Proteolysis development in enzyme-modified Cheddar cheese using natural and recombinant enzymes of Lactobacillus rhamnosus S93

Proteolysis in enzyme-modified cheese was investigated with natural crude enzyme or recombinant aminopeptidase, both derived from Lactobacillus rhamnosus S93 in the presence of a commercial proteinase, Neutrase. For production of enzyme-modified cheeses, a cheese slurry was produced and pre-incubated with Neutrase. Natural enzyme or recombinant aminopeptidase (50 units 200 g⁻¹ slurry) was added alone or in combination to the cheese slurries, which were then incubated anaerobically under vacuum at 37 °C for 1, 3 and 6 d. The greatest levels of phosphotungstic acid soluble nitrogen and free amino acids were observed in the enzyme-modified cheese containing natural enzyme followed by the one treated with a combination of the natural enzyme and recombinant aminopeptidase. The enzyme-modified cheese containing the recombinant aminopeptidase alone resulted in the complete disappearance of proline after 1 d of maturation time.     

Functional Properties of Glycated Soy 11S Glycinin

ABSTRACT: 11S-rich glycinin fraction was extracted from defatted soy flakes and glycated using glucose (at a 1:44 molar ratio of protein to sugar) through the Maillard reaction. The glycation was done at 50°C and 65% relative humidity for varying incubation periods (6, 16, 24, and 48 h). Fluorescamine and trinitrobenzenesulfonic acid (TNBS) methods both revealed a gradual increase in % glycation from 34.8% to 39.6%, 42.6%, and 46.5%, as samples were glycated from 6 to 48 h. Functional studies of the glycated 11S-rich glycinin fraction showed an initial increase in solubility during the early stages of glycation and a decrease as glycation progressed beyond 24 h. Glycation in the 1st hour of incubation also decreased protein surface hydrophobicity and fat absorption capacity (FAC). This was mainly attributed to an increase in the net negative charge induced by the introduction of the sugar moiety. As the Maillard reaction progressed (24 h and 48 h of incubation), an increase in FAC and surface hydrophobicity was observed. The results further showed an increase in foaming properties and emulsifying activity of the 11S-rich glycinin fraction with glycation (compared with control), especially at the early and middles stages of the Maillard reaction.     

Investigation of various factors for the extraction of peppermint (Mentha piperita L.) leaves

Ingredients from peppermint leaves are widely used in the food industry as food additives and natural flavours. The traditional way to produce mint extracts is via steam distillation or solvent extraction, both long and energy consuming processes. This paper investigated various extraction methods, namely room temperature extraction, reflux temperature extraction, ultrasonic assisted room temperature extraction and microwave-assisted extraction. Extraction of peppermint leaves was studied for extraction times of 5, 10, 30 and 60 min, varying the sample-to-solvent ratio, along with the study of extraction yields for three mint compounds, menthone, menthol and menthofuran. The use of microwave-assisted solvent extraction allows the reduction of process time, the reduction of solvent use, while increasing extraction yields.     

Chemical activation of piperidine by formaldehyde and formation of lysine-specific Maillard reaction products

Piperidine is considered as a lysine-specific Maillard reaction product that can be formed from free lysine through decarboxylation and deamination reactions or through cyclization of pent-4-en-1-amine, the counterpart of acrylamide from lysine. Due to the importance and reactivity of piperidine its further interaction products in glucose/lysine model system was investigated. A useful strategy based on Py-GC/MS analysis was developed using an isotope labelling technique to identify reaction products incorporating piperidine moieties. Products simultaneously possessing five lysine carbon atoms (C2′–C6′) and the Nε-amino group from lysine in addition to glucose carbon atoms were targeted using specifically labelled precursors such as [¹⁵Nα]Lysine·2HCl, [¹⁵Nε]Lysine·2HCl, [U-¹³C₆]Lysine·2HCl, [¹³C-6]Lysine·2HCl and [U-¹³C₆]Glucose. Detailed labelling studies using specifically ¹³C-enriched sugars have shown that the piperidine can form reactive 1-methylidenepiperidinium ion with formaldehyde, which is able to undergo further aldol addition reactions to form compounds, such as 3-(piperidin-1-yl)propanal and 3-(pyridin-1(4H)-yl)propanal. Furthermore, these studies have also demonstrated that oxidation of piperidine into di- and tetrahydropyridine derivatives can generate reactive eneamine moieties capable of nucleophilic attack at carbonyl groups and formation of pyridine derivatives.