Kin-Chor Kwok's research while affiliated with The Hong Kong Polytechnic University and other places

Publications (21)

Article
Full-text available
The inhibitory activities, sulfhydryl bonds and far-UV circular dichroism (CD) spectra of Kunitz and Bowman-Birk soybean trypsin inhibitors (KTI and BBTI) were measured before and after ultrasound treatments. The differences between KTI and BBTI in conformation changes and resistance to ultrasound were observed. The secondary structures of KTI were...
Article
Heating conditions are the most important variables in the processing of soymilk. the heat treatments given to soymilk during extraction, cooking, and subsequent pasteurization or sterilization, principally influence (1) the yields and nutritive quality of solids and proteins, (2) destruction of spoilage microorganisms, and (3) the colour and the f...
Article
Ultrasound assisted extraction (UAE) of saikosaponins from Radix Bupleuri (Bupleurum Chinense DC) was studied. The effects of various factors such as time (t), temperature (T), ultrasound power (I), particle size (S), solvent to solid ratio (R) and solvent concentration (C) on the yield of target components were investigated. The experimental resul...
Article
Soymilk was subjected to various heat treatments at 95, 121 and 140 °C for various lengths of time. The contents of the aglycones of isoflavone (daidzein, glycitein and genistein) of the soymilk were determined using C18 reversed-phase high-performance liquid chromatography. Genistein showed greater stability to heat treatment than daidzein and gly...
Article
Full-text available
Ellman's method is a simple, rapid and direct method to determine the SH and –S–S– group content in proteins. However, this method has difficulties in directly determining SH and –S–S– group content in soymilk because of the high turbidity and low SH group content of soymilk. In this experiment, low-turbidity protein solutions were prepared by sepa...
Article
The effect of different pH and addition of ferulic acid, tannin, cornstarch and hydrogen peroxide into the film forming solutions on in vitro protein digestibility, content of available lysine, and mechanical and water vapor barrier properties of films made of soy protein isolate were investigated in our experiment. The results showed that protein...
Article
Full-text available
Ferulic acid (4-hydroxy-3-methoxycinnamic acid), an effective component of Chinese medicine herbs such as Angelica sinensis, Cimicifuga heracleifolia and Lignsticum chuangxiong, is a ubiquitous phenolic acid in the plant kingdom. It is mainly conjugated with mono- and oligosaccharides, polyamines, lipids and polysaccharides and seldom occurs in a f...
Article
Tea polyphenols (TPs) and other materials were extracted from Chinese green tea, and their effects on trypsin inhibitors and trypsin were analysed. TPs were found to have a deactivation effect on both Kunitz trypsin inhibitor (KTI) and Bowman–Birk trypsin inhibitor (BBTI). KTI was more easily deactivated than BBTI by complexing with TPs. The deacti...
Article
Mathematical and kinetic models were set up for heat-induced quality changes in soy milk, including inactivation of trypsin inhibitor activity (TIA) and degradation of thiamin, riboflavin, color, and flavor over a wide range of time-temperature combinations with particular interest in the ultrahigh-temperature (UHT) range. On the basis of these mod...
Article
Response surface methodology (RSM) was used to investigate the effects of processing temperature and time on the inactivation of trypsin inhibitors (TI) in soymilk. The factorial experimental design consisted of four levels of temperature and six levels of time in a temperature range of 121–154 °C and a time interval of 10–90 s. A quadratic polynom...
Article
There have been many reports concerning the role of dietary fiber in lowering postprandial serum glucose, and the main mechanism was regarded as the viscosity of different dietary fibers in hampering diffusion of glucose and postponing absorption and digestion of carbohydrates. In this paper, two kinds of water-insoluble dietary fibers, water-insol...
Article
Soymilk was subjected to various heat treatments at 90, 120 and 140 °C for various lengths of time. The colour and flavour of the soymilk samples were evaluated by a sensory panel consisting of eight semi-trained assessors on (1) a 9-unit hedonic scale, with analysis based on the assumption that the units are equidistant, and (2) a 15-point hedonic...
Article
Tea polyphenols extracted from Chinese green tea were used to complex and separate bromelain from pineapple juice. The antioxidant activity of tea polyphenols and their effects on the properties of bromelain were studied. The thermal stability of bromelain was enhanced after complexing with tea polyphenols. By complexing, the activity half-life of...
Article
The kinetics of colour changes in soymilk heated over a wide range of temperatures (80°C–140°C) and times (0–180 min) were studied using both instrumental analysis and sensory evaluation methods. On the basis of the CIELAB uniform colour space, the L*-value decreased following first order kinetics, but unlike cow’s milk, soymilk did not exhibit an...
Article
Soybean trypsin inhibitors (TI) in soymilk were treated by heat and ultrasound of 20 kHz. The influence of several factors (temperature, time of treatment, pH, ultrasonic power, soymilk concentration, and ionic strength) on inactivation of TI was investigated. The results of the experiment shown that temperature was the major factor to affect the i...
Article
Soymilk was heated over a range of temperatures (90–140°C) and times (0–6 h). The available lysine, thiamine and riboflavin content of the soymilk samples were determined. There was no significant change in available lysine during a 3 h heating period at 95°C. At elevated temperatures of 120 and 140°C, optimum heat processed soymilk gave higher mea...

Citations

... In the primary wall of plants, ferulic acid can be cross-linked with polysaccharides to form a complex network structure to regulate the growth and extension of cells (Ou and Kwok, 2004). Interestingly, in the lignin biosynthesis pathway, only ferulic acid content decreased prominently under Al stress, while its content increased obviously after B application in Al-treated root ( Fig. 7A and B; Fig. S2). ...
... Ultrasound-assisted extraction (UAE) has been widely used for the extraction of nutritional material, such as lipids [8][9][10], proteins [11][12][13], flavoring, essential oils [14,15] and bioactive compounds (e.g., flavonoids [16][17][18], carotenoids [19][20][21], and polysaccharides [22][23][24]). Compared with traditional solvent extraction methods, ultrasound extraction can improve extraction efficiency and extraction rate, reduce extraction temperature, and increase the selection ranges of the solvents [25]. ...
... However, Bowman-Birk trypsin inhibitor (BBTI) was found to be resistant to the ultrasound; hence, no significant changes in the structure, as well as inhibition of BBTI, were found (Huang et al., 2008). Liang et al. (1998) also found that BBTI cannot be inhibited by ultrasound, whereas trypsin inhibitor can be inactivated by 73% with an ultrasonic power of 150 W for 5-min treatment. Later, Yang, Gao, Yang, and Chen (2015) found that inactivation of the trypsin inhibitors is ultrasonic power dependent, and a 300 W decreased the trypsin inhibitor content by 98.78% of the soybean sprouts. ...
... The contents of surface, free (surface + buried), and total sulfhydryls (free sulfhydryl + reduced disulfide groups) were measured according to a modified method of previous studies. 25,26 Before analysis, FA and/or CA and their photoproducts were removed using an ultrafiltration device as mentioned above. Exactly 0.35 mL of the samples that were concentrated to 100 μM were added to 0.7 mL of 4 mM EDTA and 0.1 M tris-glycine buffer at pH 8.0 for surface sulfhydryl determination but to 0.7 mL of 4 mM EDTA and 8 M urea in tris-glycine buffer for free sulfhydryl. ...
... Tea (Camellia sinensis) is a plant that belongs to the family Theaceae which has been reported that an essential source of numerous phytochemicals presenting health benefits such as an excellent antioxidant capacity (due to the existence of hydroxyl groups that can donate hydrogen atom) and the prevention of certain diseases (Liang et al., 1999;He et al., 2006He et al., , 2007Ozdal et al., 2013). According to Kochman et al. (2021) described that the beneficial substances that are found in Matcha green tea including epigallocatechin-3-gallate (EGCG), catechins, caffeine, and quercetin could present health-promoting properties such as anticarcinogenic and anti-Inflammatory effects, cardioprotective effects, antiviral properties, regulating carbohydrate metabolism, improving cognitive function, and prohibiting neurodegenerative disorders. ...
... As reported previously, thiamine was the most heat-sensitive vitamin, while vitamins B2 and B6 were more thermally stable (Bui et al., 2013;Fuliaş et al., 2014;Liberato & Pinheiro-Sant'Ana, 2006). However, riboflavin possessed the highest thermal stability (Kim et al., 2013;Kwok et al., 1998). Among the vitamins studied, the lowest concentration was related to vitamin B6, while vitamins B1 and B2 had nearly the same concentration range. ...
... Curcumin is the main component of C. longa, which can improve microcirculation and promote blood circulation [20]. The active ingredient of A. sinensis is ferulic acid, which can improve local microcirculation and inhibit platelet adhesion, and exhibits analgesic, antiinflammatory, and anti-bacterial activities in vitro [21]. CTCMDO is the most prescribed drug in dermatology at the Affiliated Hospital of Changchun University of Chinese Medicine, it has been clinically used for more than 85% of outpatients in the treatment of AD, rash, and other inflammatory skin diseases. ...
... According to research conducted, higher amounts of isoflavonoid compounds are present in soy compared to their content in soy beverage and soy beverage products. In general, processed products showed lower levels of isoflavones isolated from raw products, due to technological processes such as soaking, heating, and processing, which led to significant losses of isoflavones (Jackson et al., 2002;Huang et al., 2006;Ishihara et al., 2007). Also, the ratio of water and soy, grinding and separation methods, coagulation conditions (Poysa & Woodrow, 2002;Mujić et al., 2011) have an impact on the content of isoflavones as well as other components in processed soy products. ...
... For example, flours from boiled and roasted pulses (seeds of legumes) displayed 2-3 times higher water absorption capacities and higher gelation rates than flours from raw pulses [67]. Heat treatment from blanching was also found to inactivate undesirable endogenous enzymes to further improve flavour and nutrition [9], such as LOX that produce off-flavours in soy and peanut PBAEs, and trypsin or other protease inhibitors that restrict protein digestion [7,67,101]. However, blanching can also result in the loss of desirable nutrients such as proteins, choline, and folate, although the extent of such losses is dependent on the raw material and temperature used [67,101]. ...
... Soybean contains two types of trypsin inhibitors, the Kunitz trypsin inhibitor and the Bowman-Birk inhibitor which are heat stable due to presence of disulfide bridges in these inhibitors (Liu 1997, Van Der Ven et al. 2005. Heat treatment alone takes longer duration for inactivation of these compounds, whereas pressure in combination with elevated temperatures favors rapid destruction of these heat stable compounds (Kwok et al. 2002, Van Der Ven et al. 2005. Comparatively higher levels of TIA in the product processed at lower temperature and high screw speed could be attributed insufficient shear force and residence time and temperature combinations for effective destruction of inhibitors. ...