Effect of overwinter storage at three temperatures on the flavour intensity of dry bulb onions

Dry bulb onion (cv. Rijnsburger and Giant Zittau) were stored from September 1973 to late May 1974 at 2, 25°C and ambient temperature (mean 6°C). Flavour changes were monitored at intervals on freeze-dried samples by determination of (a) pyruvate, (b) lachrymator (thiopropanal S-oxide) and (c) g.l.c.-headspace total peak areas. Flavour intensity increased progressively with length of storage to about 190 days and was usually followed by a steep downturn to 240 days' storage. These changes have been interpreted in terms of incidence of sprouting and changes of respiration rates.     

The use of synthetic (±)-s-1-propyl-l-cysteine sulphoxide and of alliinase preparations in studies of flavour changes resulting from processing of onion (allium cepa l.)

Large losses of onion flavour components result from certain post-harvest processes such as cooking by boiling, dehydration, freezing etc. The mechanisms by which these losses occur have been investigated on the basis of the alliinase-precursor system and shown to include: (a) complete or partial enzyme destruction; (b) partial non-enzymic destruction of precursors; and (c) partial enzymic hydrolysis of precursors with loss of volatile reaction products. A stable, freeze-dried alliinase preparation and synthetic (±)-S-1-propyl-L-cysteine sulphoxide ((±)-PCSO) were prepared by known methods. Addition of an excess of enzyme to the processed product under optimal conditions was used in the determination of residual native substrate in the processed products and of an excess of the synthetic substrate for assay of enzymic activity. As compared with fresh onion as 100, enzymic activities of the processed products were as follows: freeze-dried 45, laboratory-frozen 18, hot-air dried 8.8–10, commercially-frozen 6.6, boiled 5.2 and pickled 0.01. Non-enzymic destruction of substrate (precursor) was greatest in the hot-air dried product (ca 80%) and least in freeze-dried onion (2.0%) Model experiments based on the alliinase preparation, (±)-PCSO and cis-S-1-propenyl-L-cysteine sulphoxide (the major component of the native onion precursors is the trans-isomer) exaggerated destruction of enzyme at 60 and 100 °C as compared with the relevant processed products, yet underestimated the substrate losses at these temperatures. It was concluded that factors other than those embodied in the model conditions were also involved.     

Effect of Welsh Onion (Allium fistulosum L.) on Breadmaking Properties

Breadmaking properties, such as bread height and specific volume, were improved in bread, made with wheat flour blended with Welsh onion (Allium fistulosum L.) powder, which is high in di‐n‐propyl disulfide (Pro₂S₂). Breadmaking properties also were improved in bread prepared from wheat flour blended with Pro₂S₂ alone. Brabender farinographs of Welsh onion powder/wheat flour and Pro₂S₂/wheat flour showed interesting properties in modifying the width of the tail. Size‐exclusion high performance liquid chromatography of the wheat proteins in the control and blended flours showed a profile of low, medium, and high molecular weight peaks. The area of the high molecular weight peak was larger in the 2 blended flours than in control, indicating this protein was important for the improvement.     

Role of precursors on greening in crushed garlic (Allium sativum) bulbs, and its control with freeze-dried onion powder

BACKGROUND: Lachrymatory factor (LF) synthase in onion bulbs reacts with S‐1‐propenyl‐L ‐cysteine sulfoxide (1‐PeCSO), a key compound in garlic greening. In this study, freeze‐dried onion powder containing LF synthase was used in treatments to control garlic greening. Prior to the use of freeze‐dried onion powder to treat greening garlic bulbs, model reactions were conducted to confirm the reactivity of 1‐PeCSO in onion bulbs to garlic greening. RESULTS: While pink pigments were generated from 1‐PeCSO, green pigments were produced from the combination of 1‐PeCSO and S‐2‐propenyl‐L ‐cysteine sulfoxide (2‐PeCSO). However, pigments were formed in the systems containing 1‐PeCSO, amino acid and alliinase. Even non‐greening garlic bulbs stored at 20 °C turned green with the reaction of 200 g L^?1 1‐PeCSO; therefore 1‐PeCSO isolated from onion bulbs had the same role as 1‐PeCSO in garlic bulbs in terms of greening. Onion bulbs turned green after the addition of 600 g L^?1 2‐PeCSO. The addition of freeze‐dried onion powder inhibited garlic greening, and treatment with 15 g kg^?1 onion powder gave the best storage stability of crushed garlic bulbs. CONCLUSION: The addition of freeze‐dried onion powder inhibited the greening in crushed garlic bulbs, and treatment with 15 g kg^?1 onion powder gave the best storage stability of crushed garlic bulbs. Copyright © 2011 Society of Chemical Industry     

One new pathway for Allium discoloration

(+)-S-(1-propenyl)-l-cysteine S-oxide (1-PeCSO) is a key compound associated with Allium discoloration. The pathway by which 1-PeCSO participates in Allium discoloration in the presence of alliinase has been established, but whether 1-PeCSO results in the discoloration in the absence of this enzyme remains unknown. In the present study, one new model reaction system containing 1-PeCSO alone in a phosphate buffer was established to simulate discoloration of white onion tissue and garlic puree. Results showed that the model system generated yellowish-green colour at pH 3.0 and red colour at pH 5.0. Two red species were isolated and identified by high-resolution multistage MS analysis, molecular formulae of which are C₂₄H₃₀N₂O₅S (red species 1) and C₂₇H₃₆N₂O₆S₂ (red species 2). Both of them are sulphur-containing pyrrole derivatives and have UV/visible maximum absorbances at 520 (species 1) and 523 nm (species 2). The discoloration reactions occurring in this new system might represent a new pathway correlated with both onion reddening and garlic greening, emphasising that protein amino acids and alliinase are not necessary during the discoloration.     

Ammonium nitrate fertility levels influence flavour development in hydroponically grown ‘Granex 33’ onion

High levels of nitrogen (N) fertility have been shown to influence bulb flavour characteristics in onion (Allium cepa L). To test the effects of lower levels of N fertility on onion bulb flavour, ‘Granex 33’ onions were grown hydroponically in a greenhouse with varying solution N levels. Eleven levels were tested by increasing the concentration of NH₄NO₃ in solutions from 20 to 140 mg l^?1 N. Mature plants were harvested and evaluated for plant leaf and bulb fresh weights (FWs), bulb soluble solids content (SSC), bulb total pyruvic acid, bulb total sulphur (S), and bulb sulphate (SO₄^2?). To determine the effect of N on the flavour biosynthetic pathway of onion, total and individual S‐alk(en)yl cysteine sulphoxides and related peptide intermediates were also tested. Leaf and bulb FWs responded quadratically to N concentration, as did total bulb S. Bulb SO₄^2? and SSC, though significantly influenced by N concentration, did not respond with a meaningful trend. Bulb pyruvic acid increased linearly with N level increases, as did (+)‐S‐propyl‐L ‐cysteine sulphoxide. Total precursors, (+)‐S‐methyl‐L ‐cysteine sulphoxide, and trans‐(+)‐S‐1‐propenyl‐L ‐cysteine sulphoxide responded quadratically to N levels. At lower N levels, trans‐(+)‐S‐1‐propenyl‐L ‐cysteine sulphoxide content was highest relative to the other precursors. However, at elevated N levels, (+)‐S‐methyl‐L ‐cysteine sulphoxide accumulated in the highest concentrations. Peptide intermediates 2‐carboxypropyl glutathione and γ‐glutamyl propenyl cysteine sulphoxide responded linearly and quadratically respectively to increasing N fertility levels. Nitrogen fertility levels can influence flavour intensity and quality and should be considered when growing onions for flavour attributes. Copyright © 2003 Society of Chemical Industry     

The levels of S-alk(en)yl-L-cysteine sulphoxides during the growth of the onion (Allium cepa l.)

Flavour precursors, the S-alk(en)yl-L -cysteine sulphoxides, change considerably in both concentration and total amount during the growth of onions. For the brown onion cv. Pukekohe Long Keeper (PLK) and for the white onion cv. Dehyso, (±)-S-1-propyl-L -cysteine sulphoxide (±PCSO) is the predominant flavour precursor, with (±)-trans-S-1-propenyl-L -cysteine sulphoxide (±PECSO) and (±)-S-1-methyl-L -cysteine sulphoxide (±MCSO) in a minor role. For PLK the greatest concentration of all three precursors is just prior to bulbing (3.6±1.1 mg g^?1 fresh weight); for Dehyso the greatest concentration is at bulbing (4.6±0.6 mg g^?1 fresh weight); Both varieties show a mid-season reduction in flavour precursor concentration (of about 45%), followed by a small but significant increase in ±PCSO concentration during the end of season leaf die-down. The total amount of the three flavour precursors per bulb in both varieties shows a maximum in late January (360±107 mg for PLK, 602±144 mg for Dehyso). In the subsequent months there is a dramatic reduction in the total amount of ±PECSO and ±MCSO, and a slight reduction in ±PCSO. Both varieties show an increase in the amount of ±PCSO at leaf die-down. The relative proportions of these flavour precursors change with bulb age and cultivar. These results suggest that white onions used for drying and processing could be harvested from bulbing onwards. Furthermore, when onion cultivars and onion plant selections are assessed for flavour, care needs to be given to the stage of maturity of the onion.     

A survey of volatile components of some allium species in terms of s-alk(en)yl-l-cysteine sulphoxides present as flavour precursors

The volatile flavour components of 27 Allium species and cultivars, mostly edible but including some decorative species for comparison, have been investigated by a series of gas and thin-layer chromatographic and u.v. spectrophotometric methods. By means of simulation experiments with synthetic precursors and intermediates, the data have been interpreted in terms of the amino acid precursors present in the intact tissues and the species classified as containing (a) S-1-propenyl-, (b) S-2-propenyl- and (c) S-methyl-L-cysteine sulphoxides as their principal flavour precursors. Characteristic examples of the three types are A. cepa L. (onion), A. sativum L. (garlic) and A. aflatunense B. Fedtschenko, respectively. An object of the work has been to demonstrate broad chemical similarities between species as well as their differences, which are emphasised in keys for classification on the basis of morphological characters. In addition to onion, leek, shallot, garlic and chives, species such as A. chinense, A. fistulosum and A. tuberosum have widespread use as food, particularly in the Far East. The literature on this aspect has been briefly summarised.     

Study on the pilot-scale extraction of onion oleoresin using supercritical CO2

Supercritical carbon dioxide (SC-CO₂) was used to produce oleoresin from dried onion by pilot-scale extraction. The results showed that the extraction pressure and temperature affected the yield and sulphur concentration of onion oleoresin. Increase of the temperature from 45 to 65°C at 300 bar resulted in an increase of the yield and the sulphur concentration of oleoresin. At the same temperature (45°C) the yield was also higher at 300 bar than 100 bar while sulphur concentration of oleoresin got smaller at 300 bar than at 100 bar. The volatile composition of oleoresin displayed practically no differences as a function of extraction parameters. Comparison of different extraction methods showed that the yield after SC-CO₂ extraction was 22 times higher than that after steam distillation, but it was 14 or 39 times less than that after alcohol extraction, shaking at 25°C or in Soxhlet apparatus, respectively. The concentration of sulphur was the highest in steam distilled onion oil while it was the lowest in the extract of hexane and alcohol (at 25°C). The results of sensory evaluation showed that oleoresin extracted by SC-CO₂ was the first in ranking (at level of significance 0·05), before steam distilled oil and alcoholic extract. There was no significant difference between steam distilled oil and alcoholic extract in ranking, but the alcoholic extract was the least desirable, since the intensity of its off odour attribute was the highest. © 1998 SCI.     

Quantitative analysis of the S-alk(en)yl-L-cysteine sulphoxides in onion (Allium cepa L.)

Quantitative analysis of each of the S-alk(en)yl-L-cysteine sulphoxides was achieved by the following procedure. A methanol: chloroform: water extract of onion tissue was purified by electrophoresis. Alk(en)yl-L-cysteine sulphoxides were separated by thin-layer chromatography (t.l.c.) on commercial silica-gel plates and were reacted with ninhydrin, the spot intensity being measured by an integrating densitometer. The synthetic analogue (±)-S-1-butyl-L-cysteine sulphoxide was used as an internal standard in each extract. In white bulb onion (cv. Southport White Globe), (±)-S-1-propyl-L-cysteine sulphoxide is the predominant flavour precursor at a concentration of 2.9 ± 0.4 mg g^?1 fresh weight. ±-S-1-methyl-L-cysteine sulphoxide and (±) trans-S-1-propenyl-L-cysteine sulphoxide are present at the lower concentrations of 0.9 ± 0.25 mg g^?1 fresh weight and 0.6 ± 0.15 mg g^?1 fresh weight respectively. Stable n-butyl, trifluoroacetyl derivatives of standards and of the alk(en)yl-L-cysteine sulphoxides in extracts, were formed. Subsequent g.c.-m.s. enabled parent ions and fragmentation patterns to be recorded and allowed the conclusive identification of the endogenous alk(en)yl-L-cysteine sulphoxides.     

Antioxidant and antimicrobial activities of the methanol extracts from pummelo (Citrus grandis Osbeck) fruit albedo tissues

The present study was conducted to evaluate the antioxidant and antimicrobial properties of methanol (100 and 80% aqueous) extracts of pummelo fruits albedo (Citrus grandis Osbeck). The antioxidant and antibacterial activity for crude extracts and isolated compounds were evaluated using free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) and Paper disc diffusion method. A 100% Methanol (MeOH) extract was steeped in water at different pH levels and partitioned with ethyl acetate (EtOAc) to give basic, acidic, neutral, and phenolic fractions. The neutral extract was found to possess maximum antioxidant and antibacterial activity. Thereafter, neutral extract was carried out on a silica gel column and eluted with hexane:EtOAc:acetone and preparative TLC (PTLC) to give oil buntan compound, linoleic acid methyl ester, β-sitosterol, sigmasterol, limonin, nomilin and meranzin hydrate were isolated. While, 80% MeOH extract was fractionated also using a silica gel column and PTLC to give isomeranzin hydrate, p-coumaric acid and caffeic acid compound. The extract concentration providing 50% inhibition (IC₅₀) was as follows; oil buntan compound 95 μg/mL, caffeic acid 45 μg/mL, p-coumaric acid 105 μg/mL, limonin + nomilin (mixture) 135 μg/mL was lower than that of synthetic antioxidant butylated hydroxyanisole (BHA) 40 μg/mL. The inhibitory zone (mm) of bacteria tested was 2.9–4.1 mm caffeic acid and 11.6–15.1 mm p-coumaric acid.     

Formation of dimethyl sulphide from S-methylmethionine in onion seedlings (Allium cepa)

Homogenates of onion seedlings catalyse the decomposition of S-methyl-methionine into dimethyl sulphide and homoserine. The reaction is rather slow and seems not to be of primary importance in onion flavour formation or S-methylmethionine metabolism. Extracts of scarlet runner bean seedlings are also active, whereas dormant onion bulb and other seedlings tested showed no or very low activity.     

Desorption isotherms,net isosteric heat and the effect of temperature and water activity on the antioxidant activity of two varieties of onion (Allium cepa L)

The standard static gravimetric method was used to determine moisture desorption isotherms (MDIs) of two onion varieties (Goudami and Galmi Violet) at 30 °C, 45 °C and 60 °C in the water activity ranging from 0.055 to 0.83. The combined effects of temperature and water activity on the antioxidant activities of the onion varieties were also studied. GAB, Oswin, Smith and BET equations were tested to fit the experimental data. The net isosteric heat of sorption was calculated. Equilibrium moisture content (EMC), total phenolic content (TPC) and antiradical activity were also measured. The isotherm and the EMC vary significantly with the onion variety and drying temperature, irrespective of water activity (a_w). Desorption isotherms were best described by the GAB model. The maximum net isosteric heats for Galmi Violet (32.58 kJ mol^?1) were greater than those of Goudami (23.50 kJ mol^?1) at each EMC. The TPC and antiradical activity of the Galmi Violet were significantly (P ≤ 0.05) higher than that of the Goudami at all investigated temperatures and water activities.     

CHARACTERIZATION OF PHYTOCHELATIN-LIKE COMPLEXES FROM FLAX (LINUM USITATISSIMUM) SEED

Proteins were extracted from dehulled and delipidated powder of flaxseed (cv. NorMan), and fractionated by DEAE‐Sephacel onion exchange chromatography. Ultraviolet absorbance scans of ion exchange fractions eluting in buffers at pH 8.6 containing 0.45 M and 0.50M NaCl revealed A₂₅₅ >A₂₈₀. Furthermore, the A₂₅₅ was reduced upon acidification and restored by adjusting to the original pH, confirming spectral characteristics typical of metal‐thiolate complexes. Characteristic circular dichroism spectra and reversible aggregation‐dissociation behavior under low and high salt conditions observed for these fractions are also typical of metal binding phytochelatins reported for other plants, while the presence of aromatic amino acids indicated by fluorescence spectra suggests some similarity to nonmetallothionein proteins. Further work is underway to investigate the prevalence of these and other complexes as well as the distribution of metals in different protein fractions of flaxseed, as a function of cultivar and geographical location.     

Respiratory parameters of onion bulbs (Allium cepa) during storage. Effects of ionising radiation and temperature

The O₂ and CO₂ respiration rates of untreated and irradiated onion bulbs (Allium cepa) at 0.15 and 0.30 kGy were measured at 4, 10 and 20 °C. The O₂ respiration rate increased for 24 h after treatment from 0.19 mmole kg⁻¹ h⁻¹ at 20 °C for control samples up to 0.26 and 0.39 mmole kg⁻¹ h⁻¹ for 0.15 and 0.3 kGy irradiated onions respectively. Respiratory quotient (RQ) increased with temperature. The Q₁₀ of the respiration of the control samples (1.61) was lower than that of any other plant tissue, but it increased with storage duration and irradiation dose. The respiration rate of control onions increased steadily over 25 weeks of storage at 4 °C, while that of the irradiated samples decreased during the same period after a peak observed after irradiation treatment. The apparent K_m for the Menten–Michaelis equation was determined on a new respirometer and averaged 1.6 kPa at 10 °C and 6.3 kPa at 20 °C. However, at this higher temperature (20 °C) apparent K_m varied with O₂ partial pressure, proving that the respiration of onion bulbs does not follow a Menten–Michaelis‐like process. The Fermentative Index (FI) of onions was measured under anoxic conditions as CO₂ production rates in mmole kg⁻¹ h⁻¹ at 4, 10 and 20 °C. © 2000 Society of Chemical Industry     

Chemical Properties and Oxidative Stability of Perilla Oils Obtained From Roasted Perilla Seeds As Affected by Extraction Methods

Abstract: The chemical properties and oxidative stability of perilla oils obtained from roasted perilla seeds as affected by extraction methods (supercritical carbon dioxide [SC‐CO₂], mechanical press, and solvent extraction) were studied. The SC‐CO₂ extraction at 420 bar and 50 °C and hexane extraction showed significantly higher oil yield than mechanical press extraction (P < 0.05). The fatty acid compositions in the oils were virtually identical regardless of the extraction methods. The contents of tocopherol, sterol, policosanol, and phosphorus in the perilla oils greatly varied with the extraction methods. The SC‐CO₂‐extracted perilla oils contained significantly higher contents of tocopherols, sterols, and policosanols than the mechanical press‐extracted and hexane‐extracted oils (P < 0.05). The SC‐CO₂‐extracted oil showed the greatly lower oxidative stability than press‐extracted and hexane‐extracted oils during the storage in the oven under dark at 60 °C. However, the photooxidative stabilities of the oils were not considerably different with extraction methods.     

PHYSICOCHEMICAL PROPERTIES OF MUSCLE AND NATURAL ACTOMYOSIN EXTRACTED FROM FARMED ATLANTIC SALMON (SALMO SALAR) STORED AT 4C

Properties of farmed Atlantic salmon (Salmo salar) obtained commercially were studied as a function of storage at 4C for 9 days. While pH increased gradually during storage for both samples, significant differences between samples were noted in water‐binding capacity (WBC) of muscle, as well as surface hydrophobicity (S_o) and sulfhydryl contents of extracted natural actomyosin (NAM). Lower S_owas observed for NAM extracted from muscle stored for 2 days, coinciding with high WBC of the muscle. In contrast, higher S_ofrom 5 to 7 day‐stored samples coincided with minimum extractability and high apparent viscosity of NAM. Reactive sulfhydryl groups were higher at the beginning and end of storage. Generally, WBC of fish muscle was dependent on pH and related to changes in S_oof NAM, while apparent viscosity increased with S_oand disulfide content. The results indicate variability in functional properties of the salmon samples during cold storage, which could be attributed to changes in physicochemical properties of NAM.     

Direct Spectroscopic Observation of Singlet Oxygen Quenching and Kinetic Studies of Physical and Chemical Singlet Oxygen Quenching Rate Constants of Synthetic Antioxidants (BHA,BHT, and TBHQ) in Methanol

Abstract: Singlet oxygen quenching by synthetic antioxidants (BHA, BHT, and TBHQ) was directly observed by spectroscopic monitoring of luminescence at 1268 nm. The luminescence data showed unambiguous evidence of singlet oxygen quenching by synthetic phenolic antioxidants with the highest activity for TBHQ, followed by BHA and BHT. The protective activities of these synthetic antioxidants on α-terpinene oxidation with chemically-induced singlet oxygen under dark further confirmed their singlet oxygen quenching abilities. Total singlet oxygen quenching rate constants (k_r + k_q) of BHA, BHT, and TBHQ were determined in a system containing α-terpinene (as a singlet oxygen trap) and methylene blue (as a sensitizer) during light irradiation, and the values were 5.14 × 10⁷, 3.41 × 10⁶, and 1.99 × 10⁸ M⁻¹s⁻¹, respectively. After the k_r value of α-terpinene was first determined, the k_r values of the synthetic antioxidants were calculated by measuring their relative reaction rates with singlet oxygen to that of α-terpinene under the identical conditions. The k_r values of the BHA, BHT, and TBHQ were 3.90 × 10⁵, 1.23 × 10⁵, and 2.93 × 10⁶, M⁻¹s⁻¹. The percent partition of chemical quenching over total singlet oxygen quenching (k_r × 100)/(k_r + k_q) for BHA, BHT, and TBHQ were 0.76%, 3.61%, and 1.47%, respectively. The results showed that the synthetic antioxidants quench singlet oxygen almost exclusively through the mechanism of physical quenching. This represents the first report on the singlet oxygen quenching mechanism of these synthetic antioxidants. Practical Application: The synthetic antioxidants, especially TBHQ, have been found to have a strong singlet oxygen quenching ability. This article also clearly showed that singlet oxygen quenching by synthetic antioxidants was mainly by the physical quenching mechanism. The results suggested that these synthetic antioxidants, especially TBHQ, could be used practically for the protection of the food components such as edible oils and vitamins against singlet oxygen induced oxidations without significant losses of antioxidant activity during storage under light.     

Modification of cotton fabric with acrylamide in the presence of K2S2O8 for improving dyeability of natural dyes

Cotton fabrics were modified using acrylamide as the aminating agent in the presence of potassium peroxodisulphate (K₂S₂O₈) as a free radical polymerisation catalyst using a pad–dry–cure technique in order to improve the dyeability of cotton fabrics with natural dyes. Pre‐soaking of bleached cotton fabric with 5 g l^?1 K₂S₂O₈ and subsequent application of 10 g l^?1 acrylamide monomer on the pre‐soaked cotton fabric, followed by drying of the padded fabric at 95°C for 5 min and curing of the dried fabric at 140°C for 5 min, produced most balanced improvements in dye uptake, tensile strength and wrinkle recovery angle for optimum retention of flexibility of the dyed substrates when pre‐treated cotton fabrics were dyed with Camellia sinensis and Punica granatum. Application of ferrous sulphate on pre‐treated cotton fabric following a pre‐salt application method and subsequently dyeing with Camellia sinensis and Punica granatum improved the depth of shade and all‐round colour fastness properties further. Infrared (IR) spectroscopy indicated that the treatment with acrylamide under the influence of K₂S₂O₈ led to incorporation of poly(acrylamide) in cotton by the process of graft co‐polymerisation using the pad–dry–cure technique.     

Kinetics of fructose on the Maillard brown colour development,pH change and antioxidative activity development in model fructose/glycine systems

Model fructose/glycine systems with fructose concentration between 0.035 and 0.28 m were incubated at temperature 45–90 °C for investigating the effects of fructose and temperature on the brown colour development, pH change and the antioxidative activity developments of Maillard reaction. The result showed that effects of fructose followed logarithm‐order kinetics on brown colour and DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) radical scavenging activity (S_DPPH) development, and first‐order kinetics on system pH decrease. However, the effect of fructose on ABTS·⁺ (2,2′‐azino‐bis[3‐ethylbenzthiazoline‐6‐sulphonic acid]) radical scavenging activity (S_ABTS) development was first order at 60–90 °C and logarithm order at 45 °C, which revealed the mutual synergistic interaction of concentration with temperature on S_ABTS development. Activation energy for S_DPPH development was lower than that for S_ABTS development, revealing that DPPH radical was more vulnerable than ABTS·⁺ radical to fructose/glycine MRPs at low temperature. But the relative vulnerability would invert at high temperature, as the Q₁₀ value for S_DPPH development was lower than that for S_ABTS development.