemometric analysis of the spectral information. This paper summarizes the objectives and essential results obtained in the scope of the project, highlighting the need for evaluating the distribution of NFC in food products commercialized in Europe, as well as the impact of the food formula/recipe and process on Maillard derived NFC food levels. The potential of the Fluoralys sensor regarding its ability to control food contamination with NFC is presented. A decrease in NFC concentration of heat processed food should allow significantly limiting the exposure of populations to NFC and consequently the potential related health risk.

Strategy for the study of the health impact of dietary Maillard products in clinical studies: the example of the ICARE clinical study on healthy adults.

The study of the health impact of dietary Maillard products (MPs) in realistic clinical studies requires the design of nutritionally equivalent diets with high and low levels of MPs. This difficult challenge may be achieved by setting the high-MP diet at the regular daily level, where the common use of grilling, frying, and roasting processes allows significant amounts of carboxymethyllysine, hydroxymethylfurfural and acrylamide to be formed. In such conditions, we show that major lipid degradation does not occur, nor does degradation of vitamin E or thiamine. Based on this finding, the low-MP diet; must be constructed accordingly, by replacing all high-temperature techniques with steam cooking or the absence of cooking. The cooking fat must be replaced with similar raw fat as seasoning in the low-MP diet, the high caloric density resulting from water loss in the high-MP diet must be compensated by higher food quantities offered in the low-MP diet, and the vitamin loss in fruit and vegetables resulting from high temperatures in the high-MP diet can be circumvented by increasing the corresponding portion size. In the ICARE study, equilibrated diets were proposed, fulfilling all nutritional needs, but with a 3- to 45-fold difference in MP concentrations. Individual quantification of nutritional and MP intakes will ensure the nutritional equivalence of the two diets and allow for quantification of the specific impact of ingested MPs.

Potential of front face fluorescence associated to PLS regression to predict nutritional parameters in heat treated infant formula models.

This work shows that front face fluorescence spectroscopy associated to partial least squares (PLS) calibration is a fast and simple method to assess the nutritional impact of heat treatment on milk samples. Emission spectra of tryptophan (Trp) and of advanced Maillard products (AMP) were recorded on intact milk samples non-heated and heated at seven temperatures (72 degrees C, 80 degrees C, 87 degrees C, 95 degrees C, 100 degrees C, 110 degrees C and 115 degrees C) for six different times (from 2 min to 9.5 min) by means of front face fluorescence. PLS calibrations were constructed in order to indirectly quantify three indicators: vitamin C, protein denaturation and accumulation of Maillard products using the fluorescence of advanced Maillard products and soluble tryptophan method (FAST). The prediction models allowed obtaining an estimation of these indicators with a relative error of 12% for vitamin C and about 18% for the FAST index and soluble whey protein ratio.

Evaluation of the maillard reaction in infant formulas by means of front-face fluorescence.

Foods are complex mixtures of macro- and micronutrients, which interact, leading to oxidation, glycation, and hydrolysis upon heating (e.g., sterilization, cooking) and storage. Their nutritional quality and safety are consequently affected, justifying the need for accurate monitoring of the evolution of the food composition during processing and shelf life. Classical chromatographic analysis as well as newly proposed rapid methods based on fluorescence spectrometry analyses were applied on whey powder-based models and commercial samples (in powdered form and ultrahigh temperature [UHT] sterilized), some of which had been previously submitted to protein hydrolysis. These samples were incubated for 48 h at 60 degrees C to mimic accelerated storage. Fluorescence fingerprints addressing modifications in the product composition during processing were recorded and analyzed by chemometric methods. Carboxymethyllysine (Nepsilon-[carboxymethyl]lysine; CML) was measured using an ELISA method. Fluorescence, recorded in a front-face mode on intact samples, is very sensitive to pertinent physicochemical changes induced by heat treatment, formulation (the moisture level in powders, presence of vitamin C and iron), and storage. Similar trends were observed between powders' fluorescence and CML-for example, a strong effect of protein hydrolysis and increasing water content. Addition of vitamin C was associated with an antioxidant effect despite the presence of iron. Good calibration models were obtained for predicting CML from fluorescence spectra both in food models and in commercial samples, although more work is needed to obtain accurate and robust calibration models. Results show the potential of nondestructively applied fluorescence spectrometry for measuring CML in formulas, a rapid, simple, and cost-effective method to monitor formula quality.

Effects of sterilization, packaging, and storage on vitamin C degradation, protein denaturation, and glycation in fortified milks.

Monitoring the nutritional quality of dietetic milk throughout its shelf life is particularly important due to the high susceptibility of some vitamins to oxidation, and the continuous development of the Maillard reaction during storage. The objective of this paper was to evaluate the vitamin C content and protein modification by denaturation and glycation on fortified milk samples (growth milks) destined for 1- to 3-yr-old children. The influences of the sterilization process, formulation, packaging, and storage duration at ambient temperature in the dark were studied. Vitamin C degradation was particularly influenced by type of packaging. The use of a 3-layered opaque bottle was associated with complete oxidation of vitamin C after 1 mo of storage, whereas in the 6-layered opaque bottle, which has an oxygen barrier, the vitamin C content slowly decreased to reach 25% of the initial concentration after 4 mo of storage. However, no significant effect of vitamin C degradation during storage could be observed in terms of Maillard reaction, despite the fact that a probable impact occurred during sterilization. Furosine content and the FAST (fluorescence of advanced Maillard products and soluble tryptophan) index-indicators of the early and advanced Maillard reaction, respectively-were significantly higher in the in-bottle sterilized milk samples compared with UHT samples, and in fortified milk samples compared with cow milk. However, after 1 mo, the impact of storage was predominant, increasing the furosine level and the FAST index at similar levels for the differently processed samples. The early Maillard reaction developed continuously throughout the storage period.In conclusion, only packaging comprising an oxygen and light barrier is compatible with vitamin C fortification of milk. Furthermore, short storage time or low storage temperature is needed to retard vitamin C degradation, protein denaturation, and development of the Maillard reaction.

Antioxidant vitamins and degenerative pathologies. A review of vitamin C.

In this review we describe how tissues are protected against free radicals and we detail the mechanisms by which the insufficient reduction of ascorbate is involved in glycation and oxidation processes on proteins.

The fluorescence of advanced Maillard products is a good indicator of lysine damage during the Maillard reaction.

The objective of this study was to determine whether in heat-treated milk-resembling models or milk there is a lag phase, before lactulosyllysine (LL) is converted into advanced Maillard products (AMP), and if there is a step during the heat treatment where LL is actively degraded into AMP. For that purpose, a low temperature (60-85 degrees C) and a long heat treatment (15-90 h) were chosen. We observe that the heat treatment first induces a parallel increase in furosine and AMP fluorescence, confirming that AMP are produced very early during the heat treatment. At this step, both indicators are correlated with each other and precisely reflect the lysine damage. After a time, however, furosine reaches a steady-state concentration, whereas AMP fluorescence still increases, remaining correlated with the lysine blockage. Nevertheless, heat treatment applied to milk does not reach this step so that AMP fluorescence appears as a rapid alternative to furosine quantification.

The FAST method, a rapid approach of the nutritional quality of heat-treated foods.

The FAST method is based on the determination of maximal fluorescence emission when exciting at 330-350 nm, which corresponds to molecular structures formed between reducing sugars or oxidizing lipids and lysine residues of proteins. This fluorescence is dependent on heat treatment and related to protein nutritional loss. Applied to a soluble extract of the food and corrected for the protein concentration of the solution obtained, using Trp fluorescence, the method allows to calculate the FAST index (FI), an indicator of the nutritional damage during heat process. The method, firstly validated on milk samples, is demonstrated here to well correlate with lysine damage on various food products, such as heat-treated milk and breakfast cereals, essentially modified by the Maillard reaction, and roasted soybean or cooked salmon, where interactions between oxidizing lipids and proteins better take place. Independently on the food product or the type of heat process, the FAST index appears always well correlated (r2: 0.84-0.98) to the lysine loss, the latter being estimated by determination of acid-released lysine, fluorescamine-reactive lysine or infrared. Shortly, roasted corn flakes appeared to be more damaged than extrudated flour (FI 100 and lysine blockage 40% instead of 55 and 30%), condensed milk more than UHT milk (FI 150 and 85% of acid-released lysine instead of 80 and 94%), and steam-cooked salmon much less than pan-fried (FI 28 instead of 372). Roasted soy can reach FI of more than 300 corresponding to chemical lysine loss of 40% and poultry-digestive lysine loss of 100%. As a conclusion, the FAST method, once precisely calibrated with pertinent nutritional indicators, should be of great interest for controlling or adapting a process in order to ensure a better nutritional quality for the food product.

Associations of age, smoking habits and diabetes with plasma vitamin C of elderly of the POLA study.

The objective of this study was to determine the associations of age and sex with plasma vitamin C (vit C) concentration taking into account smoking habits and the presence of age-related pathologies, such as diabetes. The POLA study is a population-based study on age-related eye diseases and their risk factors, and plasma Vitamin C evaluation is part of the biological parameters measured in the 1987 volunteer subjects living in Sète (South of France) and aged more than 60 years. Men had lower average plasma vit C levels than women (31.6 microM.L-1 versus 40.3 microM.L-1, p = 0.001). Plasma vit C was stable as a function of age in women but decreased in men (p = 0.02), enhancing the difference in vit C concentration between men and women with advancing age. Smoking more than 10 cigarettes a day was associated to a lower plasma vit C concentration in men (p = 0.001) but not in women, and diabetic subjects tended to have lower vit C concentrations, the difference being significant only in women (p = 0.003). We conclude that there is a clear influence of sex on plasma vit C. This difference may be due to dietary habits, or metabolism, but may also be due to different sensitivity of age, smoking and to some pathologies.

Riboflavin photodegradation and photosensitizing effects are highly dependent on oxygen and ascorbate concentrations.

Riboflavin (RF) is a normal component of the eye lens which triggers a strong photosensitizing activity when exposed to light. Upon irradiation with short wavelength radiations below 400 nm, RF-photosensitized damage may occur. However, vitamin C is present at high concentrations in the normal lens and plays an important role in inhibiting these photosensitization processes. An in vitro simple model was used with the objective of understanding better the relationships between vitamin C and oxygen concentrations on the mechanisms of RF-mediated photodegradation of tryptophan (Trp), a target particularly sensitive to photo-oxidation. Under nitrogen, the RF decomposition reached its maximal value, and vitamin C and Trp photo-oxidation was negligible. When increasing oxygen pressure, RF photodegradation dropped and vitamin C photo-oxidation strongly increased and was maximal at 100% O2. RF-induced photodegradation of Trp first increased with oxygen concentration, up to 40 microM O2, and then decreased. RF and Trp degradation were significantly protected by vitamin C so that no more than 20% of the substrates concentration were oxidized in the presence of vitamin C higher than 0.8 mM. From our results we conclude that in the specific conditions of the normal lens, the high vitamin C concentration (2 mM) is compatible with the UVA radiation hazard, despite the presence of RF. However, if lenticular vitamin C decreases below 0.8 mM, photodegradation of RF may occur and Trp may therefore be photo-oxidized by a Type-I mechanism.

Low plasma vitamin C in Alzheimer patients despite an adequate diet.

OBJECTIVE: To compare the vitamin C and E plasma levels in patients with Alzheimer's disease (AD) and to assess the vitamin C intake and nutritional status. DESIGN: Case-control study. Four groups of sex- and age-matched subjects were compared: severe AD and moderate AD, in patients with moderate AD and controls. SETTING: Community and hospitalized patients in the region of Toulouse, France. PARTICIPANTS: Patients with dementia who fulfilled criteria for Alzheimer's disease: severe Alzheimer group (N = 20), Mini-Mental State Examination (MMSE) score range 0-9; moderate Alzheimer group (N = 24), MMSE 10-23; hospitalized Alzheimer group (N = 9), MMSE 10-23. Control group (N = 19), MMSE 24-30. MEASURES: Plasma vitamin E and C were quantified by HPLC-fluorescence. Consumption of raw and cooked fruit and vegetables was evaluated in order to determine the mean vitamin C intakes. Mini Nutritional Assessment (MNA) and plasma albumin were used to measure nutritional status. RESULTS: Institutionalized and community subjects were analysed separately. MNA scores were normal in home-living Alzheimer subjects with moderate dementia and significantly lower in those with severe disease, despite normal plasma albumin levels. In the home-living Alzheimer subjects, vitamin C plasma levels decreased in proportion to the severity of the cognitive impairment despite similar vitamin C intakes, whereas vitamin E remained stable. The hospitalized Alzheimer subjects had lower MNA scores and albumin levels but normal vitamin C intakes, but their plasma vitamin C was lower than that of community-living subjects. Institutionalized Alzheimer subjects had significantly lower MNA scores but normal vitamin C and albumin levels and vitamin C intakes compared with community-dwelling subjects of similar degree of cognitive impairment. CONCLUSION: Plasma vitamin C is lower in AD in proportion to the degree of cognitive impairment and is not explained by lower vitamin C intake. These results support the hypothesis that oxygen-free radicals may cause damage.

Decrease in vitamin C concentration in human lenses during cataract progression.

Cataract formation is believed to result from an oxidative insult which decreases the antioxidant defense of the lens, particularly the vitamin C concentration. Upon oxidation, vitamin C contributes with glucose to protein glycation. It also favours tryptophan oxidation, resulting in fluorescent peptide cross-links and protein insolubilisation. The relationship between cataract and lenticular vitamin C was analysed in 48 cataractous lens nuclei classified into four severity grades, considering the sum of the colour and opacity. Ascorbic and dehydroascorbic acids were quantified by HPLC-fluorescence. The Amadori product was measured by means of furosine, advanced glycation end products by their fluorescence and tryptophan concentration by HPLC-UV. The lens vitamin C concentration significantly decreased with cataract severity, but mostly in severe brown cataracts (around 88 mumol/100 g lens in mild cataracts, and 50 mumol/100 g in dark brown lenses). The dehydroascorbic acid concentration was always low and stable (1.9 +/- 0.9 mumol/100 g), as was the furosine concentration (0.4 +/- 0.1 mumol/g). The fluorescence of insoluble advanced glycated end products was significantly higher in severe cataracts than in milder ones. The peptide tryptophan content was stable but the tryptophan to tyrosine ratio decreased and was highly correlated to the ascorbic acid concentration. Vitamin C content appears to be a good indicator of cataract severity, suggesting that oxidation could take part in cataract progression.

Effect of pH, phosphate and copper on the interaction of glucose with albumin.

Protein glycation is believed to play an important role in the development of long-term disorders associated with diabetes. Previous studies have shown that copper could activate this process; however, these experiments were performed under non-physiological conditions. In this study, in vitro experiments were carried out at near-physiological conditions to examine the catalytic activity of copper on the interaction of albumin with glucose. Changes in pH and phosphate buffering capacity were shown to affect albumin glycation. Under stable pH conditions, copper activates albumin glycation only at low protein concentrations (< 30 g l(-1)). Copper had no effect on albumin glycation at higher protein concentrations probably because the metal is chelated by the protein.

Plasma protein glycation in Alzheimer's disease.

Recent studies have suggested that formation of advanced glycation end-products (AGEs) in some brain proteins could be associated with Alzheimer's disease. These AGEs can be produced by various sugars (hexose, pentose, glyceraldehyde and oxidative products of vitamin C). In this study, we quantified plasma protein glycation specifically derived from glucose in patients with Alzheimer's disease with different grades of cognitive disorders. Two groups of Alzheimer patients were studied: a group with moderate Alzheimer's disease (n = 6, 923) and a group of subjects with diabetes (n = 31). Protein glycation was evaluated in plasma with a highly specific HPLC-UV technique, using furosine, which is the acid hydrolysis product of epsilon-deoxy-fructosyl-lysine Plasma furosine was almost two times higher in subjects with Alzheimer's disease (p<.005) than in controls, but still 50% lower than in diabetic patients (P<.02). Fasting plasma glucose levels were significantly correlated to the furosine concentration. To explain these results, an eventual impairment in glucose peripheral use or an increase in protein glycation rate associated with Alzheimer's disease should be explored.

Effect of iron and lactose supplementation of milk on the Maillard reaction and tryptophan content.

New liquid UHT milks supplemented with iron (0.9-1.4 mg/100 ml), vitamin C (1-7 mg/100 ml), lactose (2-4 g/100 ml) and linoleic acid (200-400 mg/100 ml), named growth milks, have recently become available to satisfy the specific nutritional needs of children aged 1-3 years. But the iron-vitamin C mixture could activate the lactose-induced Maillard reaction and tryptophan (Trp) oxidation in proteins. We have therefore examined the Amadori product and Trp concentrations of these milks. Forty-two commercial growth milks from five firms were analysed for the Maillard reaction and the soluble protein Trp content and compared with 64 UHT milks. The furosine concentration of total proteins was two to four times higher in 'growth' milks than in standard UHT milks, indicating a proportional loss of available lysine. The Trp fluorescence of undenatured proteins soluble at pH 4.6 was almost three times lower in 'growth' than in standard milks and Trp concentration 36% lower suggesting destruction of this oxidation-sensitive amino-acid. The mechanism of Trp destruction remains to be elucidated, and the roles of iron and Amadori products determined.

Validation of a micromethod for determining oxidized and reduced vitamin C in plasma by HPLC-fluorescence.

An HPLC micro-method with fluorescence detection has been developed to determine total vitamin C (vit C) and dehydroascorbic acid (DHA) concentrations in human plasma samples. This method is based on the rapid, specific reaction of DHA with dimethyl-o-phenylenediamine (DMPD) to form a fluorescent quinoxaline derivative that is quantified by HPLC in less than 5 minutes. The method was assessed with reference to the direct 2,4-dinitrophenylhydrazine (DNPH) colorimetric method. They were well correlated (r3 = 0.879), but the DMPD-HPLC method had the limit of detection 6 times lower than the standard method and the relative error for a vitamin standard was 10 times better than that of the standard method. The plasma DHA to total vit C ratio varied from 10 to 60%, depending on sample processing. Plasma that were immediately analysed contained 10% DHA whatever the subject's age; frozen deproteinized samples kept 1 week (-67 degrees C) had 20%, and blood samples kept for one hour at room temperature before treatment had up to 60% DHA. The ratio in capillary samples taken from the finger was 11-42%. This rapid, specific and very sensitive micro-method is well suited to routine measurements of plasma vit C.

Lack of effect of copper on advanced Maillard reaction and glucose autoxidation at physiological concentrations of albumin.

This study examines the possible action of copper on advanced glycation. Copper has been shown to induce fluorescence due to advanced-glycated-end-products (AGEs) on albumin incubated with glucose, and this was interpreted as activation of the glucose or Amadori product (AP) autoxidation. We glycated albumin (60 g/L) to several levels with increasing concentrations of glucose. The dialysed glucose-free glycated albumin was then incubated with 1.5 µmol/L copper or 1 mmol/L diethylenetriaminepentaacetic acid (DTPA), plus or minus glucose. The production of AP, measured as furosine, was similar whether DTPA or copper was present in the incubation medium. It linearly increased as a function of time and glucose concentration in both cases up to a maximum (furosine around 20 mmol/g protein), indicating saturation of the free NH2 residues on the protein. The fluorescence due to AGEs increased linearly over time for glycated albumin incubated without glucose, and exponentially when glucose was added to the incubation medium. This fluorescence was also unaffected by DTPA or copper for a glucose concentration below 125 mmol/L and initial furosine below 10 mmol/g. However copper caused a slight activation in samples with very high glucose (1.25 mol/L) and furosine (30-40 mmol/g) concentrations. We therefore find no effect of copper in this experiment, because the copper concentration is lower and the albumin higher than that used in previous studies. In these conditions, albumin chelates copper and inhibits its oxidative activity. The protein concentrations used in most in vitro studies showing a copper effect were below 10 g/L with copper often above 10 µmol/L, so that copper may act oxidatively. As the lens and arterial wall have high protein concentrations, copper should have no action on protein glycation in vivo, unless altered protein structure impedes the inactivation of copper by chelation.

Copper chelation by tryptophan inhibits the copper-ascorbate oxidation of tryptophan.

The in vitro oxidation of tryptophan (Trp) by pro-oxidant systems such as iron-ascorbate indicates that Trp is a target for oxygen radicals in vivo. The Trp in albumin and lipoproteins has been reported to be actively oxidized by hydroxyl radical (HO(•)) generating systems such as copper-ascorbate or PUFA (polyunsaturated fatty acids) respectively. The super-physiological concentrations of the oxidants used in these studies prompted us to examine the effect of low copper and ascorbate concentrations on Trp oxidation. Trp (10-5000 µmol/L) was incubated with 1.5 µmol/L copper plus ascorbate (0.113 and 1.13 mmol/L) at 37°C and its oxidation followed by fluorescence and high-performance liquid chromatography. The percentage of Trp oxidized by the ascorbate-copper system was inversely related to its concentration and positively related to the ascorbate concentration. High concentrations of Trp (above 50 µmol/L for 0.113 mmol/L and 500 µmol/L for 1.13 mmol/L ascorbate) are not significantly oxidized in the presence of ascorbate. The large drop in the percentage Trp oxidation at higher concentrations may be due to the chelation of copper by Trp. High concentrations of Trp (over 50 µmol/L) strongly prevented ascorbate oxidation by copper, and therefore inhibited the production of HO(•) needed for Trp oxidation. Protein Trp is less readily oxidized by the ascorbate-copper system than free Trp. Proteins chelate copper much better than Trp, and so inhibit its oxidative activity, at least against ascorbic acid.