Purification and Biochemical Characterization of Polyphenol Oxidase Extracted from Wheat Bran (Wan grano).

Currently, little is known about the characteristics of polyphenol oxidase from wheat bran, which is closely linked to the browning of wheat product. The wheat PPO was purified by ammonium sulfate precipitation, DEAE-Sepharose ion-exchange column, and Superdex G-75 chromatography column. Purified wheat PPO activity was 11.05-fold higher, its specific activity was 1365.12 U/mg, and its yield was 8.46%. SDS-PAGE showed that the molecular weight of wheat PPO was approximately 21 kDa. Its optimal pH and temperature were 6.5 and 35 °C for catechol as substrate, respectively. Twelve phenolic substrates from wheat and green tea were used for analyzing the substrate specificity. Wheat PPO showed the highest affinity to catechol due to its maximum Vmax (517.55 U·mL-1·min-1) and low Km (6.36 mM) values. Docking analysis revealed strong affinities between catechol, gallic acid, EGCG, and EC with binding energies of -5.28 kcal/mol, -4.65 kcal/mol, -4.21 kcal/mol, and -5.62 kcal/mol, respectively, for PPO. Sodium sulfite, ascorbic acid, and sodium bisulfite dramatically inhibited wheat PPO activity. Cu2+ and Ca2+ at 10 mM were considered potent activators and inhibitors for wheat PPO, respectively. This report provides a theoretical basis for controlling the enzymatic browning of wheat products fortified with green tea.

Insight into the effect of fatty acid composition on the texture of French fries.

BACKGROUND: Several researchers have reported that the texture of fries is affected by the fatty acid composition of oil, although the mechanism of this effect is not clear. In this regard, fries were fried in refined rapeseed oil and fully hydrogenated rapeseed oil with diverse proportions (0%, 20%, 40%, 60%, 80% and 100%) and were analyzed based on the content of moisture and oil, texture, thermal properties, crystalline properties and microstructure. RESULTS: The outcomes presented that fries fried in fully hydrogenated oil had less oil absorption and moisture loss than those fried in refined oil. The results from the texture analyzer, differential scanning calorimetry and X-ray diffraction showed that hardness, enthalpy and relative crystallinity increased with an increase in the proportion of fully hydrogenated oil. However, the peaks of starch-lipid complexes were hardly observed during frying. Furthermore, scanning electron microscopy results displayed that some physically trapped fat was observed in fries fried in mixed hydrogenated oil. Stereomicroscope images showed that the crust thickness of the fries increased slightly with an increase in the proportion of fully hydrogenated oil. CONCLUSION: Overall, the upsurge in crust thickness and oil crystals was responsible for an increase in the hardness of the fries. This indicated that the texture of fries can be manipulated by altering the fatty acid composition of the oil. © 2021 Society of Chemical Industry.

Effect of multistage process on the quality, water and oil distribution and microstructure of French fries.

The production of French fries is a multistage process (blanching, pre-frying, freezing and final frying). Pre-stage processing can result in drastic changes related to the quality of the final product. In this study, we investigated the effect of multistage process on quality properties, water and oil distribution and microstructure of fries prepared with different oils. Results showed that freezing treatment had little effect on water and oil content, color and volumetric shrinkage of pre-fried fries. Final fried fries exhibited drastic changes involved in the content and status of water and oil, color, texture, volumetric shrinkage and microstructure compared with other processing stage. Besides, magnetic resonance imaging visualized a thicker crust in finish-fried fries. Among all the oils, fries fried in high-oleic sunflower oil showed the best mouthfeel. This will provide a theoretical guidance for food enterprise to produce high-quality French fries.

Effect of microwave heating and vacuum oven drying of potato strips on oil uptake during deep-fat frying.

The properties of moisture and starch in potatoes affect the quality and oil absorption of final fried products. In this study, changes in moisture state, starch properties, and micromorphology of potato strips pretreated by microwave heating (MH) and vacuum oven drying (VOD) were investigated using low-field nuclear magnetic resonance, magnetic resonance imaging (MRI), differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy (SEM) analyses. The influence of changes in these properties on the oil content and distribution of fried potato strips was analyzed. Results showed that the decreased moisture content and changed moisture state in the pretreated samples had a positive effect on reducing the oil content. The pregelatinized starch facilitated the formation of V-type starch-lipid complexes, which formed a protective layer to prevent oil absorption. Analysis of MRI and confocal laser scanning microscopy images confirmed this finding. SEM observation showed microstructural changes might have an effect on oil absorption and its results exhibited crusts of the MH-pretreated samples thickened after frying, and the internal pores and structures of the VOD-pretreated samples became small and dense, respectively; both changes negatively affected oil absorption. Results could help understand the oil absorption behavior of starch-based food during frying and provide a basis for improving the quality and controlling the final oil content of the product.

The bioactive compounds and cellular antioxidant activity of Herbaceous peony (Paeonia lactiflora Pall) seed oil from China.

Herbaceous peony (HP) seed oil has been consumed in some regions of China, yet little information is available on its bioactive composition and antioxidant activity. This study aimed to evaluate the fatty acid compositions, micronutrients contents, and cellular antioxidant activity (CAA) of HP seed oil from five varieties. Results indicated that this oil had high percentages of monounsaturated (32.15 to 45.92%) and polyunsaturated fatty acids (58.65 to 61.95%), and the α-linolenic acid C18:3 was the highest in Fushao seed oil. Additionally, the high concentrations of tocopherol and phytosterol were found in all seed oils, and 10 individual polyphenols have been evaluated. Fushao seed oil had the highest polyphenols levels and showed higher CAA values. Both hierarchical cluster analysis and principal component analysis have been used to distinguish HP seed oil from different varieties. This information is valuable for the nutritional value and industrial interest of HP seed oil in China. PRACTICAL APPLICATION: This research showed that Herbaceous peony seed oil had higher levels of minor components and polyunsaturated fatty acids, especially, α-linolenic acid, and our results could also provide the theoretical foundation for the health benefits of Herbaceous peony seed oil as the vegetable oils. However, the variety of Herbaceous should be considered when extracting oil from Herbaceous peony seeds in the industry.

Applying sensory and instrumental techniques to evaluate the texture of French fries from fast food restaurant.

The aim of the work is to explore the relationship between the instrument and sensory data and to select the type of probes suitable for determining the texture of French fries. Ten commercial French fries were assessed using different probe types and perceived sensations through descriptive analysis. The eight sensory attributes developed by trained panelists can distinguish samples well. Simultaneously, the result of instrument data analysis revealed that the variation coefficient of three-point bending was the largest, which indicates that the measurement accuracy was lower. The compression test showed significant correlation with most of the sensory attributes (r = .64-.90), while the cut test with a Volodkevich Bite Jaws probe does not correlate with all sensory attributes (r = .03-.49). Among these instrumental methods, compression, blade with guillotine probe, and puncture test are recommended for texture measuring of French fries. These results will provide a time-saving and efficient method for determining the texture of French fries.

Comparative analysis of the oil absorption behavior and microstructural changes of fresh and pre-frozen potato strips during frying via MRl, SEM, and XRD.

This paper aimed to clarify the oil absorption behavior and microstructural changes of fresh and pre-frozen potato strips during frying, and to discuss the effects of freeze pretreatment on the oil absorption behavior of potato strips. We investigated the oil distribution; the microstructure changes in the crust, core, and potato strip surface; and the crystal pattern changes in the potato starch during frying by using magnetic resonance imaging, scanning electron microscopy, and X-ray diffraction. We monitored the profile histories of the moisture, oil and potato strip temperature, and oil uptake during frying and cooling. Results showed that during frying, the diversification of oil content in potato and oil infiltration path was closely related to the microstructure, moisture content, and temperature changes of potato strips and the interaction between starch and oil components. Moreover, freeze pretreatment significantly decreased the moisture content (P < .05) and increased oil content (P < .05) of potato strips and affected oil infiltration, microstructural changes, and starch crystallinity (P < .05) during frying. This paper may help in the further understanding of the oil absorption behavior of potato strips during frying and cooling, and may provide ideas for effective oil control measures.