Functional properties of caseinate glycoconjugates prepared by controlled heating in the ‘dry’ state

Glucose, ribose, fructose, lactose, fructo‐oligosaccharide (inulin) and a mixture of inulin and fructose were conjugated with caseinate via the Maillard reaction using controlled heating and low water activity conditions in order to improve the functional properties of caseinate for food purposes. Conjugation with ribose and glucose increased the viscosity of caseinate 28‐fold over that of the unmodified caseinate control but also produced the most browning. Glycoconjugates of caseinate–fructose reacted at a substrate ratio of 1:0.2 w/w and 60 °C at 67% relative humidity for 48 h increased the viscosity of caseinate 24‐fold with less browning. At 80% relative humidity the reaction occurred so rapidly that, within 24 h gels containing darkly coloured particulate matter were produced. Incorporation of inulin at 1:1:0.2 w/w/w caseinate/inulin/fructose prevented formation of gels and produced glycoconjugates having 15‐fold the viscosity of unmodified caseinate with minimal browning. Copyright © 2005 Society of Chemical Industry     

Norwegian‐grown Jerusalem artichoke (Helianthus tuberosus L.): morphology and content of sugars and fructo‐oligosaccharides in stems and tubers

BACKGROUND: Two field trials growing Jerusalem artichoke (Helianthus tuberosus L.) are discussed. Twenty genetic variants were compared in order to find genotypes suitable for Norwegian production. A second trial investigated the above‐ground part of early and late variants. RESULTS: The highest yield (28.7 t ha^?1) and highest amount of tubers per plant was obtained in early variants, e.g. the white Tysnes gave 1.72 kg tubers plant^?1. Early variants had a markedly lower portion of smooth tubers. Late variants gave the most preferable tuber shape, but low yield. Only a weak correlation was found between dry matter content and total content of fructo‐oligosaccharides (FOS) (r = 0.255) in the tubers. The mean content of FOS including sucrose through all variants was found to be 116 g kg^?1 fresh weight (FW) or 550 g kg^?1 dry weight (DW). The average chain length of FOS in the tubers was found to be DP3.9. There was no difference in tuber FOS content between early and late variants. The highest above‐ground amount biomass was found for the late variants when harvested in September. The content of soluble carbohydrates was found to be highest in stalks in August (sucrose and FOS major compounds). CONCLUSION: Early variants give the highest tuber yield under Norwegian growing conditions. Late variants give highest above‐ground biomass. Copyright © 2010 Society of Chemical Industry     

Variation in 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and fructo‐oligosaccharide (FOS) status in onion bulbs. Influence of temperature and storage time

Effects of storage temperature and duration on 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and trisaccharide (Tri) and fructo‐oligosaccharide (FOS) status in onion bulbs var Tenshin kept for 24 weeks at 10 and 20 °C were investigated. 1‐FEH activity peaked sharply after 10 weeks and seemed to be triggered by a decrease in sucrose content. 1‐KH activity increased during the first 8 weeks and remained stable during the last 8 weeks. Contents of Tri, FOS and total FOS decreased abruptly during the first 8 weeks; however, at 10 °C, contents of Tri, FOS (DP 3–12) and total FOS were lower than those at 20 °C. The consumption rate of fructo‐oligosaccharides also appeared to be higher at 20 °C than at 10 °C, despite the slight degradation in activities observed at this low temperature. 1‐FEH seems to be under the control of a triggering signal which induces its activity, and sucrose seems to be this biochemical signal which initiates dormancy release and the onset of sprouting, as found previously. Thus changes in carbohydrates seem to be a strong indicator of the end of the dormant state of the bulb and the beginning of the sprouting period. Copyright © 2004 Society of Chemical Industry     

Glycation sites and bioactivity of lactose-glycated caseinate hydrolysate in lipopolysaccharide-injured IEC-6 cells

During the thermal processing of milk, Maillard reactions occur between proteins and lactose to generate glycated proteins. In this study, a lactose-glycated caseinate was hydrolyzed by trypsin. The obtained glycated caseinate (GCN) hydrolysate had a lactose content of 10.8 g/kg of protein. We identified its glycation sites and then assessed it for its protective effect against lipopolysaccharide-induced barrier injury using a rat intestinal epithelial cell line (IEC-6 cells) as a cell model and unglycated caseinate (CN) hydrolysate as a reference. Results from our liquid chromatography–mass spectrometry analysis of the GCN hydrolysate verified that lactose glycation occurred at the Lys residues in 3 casein components (α_S1-casein, β-casein, and κ-casein), and this resulted in the formation of 5 peptides with the following amino acid sequences: EMPFPKYPKYPVEPF, HIQKEDVPSE, GSENSEKTTMPL, NQDKTEIPT, and EGIHAQQKEPM. The results from cell experiments showed that the 2 hydrolysates could promote cell growth and decrease lactate dehydrogenase release in the lipopolysaccharide-injured cells; more importantly, they could partially protect the damaged barrier function of the cells by increasing trans-epithelial electrical resistance, decreasing epithelial permeability, and upregulating the expression of the 3 tight junction proteins zonula occludens-1, occludin, and claudin-1. However, compared with CN hydrolysate, GCN hydrolysate showed lower efficacy in protecting against cellular barrier dysfunction. We propose that the different chemical characteristics of the CN hydrolysate and the GCN hydrolysate (i.e., amino acid loss and lactose conjugation) contributed to the lower barrier-protective efficacy of the GCN hydrolysate. During dairy processing, protein glycation of the Maillard type might have a non-negligible, unfavorable effect on dairy proteins, in view of the resulting protein glycation we found and the critical function of proteins for maintaining the integrity of the intestinal barrier.     

Compositional and degradative changes during the manufacture of dry‐cured ‘lacón’

The gross and mineral composition, the main physicochemical parameters, the protein extractability and the proteolytic (nitrogen fractions and free amino acids) and lipolytic (acidity index and free fatty acids) changes were studied throughout the manufacturing process of five batches of dry‐cured ‘lacón’, a traditional Spanish meat product made from the fore‐ham of the pig following a similar technological process to that of dry‐cured ham. The main compositional characteristics of this product are the high NaCl content and the low moisture content at the end of the curing process. The pH remained fairly stable (around 6) throughout the whole process and a fall in a_w was observed, reaching very low (0.767 ± 0.052) final average values. It was noted that 76% of the sarcoplasmic and 83% of the myofibrillar proteins became insoluble during the manufacturing process. The values of the different nitrogen fractions increased in a significant manner during manufacture, reaching low final values that indicate that ‘lacón’ undergoes a low level of proteolysis in comparison with other products manufactured by similar technologies. The high NaCl content and the intense dehydration suffered during the manufacturing process appear to be the principal causes of this reduced protein degradation. In accordance with the limited increase in the α‐amino acidic nitrogen during ripening, the total free amino acid content increased slightly but significantly from average values of 4371 mg kg^?1 dry matter in fresh pieces to average values of 13 020 mg kg^?1 dry matter in pieces at the end of the ripening process. The profile of free amino acids in the final product was similar to that observed by other authors in dry‐cured ham. The acidity of the fat increased by a factor of five. The final average values (49.9 g oleic acid kg^?1) were lower than those determined in dry‐cured ham, which indicates that ‘lacón’ undergoes less lipolysis during the ripening process than dry‐cured ham. C18 : 1, C18 : 2 and C16 were the most intensively released fatty acids during curing. The profile of free fatty acids in the end product was in agreement with that observed by other authors in dry‐cured ham. Copyright © 2003 Society of Chemical Industry     

Maillard reaction during the processing of ‘Doce de leite’

‘Doce de leite’, a dairy product widely consumed in Brazil as a dessert or cake filling, is obtained from the heat treatment of milk and sucrose. On heating, the Maillard reaction occurs with the formation of desirable brown-coloured products with a characteristic and pleasant flavour. However, the reaction can also lead to changes in nutritive value. In order to follow chemically the extension of the Maillard reaction and its effect on the nutritive value of ‘doce de leite’ its commercial processing was followed. Increases in the level of free 5-hydroxymethylfurfural and in absorption at 420 nm by pigments attached to the protein were observed. The amino acid analysis showed a significant decrease in lysine levels (33%) as well as in arginine (11%) and histidine (10%). There was also a reduction in available lysine levels, as measured by the fluorodinitrobenzene (50.6%) and by the 2,4,6-trinitrobenzenesulphonic acid (23.5%) methods. These results suggest a deleterious effect of the processing of ‘doce de leite’ on the nutritive value of the milk.     

Amino Acids Inhibitory Effects and Mechanism on 2‐Amino‐1‐Methyl‐6‐Phenylimidazo [4,5‐b]Pyridine (PhIP) Formation in the Maillard Reaction Model Systems

This study was to investigate the inhibitory effects of amino acids (AAs) on the formation of 2‐amino‐1‐methyl‐6‐phenylimidazo [4,5‐b]pyridine (PhIP) and to evaluate the inhibition mechanism of PhIP in Maillard model systems. Different AAs were individually added into model systems heat‐treated at 180 °C/1 h. The PhIP, phenylacetaldehyde (PheAce), and pyrazines derivatives were determined using HPLC and GC‐MS. AAs significantly reduced (P < 0.05) PhIP levels in a dose‐dependent response, ranking as: Trp = Lys > Pro > Leu > Met > Val > Ile > Thr > Phe > Asp, at the highest molar ratio. The PheAce content was gradually reduced with increasing AAs levels, suggesting that AAs may inhibit PhIP formation through scavenging the available PheAce. A correlation between PhIP inhibition and PheAce‐scavenging activity of AAs was observed when PheAce and AAs were heated. The variety and quantity of pyrazines formed are highly depending on the type of AAs.     

Glycation of the Major Milk Allergen β‐Lactoglobulin Changes Its Allergenicity by Alterations in Cellular Uptake and Degradation

1 Scope

During food processing, the Maillard reaction (МR) may occur, resulting in the formation of glycated proteins. Glycated proteins are of particular importance in food allergies because glycation may influence interactions with the immune system. This study compared native and extensively glycated milk allergen β‐lactoglobulin (BLG), in their interactions with cells crucially involved in allergy.

2 Methods and results

BLG was glycated in MR and characterized. Native and glycated BLG were tested in experiments of epithelial transport, uptake and degradation by DCs, T‐cell cytokine responses, and basophil cell degranulation using ELISA and flow cytometry. Glycation of BLG induced partial unfolding and reduced its intestinal epithelial transfer over a Caco‐2 monolayer. Uptake of glycated BLG by bone marrow–derived dendritic cells (BMDC) was increased, although both BLG forms entered BMDC via the same mechanism, receptor‐mediated endocytosis. Once inside the BMDC, glycated BLG was degraded faster, which might have led to observed lower cytokine production in BMDC/CD4⁺ T‐cells coculture. Finally, glycated BLG was less efficient in induction of degranulation of BLG‐specific IgE sensitized basophil cells.

3 Conclusions

This study suggests that glycation of BLG by MR significantly alters its fate in processes involved in immunogenicity and allergenicity, pointing out the importance of food processing in food allergy.     

Degradation of N‐(1‐Deoxy‐d‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐xylulos‐1‐yl)proline using thermal treatment

The formation and degradation of N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)proline, derived from the secondary amine Maillard reaction in xylose‐amino acid model solutions, were detailed in this study. The identification and quantitative analysis of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline were carried out using high‐performance anion‐exchange chromatography and high‐performance liquid chromatography. The formation of intermediate and advanced products derived from N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline was also tested using an UV‐Vis spectrophotometer to gain a better comparing of the degradation process of the two important Maillard reaction products using thermal treatment. Results showed that the degradation of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine was more significant than N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline. Moreover, xylose was tested in the degradation products of both N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline, which indicated that the degradation of N‐substituted 1‐amino‐1‐deoxyketoses was a reversible reaction to form reducing sugar.     

Formation of 4‐Hydroxyfuranones and their Precursors during Production of Worts and Beers

Laboratory beers and samples taken at each stage of production, were analysed for the flavour active 4‐hydroxyfuranones; 5‐methyl‐4‐hydroxy‐3(2H)‐furanone (MHF), 2,5‐dimethyl‐4‐hydroxy‐3(2H)‐furanone (DMHF) and 5‐(or 2)‐ethyl‐2(or 5)‐methyl‐4‐hydroxy‐3(2H)‐furanone (EMHF). The length and temperature of mashing, the length of boiling, the rate of cooling the worts and the effects of grist composition were investigated to identify the 4‐hydroxyfuranone content of worts and subsequent beers. Fermentation temperature and the use of the stabilising agents, PVPP and Lucilite PC5, on the 4‐hydroxyfuranone content of the beer was also investigated. The results demonstrated that several aspects of beer production procedures affect the furanone content of the beer, but in practice the important factors are grist composition, the rate at which the boiled wort is cooled and fermentation temperature. Fermentation has a major effect on final furanone content as yeast produces both DMHF and EMHF. The results suggest that malt levels of precursor compounds, which can be converted to 4‐hydroxyfuranones by the Maillard reaction or by yeast, may prove to be more important than the quantities of the furanones found in malt in determining the final furanone content of beer. A clearer understanding of the nature of the precursors should allow manipulation of their production and beer furanone content.     

Influence of hop harvest date of the ‘Mandarina Bavaria’ hop variety on the sensory evaluation of dry‐hopped top‐fermented beer

To impart a special hop aroma to beer, dry‐hopping is a technique that is becoming more and more popular with commercial breweries. Nevertheless, until now little was known about the factors that influence the reproducibility (and consistent product quality) of dry‐hopping with flavour varieties. One factor that could influence the sensory impressions and aroma profile compositions of dry‐hopped beers is the hop harvest date. Therefore, to determine the effects of different harvest dates of the flavour variety ‘Mandarina Bavaria’ on the aroma of top‐fermented beer, laboratory‐scale dry‐hopping trials were performed. Besides tasting sessions of brewed beers, relative quantities of selected hop‐derived, as well as beer‐originated aroma compounds, were investigated by headspace–solid‐phase microextraction–gas chromatography–mass spectrometry. Duo–trio tests between the beers hopped with pellets of different harvest dates showed no significant differences (α = 0.05) between them. In addition, these beers had similar profiles in a five‐point profile tasting scheme. On the other hand, relative concentrations of some hop‐derived aroma compounds – especially myrcene, which is known to be able to contribute to beer flavour – increased corresponding to a later harvest date, while beer originated volatiles were not different between the beers. Analytical results combined with the results of sensory evaluations led to the conclusion that the harvest date of Mandarina Bavaria was not a dominant factor in the dry‐hopping aroma of top‐fermented beers. High amounts of fermentation by‐products are likely responsible for masking effects resulting in no sensory distinctness between the samples with different hop aroma compound concentrations. Copyright © 2016 The Institute of Brewing & Distilling     

Improvement in emulsifying properties of soy protein isolate by conjugation with maltodextrin using high‐temperature,short‐time dry‐heating Maillard reaction

Soy protein isolate (SPI)–maltodextrin (MD) conjugates were synthesised using Maillard reaction under high‐temperature (90, 115 and 140 °C), short‐time (2 h) dry‐heating conditions. The loss of free amino groups in proteins and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) profile confirmed that SPI‐MD conjugates were formed and higher dry‐heated temperatures could increase the glycosylation degree. The emulsifying properties of SPI and SPI‐MD conjugates were evaluated in oil‐in‐water emulsions. The emulsions stabilised with SPI‐MD conjugates synthesised at 140 °C exhibited higher emulsifying stability and excellent storage stability against pH, ionic strength and thermal treatment compared with those synthesised at 90 °C, 115 °C and SPI stabilised emulsions. This might be due to a greater proportion of conjugated MD in SPI‐MD conjugates synthesised at 140 °C because of the higher glycosylation degree, and more conjugated MD on the droplet surface could provide steric effect and enhance the stability of the droplets in the emulsions.     

Sensory quality of ethylene‐exposed carrots (Daucus carota L,cv ‘Yukon’) related to the contents of 6‐methoxymellein,terpenes and sugars

Carrots were analysed for taste and odour and for contents of terpenes, 6‐methoxymellein and sugars during 3 weeks storage at 15 °C in an atmosphere containing ethylene (1 µl l⁻¹). The ethylene treatment caused an increase in 6‐methoxymellein and the conversion of higher amounts of sucrose to fructose and glucose compared to control carrots stored in air. This corresponded to higher sensory scores for bitterness and terpene flavour and a lower score for sweetness, as measured by an expert taste panel. Principal component analysis showed a more expressed bitter taste, earthy flavour, green flavour, terpene flavour and aftertaste in the ethylene‐treated carrots. Correlations were found between sweet taste and the content of sucrose (r = 0.91, p < 0.005) and between the contents of various terpenes (particularly γ‐terpinene, limonene and caryophyllene) and terpene flavour, green flavour, aftertaste and bitter taste (r ≥ 0.72, p < 0.05). In the air‐stored carrots these off‐flavours seemed to be masked by a high sucrose content. © 2000 Society of Chemical Industry     

Bioavailability of iron from a heat treated glucose‐lysine model food system: assays in rats and in Caco‐2 cells

The influence of Maillard reaction products (MRP) from glucose–lysine on iron bioavailability was investigated. Equimolar glucose–lysine mixtures (GL, 40% moisture) were heated (150 °C, for 30, 60 and 90 min) to prepare samples GL30, GL60 and GL90, respectively, and were used to study the influence of MRP on iron solubility, iron uptake and transport in Caco‐2 cells and iron balance in rats. After an initial increase with GL30, in vitro iron solubility decreased in the presence of most of the heated samples. The Caco‐2 cell experiments showed that Fe cell content increased in the presence of heated mixtures with respect to GL, whereas transport was less affected. Iron balance was determined in rats fed diets containing the GL30 and GL90 samples (3%) for a 21 day period and compared with that measured in a control group. Consumption of glucose–lysine heated mixtures increased total iron retention, although hemoglobin values decreased. Iron accumulations in organs such as the spleen, kidney and small intestine were observed. Copyright © 2004 Society of Chemical Industry