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OCCURRENCE OF PROTEIN-BOUND LYSYLPYRROLALDEHYDE IN DRIED PASTA
No full textThe extent of the advanced Maillard reaction (MR) involving protein-bound lysylketoses degradation that occurs in pasta drying was studied by evaluating furosine and lysylpyrrolaldehyde (LPA). By enzymatic hydrolysis followed by solid-phase extraction and ion pair reversed-phase high-performance liquid chromatography (IP-RP HPLC) with 297-nm detection, protein-bound LPA was separated without interference and quantified in pasta products using carboxy-2-pyrrolaldehyde as the external standard. Model doughs containing different amounts of cold or [U-14C]-labeled glucose or maltose and pasta processed under different heating conditions were considered. A close relationship between the accumulation behaviors of furosine and protein-bound LPA was observed, confirming that LPA is a main derivative of lysylketoses residues. Further degradation of LPA was detected only under thermal treatments not applicable in pasta drying. Under the pasta processing conditions of a semipilot plant, and with semolina of known origin and free sugar composition, LPA formation was enhanced (> 12 mg/100 g of protein) when the drying cycle included temperatures close to 80-degrees-C or higher, and pasta moisture values were close to 15% or lower. Under low-temperature (50-degrees-C) conditions, no LPA was produced. Another key parameter was the concentration of reducing sugars, the most effective being glucose. Although other aminoketoses besides lysylketoses are probably formed and degraded, furosine and LPA evaluation seems to sufficiently describe the MR extent occurring on pasta protein. Considering the undesirable sensorial changes of pasta attributable to extensive MR, the possible antinutritional properties reported for LPA, and the wide range of LPA values (from 0 to over 40 mg/100 g of protein) found in commercial spaghetti, a better control of the advanced MR in this food is advisable
Evaluation of the stable reaction products of histidine with formaldehyde or with other carbonyl compounds in dairy products
No full textCombined formaldehyde (FA) can be evaluated in cheese and other dairy products by determining spinacine (6-carboxy-1,2,3,4-tetrahydroimidazopyridine), an imino acid arising from the reaction of FA with the x-amino group of histidine. Other carbonyl compounds usually produced by fermentations can react themselves with histidine, forming molecules which interfere with the determination of spinacine. A sensitive (minimum detectable amount, 5 fmol spinacine) and interference-free HPLC method, with precolumn derivatization with o-phtalaldehyde (OPA) and 9-fluorenylmethylchloroformate (FMOC), to evaluate these histidine reaction-compounds in dairy products is described. The clean-up of the FMOC-derivatized sample has been performed for the first time with solid-phase extraction (SPE) on an amino cartridge. The method was applied to samples of casein and differently ripened cheese, the origins of which were either known or commercial, in order to quantify the natural level of spinacine (0.7-2.7 ppm) probably deriving from biogenic FA, and to detect whether FA was used in processing
Evaluation and interpretation of alkaline phosphatase activity in hard cheeses made with raw milk
No full textIdentification of rennet-whey solids in “traditional butter” by means of HPLC/ESI-MS of non-glycosylated caseinomacropeptide A
No full text‘‘Traditional butter’’ (TB) is directly obtained from milk cream according to Reg. EC No. 2991/1994. Ascertainment of TB
authenticity implies the development of an analytical method for detecting illegal addition of cream from rennet-whey cream
(RWC) to milk cream. The reference HPLC method adopted for detecting the presence of rennet-whey solids in skim milk powder
(EC Reg. No. 213/2001) is based on the determination of non-glycosylated caseinomacropeptide A (CMP A, i.e. k-CNA f 106–169).
In this paper, the same method, coupled to ESI-MS, has been applied to the water phase of butter in order to detect CMP A deriving
from usage of RWC for butter manufacturing. The reliability of this approach has been evaluated by studying the effect of both
natural creaming and cream ripening in originating CMP A or peptides with CMP-like chromatographic behaviour. Results demonstrated
that peptides other than CMP A, and interfering in the HPLC profile, can form in cream after prolonged ripening with
commercial starters of lactic acid bacteria. Furthermore, proteolysis caused by psychrotrophic bacteria was studied by inoculating
milk cream with Pseudomonas fragi ATCC 4973. In this case, different peptides, including CMP A, are cleaved from k-casein when
bacterial count is >106 cfu/g. For these reasons, only LC/MS can unequivocally show the presence of non-glycosylated CMP A and
hence the usage of RWC in manufacturing of TB. In this regard, monitoring of multicharged ions at m/z 1697.5 and 2263.2 was
adopted for recognition of monophosphorylated CMP A. Control of commercial samples by means of HPLC/ESI-MS revealed that
usage of RWC is sometimes performed in countries where butter consumption is not widespread and a large volume of rennet whey
is available
Effect of semolina quality and processing conditions on nonenzymatic browning in dried pasta
No full textCaratteristiche chimico-analitiche di composti del latte correlabili con aspetti disgenesici
No full textCOUPLING OF LACTULOSE AND FUROSINE INDEXES FOR QUALITY EVALUATION OF STERILIZED MILK
No full textThe lactulose and furosine indices, describing the extent of lactose isomerization and early Maillard reaction (MR), respectively, are widely used to evaluate the heat load in milk sterilization processes. In this work, the combination of furosine and lactulose values for sterilized milk has been used to provide additional information about the ther mal histol ll of the end-product. Samples of UHT milk and in-bottle sterilized milk processed under defined conditions (n = 46) or collected from the market (n = 160) were consider ed The effects of raw milk pH, of addition of reconstituted milk powder, of processing conditions, and of prolonged storage were investigated. A high correlation between lactulose and furosine levels was found for all the milk samples of known origin and freshly prepared. When lactulose (y) was expressed as mgL(-1) and furosine (x) as mg 100g protein(-1), the function of the correlation line,vas y = 3.02 x -41.51, with r = 0.99. High values of milk pH enhanced lactose isomerization but did not affect MR. On the contrary, milk drying only promoted intensive MR. This behaviour was also found after prolonged preheating or long storage of sterilized milk. The presence of reconstituted milk powder ol over heating of milk was identified in some commercial samples of sterilized milk
Marker molecolari di prodotto e di processo nel controllo della qualità dei prodotti alimentari
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