The Influence of Proteolytic Malt Modification on the Aging Potential of Final Wort

The dynamic changes in beer flavor are determined by its aging potential, which comprises of present free and bound-state aldehydes and their precursors. Rising flavor-active aging compounds cause sensory deterioration (flavor instability). These compounds are mainly formed upstream in the brewing process through the Maillard reaction, the Strecker degradation, or lipid oxidation. Wort boiling is an especially critical production step for important reactions due to its high temperature and favorable pH value. Amino acid concentration, as an important aging-relevant precursor, is variable at the beginning of wort boiling, mainly caused by the malt modification level, and can further influence the aging potential aging formation during wort boiling. This study investigated the effect of the proteolytic malt modification level on the formation of precursors (amino acids and dicarbonyls) and free and bound-state aldehydes during wort boiling. Six worts (malt of two malting barley varieties at three proteolytic malt modification levels) were produced. Regarding precursors, especially Strecker, relevant amino acids and dicarbonyls increased significantly with an enhanced malt modification level. Concentrations of free and bound aldehydes were highest at the beginning of boiling and decreased toward the end. A dependency of malt modification level and the degree of free and bound aldehydes was observed for 2-methylpropanal, 2-methylbutanal, and 3-methylbutanal. Generally, a higher proteolytic malt modification level tended to increase free and bound aldehyde content at the end of wort boiling. Conclusively, the aging potential formation during boiling was increased by an intensified malt modification level.

Analysis of allelochemicals in the leaves of four alpine rhododendrons by gas chromatography-mass spectrometry

Field investigations conducted in the wild alpine rhododendron forest in the Baili Rhododendron Nature Reserve found that the natural regeneration of the forest was hindered. This paper used GC-MS to identify and analyze the most abundant chemical compounds in the leaves of four of rhododendron species (Rhododendron simsii, Rhododendron decorum, Rhododendron liliiflorum, and Rhododendron pulchrum). The results showed that the chemical substances in the four rhododendron leaf samples were mainly aldehydes, alcohols, and esters. Among them, the ester content in the leaves of R. simsii is the most abundant, the alcohol content in the R. decorum is the most abundant, and the aldehyde content in the R. liliiflorum is the most abundant. These results are conducive to the protection of the rhododendron ecosystem and laid a scientific foundation for studying the difficulties of natural regeneration of rhododendron communities.

Alternative Tanning Agent for Leather Industry from a Sustainable Source

Dialdehyde starches with different aldehyde content from native corn starch were prepared by sodium periodate oxidation to be used as a tanning agent in leather making. For this purpose, native corn starch was oxidized with sodium metaperiodate in different molar ratios. After oxidation processes, the yields, solubility in water and aldehyde contents of the obtained dialdehyde starches were determined as well as structure characterizations by Proton Nuclear Magnetic Resonance Spectroscopy, Fourier Transform Infrared Spectroscopy and Gel Permeation Chromatography. Evaluating the gel permeation chromatography data, the dialdehyde starch samples which were thought to be in appropriate molecular weight/size to penetrate into skin fibers were selected to be used in the tanning process. Their tanning abilities were evaluated by investigating hydrothermal stabilities, filling and fiber isolation characteristics and physical properties determined by mechanical tests and organoleptically. From the evaluation of the results, it was revealed that sodium metaperiodate oxidized starches which have appropriate molecular weight and adequate aldehyde content has a remarkable tanning effect and can be utilized as a tanning agent with the advantages of not necessitating pickling process which means saving time and simplifying the production but more importantly offering an important advantage from an environmental point of view.

Physical Properties of Films Based on Gelatin and Dialdehyde Starch with Different Oxidation Degrees

In this study, dialdehyde starch (DAS) was prepared by oxidizing corn starch using potassium periodateas the oxidant.The aldehyde contentsin DAS weredetermined using titration with hydroxylamine and were found proportional to the molar ratio of KIO4:C6H10O5.Fourier transform infrared spectroscopy was used to confirm the breakage of the bond between C2 and C3in anhydroglucose units and the formation of -CHO group in DAS. X-ray diffractometry showed a decrease in crystallinity of starch after periodate oxidation. Thermogravimetric analysis showed reduced thermal stability of DASin comparison with the native starch. The prepared DAS was blended with gelatin to form films by casting method. Increasing aldehyde contents in DAS from 0 to 12.2% resulted in decreased moisture contents, solubility in water, and the swelling capacity of gelatin-DAS films. The value of tensile strength and elongation at break of the gelatin-DAS films rose when the aldehyde content was low (0-3.5%), but declined when the aldehyde content was high (3.5-12.2%). Slight periodate oxidation is, therefore, an effective way to enhance the mechanical characteristics of blend films from DAS and other biopolymers.

Qualitative and quantitative determination of trace aldehydes and ketones in food preservative propionic acid for quality improvement

Aiming at the difficulty in qualitative and quantitative analysis of trace compositions in food preservative propionic acid, the trace compositions and the key components influencing the total aldehyde content in...