Volume 19, Issue 7-8

To understand the gelation mechanism of mung bean starch (MBS) as affected by addition of edible alum, the physicochemical properties of MBS gels and their gelation process under 0–0.25 % of alum addition were studied. The results showed that alum incorporation enhanced the gel texture and starch-water interaction in a concentration-dependent manner. With increasing amount of alum addition, the pH value and ζ -potential of MBS decreased, while the swelling power, pasting viscosity, the leached amylose content, gelation temperature, short-range ordered structure and the crystallinity of MBS gels increased. It is believed that alum addition improved the texture of MBS gels by promoting amylose leaching, starch aggregation and recrystallization. The increase in starch-water interaction might be due to the destruction of MBS structure by polar ions and the formation of clathrates by leached amylose and Al 3+ ions.

Sunflower oil (SO) oleogel was initially prepared using 5 % (w/w) sunflower wax, hydrophobic (Span 80), or hydrophilic (Tween 80) emulsifiers. This study involved the physicochemical characterization of the batter and cake prepared through partial and complete replacement of butter with the oleogels. Batter and cake properties were improvised in T80, prepared with oleogel containing 0.015 % (w/w) of Tween 80. The polarized micrograph of the T80 batter displayed a large number of air bubbles stabilized by the wax crystals. Starch gelatinization was found highest in T80 batter and could be related to the ability of hydrophilic emulsifiers to form a complex with starch. The FTIR spectra in the T80 batter and cake displayed a reduced peak for gluten content. T80 cake crumb showed a homogenous distribution of smaller air cells supporting its softness. A reduction in the firmness and hardness of T80 was obtained from the texture studies.

This study aimed to investigate the effects of osmotic dehydration (OD) pretreatment on the drying and quality of pineapple slices dehydrated using microwave hot air rolling bed drying method. The result suggested the OD pretreatment significantly reduced the moisture content of the food material before drying. It also slightly increased the moisture ratio decreasing rate in the early stage of drying based on the formation of microchannels during the pretreatment. The pretreatment also increased overall temperature and facilitated the transition of free water to bounded water during drying. Based on the pretreatment, the undesired browning of pineapple slices during drying was significantly inhibited. However, the OD pretreatment with 60 % (w/v) sucrose solution caused significant dehydration of the sample before drying, finally resulting in more dramatic browning. Compared with the sample without OD pretreatment, the dried pretreated pineapple slices exhibited an increased amount of collapsed cell structures and pores, due to the cell deformation and water diffusion during the pretreatment. These microstructure changes finally contributed to their increased hardness, springiness and chewiness. Although the pretreatment caused a slightly higher ascorbic acid loss in the final dried food materials, the product with an improved sugar-to-acid ratio was prepared, indicating its improved acceptability. Considering the overall characteristics profile of the dried pineapple slices, the OD pretreatment using 50 % sucrose solution for 24 h was the optimum condition to develop promising dried pineapple slices products.

This study describes the in-situ growth of cobalt nanoparticles (Co NPs) to a naked-eye determination of tetracycline antibiotics in the water, honey, and milk samples as a colorimetric method. Tetracycline antibiotics bonded cobalt NPs (CoNPs-TCs) are performed light green to yellow color with high UV–vis absorbance at lambda maximum of 400 nm. Cobalt nanoparticles bonded tetracycline were characterized by using UV–vis spectroscopy, Fourier transforms infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FE-SEM). Effective parameters of the method, such as solution pH (∼8.5), reaction time (3 min), temperature (25 °C), and cobalt concentration (20 μg mL −1 ) were studied. Analytical validation is performed that the limit of determination 0.21–1.09 μg mL −1 and the limit of quantification was 0.73–3.88 μg mL −1 with a matrix match linear dynamic range from 1 to 100 μg mL −1 for tetracyclines in all water, milk, and honey samples. The accuracy and precision of the method were evaluated with real samples recovery (80–108 %, ±5) and precision (intraday, 0.73–3.75 %, n  = 3 and interday, 2.01–4.82 %, n  = 9), respectively. This method provides a rapid, simple, and inexpensive detection with acceptable sensitivity.

In this study, four typical fragrance types of rapeseed oils were investigated under short-term frying of French fries and heating processes. Volatile flavor profiles, aroma compounds, and sensory attributes were evaluated by gas chromatography–mass spectrometry (GC-MS), gas chromatography–olfactory (GC-O), and sensory evaluation. The examination showed 140 volatiles, 28 aroma compounds, as well as 8 sensory attributes were detected. Aldehydes, nitriles, and acids were principal groups in unheated delicate fragrance rapeseed oil (DFRO) and refined rapeseed oil (RRO), as well as nitriles, acids, and heterocycles in unheated strong fragrance rapeseed oil (SFRO) and umami fragrance rapeseed oil (UFRO). During heating process, the total amount of volatiles had significant increases in DFRO and RRO, whereas it was the opposite in SFRO and UFRO. Aldehyde became the most predominant group, with significant increases under thermal treatments. Compared with heated oils, most volatiles presented lower contents in fried oils. Among the volatiles, 24 compounds were formed during heating process and 6 compounds were detected solely in fried oils. Among 8 sensory attributes, the deep-fried flavor attribute was formed in thermal-treated oils. According to the statistical analysis, remarkable differences were observed among unheated and thermal-treated samples, and the differences were diminished under thermal treatments, especially frying process; however, fried SFRO and DFRO still showed obvious distinctions with the others in flavor profiles.

Dry malt extract (DME) is powder prepared by dehydrating the wort, which is mainly produced by spray drying on the market. In addition, the beer industry has problems with the nitrogen content of wort, which is not easily controlled, and with the undesired volatile dimethyl sulfide (DMS), which is caused unpleasant odors in beer. In this study, DME was prepared using spray-freeze drying (SFD) technology by comparing with freeze dried DME and spray dried DME. The results show that SFD can be used as a novel engineering technique to improve the physical properties of DME having a narrow particle size distribution as well as high solubility and flowability. The freezing process was found to migrate proteins to the droplet surface by elemental analysis, and the drying process partially modified the surface protein and SFD powder fragility characteristics to achieve the purpose of reducing nitrogen content in DME.