Kinetics of colour change of bamboo shoot slices during microwave drying

Steam explosion-assisted grinding improves the functional properties and antioxidant activity of Java tea-leaf powders (Clerodendranthus spicatus)

BACKGROUND

Java tea is widely consumed and has multiple health effects. This study established a steam explosion (SE) pretreatment method to prepare Java tea-leaf powders. The physicochemical, functional properties, phenolic extraction, and antioxidant activity of Java tea-leaf powders produced by simple and SE-assisted milling methods were investigated.

RESULTS

In comparison with simple milling, SE pretreatment broke the cell wall effectively and reduced the particle size of Java tea-leaf powders. Steam explosion-treated powders showed higher values for sensory signals, bulk and tap density, and for the water solubility index. After SE treatment, the adsorption capacities to glucose, soybean oil, and cholesterol of leaf powders were increased by up to 55, 95, and 80% respectively. The extracts from SE-treated powders also showed higher total polyphenol content and antioxidant activity.

CONCLUSION

Steam explosion treatment is helpful for the improvement of functional properties and antioxidant activity, which can benefit the development and application of Java tea-leaf powders. © 2024 Society of Chemical Industry.

Development of Oleogel-Based Fat Replacer and Its Application in Pan Bread Making

In recent years, the bakery industry has been exploring alternative fats to replace traditional solid fats. Shortening, a common baking ingredient, is produced through the hydrogenation of vegetable oils, resulting in high levels of saturated and trans fatty acids, despite its vegetable oil origin. The excessive consumption of these fats has been associated with negative health effects, including dyslipidemia and cardiovascular issues. Oleogels, incorporating hydroxypropyl methylcellulose (HPMC), xanthan gum (XG), and olive oil, were utilized to replace shortening in the production of white pan bread. The substitution of shortening with oleogel in the white pan bread preparation demonstrated potential reductions in saturated fat, trans fat, and the ratio of saturated fat to unsaturated fatty acids. Specifically, with the complete substitution of shortening with oleogel, saturated fatty acids decreased by 52.46% and trans fatty acids by 75.72%, with unsaturated fatty acids increasing by 57.18%. Our findings revealed no significant difference in volume between bread made with shortening and bread with up to 50% shortening substitution. Moreover, when compared to bread made with shortening and 50% oleogel substitution, no adverse effects on the quality characteristics of volume and expansion properties were observed, and the retrogradation rate was delayed. This study suggests that incorporating oleogels, formed with hydrocolloids such as HPMC and XG, to replace shortening in bread, in conjunction with traditional solid fats, provides positive effects on the quality and nutritional aspects of the bread compared to using oleogel alone. Through this study, we demonstrate the use of oleogels as a healthier alternative to shortening, without reducing the bread's quality, thus offering a practical solution to reduce unhealthy fats in bakery products.

Investigation of the effects of corn flour, Spirulina powder, and buffalo yogurt on the quality characteristics of gluten-free muffins

This study aimed to investigate the properties of buckwheat flour-based gluten-free muffins formulated by using corn flour (CF), Spirulina powder (SP), and buffalo yogurt (BY) levels as the factors in the Box-Behnken experimental design. The color values, total soluble polyphenol content (TPC), radical scavenging activity (RSA), specific volume, moisture content, and baking loss results were evaluated as the response variables in the design. The buckwheat flour in the control sample was substituted with CF and SP. Cow yogurt was used in the control muffin instead of milk and was substituted with BY at different levels in other samples. Among the response variables, TPC and RSA values were selected for the optimization studies. Decreasing the CF and SP levels in the formulations resulted in observing higher TPC and RSA values. Three optimal formulations were obtained by response surface methodology. Both cow and buffalo yogurt did not change the properties of the muffins adversely compared to milk. Increasing the SP content made the muffins firmer and caused a decrease in the L*, a*, b*, and browning index values of the muffins. However, sensory scores of SP-containing muffins were also satisfactory.

Enhancing peach slices radio frequency vacuum drying by combining ultrasound and ultra-high pressure as pretreatments: Effect on drying characteristics, physicochemical quality, texture and sensory evaluation

To maximally maintain fruits and vegetables quality after harvest, this study used ultrasonic (US) and ultra-high pressure (UHP) techniques as pretreatments for radio frequency vacuum (RFV) drying of peach slices, and investigated the effects of different pretreatments (US, UHP, UHP-US, and US-UHP) on drying characteristics, physicochemical qualities, texture properties, and sensory evaluation of peach slices. Results showed that the drying rate was increased by 15.79 ∼ 54.39 % and the contents of pectin, hemicellulose, total phenolic, total flavonoid, phenolic acids, individual sugar annd antioxidant of the samples were significantly increased after US combined with UHP pretreatment (P < 0.05). US-UHP + RFV dried peach slices obtained brighter color, better texture attributes of hardness, cohesiveness, chewiness, springiness, and resilience. The dehydrated samples pretreated by UHP-US had the best overall acceptance, appearance, and crispness with lower off-odor and sourness compared to the dehydrated peach slices with US and UHP pretreatment. Notably, the highest cellulose and organic acids were found in dehydrated peach slices by control, followed by samples US, and samples with UHP pretreatment. The microstructure showed that the internal organization of peach slices appeared as uniform and regular honeycomb porous structure after US-UHP pretreatment. The findings may provide theoretical reference for the development of energy-efficient and high-quality drying technology for fruits and vegetables.

Safety improvement of the open sun dried Egyptian Siwi dates using closed solar dryer

Egyptian Siwi dates dried using the open sun drying is exposed to different contaminants. So, the current study aims to use the closed solar dryer to improve Siwi date safety. The impact of washing and closed solar drying on the levels of microbial load, aflatoxins and heavy metals in Egyptian Siwi dates (ESD), in comparison to traditional open sun drying methods were examined. Two different drying techniques were employed to dry 300 kg of ESD. The microbial load was assessed following the two drying procedures. The levels of aflatoxins and heavy metals were analyzed using High-performance liquid chromatography (HPLC) and Inductively Coupled Plasma (ICP) techniques, respectively, after both drying methods. Additionally, the influence of storage time on the microbial load of the ESD was also evaluated using standard methods. The findings of the current study demonstrated that the closed solar drying significantly reduced the total bacterial and fungal counts by 96 % and 93 %, respectively, when compared to open sun-drying. No aflatoxins were detected in both fresh Siwi dates and Siwi dates dried using closed solar drying. However, after open sun drying, two aflatoxins; aflatoxin B1 (AFB1) and aflatoxin G1 (AFG1), were detected in the ESD, with concentrations of 0.95 and 0.23 μg kg-1, respectively. The closed solar drying significantly decreased the levels of lead (Pb), cadmium (Cd), copper (Cu), nickel (Ni), chromium (Cr), zinc (Zn), manganese (Mn), and iron (Fe) in the dried dates by 96 %, 94 %, 48 %, 71 %, 64 %, 4 %, 26 %, and 7 %, respectively, when compared to open sun drying. The stored Siwi dates that was exposed to the open sun drying showed a higher increase in bacterial (4.86 log CFU/g) and fungal (4.46 log CFU/g) counts. However, the stored Siwi dates that was exposed to the closed solar dryer showed a lower increase in bacterial (3.21 log CFU/g) and fungal (2.51 log CFU/g) counts. So, the duration of storage significantly impacted the microbial loads of the closed solar dried dates as compared to open sun drying. Overall, closed solar drying reduced the levels of investigated contaminants and extended the shelf life of ESD, thereby enhancing their safety for human consumption.

Microwave infrared vibrating bed drying of ginger: Drying qualities, microstructure and browning mechanism

In this study, microwave infrared vibrating bed drying (MIVBD) method was used to dry ginger and the key characteristics of the product were determined, in terms of drying characteristics, microstructure, phenolic and flavonoid contents, ascorbic acid (AA), sugar content, and antioxidant properties. The mechanism of sample browning during drying was investigated. The results showed that increased infrared temperature and microwave power increased the drying rate and caused microstructure damage to the samples. At the same time, which caused the degradation of the active ingredients, promoted Maillard reaction between reducing sugar and amino acid, and caused the increase of 5-hydroxymethylfurfural, then the degree of browning increased. The AA reacted with amino acid to also caused browning. Antioxidant activity was significantly affected by AA and phenolics (r > 0.95). The quality and efficiency of drying can be effectively improved by MIVBD, and the browning can be reduced by controlling infrared temperature and microwave power.

Thermal stabilisation of cocoa fruit pulp - Effects on sensory properties, colour and microbiological stability

To improve cocoa pulp's shelf-life, preservation processes are necessary while maintaining the quality of the pulp. We applied pasteurisation and UHT-treatment and investigated different quality parameters: dry matter content, water activity, total soluble solids, colour and peroxidase activity. Both technologies inactivated peroxidase successfully. The colour of the pasteurised pulp was similar to the fresh, while UHT-treated pulp was more brownish. The sensory properties were investigated in detail by descriptive analysis and the identification of aroma-active volatile organic compounds. Fresh pulp revealed the highest aroma intensity for attribute unripe banana-like, whereas UHT-treated pulp scored highest in the intensity of attribute tropical fruit-like. Pasteurised pulp showed strong similarities to the fresh pulp. Fresh cocoa pulp exhibited 74 aroma-active regions identified by GC-MS/O. UHT-treated and pasteurised pulp accounted for 66 and 60 aroma-active regions, respectively. Five identified substances were only found in the fresh and pasteurised pulp, namely: δ-carene, 1-pentanol, 3-(methylthio)propanol, phenol and δ-undecalactone. Similarly, fresh and UHT-treated pulp shared ten exclusive odorants, such as decanal, geraniol, and δ-nonalactone. The pasteurised and UHT-treated pulp shared two compounds, δ-decalactone and 5-(hydroxymethyl)furfural. Furthermore, the thermally treated pulps could be stored at 4 °C and 23 °C for 24 weeks without observing a significant growth of microorganisms. The rate of non-enzymatic browning was higher in samples stored at 23 °C compared to those stored at 4 °C, leading to higher browning indices. We demonstrated that pasteurisation and ultra-high temperature treatment are suitable technologies for the stabilisation of cocoa fruit pulp. These resulted in prolonged shelf-lifes and minimal changes in the sensory prorperties of the treated pulps, characterised by a reduction in the aroma diversities. This work provides important insights for the thermal stabilisation of further side-streams.

Bamboo Shoots Modulate Gut Microbiota, Eliminate Obesity in High-Fat-Diet-Fed Mice and Improve Lipid Metabolism

Bamboo shoots (BS) have a variety of nutritional benefits; however, their anti-obesity effect and its underlying mechanism of action are still unclear. In this study, we investigated the protective effect of BS against high-fat diet (HFD)-induced gut dysbiosis in mice. After 12 weeks of feeding C57BL/6J mice either on a normal or an HFD with or without BS, metabolic indicators, including blood lipids and glucose tolerance, were measured. 16S rRNA gene sequencing and metabolomics were used to identify alterations in gut microbiota composition and fecal metabolic profiling. The results demonstrated that BS supplementation reduced body weight by 30.56%, mitigated liver damage, and improved insulin resistance and inflammation in obese mice. In addition, BS increased short-chain fatty acid (SCFA) levels and SCFA-producing bacteria (e.g., Lachnospiraceae_NK4A136_group and Norank_f_Muribaculaceae), and reduced levels of harmful bacteria (e.g., Blautia and Burkholderia-Paraburkholderia). Finally, BS increased many beneficial fecal metabolites, such as fatty acids and bile acids, which are highly relevant to the altered gut microbiota. Based on the modulatory effect of BS on microbiota composition and gut metabolite levels observed in this study, we suggest that BS may be beneficial in treating obesity and its related complications.

Antioxidants of Amaranth, Quinoa and Buckwheat Wholemeals and Heat-Damage Development in Pseudocereal-Enriched Einkorn Water Biscuits

A viable approach to improve the nutritional quality of cereal-based foods is their enrichment with pseudocereals. The aim of this research was to evaluate the antioxidant properties of amaranth, quinoa and buckwheat, and the heat damage of water biscuits (WB) produced from either wholemeal or refined flour of einkorn and enriched with 50% buckwheat, amaranth or quinoa wholemeal. Buckwheat had the highest tocols content (86.2 mg/kg), and einkorn the most carotenoids (5.6 mg/kg). Conjugated phenolics concentration was highest in buckwheat (230.2 mg/kg) and quinoa (218.6 mg/kg), while bound phenolics content was greatest in einkorn (712.5 mg/kg) and bread wheat (675.7 mg/kg). The all-wholemeal WB had greater heat damage than those containing refined flour (furosine: 251.5 vs. 235.8 mg/100 g protein; glucosylisomaltol: 1.0 vs. 0.6 mg/kg DM; hydroxymethylfurfural: 4.3 vs. 2.8 mg/kg DM; furfural: 8.6 vs. 4.8 mg/kg DM). The 100% bread wheat and einkorn wholemeal WB showed greater heat damage than the WB with pseudocereals (furfural, 9.2 vs. 5.1 mg/kg; glucosylisomaltol 1.1 vs. 0.7 mg/kg). Despite a superior lysine loss, the amino-acid profile of the pseudocereals-enriched WB remained more balanced compared to that of the wheats WB.

Effect of Pulsed Electric Field Pre-Treatment and the Freezing Methods on the Kinetics of the Freeze-Drying Process of Apple and Its Selected Physical Properties

The aim of this study was to investigate the effect of application of pulsed electric field (PEF) and different freezing methods (fast, slow and vacuum freezing) on the drying kinetics as well as selected physical properties of freeze-dried apple. The apples were subjected to PEF treatment with range of pulses from 0 to 160 and the intake energy from 0 to 1327 kJ·g⁻¹. Apples with and without PEF treatment were frozen with different rates and the freeze-dried. The water content, water activity and colour attributes of freeze-dried apples were investigated. Regression analysis and fitting procedures showed that among six different models, the Midilli et al. model the best described the drying curves of all dried samples. The highest value of the parameter L* = 71.54 was obtained for freeze-dried sample prepared without PEF pre-treatment and fast frozen. Application of PEF pre-treatment resulted in increase in browning index of freeze-dried apples (BI). The studies confirmed the positive effect of PEF on the freeze drying rate only in the case of the slow or fast freezing of the material after the application of low-energy PEF treatment. However, the increase in drying rate was also observed after application of slow and vacuum freezing of the material without PEF pre-treatment. These technologies can be recommended for optimization of the freeze drying process of apples. The statement that the freeze drying process with application of appropriately selected PEF processing parameters causing only partial destruction of cell membranes can be considered as an innovative contribution to the development of science about the possibilities of PEF application.

Study on the Incorporation of Oat and Yeast β-Glucan into Shortbread Biscuits as a Basis for Designing Healthier and High Quality Food Products

According to international health and food organizations and authorities, people should limit fat intake since fat is the most caloric component of food and it is often a source of unsafe saturated fatty acids (FA) and trans isomers. The greatest health benefits come from replacing shorts with dietary fiber molecules. The aim of the study was to determine the possibility of reducing shortening content, which has an undesirable profile of FA, by addition of β-glucan molecules in shortbread biscuits. The effect of oat and yeast β-glucan supplementation on physical and sensory quality of products with reduced fat content (max 15%) were studied. It was shown that the substitution of shortening by β-glucan in shortbread biscuits is possible to a limited extent. Reduction in product energy value (up to 36 kcal/100 g) and content of undesirable FA (maximum 2.1 g/100 g) and increased of β-glucan content, regardless of the type, caused deterioration of biscuits quality and affected changes during storage. The substitution of shortening by β-glucan in food is a good way to improve nutritional value by increasing the amount of dietary fiber molecules, reducing calories, and amount of SFA in diets.

Highly Efficient Computationally Derived Novel Metagenome α-Amylase With Robust Stability Under Extreme Denaturing Conditions

α-Amylases are among the very critical enzymes used for different industrial purposes. Most α-amylases cannot accomplish the requirement of industrial conditions and easily lose their activity in harsh environments. In this study, a novel α-amylase named PersiAmy1 has been identified through the multistage in silico screening pipeline from the rumen metagenomic data. The long-term storage of PersiAmy1 in low and high temperatures demonstrated 82.13 and 71.01% activities after 36 days of incubation at 4 and 50°C, respectively. The stable α-amylase retained 61.09% of its activity after 180 min of incubation at 90°C and was highly stable in a broad pH range, showing 60.48 and 86.05% activities at pH 4.0 and pH 9.0 after 180 min of incubation, respectively. Also, the enzyme could resist the high-salinity condition and demonstrated 88.81% activity in the presence of 5 M NaCl. PersiAmy1 showed more than 74% activity in the presence of various metal ions. The addition of the detergents, surfactants, and organic solvents did not affect the α-amylase activity considerably. Substrate spectrum analysis showed that PersiAmy1 could act on a wide array of substrates. PersiAmy1 showed high stability in inhibitors and superb activity in downstream conditions, thus useful in detergent and baking industries. Investigating the applicability in detergent formulation, PersiAmy1 showed more than 69% activity after incubation with commercial detergents at different temperatures (30–50°C) and retained more than 56% activity after incubation with commercial detergents for 3 h at 10°C. Furthermore, the results of the wash performance analysis exhibited a good stain removal at 10°C. The power of PersiAmy1 in the bread industry revealed soft, chewable crumbs with improved volume and porosity compared with control. This study highlights the intense power of robust novel PersiAmy1 as a functional bio-additive in many industrial applications.

Development of a packaging, storage and transportation cabinet for paddy straw mushroom

Shelf-life of paddy straw mushroom could be extended to 3 days by pre-cooling mushrooms in air at 14 °C for 2 h followed by packing in 75 µ thick high impact polystyrene punnets with 1.2% perforations as primary package and subsequently stored in expanded polystyrene (EPS) cabinet as secondary package. The EPS cabinet has been designed for transportation of mushroom with ice as cooling aid to maintain the optimum storage temperature. Temperature profile inside the cabinet was studied under no-load and full-load condition. The temperature inside the cabinet with 6 kg pre-cooled paddy straw mushroom (packed in 24 number of punnets @ 250 g mushroom per punnet having 1.2% perforations) and 6 kg ice in the partition chamber, was maintained at optimum storage temperature of 15 ± 2 °C (92 ± 1% RH) up to 18 h. Results of the study suggest that the technology could be successfully adopted by the paddy straw mushroom growers and traders for storage, transportation and marketing for loss reduction and higher return.

Drying characteristics and quality attributes of apple slices dried by a non-thermal ultrasonic contact drying method

Drying is one of the most prevalent methods to reduce water activity and preserve foods. However, it is also the most energy-intensive food processing unit operation. Although a number of drying methods have been proposed and tested for the purpose of achieving a time- and energy-efficient drying process, almost all current drying methods still rely on thermal energy to remove moisture from the product. In this study, a novel use of power ultrasound was explored for drying of apple slices without the application of heat. The non-thermal ultrasound contact drying (US-CD) was performed in the presence of an air stream (26-40 °C) flowing over product surface to remove mist or vapor produced by the ultrasound treatment. The effects of the non-thermal US-CD, hot-air drying (HAD), and freeze drying (FD) on the changes in rehydration ratio, pH, titratable acidity, water activity, color, glass transition temperature, texture, antioxidant capacity, total phenols, and microstructures of the samples were evaluated. The moisture content of the apple slices reached below 5% (w.b.) after 75-80 min of US-CD, which was about 45% less than that of the HAD method. The antioxidant capacity and total phenol contents of the US-CD samples were significantly higher than that of the AD samples. The non-thermal ultrasonic contact drying is a promising method which has the potential to significantly reduce drying time and improve product quality.

Improving the quality of gluten-free bread by a novel acidic thermostable α-amylase from metagenomics data

Development of gluten-free products is important due to their role in gluten related disorders and health improvement. α-Amylase enzymes have shown to have a positive effect on wheat bread quality. This study aimed to screen in-silico a novel acidic-thermostable α-amylase (PersiAmy2) from the sheep rumen metagenome to increase the quality of gluten-free bread. The PersiAmy2 was cloned, expressed, purified and characterized. The enzyme was highly stable at a wide range of pH, temperature and storage conditions. The PersiAmy2 had excellent activity in the presence of ions, inhibitors, and surfactants. Utilization of the acidic thermostable PersiAmy2 in gluten-free bread resulted in a softer crumb, higher specific volume, porosity, moisture content and caused a darker crust color. The rheological measurement showed a solid-elastic behavior in batters. Also the addition of this enzyme reduced the firmness. From the results of this study it can be concluded that the PersiAmy2 can be used to improve the quality of gluten-free bread.

Applicability of Pulsed Electric Field (PEF) Pre-Treatment for a Convective Two-Step Drying Process

Available literature and previous studies focus on the Pulsed Electric Field (PEF) parameters influencing the drying process of fruit and vegetable tissue. This study investigates the applicability of PEF pre-treatment considering the industrial-scale drying conditions of onions and related quality parameters of the final product. First, the influence of the PEF treatment (W = 4.0 kJ/kg, E = 1.07 kV/cm) on the convective drying was investigated for samples dried at constant temperatures (65, 75, and 85 °C) and drying profiles (85/55, 85/65, and 85/75 °C). These trials were performed along with the determination of the breakpoint to assure an industrial drying profile with varying temperatures. A reduction in drying time of 32% was achieved by applying PEF prior to drying at profile 85/65 °C (target moisture ≤7%). The effective water diffusion coefficient for the last drying section has been increased from 1.99 × 10-10 m2/s to 3.48 × 10-10 m2/s in the PEF-treated tissue. In case of the 85/65 °C drying profile, the PEF-treated sample showed the highest benefits in terms of process efficiency and quality compared to the untreated sample. A quality analysis was performed considering the colour, amount of blisters, pyruvic acid content, and the rehydration behavior comparing the untreated and PEF-treated sample. The PEF-treated sample showed practically no blisters and a 14.5% higher pyruvic acid content. Moreover, the rehydration coefficient was 47% higher when applying PEF prior to drying.

Changes in chemical composition and biological activity of essential oil from Thomson navel orange (Citrus sinensis L. Osbeck) peel under freezing, convective, vacuum, and microwave drying methods

Thomson navel orange peel is a by-product of citrus processing, which contains high levels of bioactive compounds advantageous to human health, nevertheless due to its high moisture content it is exceedingly perishable. Drying is among the most common preservation methods, which could prolong the plants shelf-life via reducing their moisture value. Taking this into account, depending on their type and conditions, drying techniques could degrade plant heat-sensitive metabolites and lead to quality decline. Therefore, the goal of this paper was to investigate the influence of seven drying methods named sun, shade, oven, vacuum oven, microwave, and freeze-drying with different drying conditions on the physical properties, for example, bulk density and color (L*, a*, b*, ΔE, and browning index (BI)) and essential oil characteristics such as extraction yield, chemical composition, antioxidant (total phenolic content (TPC), DPPH, and FRAP essays), and antimicrobial (MIC and MBC) activities of Thomson peel and determine the superior drying procedure. Results showed that freeze-dried sample had the highest retention of L* (48.54) and b* (49.00) values, lowest BI (216.11) as well as highest EO extraction yield (6.90%), TPC (60.10 GAE/100 g), FRAP (0.52% at 80 mg/ml), and lowest IC50 (5.00 mg/ml), MIC and MBC compared with other drying treatments. Therefore, it could be inferred that freeze-drying is the most efficient drying approach in respect of preserving both physical and EO attributes of Thomson peel.

Review of recent applications and research progress in hybrid and combined microwave-assisted drying of food products: Quality properties

The growing concerns over product quality have increased demand for high quality dried food products and encouraged researchers to explore and producers of such products to implement novel microwave (MW)-assisted drying methods. This paper presents a critical review of the key principles and drawbacks of MW-assisted drying as well as needs for future research. In this article, recent research into application of microwaves as an alternative heat source, applications and progress in hybrid MW-assisted drying that rely on various drying media and combined two or three stages of MW-assisted drying for the preservation of food products is reviewed critically. The effect of different MW-assisted drying methods, conditions and initial pretreatments on the thermophysical properties, color, nutritional value and rehydration potential of dried food products is discussed in detail along with the discussion on how the material properties evolve and change in structure, color, and composition during MW-assisted drying and recent attempts at mathematical modeling of these changes made for different fruits and vegetables. It should be noted that most of the published results were obtained in laboratory-scale dryers. Pilot-scale testing is needed to bridge the gap between laboratory research and industrial applications to fulfill the potential for novel hybrid and combined MW-assisted drying methods and to expand their role in food processing.

Expeller Barrel Dry Heat and Moist Heat Pressure Duration Induce Changes in Canola Meal Protein for Ruminant Utilisation

Simple Summary

Canola meal, a by-product of oil production from canola seed, is a source of protein commonly incorporated into dairy and feedlot rations. Processing conditions and pressure treatments can alter the quality of protein in canola meal. In this study, the impact of expeller dry heat and moist heat pressure duration time on general nutritional properties, in vitro protein degradability, Maillard reaction product formation, and molecular and microscopic structural characteristics of canola meal were investigated. Increased dry heat temperature rapidly increased digestible protein and non-protein nitrogen content, and constricted amide II secondary structure. Increased moist heat pressure treatment duration promoted browning, and the conversion of protein to more intermediately and slowly degradable forms. Dry heat and moist heat pressure affected meal protein solubility and protein and lipid-related functional groups. Moist heat pressure fragmented canola meal into enzyme-resistant aggregates with crevices containing oil bodies. Induced changes may impact the supply of protein and amino acids and subsequently the yield and composition (protein and lipid) of milk produced by dairy cows. These findings benefit producers of canola meal by further describing the effects of processing and treatment conditions on protein characteristics, particularly those which affect the production potential of ruminants fed canola meal as a source of protein.

Abstract

To improve the protein nutritional quality of canola (Brassica napus L.) meal, further investigation of the effects of processing conditions and post-production treatments is desirable. The impact of barrel dry heat temperature (20 °C (cold press) and 100 °C (expeller)) and moist heat pressure (MHP) duration time on general nutritional properties, Maillard reaction product (MRP) formation, in vitro protein degradability, and molecular and microscopic structural characteristics of canola meals were investigated. Increased MHP duration reduced (p < 0.05) dry matter, soluble protein, rapidly degradable protein, yellowness (early MRP), whiteness (late MRPs), absorbance at 294 nm (intermediate MRPs), and amide I; and increased (p < 0.05) non-protein N, neutral detergent fibre, neutral detergent insoluble crude protein (CP), intermediately and slowly degradable protein, in vitro effective CP degradability, redness, degree of colour change, and browning. Increased dry heat temperature reduced (p < 0.01) CP and rapidly degradable protein, constricted amide II, reduced (p < 0.05) protein solubility in 0.5% KOH and increased (p < 0.05) acid-detergent fibre and intermediate MRPs. Browning index and redness exhibited potential as rapid indicators of effective CP degradability and soluble protein, respectively. Dry heat and MHP altered (p < 0.05) lipid-related functional groups. Dry heat affected napin solubility, and MHP altered cruciferin and napin solubility. Application of MHP induced the formation of proteolysis-resistant protein aggregates with crevices containing oil bodies. Induced changes may impact the supply of proteins and amino acids and subsequently the yield and composition (protein and lipid) of milk produced by dairy cows.

Buffalo cheese whey hydrolyzed with Alcalase as an antibrowning agent in minimally processed apple

Buffalo whey was hydrolyzed with Alcalase for different times t_i (i = 0, 0.5, 1, 2, 3, 4 or 6 h) and the browning inhibition of minimally processed apples was investigated. The hydrolysis process was followed by determination of the degree of hydrolysis. In order to understand possible modes of action on the enzymatic browning, whey was submitted to the analysis of antioxidant activity (ABTS^·+ radical sequestration, Fe²⁺ chelating activity and reducing power), reactivity with quinones and inhibitory activity on polyphenol oxidases (PPO) extracted from Red Delicious apples. Buffalo whey showed significant increase in degree of hydrolysis, antioxidant activity, reactivity with quinones and PPO-inhibitory activity as a function of the hydrolysis time. Maximum PPO-inhibitory activity was observed from 4 h hydrolysis (t_4h hydrolysate), reaching about 50% inhibition. Then, slices of minimally processed apples were immersed in a buffered solution of the t_4h hydrolysate, packed and subjected to instrumental color evaluation during storage for up to 6 days. As for the ability to inhibit the browning of the minimally processed apples, the hydrolyzate kept the L∗ parameter of the apples during 6 days of storage, not statistically differing from the metabisulfite. In addition to the luminosity, the hydrolyzed whey was able to maintain the browning index of the apples at lower values during this storage time compared to the non-hydrolyzed whey. These results evidence possible applications of buffalo whey hydrolyzed with Alcalase as a natural substitute for additives conventionally used in the control of enzymatic browning in foods.

Using Thymus carmanicus and Myrtus communis essential oils to enhance the physicochemical properties of potato chips

The aim of this study was to evaluate the antioxidant effects of the essential oils of Myrtus communis leaves and Thymus caramanicus aerial parts in order to improve the physicochemical properties of potato chips. Sunflower oil without any antioxidant (control group) was fortified with BHA or TBHQ antioxidants (200 ppm), and M. communis or T. caramanicus essential oils (3,000 ppm). The effects of the antioxidant behavior of these compounds on the physicochemical properties of potato chips were analyzed by measuring peroxide value (PV), acid value (AV), and thiobarbituric acid (TBA). In addition, changes occurring in oxidation stability, texture, and color were evaluated. The results revealed that samples containing either M. communis or T. carmanicus showed a significant decrease in PV, as compared to the control sample. Compared with the control, the extracted oil of potato chips with M. communis or T. carmanicus led to the significant reduction in AV (p < .05). The results also revealed the addition of the essential oils of M. communis or T. carmanicus was obviously effective in preventing the TBA increasing value. Based on the results obtained by the Rancimat test, either T. carmanicus or M. communis essential oils could significantly increase the shelf-life of potato chips, as compared with the control sample (p < .05). The hardness of potato chips was decreased in M. communis or T. carmanicus groups (p < .05), as compared to the control sample. Neither M. communis nor T. carmanicus essential oils had any negative effects on the lightness values, as compared to the control (p > .05). Based on the results, the physicochemical properties of potato chips could be improved with the addition of these essential oils.

Real-time color change monitoring of apple slices using image processing during intermittent microwave convective drying

An intermittent microwave convective drying method combined with a real-time computer vision technique was employed to detect the effect of drying parameters on color properties of apple slices. The experiments were performed at air temperature of 40 to 80℃, air velocities of 1–2 m/s, microwave powers of 200–600 W, and pulse ratios (PRs) of 2–6. Drying rate and drying time varied from 0.014 to 0.000001 min−1 and 27 to 244 min, respectively. The normalized lightness values had ascending and descending parabolic trends with decrease in product moisture content. With descending dimensionless moisture content, redness, yellowness, color change, hue angle, and chroma were enlarged. The normalized redness values changed from −4 to 3. Models relating drying parameters with drying time, drying rate, and lightness were obtained and found to be significant ( P < 0.01). Results indicated that microwave power and PRs had more influence on lightness and color change than other parameters.

Drying of restructured chips made from the old stalks of Asparagus officinalis: impact of different drying methods

BACKGROUND

Old stalks of Asparagus officinalis, which account for one third of the total length of each spear, are always discarded as waste. To make full use of the resource, a kind of restructured Asparagus officinalis chip was made. The effects of pulse-spouted microwave-assisted vacuum drying (PSMVD), microwave-assisted vacuum drying (MVD) and vacuum drying (VD) on texture, color and other quality parameters of restructured chips were then studied to obtain high-quality dried chips.

RESULTS

Results indicated that the drying time was significantly affected by drying methods, and PSMVD had much better drying uniformity than MVD. The expansion ratio and crispness of chips increased with increasing microwave power and vacuum degree. The browning reaction of samples in VD was more serious, which was confirmed by the results of color test and electronic nose.

CONCLUSIONS

The PSMVD drying method showed much better drying uniformity than MVD. The dried chips obtained by PSMVD showed optimal quality and were more readily accepted by consumers. © 2015 Society of Chemical Industry.

Color Change Kinetics of Tea Leaves During Microwave Drying

In the present study, the effect of microwave power and sample amount on color change kinetics of tea leaves was investigated during microwave drying. Hunter L, a and b system was used for the color change of the materials; and the total color change (ΔE), chroma, hue angle and browning index (BI) were calculated by using these values. The color of the tea leaves was shifted towards the darker region after the microwave drying process. The mathematical modeling study of color change kinetic showed that a, b, chroma and BI fitted to a first-order kinetic model, while L, total color change (ΔE) and hue angle followed a zero-order kinetic model. For calculation of the activation energy for color change kinetic parameters, the exponential expression based on Arrhenius equation was used.