Fast quantitative analysis and chemical visualization of amylopectin and amylose in sweet potatoes via merging 1D spectra and 2D image.

The quantitative analysis and spatial chemical visualization of amylopectin and amylose in different varieties of sweet potatoes were studied by merging spectral and image information. Three-dimensional (3D) hyperspectral images carrying 1D spectra and 2D images of hundreds of the samples (amylopectin, n = 644; amylose, n = 665) in near-infrared (NIR) range of 950-1650 nm (426 wavelengths) were acquired. The NIR spectra were mined to correlate with the values of the two indexes using a linear algorithm, generating a best performance with correlation coefficients and root mean square error of prediction (rP and RMSEP) of 0.983 and 0.847 g/100 mg for amylopectin, and 0.975 and 0.500 g/100 mg for amylose, respectively. Then, 14 % of the wavelengths (60 for amylopectin, 61 for amylopectin) were selected to simplify the prediction with rP and RMSEP of 0.970 and 1.103 g/100 mg for amylopectin, and 0.952 and 0.684 g/100 mg for amylose, respectively, comparable to those of full-wavelength models. By transferring the simplified model to original images, the color chemical maps were created and the differences of the two indexes in spatial distribution were visualized. The integration of NIR spectra and 2D image could be used for the more comprehensive evaluation of amylopectin and amylose concentrations in sweet potatoes.

Effect of different cooking times on the fat flavor compounds of pork belly.

Fat has a great impact on the meat product flavor, which is influenced by cooking time. This study explored the effect of different steaming times on the fat flavor of pork belly. A total of 14 aldehydes, 11 ketones, 6 esters, 4 alcohols, and 1 acid volatile compounds were identified through gas chromatography ion mobility spectrometry (GC-IMS). The relative odor activity value (ROAV) combined with the principal component analysis (PCA) method showed that the aroma of pork belly fat was considerably different under different steaming times. The quantity of key volatile compounds with ROAV ≥ 1, namely, heptanal, ethyl hexanoate, 2-methylbutanal-m, 3-methylbutanal, ethyl acetate, and 2, 3-butanedione increased considerably in the fat after steaming. The fat gives rise to two key volatile compounds, hexanal-d and 1-heptanol, after steaming for 30 min. Similarly, ethyl formate and 3-hydroxy-2-butanone were obtained as the key volatile compounds after steaming for 180 min. PRACTICAL APPLICATIONS: Pork belly is the main ingredient of Chinese traditional dishes such as Dongpo's pork and braised pork in brown sauce. When heated for extended periods of time, the high fat content of pork belly gives rise to important precursors that influence the flavor characteristics of these dishes. However, studies comparing the diversities of volatile compounds in pork belly fat exposed to different heating times are sparse. To address this gap in literature, this study identified the flavor components of pork belly fat exposed to different heating times. The data from this study can act as a framework for further flavor research on pork belly products.

Effects of different cooking methods on volatile flavor compounds of chicken breast.

Chicken is one of the highest selling meats worldwide. Different cooking methods produce various flavor compounds in cooked chicken, which affect consumers' food choices. In this study, the volatile flavor components of Gushi chicken breast after stewing and air frying were detected using gas chromatography-ion mobility chromatography (GC-IMS) and principal component analysis (PCA), and the relative odor activity value (ROAV) was determined using PCA. A total of 43 volatile substances were identified. 3-(methylthio)propionaldehyde-M and benzene acetaldehyde can be used as characteristic flavor markers in the air-fried chicken breast.ethyl acetate, (E)-2-octenal-D, and 2-ethyl-1-hexanol-D can be used as characteristic flavor markers in the stewed chicken breast. Because these five substances have the most obvious contrast in the fingerprint. The following part describes the specific substances that have mainly contributed to the flavor system in the volatile system obtained by different cooking methods. Finally, the main flavor compounds of the stewed chicken breast were 3-methylbutanal-D, octanal-D, (E)-2-nonenal, and other 11 types of compounds (ROAV ≥1). Nine types of compounds (ROAV ≥1), including 3-methylbutanal-D, (E)-2-nonenal-M octanal-M, and hexanal-M, were the main compounds to characterize the air-fried chicken breast. PRACTICAL APPLICATIONS: GC-IMS technology combined with the principal component analysis of ROAV can be used to rapidly identify the main flavor substances and the flavor substances having an important role in modifying the overall taste of the sample. It plays a considerably important role in the aroma recombination of substances and can play a role in food processing.

Komagataeibacter cocois sp. nov., a novel cellulose-producing strain isolated from coconut milk.

Phylogenetic analysis was performed on a cellulose-producing strain, designated WE7T, isolated from contaminated coconut milk. The analysis utilized nearly complete 16S rRNA gene sequences, as well as concatenated partial sequences of the housekeeping genes dnaK, groEL and rpoB, and allowed identification of the strain as belonging to the genus Komagataeibacter. DNA-DNA correlation or average nucleotide identity analysis was performed between WE7T and its closest phylogenetic neighbours, and the resulting values were below the species level (<70 % and <95 %), suggesting that the strain represents a novel species in genus Komagataeibacter. Strain WE7T was coupled with Komagataeibacter species more tightly than with Gluconacetobacter species in a 16S rRNA gene sequence phylogenetic tree. Strain WE7T can be differentiated from closely related Komagataeibacter and Gluconacetobacter entanii species by the ability to grow on the carbon sources d-mannitol, sodium d-gluconate and glycerol, the ability to form acid by d-fructose, sucrose, d-mannitol, d-galactose and ethanol, and the ability to grow without acetic acid. The major fatty acid of WE7T is C18 : 1ω9c (52.3 %). The DNA G+C content of WE7T is 63.2 mol%. The name Komagataeibacter cocois sp. nov. is proposed, with the type strain WE7T (=CGMCC 1.15338T=JCM 31140T).

[Microbial NAD synthetase and its inhibitors--a review].

Nicotinamide-adenine dinucleotide (phosphate) (NAD(P)) metabolism involves many fundamental cellular events, such as energy metabolism, maintenance of redox homeostasis and regulation of cell longevity. Inhibitors of essential enzymes of NAD(P) biosynthetic pathways might be promising leads for novel antibiotics, such as the NAD synthase inhibitors. This review described the crystal structural, functional properties, regulator and structure-based inhibitors design for NAD synthase. This might provide the basis for developing NAD-based therapeutics.

Comparative genomics of NAD(P) biosynthesis and novel antibiotic drug targets.

NAD(P) is an indispensable cofactor for all organisms and its biosynthetic pathways are proposed as promising novel antibiotics targets against pathogens such as Mycobacterium tuberculosis. Six NAD(P) biosynthetic pathways were reconstructed by comparative genomics: de novo pathway (Asp), de novo pathway (Try), NmR pathway I (RNK-dependent), NmR pathway II (RNK-independent), Niacin salvage, and Niacin recycling. Three enzymes pivotal to the key reactions of NAD(P) biosynthesis are shared by almost all organisms, that is, NMN/NaMN adenylyltransferase (NMN/NaMNAT), NAD synthetase (NADS), and NAD kinase (NADK). They might serve as ideal broad spectrum antibiotic targets. Studies in M. tuberculosis have in part tested such hypothesis. Three regulatory factors NadR, NiaR, and NrtR, which regulate NAD biosynthesis, have been identified. M. tuberculosis NAD(P) metabolism and regulation thereof, potential drug targets and drug development are summarized in this paper.