Variety and storage conditions affect the precursor content and amount of acrylamide in potato crisps

BACKGROUND: Acrylamide, a probable human carcinogen, is formed from the amino acid asparagine and reducing sugars when potato products are processed at high temperatures. This is a two‐year study on five Swedish‐grown potato clones, two of which are adapted to cold storage. The clones represented a wide range of precursor concentrations: asparagine, 3.7–15.3 mg g^?1; reducing sugars, 0.9–14.9 mg g^?1. Crisps were prepared in laboratory‐scale equipment mimicking industrial processing conditions. RESULTS: Potatoes stored at 4 °C had significantly higher levels of glucose and fructose than potatoes stored at 8 °C. Acrylamide levels were significantly higher in crisps made from potatoes stored at 4 °C. Two clones with a large difference in asparagine concentration but similar glucose and fructose concentrations gave crisps with significantly different acrylamide contents. The lowest levels of acrylamide were found in crisps made from the potato variety with the lowest asparagine concentration. CONCLUSION: The findings show that variety and storage conditions influence the levels of precursors. Acrylamide formation in crisps can be reduced by using potato varieties with low levels of both asparagine and reducing sugars. Mass transport of precursors during heating is suggested to be important for acrylamide formation in potato crisps. Copyright © 2007 Society of Chemical Industry     

Bioactive components and antioxidant capacity of Chinese bayberry (<Emphasis Type="Italic">Myrica rubra</Emphasis> Sieb. and Zucc.) fruit in relation to fruit maturity and postharvest storage

Total phenolics, flavonoids, anthocyanins, cyanidin-3-O-glucoside (Cy-3-glu) and antioxidant capacity of Chinese bayberry fruit (Myrica rubra Sieb. and Zucc.) differed among the four cultivars “Baizhong” (white), “Fenhong” (pink), “Wuzhong” (red) and “Biqi” (dark red). Antioxidant capacity determined by both the ferric reducing antioxidant power (FRAP) assay and 2,2-diphenyl-2-picrylhydrazyl (DPPH^.) radical scavenging capacity was significantly correlated with the antioxidant components in the fruit, and directly related to fruit color. Cy-3-glu accounted for at least 82, 38, and 12% of the total antioxidant capacity in “Biqi”, “Wuzhong” and “Fenhong” fruits, respectively. No detectable Cy-3-glu was found in “Baizhong” fruit. Greater fruit maturity was associated with higher levels of all the bioactive components and antioxidant capacity. Significant increases were also found during postharvest storage of “Biqi” fruit held at either 20 °C for 2 days or 0 °C for 5 days. However, these levels decreased during a 2-day shelf-life at 20 °C after 5 days at 0 °C. These results show that storage and shelf-life conditions are important if health-based bioactive components of bayberry fruit are to be maintained after harvest.     

Modified Atmosphere Packaging of “Napoleon” Cherry: Effect of Packaging Material and Storage Time on Physical,Chemical, and Sensory Quality

Effects of modified atmosphere and polymeric packaging material on the physical (mass loss, color, firmness), chemical (pH, total titratable acidity, total soluble solid, total phenolic content, total anthocyanin content), and sensory quality of “Napoleon” cherry (Prunus avium L. “Napoleon”) were studied. While lightness (L*) remained fairly unchanged, redness (a*), yellowness (b*), and chroma (C*) decreased during a 42-day storage period, resulting in darker fruit. Firmness did not differ significantly from the initial values (P ≤ 0.05) after 42 days of storage at 0°C. pH increased for all treatments over the storage period. In general, total titratable acidity increased during the first 2 weeks, and then decreased afterwards. Packaging significantly reduced mass losses, which were 24.08%, 0.50%, 0.39%, and 0.81% for control (unpackaged), polypropylene tray/biaxially oriented polypropylene film (PP/BOPP), polypropylene tray/cast polypropylene film, and polyvinyl chloride-polyethylene tray/polyethylene terephthalate-polyethylene films, respectively. Modified atmosphere packaging was found beneficial on extending the shelf life of fruit during storage. The shelf life of “Napoleon” cherries was suggested as 28 days for packaged samples and 14 days for unpackaged samples at 0°C. Samples packaged with PP/BOPP under 21% O₂ 79% N₂ preserved their physical, chemical, and sensory quality better than other treatments.     

Ultrasonic-assisted leaching of glucose and fructose as an alternative mitigation technology of acrylamide and 5- hydroxymethylfurfural in potato chips

The effect of ultrasound (480 W, 40 kHz) on the leaching of reducing sugars during the water soaking of potatoes slices (60, 70 and 80 °C- 1, 8 and 15 min) was investigated to reduce the formation of acrylamide (AA) and 5-hydroxymethylfurfural (5-HMF) in potato chips.Ultrasound (US) influenced abruptly the reducing sugar leaching during the first 15 min, significantly increasing their extraction rate (glucose: 60%, fructose: 30%) at all evaluated temperatures. When potato slices were treated with US, the formation of AA (~95%) and 5-HMF (~96%) were reduced significantly after frying. Although AA content did not correlate with glucose and fructose concentrations, 5-HMF did (r²: 0.80 and 0.83, respectively), probably because reducing sugars are their main precursors. The AA and 5-HMF concentrations of potato chips presented good correlation coefficient (r²:0.76), suggesting the use of 5-hydroxymethylfurfural as an acrylamide indicator for potato chips.     

Changes in antioxidants and taste-related compounds content during cold storage of fresh-cut red sweet peppers

Changes in antioxidants (ascorbic acid, phenolic compounds and carotenoids) and in taste-related compounds (sugars and organic acids) content were monitored in fresh-cut red sweet peppers (Capsicum annuum L., local ecotype “Peperone Cornetto di Pontecorvo”) during 9 days of cold storage. Pepper slices were placed in polystyrene trays, wrapped with a polyvinyl chloride film, and stored at 4 °C or at 8 °C; besides, to evaluate the effect of a prestorage hot water treatment, half of the slices were subjected to a dipping treatment in water at 53 °C for 4 min, before packaging and storage. During storage limited changes in O₂ and CO₂ concentrations were observed within all packages. Storage temperature strongly affected weight loss: at the end of the storage time it was <3 and >10% in fruits stored at 4 and 8 °C, respectively. Sugars (glucose and fructose) content showed a significant increase (+11%) only in fruits stored at 8 °C; this change was due to a concentration effect associated to water loss. A higher increase (+23 and +17% in fruits stored at 8 and 4 °C) was observed in organic acids (citric and malic) content. Minimal processing and storage produced only a quite limited degradation of ascorbic acid. Both hydroxycinnamic acid derivatives and flavonoids accumulated in fruits stored at 8 °C (and not heat treated), whereas at 4 °C phenolics accumulation appeared to be partially inhibited. All the main carotenoids (capsanthin, cucurbitaxanthin A, zeaxanthin, β-carotene and β-cryptoxanthin) markedly accumulated in fruits stored at 8 °C (not heat treated), and showed a general decrease at 4 °C. Hot water treatment did seem to affect organic acids metabolism, though it did not promote ascorbic acid degradation. In addition, it inhibited both phenolics and carotenoid accumulation in fruits stored at 8 °C.     

Acrylamide and 5-hydroxymethylfurfural formation during baking of biscuits: NaCl and temperature–time profile effects and kinetics

The present study aimed to investigate the effect of recipe and temperature–time on the formation of acrylamide and 5-hydroxymethylfurfural (HMF) during biscuit baking. Baking experiments were performed with biscuits of two different recipes, with and without NaCl, at 180 °C, 190 °C and 200 °C. Acrylamide and HMF reached highest concentrations at 200 °C for both recipes. The presence of NaCl in the biscuit formulation lowered acrylamide concentrations at 180 °C and 190 °C but not at 200 °C, and led to higher concentrations of HMF at all the tested temperatures. Sucrose hydrolysis was a key step in acrylamide and HMF formation during biscuit baking, even though a significant amount of acrylamide already had formed before the onset of sucrose hydrolysis. A lag phase was observed before sucrose hydrolysis occurred, which might depend on the melting of crystalline sucrose occurring at approximately 180 °C.A mathematical model based on the chemical reaction pathways was developed for the recipe with NaCl baked at 200 °C. The model described the chemical evolution during the last part of biscuit baking, and accurately predicted acrylamide and HMF content at the end of baking. The model showed the significant contribution of the reducing sugars to the formation of both acrylamide and HMF. The model could not be extended to the entire baking period because it was not possible to incorporate the lag phase observed before sucrose hydrolysis. The results reported in this study confirm that the kinetics of acrylamide and HMF formation in real food and dry systems may depend on the physical state of their precursors.     

Survival characteristics of Salmonella Typhimurium and Escherichia coli O157:H7 in minimally processed lettuce during storage at different temperatures

Salmonella Typhimurium and Escherichia coli O157:H7 strains were inoculated in minimally processed lettuce samples and survival characteristics of these pathogens during storage at two different temperatures. One group of samples was kept at refrigerator at +4 °C, another group was kept at ambient temperature (+25 °C). According to data obtained, the factor “temperature” significantly affected the pathogen bacteria counts of the samples (P < 0.05). Counts of these two pathogen bacteria were decreased in minimally processed lettuce during storage at +4 °C.     

Effect of chlorpropham (CIPC) on carbohydrate metabolism of potato tubers during storage

Two chipping cultivars, Snowden and Monona, with or without Chlorpropham (CIPC) application, were stored in darkness at 10–12 °C and approximately 95% humidity, following the 1997 growing season. Chip color, dry matter, and protein contents were monitored over 30 weeks of storage. Tuber concentrations of sucrose, reducing sugars, and major metabolites, as well as enzymes involved in glycolysis, oxidative pentose phosphate pathway, anaerobic and oxidative respiration were monitored during storage. Respiration, as measured by CO₂ production, was significantly (P⩽0.05) suppressed in CIPC-treated tubers. CIPC treatment had no significant (P>0.05) effect on chip color quality or tuber concentrations of protein, dry matter, sucrose, reducing sugars, or the assayed enzymes and metabolites of glycolysis (phosphofructokinases, NADH, ATP). The metabolite NADPH was higher in untreated tubers, consistent with its role in anabolic biosynthetic pathways involved in sprout production. Concentrations of ethanol and lactate, products of anaerobic respiration, were significantly (P⩽0.05) higher in the CIPC-treated Snowden tubers, relative to the untreated tubers.     

Combined Effects of Gamma Irradiation and Blanching Process on Acrylamide Content in Fried Potato Strips

Potato tubers were irradiated in ⁶⁰Co gamma station at different doses in order to investigate the effect of gamma irradiation on acrylamide formation in fried potato strips. Acrylamide content due to the irradiation treatment was reduced by 20–54% compared to a control after frying the irradiated tubers. While apply a blanching process, using warm tap water, to potato strips before frying has decreased acrylamide by 61%. A combination of gamma irradiation and a blanching process, which was applied in this work, showed a maximum decrease in acrylamide formation to reach 78% in fried potatoes.     

Changes in biogenic amine contents, non-protein nitrogen and crude protein during curing and thermal processing of M. longissimus, pars lumborum of pork

Changes in histamine, putrescine, cadaverine and tyramine, weight, dry matter, crude protein and non-protein nitrogen were studied during immersion-curing (brine with NaNO₂ and NaCl content of 0.6 g/l and 99.4 g/l, respectively and brine with NaNO₂ and NaCl content of 0.6 g/l and 199.4 g/l, respectively) and boiling and grilling (70 °C core temperature) of both “fresh” and “stored” (storage 5 days at 4 °C) pork loin chops. Amine concentrations were significantly higher in “stored” pork; this difference was preserved during most of the processing techniques. Correlations of amines with nonprotein nitrogen were weak and not significant, but strong and significant for putrescine: cadaverine (r=0.89) as well as putrescine: tyramine (r=0.95). Amine reductions for “fresh” pork were not pronounced. In “stored” pork both cooking in water (water/meat = 1:1, weight base) and curing in the less concentrated brine resulted in mean reductions of 65, 77, and 68% for putrescine, cadaverine and tyramine, respectively. Boiling of cured samples yielded reductions of 50–77, 74–80, 67–71, and 77–91% for histamine, tyramine, putrescine and cadaverine, respectively.

Biochemical and textural changes in trifoliate yam Dioscorea dumetorum tubers after harvest

Biochemical and textural changes were investigated in trifoliate yam Dioscorea dumetorum tubers, after harvest, in an attempt to study the chemical and physical changes associated with the raw and cooked tubers and how these relate to the hardening phenomenon of the tubers after harvest. A 2×2×3×4 factorial experiment, with cultivar, storage condition, treatment and storage time as their respective variables, was done. Samples were analysed for moisture, starch, reducing sugars, alcohol-soluble sugars, acid and neutral detergent fibre, cellulose, hemicellulose and lignin. The Warner–Bratzler test cell was used in a TA.XT2 Texture Analyser to measure the hardness of cooked tubers. The moisture and starch contents of the tubers decreased from 77.8 to 70.4% and 70.5 to 66.5 g/100g, respectively in a period of 72 h of storage, suggesting rapid dehydration after harvest and breakdown of starch. All the other chemical indices increased with storage time. These changes were influenced by the storage temperature and the treatment given to the tubers prior to storage. In general, samples stored at 4 °C showed smaller changes in the chemical indices than those at 28 °C, suggesting a temperature-dependence of the changes. Both cultivars of yam showed increase in hardness with storage time. A high correlation (r=0.9503–0.9913) was noted between the texture and the chemical indices of the white cultivars. Storage of the trifoliate yam, Dioscorea dumetorum, immediately after harvest, leads to reduction in moisture and starch contents and increase in sugars and structural polysaccharides. Low temperature storage may reduce the hardening phenomenon. A mechanism for the hardening phenomenon has been proposed.     

Modified-atmosphere packaging of minimally processed “Lollo Rosso” (Lactuca sativa) Phenolic metabolites and quality changes

 The effect of modified-atmosphere packaging (MAP) on the amount of soluble phenolics in, and the visual appearance of, white, green and red tissues of minimally processed “Lollo Rosso” lettuce were evaluated. Minimal processing induced a two-fold increase in the amount of soluble phenylpropanoids in the midribs during storage in air at 5°C. When the lettuce was stored in the presence of 2–3% O₂ and 12–14% CO₂, this increase was not induced and no browning was observed. A particularly marked decrease in the amount of phenylpropanoids was observed in MAP-stored green and red tissues. The concentrations of flavonoids and anthocyanins did not change much in midribs and green tissues, while they were significantly degraded in red tissues under MAP conditions. MAP storage proved useful in the prevention of browning, the main cause of quality loss in minimally processed “Lollo Rosso” lettuce. However, MAP storage was not so beneficial for the preservation of the quality of red tissues and, in fact, their overall visual quality, texture, aroma and macroscopic breakdown under MAP conditions were worse than those of air-stored tissues. Received: 5 November 1997     

Modified-atmosphere packaging of minimally processed “Lollo Rosso” (Lactuca sativa) Phenolic metabolites and quality changes

 The effect of modified-atmosphere packaging (MAP) on the amount of soluble phenolics in, and the visual appearance of, white, green and red tissues of minimally processed “Lollo Rosso” lettuce were evaluated. Minimal processing induced a two-fold increase in the amount of soluble phenylpropanoids in the midribs during storage in air at 5°C. When the lettuce was stored in the presence of 2–3% O₂ and 12–14% CO₂, this increase was not induced and no browning was observed. A particularly marked decrease in the amount of phenylpropanoids was observed in MAP-stored green and red tissues. The concentrations of flavonoids and anthocyanins did not change much in midribs and green tissues, while they were significantly degraded in red tissues under MAP conditions. MAP storage proved useful in the prevention of browning, the main cause of quality loss in minimally processed “Lollo Rosso” lettuce. However, MAP storage was not so beneficial for the preservation of the quality of red tissues and, in fact, their overall visual quality, texture, aroma and macroscopic breakdown under MAP conditions were worse than those of air-stored tissues. Received: 5 November 1997     

Spermine and spermidine concentrations in pork loin as affected by storage, curing and thermal processing

Spermine and spermidine concentrations in pork loin as affected by three factors used in food processing [immersion-curing (10% brine: NaNO₂ and NaCl content of 0.6 and 99.4 g/l, respectively, and 20% brine: NaNO₂ and NaCl content of 0.6 and 199.4 g/l, respectively), boiling and grilling (70 °C core temperature) and storage of raw loin chops (“non-stored” versus storage at 4 °C for 5 days)] were studied. Spermidine and spermine concentrations of the “non-stored” raw loin chops were 2.7±0.7 and 19.8±1.5 mg/kg (fresh weight), respectively. Storage effects were negligible. Curing in 20% brine resulted in statistically significant spermidine decreases as compared to non-cured meat (p=0.04). Statistically significant decreases of spermine were observed for curing in 20% brine as compared with 10% brine (p=0.08), and boiling of meat in an equal amount of water compared to raw meat and grilled meat (p=0.03). Combined curing in 20% brine and cooking in an equal amount of water resulted in 2.0±1.0 mg/kg spermidine and 14.4±2.6 mg/kg spermine. Combined common food processing techniques resulted in a decrease of spermine and spermidine concentrations in pork loin of maximum 26% only. The latter should be considered as relevant for consumers for which the dietary polyamine uptake is critical.     

Quantitative evaluation of resveratrol enrichment induced by UV stimulus in harvested grapes

A mathematical model was proposed to quantitatively describe resveratrol induction in harvested grapes. In the model, k₁ and k₂ were defined, which were the reaction rate constants for induction during direct UV irradiation and for the time-delayed induction after removing UV irradiation, respectively. During storage after UV irradiation, k₂ decreased with time, whereas k₁ remained constant. The portion induced by the direct irradiation effect was much more than that induced by the time-delayed effect. When UV energy of 610.2 mJ/cm² was applied to ‘Gerbong’ grapes with an initial resveratrol content of 1.15 μg/g, their contents were 8.99 and 9.20 μg/g at day 1 and 6 during storage at 0°C, respectively. In the same situation, resveratrol content of 8.99 μg/g improved to 10.56 μg/g during storage at 20°C. This approach which enriched a health-functional compound through the modulation of metabolism after harvest might be a valueadding method for fresh food industry.     

Higher acrylamide contents in French fries prepared from “fresh” prefabricates

A recent campaign indicated that French fries prepared from fresh prefabricates stored at about 4 °C had a double acrylamide content compared to those from frozen products. During storage at 4 °C, reducing sugars were liberated which enhance acrylamide formation. Even with boiling water, blanching did not completely inactivate the alpha amylase. Pre-frying was more effective, but conditions of 170 °C/60 s, as often applied, were still only at the borderline of suppressing liberation of reducing sugar. It is concluded that processing conditions of fresh prefabricates for potato products like French fries and roasted or baked products should be revisited to prevent liberation of reducing sugar during storage and enhanced acrylamide formation.     

Acrylamide in Foods: Chemistry and Analysis. A Review

Acrylamide is a potential cause of a wide spectrum of toxic effects and is classified as probably “carcinogenic in humans”. The discovery of acrylamide in human foods has given rise to extensive studies exploring its formation mechanisms and levels of exposure and has spurred search into suitable analytical procedures for its determination in foodstuffs. However, the exact chemical mechanisms governing acrylamide formation are not yet known and cheap, convenient, and rapid screening methods are still to be developed. Acrylamide in food is produced by heat-induced reactions between the amino group of asparagine and the carbonyl group of reducing sugars along with thermal treatment of early Maillard reaction products (N-glycosides). Similarly, the decarboxylated Schiff base and decarboxylated Amadori compounds of asparagine as well as the Strecker aldehyde have been proposed as direct precursors and intermediates of acrylamide. Corresponding chromatographic methods are used to determine various structural groups present in Maillard reaction model systems. Gas chromatography-mass spectrometry and liquid chromatography with tandem mass spectrometry analysis are both acknowledged as the main, useful, and authoritative methods for acrylamide determination. This review is an attempt to summarize the state-of-the-art knowledge of acrylamide chemistry, formation mechanisms, and analytical methods. Special attention is given to comparison of different chromatographic techniques, particularly the novel, simple, and low-cost methods of its determination.     

Analytical characterization and the impact of ageing on anthocyanin composition and degradation in juices from five sour cherry cultivars

Five different sour cherry cultivars were processed to sour cherry juices in order to analyze their composition and the impact of storage on anthocyanin composition. Regarding primary juice parameters all cultivars showed high dry masses (13.8–17.2° Brix) and sugar free extracts (59.4–74.3 g/L). Anthocyanins were identified as cyanidin-3-(2^G-glucosylrutinoside), cyanidin-3-(2^G-xylosylrutinoside), cyanidin-3-sophoroside, cyanidin-3-glucoside, cyanidin-3-rutinoside, and peonidin-3-rutinoside. Besides the original anthocyanins, 5-carboxypyrano-anthocyanins occurred as new reaction products during storage. HPLC-MSⁿ experiments revealed, that a further ageing pigment was probably resulting from the reaction of an original anthocyanin with acetaldehyde. A significant decline of the original anthocyanin concentrations could be observed (70–75%) during 6 months of storage at 20 °C. Degradation kinetics of anthocyanins were calculated taking the reaction rate as first order. Colourless polyphenol concentrations and antioxidant capacities (TEAC) of the juices were not affected during storage.     

Browning susceptibility of minimally processed Baby and Romaine lettuces

 This study was conducted to determine the effects of cultivar, tissue susceptibility and storage temperature on the keeping quality of minimally processed Baby and Romaine lettuces. Midrib and photosynthetic tissues were lightly processed and stored for up to 7 days at 5  °C and 13  °C. Changes in L ^* and a ^* values and absorbance at 430 nm were compared. The relationship between polyphenols, phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) activities and browning was examined. Measurements of L ^* and a ^* values on midribs showed that browning discoloration was the same for Baby as for Romaine lettuces and there was no relationship for temperature. In addition, L ^* and a ^* values in photosynthetic tissue indicated a decrease in green pigmentation during storage, especially at 13  °C. For both kinds of tissue at the end of cold storage an increase in soluble brown polymers was detected. In midribs, total phenolics increased significantly throughout the storage period because of the tissue-wounding response. The photosynthetic tissue had a higher phenolic content than the midrib one. For both kinds of tissue an increase in PPO activity occurred throughout cold storage. On the other hand, PAL activity in midrib tissue only increased initially, followed by a slow decline to reach normal levels. Browning potential estimated by L ^* values correlated significantly (P>95%) with PPO activity and with absorbance at 430 nm for Romaine lettuce. Based on colour and browning potential no differences between Romaine and Baby lettuce cultivars were observed. However, photosynthetic tissue was the most suitable tissue for the preparation of minimally processed salad mixes because of its high phenolic content. Received: 28 September 1998     

Extending the Shelf Life of Fresh Sweet Corn by Shrink-Wrapping, Refrigeration, and Irradiation

Chemical, physical, sensory, and microbiological changes were monitored during storage of unwrapped and shrink-wrapped fresh sweet corn at 10° and 20°C. Wrapping essentially eliminated moisture loss and resulted in elevated carbon dioxide and decreased oxygen concentrations within packages. These effects, together with refrigeration markedly reduced the changes associated with senscence and post harvest deterioration, and hence resulted in at least a threefold extension in shelf life. The water-saturated atmosphere, however, enhanced microbial growth on shrink-wrapped corn. The initial microbial population was effectively decreased by treating the wrapped corn with 0.5 or 1.0 kGy (Co⁶⁰) irradiation.