Shenghua He

Effect of ball-milling on the physicochemical properties of maize starch

The effect of ball-milling on physicochemical properties of maize starch was evaluated. Results found that the cold water solubility (CWS) of maize starch was positively correlated with the time of milling up to 3 h. There was no significant influence of using a ceramic pot versus a stainless steel pot on CWS. However, following 5 h of ball-milling CWS increased quite dramatically in the ceramic pot (72.6%) and in the stainless steel pot (70.7%), as compared to the untreated maize starches (2.9%). In addition, as CWS increased, the regions of amorphism enlarged at the expense of the crystalline regions, resulting in a change from the native starch state (oval with a smooth surface) to having more of a rough, abrasive surface. Finally, the transparency of the starch increased as CWS increased and that the syneresis of freeze–thawed ball-milled maize starch also increased with an increase in the number of freeze–thaw cycles.

Isolation of halophilic lactic acid bacteria from traditional Chinese fermented soybean paste and assessment of the isolates for industrial potential

Lactic acid bacteria (LAB) from traditional Chinese fermented soybean paste were isolated and identified. A total of 61 LAB were selectively obtained from 32 homemade Chinese soybean pastes. The isolated LAB were divided into two groups by their salt tolerance, 28 halophilic LAB and 33 non-halophilic LAB. Phenotypic analysis showed that these LAB belonged to four genera and 13 species. Tetragenococcus halophilus was the predominant species in the identified strains. Four species of LAB were firstly isolated from fermented soybean food product, Lactobacillus panis, Lactobacillus pentosus, Lactobacillus vaccinostercus and Lactobacillus collinoides. T. halophilus T5 showed vigorous growth and fast acidification in high salt concentration. The volatile compounds of mixed microorganism soybean paste with T. halophilus T5, Zygosaccharomyces and Torulopsis candida, during the different fermentation stage were higher in number than those of normal soybean paste at same processing procedure.

Effect of the heat-induced whey proteins/κ-casein complex on the acid gelation of yak milk

The effect of the heat-induced whey proteins/κ-casein complex on the acid gelation of yak milk was investigated. Both soluble whey protein/κ-casein complexes and the surface as micelle-bound complexes change the rheological properties of yoghurt. However, the soluble whey protein/κ-casein complexes were predominant in increasing the storage modulus (G′), water-holding capacity and firmness of acid gelation than micelle-bound complexes. The water-holding capacity and firmness increased with the increase of the amount of the soluble whey protein/κ-casein complexes. The water holding capacity and firmness of yoghurt from heated yak milk at pH 7.0 was higher than that at pH 6.6 and pH 7.4. The result also indicated that the amount of soluble heat-induced whey protein/κ-casein complexes were predominant in increasing the water holding capacity and firmness of yoghurt than the micelle-bound protein complexes.

Effect of pH on the formation of serum heat‐induced protein aggregates in heated yak milk

Serum heat-induced protein aggregates at various pH levels were isolated from heated yak milk by size-exclusion fast protein liquid chromatography. Analysis by reversed-phase high-performance liquid chromatography showed that β-lactoglobulin and κ-casein were the two main proteins in these aggregates. The amount of serum heat-induced protein aggregates increased from pH 6.6 to 7.4, whereas the content of β-lactoglobulin in aggregates decreased from 61.9% at pH 6.6 to 50.4% at pH 7.2, and then increased to 51.3% at pH 7.4. The content of κ-casein, αs1-casein and β-casein increased from pH 6.6 to pH 7.4. These results show that serum heat-induced protein aggregates are pH dependent.

Properties of emulsions from milk fat globule membrane and its components

ABSTRACT This work aimed to investigate the properties of emulsions prepared with milk fat globule membrane (MFGM) and its components, which are milk fat globule membrane proteins (MFGMPs) and milk fat globule membrane lipids (MFGMLs). The results demonstrated that the particle size of emulsions prepared with MFGM and MFGMPs decreased with increasing concentrations (from 1% to 4%); however, these droplet sizes were smaller than those prepared with MFGMLs of the same concentration. In addition, the emulsion prepared with MFGMLs showed a clear phase separation, as opposed to those from MFGM and MFGMPs. These results indicated that MFGMLs alone could not contribute to the stability of the emulsions. The microscopic images also confirmed that the droplet sizes of emulsions prepared with MFGM and MFGMPs were smaller than those prepared with MFGMLs. Moreover, the emulsions prepared with MFGM and MFGMPs had lower shear stress than those prepared with MFGMLs. The MFGM and MFGMPs were found to be sensitive to pH; thus, their physical stabilities behaved according to their pH. The heat treatment results showed that the emulsions prepared with MFGM were stable over the heat of temperature ranging from 35°C to 85°C, whereas those prepared with MFGMPs were stable to heat of temperature ranging from 35°C to 65°C and became unstable at the temperature of over 65°C.

Characterization and bioaccessibility of β-carotene in re-assembled casein

The characterization and bioaccessibility of β-carotene (β-CE) in re-assembled casein (CN) were investigated in this study. At pH 4.6, β-CE in re-assembled CN significantly lowered the zeta-potential to a negative value compared to that of CN. The morphology of β-CE in re-assembled CN was characterized by atomic force microscopy. β-CE in re-assembled CN exhibited a more uniform and homogenous dispersion, with peak-to-valley differences of 6.8 nm rather than 91.3 nm for the pure β-CE. β-CE in re-assembled CN can effectively protect β-CE against degradation under conditions of heat and ultraviolet radiation. The antioxidant activity of β-CE when it was encapsulated in re-assembled CN was significantly higher than β-CE in control samples under both experimental conditions. The total release rate of β-CE was 76.7% and 63.4% by trypsin and pepsin hydrolysis, respectively. These results indicated a feasible application in the food industry.

The compositional factors involved in the heat stable sensitivity of yak milk

The compositional factors involved in the heat stable sensitivity of yak milk were investigated. Compared to heat-unstable yak milk, heat-stable yak milk samples were characterized by higher pH, non-protein-nitrogen, soluble proteins, whey protein, urea, P, a lower soluble Ca and ratio of Ca to P. The content of κ-casein in heat-stable yak milk is higher than in heat-unstable yak milk. The content of αs1-casein in heat-stable yak milk is lower than in heat-unstable yak milk. For whey proteins, the content of β-LGA and β-LGB in heat-stable yak milk is higher than in heat-unstable yak milk.

Physical, textural, and rheological properties of whipped cream affected by milk fat globule membrane protein

ABSTRACT This work aims at improving the textural and whipping properties of whipped cream by the addition of milk fat globule membrane protein. The determination of particle size distribution and average diameter of whipped cream showed that the small particle size was shifted to a larger range after milk fat globule membrane protein was added. The average particle size (d3,2) of whipped cream reached a maximum value of 5.05 µm at 1% milk fat globule membrane protein, while slowly decreased with increasing milk fat globule membrane protein levels from 2% to 5%. In addition, the partial coalescence of fat increased with the increase of milk fat globule membrane protein levels, and the correlation between the whipping time and the overrun of whipped cream was positive. The addition of milk fat globule membrane protein also altered the rheological behaviour of whipped cream, resulting in the increase of modulus G′ and the loss modulus G″. The results also indicated that higher milk fat globule membrane protein level decreased the serum loss of whipped cream while improved its stability. While milk fat globule membrane protein levels had no significant effect on viscosity, its increasing levels effectively improved the hardness, consistency, and viscosity of whipped cream.

Effect of pH and Heat-Induced on the Yak ÃÂ-Lactoglobulin Denaturation andAggregation

The effect of pH and heating temperature on yak (β-Lactoglobulin) β-Lg denaturation/aggregation was investigated. Temperature and pH significantly influenced the rate and content of yak β-Lg denaturation/aggregation and the protein formation in solution. The content of native β-Lg monomer decreased with increase in temperature at all pH range. β-Lg was heated above 80°C the content of native β-Lg monomer at pH 4.5-5.5 was reduced markedly than higher pH range from 6.5 to 8.5. Meanwhile the formations and content of yak β-Lg solution were complication at pH from 6.5 to 8.5 after heated 80°C and 90°C. The trend of hydrodynamic diameter and particle size was similar. The particle size in yak β-Lg solution increased markedly form (52 and 75 nm) pH 8.5 to (345 and 489 nm) pH 4.5 when β-Lg was heated at 80°C and 90°C, respectively. pH and heating temperature are important parameters that can influence the heat-induced denaturation/aggregation and the characteristic of yak β-Lg and yak whey proteins. And these researches provide some basis date and results to better understanding the mechanism of yak β-Lg denaturation, disulphide-linked aggregation and precipitation.

Genetic variation in the αS1-casein of Chinese yak (Bos grunniens)

Abstract The aim of this study was to investigate diversity of the αS1-casein gene in Maiwa yak. A polymorphism of αS1-casein gene has been identified in Chinese Maiwa yak by PCR single-strand conformation polymorphism protocol. Comparing the X59856 sequence, some non-coding and coding DNA variants of yak CSN1S1 gene were detected in this present study, including KJ397913 (promoter region, 9969A/G, 9984 A/G, 10153 C/T, 10175 A/C, 10261 G/C), KJ397914 (promoter region 10261 G/C), KJ397896 (intron III, 14862 T/C), KJ397897 (intron III, 14862 T/C, and deleted 14944-14946 CTT), KJ397899 (intron IV, 15297 A/C), KJ397901 (intron VIII, 17503 A/C, 17666 A/C), KJ397902 (exon IX, 18901C/A, intron IX, 18970 T/G, 19088 add A, 19120 add A, 19202 add T, 19296 G/T), KJ397903 (intron IX, 18970 T/G, 19088 add A, 19120 add A, 19202 add T, 19296 G/T), KJ397904 (intron IX, 19537 T/G, 19539T/G, 19599G/A, 19638 C/T), KJ397905 (intron XIV, 23402 T/G, 23417 C/T, 23480 T/C, 23511 G/A), and KJ397907 (intron XVI, 25976 G/T; exon XVII, 26181A/G). The polymorphism of αS1-casein gene may be helpful for future studies on genetic variation within and between yak populations or on associated traits.