Effects of chitosan-based coating and modified atmosphere packaging (MAP) on browning and shelf life of fresh-cut lotus root (Nelumbo nucifera Gaerth)

The present study investigated the effect of chitosan coating containing antibrowning agents and modified atmosphere packaging (MAP) on the browning and shelf life of fresh-cut lotus root stored at 4 °C for 10 days. The atmosphere in the packages was evaluated for O₂ and CO₂ concentrations. The browning on the surface of lotus root slices was prevented by chitosan-based coating and MAP treatment. L* values of coated + MAP and control samples were 68.8 and 48.9 after 8 days storage, respectively. For a^? and b^? values, samples of coated + MAP treatment had the slowest increasing trends among all the treatments. At the end of storage, the coated + MAP samples exhibited the lowest polyphenol oxidase (PPO) activity and malondialdehyde (MDA) content. Its highest overall visual quality (OVQ) scores (> 7) demonstrated that chitosan-based coating + MAP treatment could provide a better inhibitory effect on the browning and extend the shelf life of fresh-cut lotus root.Industrial relevance: Fresh-cut vegetables have drawn the attention of industry as a novel lightly processed product. Both edible coating and MAP treatment cause changes in atmosphere composition and respiration rate of lotus root slices. This combined treatment could be used to control the browning and improve the storage life of this fresh-cut vegetable. This information could be useful for the development of novel application to edible coating and MAP design for lightly processed lotus root.     

不同清洗处理对鲜切莲藕贮藏期褐变的影响

研究弱酸电解水、强酸电解水、次氯酸钠、去离子水4 种不同清洗处理对鲜切莲藕在4 ℃条件下贮藏14 d期间,色差值（L*、a*、b*,ΔE*及色相角）、褐变度、多酚氧化酶（PPO）活性及整体感观质量的变化。结果表明：弱酸电解水（pH 5.65,有效氯剂量 48 mL/L,氧化还原电位800 mV）能够有效保持鲜切莲藕的色泽品质和整体感观质量值,同时抑制褐变,降低PPO活性,有效地改善鲜切莲藕的贮藏品质,延长货架期。     

Use of high-concentration-short-time chlorine dioxide gas treatments for the inactivation of Salmonella enterica spp. inoculated onto Roma tomatoes

Salmonella outbreaks have been recently linked to the consumption of fresh tomatoes. Thus, there is a need to develop systems that reduce the risk of microbial contamination to increase product shelf-life and keep fresh fruit attributes. The objectives of this study were to evaluate high-concentration-short-time chlorine dioxide gas treatments effects on Salmonella-inoculated Roma tomatoes and determine the optimal treatment conditions for microbial inactivation and shelf-life extension. Effects of ClO₂ concentration (2, 5, 8 and 10 mg/l) and exposure time (10, 30, 60, 120 and 180 s) on inoculated Roma tomatoes were studied. Salmonella enterica strains, serotype Montevideo, Javiana and Baildon, were used to experimentally inoculate the food product. After ClO₂ treatments, tomatoes were stored at room temperature for 28 days. Inherent microbial population, change in tomato color, and chlorine dioxide gas residuals were evaluated. ANOVA analysis showed that both ClO₂ concentration and treatment time were significant (p < 0.01) for Salmonella inactivation. Surviving Salmonella populations of 3.09, 2.17 and 1.16 log CFU/cm² were obtained treating tomatoes with 8 mg/l ClO₂ for 60 s, 10 mg/l ClO₂ for 120 s, and 10 mg/l for 180 s, respectively (initial Salmonella population: 6.03 ± 0.11 log CFU/cm²). The selected treatments significantly reduced background microflora (p < 0.05), while fruit color and residual contents were not significantly different (p > 0.05), as compared to the control. Results suggest the potential for high-concentration-short-time treatments ClO₂ gas as an effective pathogen inactivation technology for large-scale produce packing operations.     

Effects of aqueous chlorine dioxide treatment on polyphenol oxidases from Golden Delicious apple

Effects of chlorine dioxide (ClO₂) treatment on the activity and characteristics of polyphenol oxidase (PPO) in Golden Delicious apples were studied. The treatment with 50 mg/l ClO₂ for 1 h did not affect some characteristics of the PPO, including its optimum pH value (5.0) and temperature (40 °C) as well as the maximum absorption wavelength (412 nm) of the final products. With increasing ClO₂ concentrations from 0 to 100 mg/l, the value reduced and value changed irregularly. When the concentration of ClO₂ increased from 0 to 60 mg/l, residual PPO activities significantly decreased, showing a negative linear-correlation with ClO₂ concentration. For 10 and 50 mg/l ClO₂ treatments, partial inhibition of PPO was achieved within 0.5 h and the PPO activities did not significantly decrease after 0.5 h. The inhibition and inactivation of PPO by ClO₂ treatment were observed at processing temperatures (30 and 70 °C) and storing temperatures (20, 0-4, and −18 °C).     

Polyphenol oxidase activity,phenolic acid composition and browning in cashew apple (Anacardium occidentale, L.) after processing

This study describes the extraction and characterisation of cashew apple polyphenol oxidase (PPO) and the effect of wounding on cashew apple phenolic acid composition, PPO activity and fruit browning. Purification factor was 59 at 95% (NH₄)₂SO₄ saturation. For PPO activity, the optimal substrate was catechol and the optimum pH was 6.5. PPO K_m and V_max values were 18.8 mM and 13.6 U min⁻¹ ml⁻¹, respectively. Ascorbic acid, citric acid, sodium sulphite and sodium metabisulphite decreased PPO activity, while sodium chloride increased PPO activity. Wounding at 2 °C and 27 °C for 24 h increased PPO activity but storage at 40 °C reduced PPO activity. Gallic acid, protocatechuic acid and cinnamic acid (free and conjugate) were identified in cashew apple juice. Cutting and subsequent storage at 40 °C hydrolysed cinnamic acid. 5-Hydroxymethylfurfural content in cashew apple juice increased after injury and storage at higher temperatures, indicating non-enzymatic browning.     

Physicochemical changes in fresh-cut wax apple (Syzygium samarangenese [Blume] Merrill & L.M. Perry) during storage

Physicochemical changes, such as peel and flesh colours, total anthocyanin content, browning index, firmness, total soluble solid (TSS), titratable acidity (TA), sugar acid ratio (TSS/TA), antioxidant capacity, total phenolic content and ascorbic acid content, in fresh-cut Taaptimjan wax apple fruit stored at 4 ± 2 °C and 12 ± 2 °C for 7 days were investigated. The skin of fresh-cut fruit stored at 4 ± 2 °C showed higher a^∗ value, chroma and total anthocyanin content and lower hue angle than those stored at 12 ± 2 °C. Lightness (L^∗ value) and whiteness index of the fresh-cut fruit flesh stored at 12 ± 2 °C showed significantly lower than those stored at 4 ± 2 °C which related to an significant increase in browning index. Firmness, total soluble solid, titratable acidity and sugar acid ratio did not significant changes during storage. Antioxidant capacity and total phenolic content increased throughout storage. Ascorbic acid content of the fresh-cut fruit stored at 4 ± 2 °C remained constant throughout storage whilst ascorbic content at 12 ± 2 °C decreased and was lower than that at 4 ± 2 °C. At 4 ± 2 °C antioxidant capacity and ascorbic acid content were higher than that stored at 12 ± 2 °C whilst there was no significant difference in total phenolic content. In conclusion, the reduction of whiteness index and the increase in browning index of fresh-cut wax apple flesh were the key factors affecting its quality and storage at 4 ± 2 °C could reduce the change in the flesh colour and maintained the peel colour and nutritional values of fresh-cut wax apple fruit during storage.     

Kinetic model of apple juice enzymatic browning in the presence of cyclodextrins: The use of maltosyl-β-cyclodextrin as secondary antioxidant

Enzymatic browning reactions limit the commercial shelf life of apple juice, so that colour preservation during storage is one of the main objectives of fruit processors. In this paper, the colour of fresh apple juice was evaluated in the presence of different types of cyclodextrins (CDs) (α-CD, β-CD, γ-CD and maltosyl-β-CD), compounds that bind or complex polyphenol oxidase substrates. The effectiveness of CDs as browning inhibitors was determined as the difference between the colours observed in the CD-treated sample and the controls, using the colour space CIE-L^∗, a^∗, b^∗ system. Although the effect of CDs on apple juice enzymatic browning has been studied, the action mechanism involved remains a subject of controversy. In this work, we have kinetically modelled apple juice enzymatic browning in the absence and presence of maltosyl-β-CD. The complexation constant between the mixtures of diphenols present in apple juice and maltosyl-β-CD was calculated (K_c = 4.09 mM⁻¹). Different concentrations of maltosyl-β-CD modified the evolution of lightness (L^∗), total colour (ΔE^∗) and hue angle (H^∗) because of the higher affinity constant it shows for the compounds responsible for apple juice browning than do α-CD, β-CD and γ-CD. Moreover, in this paper we show that maltosyl-β-CD can enhance the ability of ascorbic acid to prevent the enzymatic browning due to the protective effect of maltosyl-β-CD against ascorbic acid oxidation. Hence, maltosyl-β-CD seems to act as a “secondary antioxidant”, reducing apple juice browning and enhancing the naturally occurring antioxidant capacity of a food.     

Dual effectiveness of sodium chlorite for enzymatic browning inhibition and microbial inactivation on fresh-cut apples

The dual effectiveness of sodium chlorite for browning inhibition and microbial inactivation on fresh-cut apples was investigated and compared to other anti-browning and antimicrobial agents. Results indicate that sodium chlorite significantly (P < 0.001) inhibited the browning reaction of fresh-cut Red Delicious apples stored at 5 °C for 14 days. This treatment also significantly reduced polyphenol oxidase activities. Treatments with acidified sodium chlorite, calcium chloride, or calcium ascorbate exhibited strong inhibition on apple browning during the early storage, these treatment effects diminished after 7 days in storage. Combining calcium chloride with sodium chlorite further significantly (P < 0.001) improved the firmness of apple slices, and browning inhibition during storage. Additionally, treatments with acidified sodium chlorite, sodium chlorite, or the combination of sodium chlorite and calcium chloride significantly (P < 0.001) reduced Escherichia coli populations on fresh-cut apples by 3.0, 3.6, and 3.9 log cfu g⁻¹ over the water control. The dual effectiveness of sodium chlorite to inhibit enzymatic browning and inactivate E. coli may allow this compound to achieve a prominent role in improving the quality and safety of products in the fresh-cut apple and other food industries.     

Effectiveness of ozone in combination with controlled atmosphere on quality characteristics including lignification of carrot sticks

Fresh-cut carrots were ozonized in water (1:2 w/v; @ 200 mg O₃/h) for 10 min and stored under controlled atmosphere (CA) conditions (2% O₂, 5% CO₂ and 93% N₂) at 6 ± 1 °C and 85% RH for up to 30 d. Ozonation was found to reduce lignification and maintaining the keeping quality of fresh-cut carrots during CA storage. The maximum decrease in respiration and ethylene emission rates were obtained by the combination of CA with ozone followed by CA alone and ozonation compared with the control samples kept under low temperature (6 ± 1 °C). Significant (p < 0.05) reduction in ascorbic acid, carotenoids and oxidative enzymes such as polyphenol oxidase (PPO) and peroxidase (POD) were observed due to ozonation and CA storage. The control of lignification by ozone in synergy with CA was characterized by decrease in L∗ values. The results highlighted the positive role of ozonation in combination with CA storage in controlling lignification and microbial spoilage of carrot sticks.     

Light exposure inhibiting tissue browning and improving antioxidant capacity of fresh-cut celery (Apium graveolens var. dulce)

Fresh-cut celery is perishable and susceptible to tissue browning during storage. In this study, the effect of continuous light exposure (2000 lux) on browning related enzyme activity of fresh-cut celery was investigated during 8 d storage at 7 °C using darkness (0.2 lux) as control. Light exposure significantly suppressed polyphenol oxidase (PPO) and peroxidase (POD) activities, and subsequently decreased soluble quinone accumulation and browning index (BI) evolution during storage. In addition, phenylalanine ammonia lyase (PAL) activity, total phenol (TP) content, and antioxidant capacity (AC) values were all higher when the fresh-cut celery samples were exposed to light than in darkness during storage. A significant positive correlation between TP and AC was observed at both light (R = 0.884, P < 0.01) and dark (R = 0.705, P < 0.01) conditions.     

短波紫外线处理对鲜切莲藕酶促褐变的影响

以'粉红藕'为试材,研究了短波紫外线处理对鲜切莲藕4℃冷藏过程中褐变效果的影响。主要分析了不同照射剂量(1.0、3.0和5.0 kJ/m2)下鲜切莲藕色泽、失水率、硬度、没食子酸含量、儿茶酚含量、多酚氧化酶(PPO)和超氧化物歧化酶(SOD)活性等对生理生化指标的影响。结果表明,5.0 kJ/m2剂量UV-C处理的鲜切莲藕褐变指数在贮藏第12 d时低于30,显著低于对照和其他处理组(P<0.05),5.0 kJ/m2剂量UV-C处理可通过抑制褐变底物儿茶酚、没食子酸与PPO反应来延缓鲜切莲藕的酶促褐变,并通过延缓硬度的下降,提高鲜切莲藕的贮藏品质。综合保鲜效果得出,12 d的贮藏期内,5.0 kJ/m2剂量UV-C处理抑制鲜切莲藕的褐变效果最佳。     

高浓度二氧化碳气调包装通过调节酚代谢抑制鲜切莲藕的酶促褐变

鲜切莲藕褐变的主要原因是酶促褐变,高浓度CO_2气调包装(Modified-atmosphere packaging,MAP)可以有效延缓鲜切果蔬褐变,而苯丙氨酸解氨酶(L-phenylalanine ammonia-lyase,PAL)、多酚氧化酶(Polyphenol oxidase,PPO)和过氧化物酶(Peroxidase,POD)的编码基因是引起果蔬褐变的主要基因。然而,高浓度CO_2 MAP对鲜切莲藕片PAL、PPO、POD酶及其编码基因表达的影响却鲜有报道。本文分析了100%CO_2MAP对鲜切莲藕贮藏过程中褐变度、总酚含量、PAL、PPO和POD酶活性及其编码基因表达的影响。结果表明:100%CO_2 MAP对延缓鲜切莲藕褐变有较好效果,且100%CO_2 MAP贮藏期间鲜切莲藕PAL、PPO和POD酶活性随褐变程度的增加而同步变化。此外,Nn PAL1,Nn PPOA和Nn POD2/3的表达变化与PAL,PPO和POD酶活性的变化及褐变相一致,说明高浓度CO_2 MAP可能通过下调Nn PAL1,Nn PPOA和Nn POD2/3的表达来延缓鲜切莲藕褐变。     

Biochemical properties and potential endogenous substrates of polyphenoloxidase from chufa (Eleocharis tuberosa) corms

Polyphenoloxidase (PPO) was partially purified from chufa corms through ammonium sulphate precipitation and dialysis. Biochemical properties of chufa PPO were analysed using exogenous substrate catechol. Optimal pH and temperature for PPO activity were 5 and 45 °C. Ethylenediaminetetraacetic acid disodium salt and l-cysteine could not inhibit the PPO activity. However, sodium thiosulphate pentahydrate exhibited the strongest inhibiting effect, followed by ascorbic acid and anhydrous sodium sulphite. Except for K⁺, other metal ions such as Zn²⁺, Cu²⁺, Fe³⁺, Ca²⁺, Fe²⁺ and Na⁺ accelerated the enzymatic reaction between catechol and PPO. Kinetic analysis showed that the apparent K_m and V_max values were around 10.77 mM and 82 units/ml min. In addition, (−)-gallocatechin gallate, (−)-epicatechin gallate and (+)-catechin gallate isolated and identified from chufa corms were supposed to be the potential endogenous PPO substrates due to their ortho-diphenolic or pyrogallolic structures. These polyphenols might be catalysed by PPO, resulting in the browning of chufa corms after fresh-cut processing.     

Fruit quality and physiological responses of litchi cultivar McLean's Red to 1-methylcyclopropene pre-treatment and controlled atmosphere storage conditions

The effect of 1-MCP pre-treatment and two different controlled atmosphere storage conditions (CA-1, 17% O₂ + 6% CO₂; CA-2, 7% O₂ + 3% CO₂) on fruit quality parameters and physiological changes with respect to pericarp browning in ‘McLean's Red’ litchi were investigated. Fruits were pre-treated with 1-MCP (500 nl/l) and held at CA-1 or CA-2 for 21 d at 2 °C and at 90% RH. Stand-alone CA-1 or stand-alone CA-2 and the commercially adopted sulphur dioxide (SO₂) treatment were included in this study for comparison. Of the five treatments 1-MCP + CA-1 was most effective in preventing browning, loss of red colour (colour value a*) of the pericarp, ascorbic acid content; and retaining acceptable SSC/TA and taste. Fruit from 1-MCP + CA-1 showed higher overall acceptance after 21 d storage without any off-flavour according to the sensory panel data.1-MCP + CA-1 reduced the polyphenol oxidase (PPO) and peroxidase (POD) activity, retained membrane integrity and anthocyanin content during storage. Although SO₂ treatment prevents browning it showed negative effects on SSC/TA, taste and membrane integrity. Stand-alone CA-2 condition indicated higher pericarp browning, PPO, POD activity and loss of membrane integrity. Therefore, 1-MCP pre-treatment and CA-1 retains overall fruit quality for up to 21 d.     

Effects of various sulphuring methods and storage temperatures on the physical and chemical quality of dried apricots

The effects of different sulphuring methods, i.e. sulphuring by “burning the elemental sulphites (BES),” “SO₂ gas from liquified SO₂ tank (SG)” and “dipping into sodium metabisulphite solution (DSM)” on the colour (brown colour formation and carotenoid degradation) and the loss of SO₂ in apricots from Hac?halilo?lu and Kabaa?? varieties stored at 5, 20 and 30 °C for a year were investigated. There were significant effects of variety, sulphuring method and especially storage at 30 °C on the brown colour formation and loss of SO₂ (P < 0.05). As storage temperature–time increased, β-carotene content decreased. Sulphuring methods and variety did not show significant effect on β-carotene content (P > 0.05). The changes in L^∗, b^∗ and C^∗ values were directly associated with β-carotene content and browning values. The most suitable method for all samples, except for Hac?halilo?lu variety stored at 30 °C (BES), is SG, because the samples retained their attractive golden yellow colour during storage.     

Using polysaccharide-based edible coatings to maintain quality of fresh-cut Fuji apples

The effect of alginate and gellan-based edible coatings on the shelf-life of fresh-cut Fuji apples packed in trays with a plastic film of a known permeability to oxygen (110 cm³ O₂ m⁻² bar⁻¹ day⁻¹) was investigated by measuring changes in headspace atmosphere, color, firmness and microbial growth during 23 days of storage at 4 °C. Concentration of O₂ and CO₂ in the package was measured and no significant differences between coated and uncoated fresh-cut apples were observed. Ethylene concentration in coated apples seemed to be delayed since it remained below 50 μl l⁻¹ throughout the whole refrigerated storage period, while production of this gas was detected in uncoated apples from the very initial days of storage. Coated apple wedges exhibited ethanol and acetaldehyde formation from the second week of storage indicating fermentative metabolism. Polymers were crosslinked with a calcium chloride solution, to which the antibrowning agent N-acetylcysteine was added, being incorporated into the coatings formulation and helping to maintain firmness and color of apple wedges during the entire storage time. The application of the edible coatings also retarded the microbiological deterioration of fresh-cut apples. Alginate and gellan edible coatings effectively prolonged the shelf-life of Fuji apple wedges by 2 weeks of storage compared with the control apple slices which showed a considerable cut surface browning and tissue softening from the very early days of storage, limiting their shelf-life to less than 4 days.     

Efficacy of sodium chlorite as an inhibitor of enzymatic browning in apple slices

Sodium chlorite (SC) is an effective sanitizer for inhibiting microbial growth. This investigation was conducted to determine the efficacy of SC as a browning control agent for use on fresh-cut apple slices, applied alone, or in conjunction with organic acids. Additionally, the authors compared the efficacy of SC to that of acidified sodium chlorite (ASC) and to several other salts and examined the effect of pH and several different organic acids on efficacy of SC. The fresh-cut apple slices were dipped in treatment solutions for 1 min, then drained and placed in plastic containers at 20 °C for 24 h, and finally stored in polyethylene bags at 5 °C for 2 weeks. Color was measured periodically during storage. Lightness (L) values for all treated and control samples measured at 4 h, 24 h, and 2 weeks of storage were compared to L value for untreated samples measured immediately after cutting. Percent decrease in L-values was calculated for each sample at each time interval. Apple slices treated in ASC or SC solution had a significantly smaller decrease in L value indicating less browning than those treated in citric acid or water control at 4 h (P < 0.01), and with the exception of 1 g L⁻¹ ASC and 0.1 g L⁻¹ SC, all other ASC and SC treated slices still had significantly less browning than those for the water control (P < 0.01) at 24 h. After 2 weeks of storage, only SC (0.5–1.0 g L⁻¹), sodium bisulfite (0.5 g L⁻¹) and calcium l-ascorbate (10 g L⁻¹) continued to inhibit browning. Treatment with 0.5 g L⁻¹ SC and pH adjusted in the range from 3.9 to 6.2 using citric acid (CA) reduced browning more effectively than 0.5 g L⁻¹ SC without pH adjustment. Two organic acids, salicylic acid and cinnamic acid, when added to SC solution, were found to achieve even better inhibition of browning than CA at the same pH value.     

A comparison study between antioxidant and mutagenic properties of cysteine glucose-derived Maillard reaction products and neoformed products from heated cysteine and hydroxymethylfurfural

It was previously reported that Maillard reaction products (MRP) obtained from glucose with cysteine (1 M/0.25 M) mixtures and compounds generated during the mixing of heated cysteine with HMF solutions (Mix) were prone to inactivate various vegetal polyphenoloxidases (PPO). In this study, antioxidant properties of these model systems were compared using in vitro assays (AAPH°, DPPH° and TMM tests). Results showed that antioxidant activity observed in MRP and the Mix could be attributed to the sulfhydryl group of cysteine. The Mix behaved like a non-competitive inhibitor towards eggplant PPO (K_i = 0.7 μM). A highly active fraction, devoid of thiol compound and HMF, was obtained after fractionation of the Mix by SPE. The Mix was as efficient as metabisulfite in preventing enzymatic browning of apple puree (CIE-La^∗b^∗). MRP, the Mix and HMF could not be considered as mutagenic in the Salmonella microsome assay using Salmonella typhimurium TA98 and 102 strains.     

The application of high-concentration short-time chlorine dioxide treatment for selected specialty crops including Roma tomatoes (Lycopersicon esculentum), cantaloupes (Cucumis melo ssp. melo var. cantaloupensis) and strawberries (Fragaria × ananassa)

The effects of high-concentration short-time chlorine dioxide (ClO₂) gas treatment on food-borne pathogens inoculated onto the surface of tomatoes, cantaloupes, and strawberries were studied. Produce were spot-inoculated with a mixture of Salmonella enterica (serotypes Montevideo, Javiana and Baildon), Escherichia coli O157:H7 (serotypes 204 P, EDL 933 and C792) or Listeria monocytogenes (serotypes Scott A, F 5069 and LCDC 81-861), and treated with ClO₂ gas at 10 mg/l for 180 s. After ClO₂ gas treatment, surviving populations were determined and shelf-life studies were conducted (microbial spoilage population, change in color and overall appearance). Significant microbial reduction (p < 0.05) was observed for all treated samples. Nearly a 5 Log CFU/cm²Salmonella reduction was found on tomatoes, cantaloupe and strawberries, while a ∼3 Log CFU/cm² reduction was observed for E. coli and Listeria on all produce surfaces. E. coli and Listeria appeared to be more resistant to ClO₂ gas as compared to Salmonella spp. Treatments significantly (p < 0.05) reduced initial microflora population, while produce color surface was not significantly influenced, as compared to the control (p > 0.05). Results obtained suggest the potential use of high-concentration short-time ClO₂ gas treatment as an effective online pathogen inactivation technology for specialty crops in large-scale produce packing operations.     

Color changes in fish during grilling – Influences of heat transfer and heating medium on browning color

Samples of red sea bream (Pagrus major) were grilled under radiant (far-infrared radiation, FIR) and convective (superheated steam, SHS) heating. The temperature and color (CIE L^∗, a^∗, and b^∗ values) of the sample surface were monitored over time, using SHS, dry air, and N₂ as heating media. The rate of L^∗ changes was evaluated by treating the browning reaction as first-order. Color changes based on a^∗ and b^∗ values were effectively correlated with the L^∗ value, using empirical equations. A slower reduction in L^∗ for heating with SHS rather than FIR was obtained, probably because of different activation energies (31.5 and 50.7 kJ mol⁻¹) and frequency factors (8.2 and 4759 s⁻¹). The order of reductions in L^∗ was dry air > N₂≒$\fallingdotseq$ SHS. The absence of O₂ in the heating medium could be the reason for the delay in the browning reaction during heating using N₂ and SHS.