•Ultrasonic and thermal Maillard reactions were compared through kinetic studies.•Ultrasonic Maillard reaction needed lower activation energy than thermal one.•Three volatile compounds were generated in ultrasonic system but not in thermal one.This study compared the effects of high-intensity ultrasound on Maillard reaction (MR) with those of thermally produced MR using a model system of d-xylose and l-lysine. The ultrasonic MR process had higher depletion rates of reactants and higher generation rates of intermediate MR products (MRPs) and melanoidins under relatively low processing temperatures (55 and 60 °C). However, the rates were lower for ultrasonic MR than thermal MR when the processing temperature increased to 65, 70 and 75 °C. Overall, ultrasonic MR had relatively low activation energy (Ea) compared to thermal MR (e.g. 55.59 vs. 80.42 kJ mol−1 for d-xylose depletion). Moreover, ultrasonic MR could produce at least one N-containing pyrazine (3-ethyl-2,5-dimethylpyrazine), one N-containing amine (butyl amine) and one O-containing volatile compound (maltol) that were absent from thermal MR. The difference in flavour generation might be a result of the extremely high, albeit momentary, temperature and pressure condition produced by high-intensity ultrasound.

•Tg for all the powders significantly decreased at 45 °C and 60 °C.•Confocal analysis revealed different levels of surface fat for all milk powders.•XRD analysis on the aged powders showed there was no lactose crystallisation.Three different infant formulas (P1, P2 and P3) were characterised, and changes in their physicochemical properties under three different ageing conditions (i.e. 25 °C, 45 °C and 60 °C) were established. At 60 °C, all of the three powders exhibited increased moisture content, which was consistent with an increase in water activity. The GAB sorption model fitted for P1 while P2 and P3 did not follow the same sorption isotherm pattern. The glass transition temperature (Tg) for all of the powders significantly decreased at 45 °C and 60 °C. Confocal analysis revealed that all three powders had different concentrations of surface fat, and fat globules migrated from within the powders to the powder surface during storage under the conditions described. XRD analysis of the aged powders showed no occurrence of lactose crystallisation.

•Surface free-fat and caking strength increased significantly at 60 °C.•High-melting point fatty acids were present on surface of P1 powder particles.•Melting characteristics by DSC were consistent with fatty acid composition analysis.•CLSM analysis showed large fat globules after 6 weeks’ storage.Three commercial infant formulas (denoted as P1, P2 and P3) were stored at 25, 45 and 60 °C for up to 6 weeks to study the caking phenomenon caused by fat bridging. At 60 °C, both the surface free-fat content and the caking strength increased significantly. Analysis of the fatty acid composition of P1 showed that high-melting-point fatty acids were present on powder surface whereas low-melting-point fatty acids remained within powder particles. There was no preferential migration or retention of specific fatty acids in P2. The stearic acid content in the surface free-fat of P3 increased, largely due to a concentration gradient which contributed to the increased caking strength. The melting characteristics of surface free-fat analyzed by DSC were consistent with their fatty acid compositions analyzed by GC–MS/FID. Confocal laser scanning microscopy (CLSM) showed higher occurrence of large fat globules after 6 weeks’ storage.

•Bread crust/skin dominated people’s chewing behaviour and texture perception.•Heterogenous samples had more complex bolus formation but not texture perception.•Muscle activity and chewing rhythm were modulated differently.•Muscle activities were adjusted based on the changes in bolus hardness.This study aimed to understand the impact of bread structure and its dynamic transformation on people’s chewing behaviour and texture perception. Results from 20 trained panellists showed that bread crust/skin was the dominating factor in oral processing. This ‘outer layer’ introduced a mechanical contrast which increased chewing effort, lowered swallowing thresholds but did not elicit more a complex texture sensation. Furthermore, a single-panellist study was conducted as a proof-of-concept to demonstrate a new temporal correlation method. Progressive fragmentation and hydration diminished the differences between heterogeneous and homogeneous samples, leading to converged bolus properties and chewing effort. However, the differences in texture perception and chewing frequency due to the presence of the crust/skin were not diminished and even became larger throughout oral processing. Hence, chewing force and chewing rhythm might have different modulation mechanisms. Overall, bolus hydrated sensation was largely used by the panellist to gauge the swallowing point while bolus texture was used in a feedback control to regulate the mastication behaviour.

A Maillard reaction (MR) model system of D-glucose and L-methionine at pH of 10.0 assisted by high-intensity ultrasound was studied based on a MR scheme. Activation energy (Ea) values for the depletion of D-glucose and the generation of intermediate MR products (MRPs), including 1-deoxyglucosone (1-DG) and 3-deoxyglucosone (3-DG), were calculated. The Ea values in ultrasonic MR were further compared with those obtained using a conventionally thermal treatment under the same processing temperature and duration. Results indicated that the Ea values for the depletion of D-glucose and the generation of 1-DG and 3-DG in ultrasonic MR were significantly lower than those in thermal MR, whereas the Ea values for the isomerization of D-glucose in ultrasonic MR was significantly higher than that in thermal MR. Moreover, melanoidins and methional generated in ultrasonic MR were found to have always significantly higher concentrations than those in thermal MR. Similarly, the concentration of another volatile MRP in ultrasonic MR, i.e., 2,5-dimethylpyrazine, was higher than that in thermal MR but not always significantly. Lastly, the samples processed by ultrasound had significantly higher free radical scavenging capacities compared with the samples by thermal MR at 60 °C; however, no significant difference was found at relatively high processing temperatures, i.e., 70 and 80 °C. These findings may be due to active hydroxyl radicals (·OH) generated by cavities under a high temperature and pressure environment that was produced by high-intensity ultrasound wave.

•Vacuum mixing did not affect yeast activity and gas release kinetics.•Increased mixing time improved gas release and dough development.•Vacuum mixing reduced the dough growth during proofing.•Vacuum mixing produced denser and harder baked bread.•Vacuum mixing produced softer and less chewy steamed bread.The combined effects of reduced mixer headspace pressure and mixing duration on the yeast activity, proofing and quality of dough and bread made from both high-protein flour (HPF) and low-protein flour (LPF) were addressed in this study. Rheofermentometer analysis showed that a reduction in mixer headspace pressure up to 0.08 MPa did not affect the overall gassing power of yeast in either of the two dough matrices. An increase in mixing duration sped up the mass transfer rate of CO2 at the initial stage of fermentation, leading to a faster expansion of dough volume at the beginning. Moreover, an increase in mixing time promoted dough development and gas inclusion, which resulted in a increased volume of dough and bread, as well as a softer texture of both baked bread and steamed bread. In general, reduced headspace pressure produced baked bread of smaller volume, denser structure and harder texture. On the other hand, vacuum mixing produced steamed bread with softer texture without significantly changing the bread’s volume and porosity.

•Our nanocomposite film showed a significantly reduced O2 permeability, up to 99%.•O2 permeability reduction was more pronounced at 20% RH and 50 °C.•Nanocomposite packaging reduced ascorbic acid oxidation in tomato paste by up to 88%.•Lycopene oxidation in tomato paste was reduced by up to 37%.•Colour change in tomato paste was reduced by up to 67%.The effectiveness of a novel, laminated clay/polyvinyl alcohol nanocomposite food-packaging film was examined by barrier analysis and food shelf-life monitoring. The effect of storage conditions on the film's oxygen permeability was studied and compared to commercial LLDPE/PET film as control. Additionally, pouches of 14 cm × 10.5 cm prepared from both films were filled with tomato paste as the food model, and stored at different temperatures (20–50 °C) and humidities (20–85% RH) for 10 days. Incorporating a coating layer containing 30 wt% (d.b.) of clay into polymer was found to improve its barrier properties, with drastic reduction of oxygen transmission rates (OTR) up to 99%, especially at 20% RH. While surrounding humidity affected the OTR of composite film significantly more than that of control film, the OTR of composite film was lower and less susceptible to temperature changes. The changes of food physical-chemical properties with time showed that the pouches of composite film significantly decreased ascorbic acid and lycopene oxidation of tomato paste by up to 88 and 37%, respectively. Furthermore, no discolouration occurred to the samples packaged by the nanocomposite film as compared to the control.Industrial relevanceA novel clay/polyvinyl alcohol nanocomposite film was developed with excellent barrier properties against oxygen. Evaluation of the performance of this food-packaging film indicated that incorporation of montmorillonite enhanced food preservation as suggested by decreased ascorbic acid and lycopene oxidation, and no discolouration of tomato paste. This new approach could be adopted by the food industry to assist commercial producers and retailers for preserving and extending the shelf-life of a variety of food products.

Process control has become increasingly important for the food industry since the last decades due to its capability of increasing yield, minimizing production cost, and improving food quality. New developments for control strategies such as artificial neural networks and model-based controls as well as their applications have brought several new prospects to the food industry. Food processes are mostly nonlinear and show different process dynamics with various raw materials and different processing conditions. Therefore, advanced process control techniques are highly invaluable compared to classical control approaches. In this review, advanced control strategies, particularly model-based controllers, fuzzy logic controllers, and neural network-based controllers, are firstly described with their main characteristics. A number of applications of the advanced control strategies are then discussed according to different food processing industries such as baking, drying, fermentation/brewing, dairy, and thermal/pressure food processing.

•We reported the quality and digestion behaviors of bread fortified with ABREP.•We developed a model to describe the digestion rate of bread with/without ABREP.•This study can be a reference for understanding the digestibility of bread with ABREP.•This study offers a new approach for producing bread with a lower digestion rate.Anthocyanin-rich black rice extract powder (ABREP) as a nutraceutical source was fortified into bread. The quality and digestibility behaviors of bread with ABREP were evaluated through instrumental and in vitro digestion studies. The quality of bread with 2% of ABREP was not significantly (p > 0.05) different from the control bread; however, increasing the ABREP level to 4% caused less elasticity and higher density of bread. A mathematical model was further developed to systemically describe the trajectory of bread digestion. The digestion rates of bread with ABREP were found to be reduced by 12.8%, 14.1%, and 20.5% for bread with 1%, 2%, and 4% of ABREP, respectively. Results of the study suggest that the fortification of anthocyanins into bread could be an alternative way to produce functional bread with a lower digestion rate and extra health benefits.

•The stability of thermal-treated anthocyanin solutions over storage was evaluated.•Elevated temperatures resulted in higher rates of color change.•A model was established for the color change of anthocyanin solutions.•The amount of anthocyanins in solutions over storage was measured.•The antioxidant capacity was affected by heating and subsequent storage.Many anthocyanin-containing foods are thermally processed to ensure their safety, and stored for some time before being consumed. However, the combination of thermal processing and subsequent storage has a significant impact on anthocyanins. This study aimed to investigate the color, chemical stability, and antioxidant capacity of thermally treated anthocyanin aqueous solutions during storage at 4, 25, 45, and 65 °C, respectively. Anthocyanin aqueous solutions were thermally treated before storage. Results showed that the degradation rate of anthocyanins in aqueous solutions was much faster than those in real food. The color of the anthocyanin aqueous solutions changed dramatically during storage. The anthocyanin aqueous solutions stored at 4 °C showed the best chemical stability. Interestingly, the antioxidant capacity of the anthocyanin aqueous solutions stored at lower temperatures remained the same; however, the antioxidant capacity of those thermally treated at 120 or 140 °C and stored at 45 or 65 °C significantly decreased.

•Results of in silico studies supported those of in vitro studies.•Cyanidin-3-glucoside had the highest inhibitory activity.•The four anthocyanins showed competitive inhibitions against α-amylase.•Side chain of GLU233 was showed to play a key role in the inhibition.The inhibition activities and mechanisms of four anthocyanins including cyanidin-3-glucoside, cyanidin-3,5-glucoside, cyanidin-3-rutinoside, and peonidin-3-glucoside, against porcine pancreatic α-amylase were investigated through in vitro and in silico studies. The in vitro inhibition study demonstrated that the four anthocyanins competitively inhibited porcine pancreatic α-amylase, which was later verified by the in silico   molecular docking study that showed all the anthocyanins bound exclusively to the active site of porcine pancreatic α-amylase. Cyanidin-3-glucoside was found to have the highest inhibition activity with the KiKi value of 0.014 mM, followed by cyanidin-3-rutinoside, cyanidin-3,5-glucoside, and peonidin-3-glucoside with the KiKi value of 0.019, 0.020, and 0.045 mM, respectively. Results obtained from the in silico study also showed that the four anthocyanins were surrounded by the side chains of the active site of porcine pancreatic α-amylase, among which the side chain of GLU233 was supposed to play a key role in imparting the inhibition activity of anthocyanins.

•High intensity ultrasound processing was applied to a cysteine–xylose model system.•Sonication of model system generated odor-active Maillard reaction products.•Reaction products 2-methylthiophene and tetramethyl pyrazine were optimized.•Sonication generated fewer sulfur-containing odor compounds than heating.•Degassing effect of ultrasonic treatment must be considered in flavor generation.Application of high intensity ultrasound has shown potential in the production of Maillard reaction odor-active flavor compounds in model systems. The impact of initial pH, sonication duration, and ultrasound intensity on the production of Maillard reaction products (MRPs) by ultrasound processing in a cysteine–xylose model system were evaluated using Response Surface Methodology (RSM) with a modified mathematical model. Generation of selected MRPs, 2-methylthiophene and tetramethyl pyrazine, was optimal at an initial pH of 6.00, accompanied with 78.1 min of processing at an ultrasound intensity of 19.8 W cm−2. However, identification of volatiles using gas chromatography–mass spectrometry (GC/MS) revealed that ultrasound-assisted Maillard reactions generated fewer sulfur-containing volatile flavor compounds as compared to conventional heat treatment of the model system. Likely reasons for this difference in flavor profile include the expulsion of H2S due to ultrasonic degassing and inefficient transmission of ultrasonic energy.

•Soy sauce powders were produced using crystalline carbohydrates and maltodextrin.•Cellulose or waxy starch could increase the crystallinity of the soy sauce powders.•The soy sauce powders were more stable and less likely to cake during storage.This study aimed to reduce stickiness and caking of spray dried soy sauce powders by introducing a new crystalline structure into powder particles. To perform this task, soy sauce powders were formulated by using mixtures of cellulose and maltodextrin or mixtures of waxy starch and maltodextrin as drying carriers, with a fixed carrier addition rate of 30% (w/v) in the feed solution. The microstructure, crystallinity, solubility as well as stickiness and caking strength of all the different powders were analysed and compared. Incorporating crystalline carbohydrates in the drying carrier could significantly reduce the stickiness and caking strength of the powders when the ratio of crystalline carbohydrates to maltodextrin was above 1:5 and 1:2, respectively. X-ray Diffraction (XRD) results showed that adding cellulose or waxy starch could induce the crystallinity of powders. Differential Scanning Calorimetry (DSC) results demonstrated that the native starch added to the soy sauce powders did not fully gelatinize during spray drying.

A novel clay/polymer composite film was prepared by applying a modified clay polymer suspension containing montmorillonite nanoparticles onto bi-axially oriented polypropylene films to form three-layer barrier film via lamination. The suitability of the film to be used as a food contact material was assessed with a focus on two-side migration into specified food simulants (water, 3 % acetic acid, 15 % ethanol, olive oil, grapeseed oil and coconut oil) under three different temperatures. It was found that migration levels increased with increasing contact time and temperature. Among the aqueous food simulants tested, the 3 % acetic acid solution demonstrated the highest migration levels, while the water was the least efficient migrating medium. Migration into fatty simulants was observed to be greater than those into aqueous solutions, but independent of their fatty acid composition. The results provided adequate guarantees for the developed film to be applied for food packaging materials. A numerical model based on Fick’s diffusion theory was developed to predict the extent of migration from the multilayer film at any time of exposure in aqueous simulants. Measurements of migration were combined with computer simulations to yield reliable estimates of the diffusion and partition coefficients in the system, which showed an Arrhenius behaviour. The model was solved using a finite element method, and the predicted results and experimental data agreed very well, indicating the rate-controlling steps of diffusion within the polymer in the migration process.

Anthocyanin-rich black rice powder was incorporated into bread, and the stability of two specific anthocyanins, cyanidin-3-glucoside and cyanidin-3-rutinoside, during baking was investigated. Various baking conditions included different baking temperatures (200, 220, and 240 °C) and baking durations (0, 2, 4, 6, 8, 10, and 12 min). Non-isothermal kinetic models were successfully established for the two anthocyanins in both bread crumb and crust. The derived degradation rate (kref) of cyanidin-3-glucoside and cyanidin-3-rutinoside in bread crumb at the reference temperature (Tref) of 65 °C were 2.49 × 10−5 and 1.93 × 10−5 s−1, respectively. The kref values of cyanidin-3-glucoside and cyanidin-3-rutinoside in bread crust (Tref = 125 °C) were 5.37 × 10−4 and 5.72 × 10−4 s−1, respectively. The color development of bread crust and crumb was measured and expressed as L*C*H° values. While the color of bread crust was significantly subjected to variations in oven operating parameters, the color of bread crumb was relatively less affected by baking conditions. The antioxidant capacity and total phenolic content of bread samples were measured using DPPH and Folin-Ciocalteu assays, respectively. Results showed that in bread crumb, both the antioxidant capacity and the total phenolic content decreased; however, an increase in both was observed in bread crust.

Frozen dough made using flour of higher protein content (9.5–11 %) had better resistance to freezing damage than those made using flour of lower protein content and resulted in steamed bread whose specific volume, form ratio and texture were closer to those of bread made from fresh dough. The effects of flour protein content and freezing conditions (freezing air temperature and air speed) on dough and steamed bread quality were investigated in this study. Compared to nonfrozen control, the freezing process caused a deterioration to gluten network as well as a decrease in yeast activity, which resulted in lower maximum dough height and less total gas production, leading to steamed bread of lower specific volume and form ratios, and increased hardness. Faster freezing rates resulted in dough with higher extensibility and a less damaged dough microstructure but led to a decrease in total gas production as yeast activity was compromised. The extreme freezing conditions of −20 °C and air speed of 0 m/s and −40 °C and air speed of 6 m/s had the poorest dough and steamed bread quality. Samples frozen at −30 °C had better form ratio of steamed bread than those frozen at −20 °C and −40 °C, while those frozen at −40 °C had the lowest specific volume. A moderate air speed of 3 m/s resulted in higher volume of total gas production and dough height, as well as better steamed bread texture.

•Commercial ready-to-drink (RTD) green tea samples were analysed by HPLC.•Taste reconstruction and omission studies were conducted on RTD tea.•Sample recombinants were found to be similar to commercial samples.•Regression models were obtained to predict bitterness and astringency intensities.•Caffeine and EGCG were identified to be the main non-volatile compounds.Thirty-nine non-volatile compounds in seven ready-to-drink (RTD) green tea samples were analysed and quantified using liquid chromatography. Taste reconstruction experiments using thirteen selected compounds were conducted to identify the key non-volatile tastants. Taste profiles of the reconstructed samples did not differ significantly from the RTD tea samples. To investigate the taste contribution and significance of individual compounds, omission experiments were carried out by removing individual or a group of compounds. Sensory evaluation revealed that the astringent- and bitter-tasting (−)-epigallocatechin gallate, bitter-tasting caffeine, and the umami-tasting l-glutamic acid were the main contributors to the taste of RTD green tea. Subsequently, the taste profile of the reduced recombinant, comprising of a combination of these three compounds and l-theanine, was found to not differ significantly from the sample recombinant and RTD tea sample. Lastly, regression models were developed to objectively predict and assess the intensities of bitterness and astringency in RTD green teas.

•The combined effects of pH and high temperature on two anthocyanins were revealed.•The antioxidant capacity under the above conditions was evaluated.•pH 5.0/6.0 was a transition range where the loss of anthocyanins was accelerated.•Results can be used in quantifying the stability of individual anthocyanins.The stability of two cyanidin-based anthocyanins from black rice in an aqueous system containing them with a pH range of 2.2–6.0 was investigated at temperatures ranging from 100 to 165 °C. Within these pH and temperature ranges, the stability of the two anthocyanins was found to decrease gradually with increasing pH. The lowest (8.99 × 10−4 s−1) and highest (0.120 s−1) degradation rate constants for cyanidin-3-glucoside were obtained at pH 2.2 & 100 °C and pH 6.0 & 165 °C, respectively, whereas those for cyanidin-3-rutinoside were 5.33 × 10−4 s−1 at pH 2.2 & 100 °C and 7.39 × 10−2 s−1 at pH 5.0 & 165 °C, respectively. Antioxidant capacity analysis was conducted on thermally processed anthocyanin solutions to further evaluate the effects of pH and thermal treatment on the anthocyanins. The total antioxidant capacity of samples after thermal treatments under various pHs was found to remain at a similar level.

•We investigated the non-isothermal degradation of two anthocyanins.•We evaluated the uncertainties of kinetic parameters using Monte Carlo simulation.•We further measured the antioxidant capacity of samples before and after thermal process.•Cyanidin-3-rutinoside exhibited higher activation energy than cyanidin-3-glucoside.•No significant difference in the antioxidant capacity amongst the samples was observed.The non-isothermal degradation of two cyanidin-based anthocyanins, cyanidin-3-glucoside and cyanidin-3-rutinoside, was investigated in aqueous system within the temperature range from 100 to 165 °C, and the degradation kinetics was modelled using Monte Carlo simulation. The two anthocyanins showed different stability, with cyanidin-3-glucoside exhibiting a higher degradation rate than cyanidin-3-rutinoside. The derived degradation rate at the reference temperature of 132.5 °C and activation energy of cyanidin-3-glucoside and cyanidin-3-rutinoside were 0.0047 and 0.0023 s−1, and 87 and 104 kJ/mol, respectively. The antioxidant capacity of the thermally processed anthocyanins solutions was measured by using ABTS and DPPH assays. Results showed that the antioxidant capacity of the samples remained at the same level during the thermal treatment process under various conditions, i.e., there was no significant difference (P > 0.05) in the antioxidant capacity amongst the samples despite their significantly different contents of the two anthocyanins.

Green tea extract (GTE) was fortified into steamed bread as a functional ingredient to enhance its nutritional values. However, GTE might inhibit α-amylase activity and interact with gluten proteins, causing adverse effects on dough development and final loaf volume. This research investigated the effects of GTE and fungal alpha-amylase (FAA) on rheofermentometer characteristics, dough inflation parameters, and the specific volume of both dough and steamed bread. Rheofermentograph showed that the fortification of GTE did not affect the gassing power of yeast while it slightly inhibited the activity of FAA. Fortification of GTE at the level of 1.0 % decreased the dough inflation parameters and the specific volume of steamed bread. On the other hand, fortification of 60 ppm FAA enhanced the dough inflation parameters and increased the specific volume of steamed bread. Addition of 60 ppm FAA was able to fully compensate for the reduction of specific volume caused by the addition of 1.0 % GTE. Fortification of 0.50 % GTE produced steamed bread whose specific volume was not significantly different from that without GTE.

A green tea extract (GTE) was incorporated into biscuit as a source of tea catechins. The stability of tea catechins in the biscuit making process was studied. A method was developed for the separation and quantification of tea catechins in GTE, dough, and biscuit samples using a RP-HPLC system. GTEs at 150, 200, and 300 mg per 100 g of flour were formulated. The results obtained showed that green tea catechins were relatively stable in dough. The stability of (−)-EGCG and (−)-ECG was determined at an interval of every 2 min during baking. Their stability decreased as the baking progressed and increased as the concentration of GTE was increased in the biscuit dough. The stability of (−)-EGCG also increased as pH of the dough was reduced and made less alkaline.Research highlights► A RP-HPLC method was developed for the separation and quantification of tea catechins in green tea extract, biscuit dough, and biscuit samples. ► Green tea catechins were relatively stable in the biscuit dough. ► The relative stability of catechins in the biscuit system can be sequenced as (−)-CG > (−)-GCG > (−)-ECG > (−)-EGCG. ► Percentages of (−)-EGCG and (−)-ECG in the dough and biscuit increased as the initial concentration of GTE was increased. ► Retention rates of green tea catechins were improved by reducing the pH of the dough.

It is a challenging task to rapidly determine the quality of frying oils at various stages of frying. This study aims to evaluate the performance of eight different rapid test kits on three different types of oils, viz palm olein, cooking oil (a blend of palm olein, sesame oil and peanut oil) and sunflower oil. Two commonly consumed foods, French fries and chicken nuggets were selected as the frying food materials. Out of the eight test kits, five of them, namely FASafe™, 3M™ Low Range Shortening Monitor, Fritest®, Oxifrit-Test® and TPM Veri-Fry® were based on colorimetric reactions; whereas the other three test kits, namely Food Oil Monitor 310, Testo 265 and CapSens 5000 were based on dielectric constant. It was found that the test kits based on physical parameter provided more objective and valuable results as compared to those based on colorimetric reactions.

The stability of refined, bleached and deodorised (RBD) palm olein was studied under both repeated frying and controlled heating conditions. Two different frying foods i.e. chicken nuggets and French fries were used to evaluate the oil performance under various frying conditions. Thermo-oxidative alterations were measured through various physical and chemical parameters. Total polar compounds (TPC), polymeric triglycerides (PTG), blueness (b∗ value), chroma (C∗ value), refractive index and viscosity increased linearly with the number of frying/heating cycles. Palmitic acid content increased and linoleic acid content decreased linearly with the number of frying cycles. No significant changes in oleic acid were detected. Thermo-oxidative reactions induced under the heating conditions were found to be faster as compared to those under the frying conditions. The PTG formed at the end of heating cycles (16.42%) were substantially higher as compared to those formed at the end of frying French fries (9.72%) and chicken nuggets (5.34%).

Simulated frying experiments were performed on three different types of oils with French fries as the fried food. Comparison of frying oil samples was then made with their control counterparts (i.e. oil samples heated without food). Three different methods, gas chromatography (GC), attenuated total reflection (ATR) AOCS method Cd 14d-99 and attenuated total reflection negative second derivative absorbance (−2D ATR), were applied to quantify total trans fats. The total trans fats were found to be higher in the frying oil samples as compared to the control samples, which might be due to the presence of a high amount of trans fats in the pre-fried and frozen French fries. In general, the ATR AOCS method Cd 14d-99 produced lower amounts of trans fatty acids and the −2D ATR absorbance method produced higher amounts when compared with those obtained by gas chromatography.

The headspace solid-phase microextraction (HS-SPME) technique combined with GC–MS was evaluated to study 33 selected flavour compounds released from chewing gum. The operating conditions of SPME were optimised, including different fibres (PDMS, DVB/CAR/PDMS, PA and PDMS/DVB), sample size, extraction time and temperature. The results indicated that while HS-SPME was a rapid and valuable technique, poor reproducibility occurred under all conditions. It was found that this deficiency could be alleviated by utilising mathematical modelling techniques, an approach which had not been previously used in the analysis of flavour compounds in chewing gum by HS-SPME. Compared to the instrumental analysis data themselves, the models provided more insights to the release behaviour of flavour compounds from chewing gum and the more reproducible kinetic rate constants might be used for comparing the release of different compounds or the same compound under different conditions.

Further to part I of this study, this paper discusses mathematical modeling of the relationship between caramelization of several sugars including fructose, glucose, and sucrose and their glass transition temperatures (Tg). Differential scanning calorimetry (DSC) was used for creating caramelized sugar samples and determining their glass transition temperatures (Tg). UV−vis absorbance measurement and high-performance liquid chromatography (HPLC) analysis were used for quantifying the extent of caramelization. Specifically, absorbances at 284 and 420 nm were obtained from UV−vis measurement, and the contents of sucrose, glucose, fructose, and 5-hydroxymethyl-furfural (HMF) in the caramelized sugars were obtained from HPLC measurements. Results from the UV and HPLC measurements were correlated with the Tg values measured by DSC. By using both linear and nonlinear regressions, two sets of mathematical models were developed for the prediction of Tg values of sugar caramels. The first set utilized information obtained from both UV−vis measurement and HPLC analysis, while the second set utilized only information from the UV−vis measurement, which is much easier to perform in practice. As a caramelization process is typically characterized by two stages, separate models were developed for each of the stages within a set. Furthermore, a third set of nonlinear equations were developed, serving as criteria to decide at which stage a caramelized sample is. The models were evaluated through a validation process.

(–)-Epigallocatechin gallate (EGCG) is the most abundant catechin in green tea, which has been linked with many health benefits. To ensure the conceivable health benefits from thermally processed products, a kinetic study on the stability of (–)-EGCG in aqueous system was carried out using a HPLC-UV system and Matlab programming. Simultaneous degradation and epimerization of (–)-EGCG were characterized during isothermal reactions at low temperatures (25–100 °C) combined with previously conducted experimental results at high temperature (100–165 °C); the degradation and epimerization complied with first-order reaction and their rate constants followed Arrhenius equation. Mathematical models for the stability of (–)-EGCG were established and validated by the reactions at 70 °C and with varied concentrations from different catechin sources. Two specific temperature points in the reaction kinetics were identified, at 44 and 98 °C, respectively. Below 44 °C, the degradation was more profound. Above 44 °C, the epimerization from (–)-gallocatechin gallate (GCG) to (–)-EGCG was faster than degradation. When temperature increased to 98 °C and above, the epimerization from (–)-GCG to (–)-EGCG became prominent. Our results also indicated that the turning point of 82 °C reported in the literature for the reaction kinetics of catechins would need to be re-examined.

This study aims to investigate the relationship between caramelization of several sugars including fructose, glucose, and sucrose and their glass transition temperature (Tg). Differential scanning calorimetry (DSC) was used for creating caramelized sugar samples as well as determining their glass transition temperature, which was found to decrease first and then increase as the holding time at the highest temperature increased. The extent of caramelization was quantified by UV−vis absorbance measurement and high-performance liquid chromatography analysis. Results showed that the amount of small molecules from the degradation of sugar increased very fast at the beginning of heating, and this increase slowed down in the later stage of caramelization. On the other hand, there was a lag phase in the formation of large molecules from the degradation of sugar at the beginning of heating, followed by a fast increase in the later stage of caramelization. The obtained results clearly indicate the impact of melting condition on the Tg of sugars through formation of intermediates and end products of caramelization. Generally, when the heating condition is relatively mild, small molecules are formed first by decomposition of the sugar, which leads to a decrease of the overall Tg, and as the heating time becomes longer and/or the heating condition becomes more severe, polymerization takes over and more large molecules are formed, which results in an increase of the overall Tg. Mathematical modeling of the relationship will be presented as part II of the study in a separate paper.

The impact of high pressure treatments (HPT) on some physicochemical properties of normal corn, waxy corn, wheat, and potato starches were studied. Three high pressure treatments were applied: HPT1 (740–880 MPa from 5 min to 2 h), HPT2 (960–1100 MPa for 24 h) and HPT3 (1500 MPa for 24 h). Using differential scanning calorimetry (DSC), it was found that the gelatinization temperature of starch was lowered by 3.0–6.6 °C after high pressure treatment and the corresponding gelatinization enthalpy was also reduced. In addition, these changes were irreversible and maintained during storage at 25 °C for up to 6 months. However, the birefringence of native and high pressure treated starch was not visually different in polarized light. For starches of same biological origin, their X-ray diffraction patterns were also similar. Using scanning electron microscopy (SEM), it was revealed that the high pressure treatments altered the shape of starch granules and changed their surface appearance.

•Vacuum mixing had a significant impact on the development of gluten network.•The effect of vacuum mixing depended on the mixing time and the flour type.•Moderate vacuum promoted the development of high-protein flour dough.•Vacuum mixing delayed the onset of overmixing of low-protein flour dough.The effects of reduced headspace pressure on the development of gluten network in doughs made from both high-protein flour (HPF) and low-protein flour (LPF) were investigated. The effect of vacuum mixing was found to be dependent on both flour-type and mixing-time. A significant increase in dough extensibility was observed when the HPF dough was mixed under moderate vacuum of −0.04 MPa for 3 min as compared to the one mixed under atmospheric pressure for the same duration. This was attributed to the formation of a more extensive gluten network associated with an increased disulphide bond density and a significantly higher β-sheet to β-turn ratio. On the other hand, over-mixing was observed in the LPF dough that was mixed for 5 min under atmospheric pressure. Applying moderate vacuum of −0.04 MPa allowed the LPF dough to withstand longer mixing time, as indicated by its increased disulphide bond density and biaxial extensibility compared to the control dough mixed under atmospheric pressure. Results of this study suggest the potential of applying vacuum to reduce the mixing time required for high protein flour and to prevent the over-mixing of low protein flour.

This review focuses on the effects of freezing storage on the microstructure and baking performance of frozen doughs, and provides an overview of the activities of dough improvers, including emulsifiers, hydrocolloids and other improvers used in frozen dough applications. The overall quality of bread baked from frozen dough deteriorates as the storage of the dough at sub-zero temperatures increases due to several factors which are discussed. Lipid-related emulsifiers such as diacetyl tartaric acid esters of mono and diglycerides and sucrose esters employed as anti-staling agents, dough modifiers, shortening sparing agents, and as improvers for the production of high-protein bread have also been employed in frozen doughs. Hydrocolloids are gaining importance in the baking industry as dough improvers due to their ability to induce structural changes in the main components of wheat flour systems during breadmaking steps and bread storage Their effects in frozen doughs is discussed. Other dough improvers, such as ascorbic acid, honey and green tea extract, are also reviewed in the context of frozen doughs.

•Various processing conditions produced bread with distinct structure and texture.•Dry and thick bread crust increased chewing effort and reduced bolus particle size.•The most porous crumb required the greatest masticatory force.•The densest bread crumb required the longest chewing time.•Both bread crumb and crust were influential during oral digestion.The strong interconnection between food structure and its resistance to breakdown is the rationale behind designing bread structure to control its digestion, starting from the oral phase. Three types of bread, i.e. baguette, baked bread and steamed bread, with distinct cellular structures and textures were prepared by only varying the processing conditions. Baguette with thick and dry curst required a larger chewing force and a longer chewing time than steamed bread which has a moist and soft skin. Greater chewing effort resulted in more saliva impregnated and smaller particle size in baguette bolus which might elevate starch digestion and glycaemic response. The impact of crumb structure on oral processing was more complicated which involved both the mechanical strength of the crumb and the textural perception it elicited. Strong correlation was found among bread structure, texture, and oral processing behavior. Our study demonstrated that two important factors, grain feature of bread crumb and the relative portion of bread crust, should be considered when designing bread structure.

•A continuous ultrasonic processing system was set up and applied to Maillard reaction.•Ultrasound significantly decreased activation energy required for Maillard reaction.•A different flavour profile was generated by ultrasonic Maillard reaction.In this paper, a continuous ultrasonic processing system was established and firstly applied to a Maillard reaction (MR) model system of d-glucose and l-serine. Furthermore, the effects of high-intensity ultrasound assisted MR were compared with those of thermally induced MR through kinetic modelling. The ultrasonic MR had higher depletion rates of reactants as well as higher generation rates of intermediate and final MR products (MRPs) at relatively low processing temperatures (55 and 60 °C). However, both rates were lower for ultrasonic MR than thermal MR when the temperature was raised to 70 and 75 °C. Moreover, the ultrasonic MR had significantly lower activation energy compared with thermal MR. Lastly, three pyrazines, two amines and five O-containing flavour compounds were only produced in ultrasonic MR, not in thermal MR. The difference in flavour generation was attributed to the extremely high, albeit momentary, temperature and pressure condition produced by high-intensity ultrasound.Industrial relevanceUltrasound-assisted processing, a novel technology for non-thermal processing, has been utilized as an alternative to conventional thermal processing. High, albeit momentary, temperature and pressure that are generated by high-intensity ultrasound during processing provide a favourable environment for a number of chemical reactions. Moreover, strong shear stress, turbulence and agitation are among the unique characteristics generated by high-intensity ultrasound, which help to keep excellent mixing during food processing. In our study, a continuous ultrasonic processing system was established so as to achieve a good temperature control as well as to minimize the loss of volatile products during processing, which are major concerns to any liquid-based processing with ultrasound. Furthermore, a Maillard reaction (MR) model system of d-glucose and l-serine under the continuous ultrasonic processing were studied and compared to the most common batch processing of thermal MR through kinetic investigation at the same processing temperature and time conditions. The kinetic models that focused on reactants, intermediates, and final MR products (i.e. melanoidins and flavour compounds), and the kinetic parameters obtained for the MR system may enable controlling the reaction at industrial scale. The different flavour profile that was generated in ultrasonic MR points to new approaches to the food flavour industry to produce more alternatives and varieties.

Tea catechins have been linked with many health benefits including prevention of oxidative DNA damage and improvement on blood flow and liver function. Fortifying bread with (−)-epigallocatechin gallate (EGCG), a principal catechin in green tea, would turn the bread into a functional food. This study aimed to establish mathematical models for the stability of EGCG during bread baking process. It was found that EGCG underwent thermal degradation and epimerizations simultaneously, which all followed first-order reaction kinetics during bread baking. Mathematical models for the stability of EGCG were successfully established, which accounted for not only simultaneous thermal reactions, but also varying moisture content and temperature profile in the crumb and crust. The corresponding rate constant (k) of the reaction kinetics followed Arrhenius equation. The activation energy (Ea) of the reactions previously obtained from aqueous systems remained unchanged in the bread baking system, while the frequency factor (A) changed significantly. The developed mathematical models enable prediction of the amount of tea catechins in the fortified bread under various baking conditions.

Temperature is the dominating factor in various physiochemical changes during baking, including starch gelatinization, protein denaturation, enzymatic reactions and browning reactions, which collectively determine the final bread quality. However, often the design and performance of many industrial temperature controllers are not optimized. To circumvent this problem, the possibility of applying a two-dimensional (2D) computational fluid dynamics (CFD) model to the process control design for an industrial continuous bread baking oven was explored in this paper. A feedback control system was incorporated into the CFD model through user-defined functions (UDF). UDF was used to monitor the temperature at specific positions in the oven, and to define the thermal conditions of burner walls according to the control algorithm. A feedback control system with multiple decoupled PI controllers was designed and evaluated. The controller performed satisfactorily in response to disturbances and setpoint changes. With the establishment of the new process control system, the need of a preheating step required in typical industrial operations was re-evaluated. It was found that, under the control system, the elimination of the initial preheating to 550 K would not significantly affect the dough/bread top surface temperature profile across all baking zones.

Glass transition and enthalpy relaxation of sucrose, glucose syrup solid (GSS) prepared from tapioca starch syrup, and their mixtures (75/25, 50/50, 25/75 sucrose/GSS) have been investigated in terms of Couchman–Karasz equation and Kohlrausch–Williams–Watts model parameters using differential scanning calorimetry data. Addition of glucose syrup solid up to 50% did not significantly increase the mixture’s glass transition temperature compared to the sucrose’s glass transition temperature. Addition of glucose syrup solid into sucrose increased the mean relaxation time τ dramatically at all aging temperatures. In general, the more glucose syrup solid added, the longer the mean relaxation time of the mixture, at the aging temperature that has the same level below its glass transition temperature. Addition of glucose syrup solid into sucrose up to 50% did not change the relaxation susceptibility significantly. Addition of glucose syrup solid into sucrose increased the relaxation time distribution spectrum and generally decreased the β values.

Apple cubes of 1 cm3 were coated by using 20% and 50% (w/v) maltodextrin solutions, respectively. They were subsequently dried in an oven at 70 °C for 10 and 40 min, respectively, to solidify the coating. Osmotic dehydration was then conducted to both coated and non-coated samples under the process temperature of 30 °C and osmotic solution concentration of 61.5% (w/v) sucrose. The food to solution ratio was kept constant at 1:20 throughout the osmotic dehydration process. Results showed that the coated samples using 20% (w/v) maltodextrin solution and oven-dried for 40 min yielded negative dry matter gain and sugar gain during the osmotic dehydration process. Furthermore, the coated samples using 50% (w/v) maltodextrin solution and oven-dried for 10 and 40 min also yielded negative dry matter gain and sugar gain during the osmotic dehydration process. Possible reasons for these unusual negative gains were investigated, including dissolution of the coating material during the osmotic dehydration process and strong correlation between the drying time and shrinkage of the cells within the apple cubes. In addition, moisture loss of the coated samples was much smaller than that of non-coated samples. Instrumental texture profile analysis (TPA) of the non-coated and coated samples was performed, measuring the quality attributes such as hardness, brittleness, springiness and cohesiveness. Results showed that the structure of most samples was altered after the osmotic dehydration except those coated using 50% or 20% (w/v) maltodextrin solutions and oven-dried for 10 min.