The Effect of Antibrowning Agents on Inhibition of Potato Browning,Volatile Organic Compound Profile,and Microbial Inhibition

Abstract: Burbank and Norkotah potato slices were dipped into 3% sodium acid sulfate (SAS), citric acid (CA), sodium erythorbate (SE), malic acid (MA), sodium acid pyrophosphate (SAPP), or a combination of SAS‐CA‐SE. Browning by polyphenol oxidase (PPO) obtained from potato extract with 0.04 to 0.016 g/mL of antibrowning solutions at pH 2.0 to 6.9 were measured by UV‐Vis spectroscopy. The color of slices dipped in antibrowning solutions at pHs 2 to 7 and stored at 4 °C for 15 d was measured every 5 d by colorimeter. Headspace analysis of volatiles in raw and cooked potato samples was performed by selected ion flow tube mass spectrometer (SIFT‐MS) and soft independent modelling by class analogy (SIMCA) analysis of the calculated odor activity values (OAV) determined interclass distances. Microbial growth was measured at 15 d. At unadjusted pHs (1.1 to 7.1), the PPO browning of the control and samples with SAPP was not significantly different, SAS, CA, and MA produced some inhibition and SE and SAS‐CA‐SE prevented browning. At pH 5 to 7, only SE and SAS‐CA‐SE were effective browning inhibitors. Based on the color of potato slices, SE was the most effective at pH 2 to 7, but SAS was most effective at unadjusted pH. Cooking increased volatile levels in the treated potatoes and decreased differences between volatile profiles. Differences between cooked samples may not be noticeable by the consumer because volatiles with high discriminating powers have low OAVs. SAS, CA, and SAS‐CA‐SE treatments inhibited microbial growth but SAPP, control, and SE did not, most likely due to pH. Practical Application: Antibrowning agents inhibit polyphenol oxidase, increasing shelf life and consumer acceptability of processed raw potato products by preserving the color. Their effectiveness was shown to be mainly due to a pH effect, except SE, which was not pH dependent. MA, CA, and SAS‐CA‐SE are better acidulants for inhibition of color change as well as growth of spoilage bacteria, yeast, and mold than SAPP, the industry standard.     

Comparison of sodium acid sulfate to citric acid to inhibit browning of fresh-cut potatoes

Abstract: Sodium acid sulfate (SAS) dip treatments were evaluated against a distilled water control and citric acid (CA) to compare its effectiveness in reducing enzymatic browning of raw, French‐fry cut potatoes. Two separate studies were conducted with dip concentrations ranging from 0%, 1%, and 3% in experiment 1 to 0%, 2%, and 2.5% in experiment 2 to determine optimal dip concentrations. Russet Burbank potatoes were peeled, sliced, and dipped for 1 min and stored at 3 °C. Color, texture, fry surface pH, and microbiological analyses were conducted on days 0, 7, and 14. The 3% SAS‐ and CA‐treated samples had significantly (p < 0.0001) lower pH levels on fry surfaces than all other treatments. Both acidulants had significantly (p ≤ 0.05) lower aerobic plate counts compared to controls in both studies by day 7. However, SAS appeared to be the most effective at the 3% level in maintaining a light fry color up to day 14 and had the highest L‐values than all other treatments. The 3% SAS‐treated fry slices appeared to have the least change in textural properties over storage time, having a significantly (p = 0.0002) higher force value (kg force [kgf]) than the other treatments during experiment 1, without any signs of case‐hardening that appeared in the control and CA‐treated samples. SAS was just as comparable to CA in reducing surface fry pH and also lowering microbial counts over storage time. According to the results, SAS may be another viable acidulant to be utilized in the fresh‐cut fruit and vegetable industry.     

The effectiveness of ozone and acidulant treatments in extending the refrigerated shelf life of fresh-cut potatoes

Abstract: The objective of the study was to determine the effectiveness of acidulant dip treatments (with or without aqueous ozone) to reduce enzymatic browning and to extend the shelf life of fresh‐cut potato slices during refrigerated storage (4 °C) for 28 d. Potato slices subjected to aqueous ozone (2 ppm) had significantly (P≤ 0.05) higher L‐values and lower a‐values, but ozone did not appear to have any effect on aerobic plate counts (APCs) or polyphenol oxidase (PPO) activity. NatureSeal (NS) and sodium acid sulfate (SAS) were the most effective acidulant treatments in reducing browning (significantly [P≤ 0.05] higher L‐values, lower a‐values, and browning index values) regardless of ozone treatment. NS and SAS also had lower PPO activity compared to other treatments on days 0 and 28, and significantly (P≤ 0.05) lower APCs (≤2.00 log CFU/g) over refrigerated storage. Therefore, the SAS treatment was comparable to NS, a commercially available product, and showed promise as an effective antibrowning dip to reduce browning and spoilage in fresh‐cut potato products. Practical Application: A 1% SAS dip treatment which included 1% citric and 1% ascorbic acid was found to be an effective antibrowning dip for fresh‐cut potatoes along with NatureSeal®'s PS‐10, compared to other treatments. They were both effective in maintaining low microbial counts over refrigerated storage. Additionally, aqueous ozone washes (2 ppm) showed significant benefits to reduce browning; however, ozone did not affect microbial counts or PPO enzyme activity. Therefore, the SAS treatment could have potential use in the fruit and vegetable industry to reduce browning and spoilage in fresh‐cut potato products.     

Exogenous methyl jasmonate diminishes the formation of lipid‐derived compounds in boiled potato (Solanum tuberosum L.)

BACKGROUND: During potato storage the tubers tend to develop off‐flavours, mainly due to lipid‐derived aldehydes, whose formation is increased after boiling or processing. This may become a problem when boiled or precooked potatoes are used. Methyl jasmonate (MJ) is a phytohormone capable of modifying plant and food composition. The aim of this work was to control the formation of off‐flavours in different cultivars of raw potato during storage by MJ treatment. RESULTS: The use of Carbowax 20M as support in MJ emulsion resulted in significantly (P < 0.05) lower levels of lipid‐derived compounds than the use of lanolin. Levels of the lipid‐derived aldehydes propanal, hep‐2‐enal, nonanal, oct‐2‐enal and hexanal, although dependent on variety, generally decreased significantly (P < 0.05) after treatment with MJ/Carbowax 20M emulsion. Sugar‐derived compounds such as pyridine and furfural, however, were not affected by this treatment. CONCLUSION: Treatment with MJ/Carbowax 20M can be used to diminish the formation of off‐flavours in boiled potato. However, this treatment is not useful to avoid the sweetening caused by sugar‐derived products. Additional advantages of exogenous MJ are a delay in the appearance of sprouting and aging and hence prolongation of the storage life of potato tubers. Copyright © 2010 Society of Chemical Industry     

Radiation preservation of foods of plant origin. Part 1. Potatoes and other tuber crops

In Part 1 of a planned series of articles on preservation of foods of plant origin by gamma irradiation, the current state of research on the technological, nutritional, and biochemical aspects of sprout inhibition of potatoes and other tuber crops are reviewed. These include varietal responses, dose effects, time of irradiation, pre‐ and postirradiation storage, and handling requirements; postirradiation changes in carbohydrates, ascorbic acid, amino acids, and other nutrients; respiration; biochemical mechanisms involved in sprout inhibition; wound healing and microbial infection during storage; formation of wound and light‐induced glycoalkaloids and identification of irradiated potatoes. The culinary and processing qualities with particular reference to darkening of boiled and processed potatoes are discussed. The prospects of irradiation on an industrial scale as an alternative to chemical sprout inhibitors or mechanical refrigeration are considered.     

PHYSICAL-CHEMICAL AND SENSORY QUALITY EVALUATION OF POTATO VARIETIES (SOLANUM TUBEROSUM L.)

Seven table potato varieties were studied for pH, soluble solids content, moisture, firmness, color, external appearance of raw tubers and flavor and texture of the fried and boiled product. Monalisa was the most appreciated variety regarding external appearance, Bartina was preferred for the flavor of the fried product while Victoria and Desiree were the best for flavor and texture of boiled potatoes. The different scores by variety depending on frying or boiling suggest a specific use for each variety. Soluble solids content, pH, and moisture determinations showed minimal differences between varieties. Firmness was highest in the two varieties with the least moisture (Desiree and Victoria) and lowest in varieties with a high degree of moisture (Bartina and Caesar); fresh potato firmness had a positive correlation with these sensorial parameters when the product was boiled. All colorimetric parameters were useful to discriminate red skin from yellow‐white skin varieties.     

In vitro availability of starch in heat‐treated potatoes as related to genotype,weight and storage time

The objective of the study was to determine the influence of potato variety, weight and storage time after lifting on the glycaemic index (GI) and resistant starch (RS) content predicted from measurement of the rate and extent of in vitro starch hydrolysis, respectively. The potatoes were either boiled, or boiled and subjected to different heat‐cycling conditions selected to promote retrogradation of amylose or amylopectin, respectively. The hydrolysis indices (HI) and predicted GIs of all 19 potato products were high and fell within narrow ranges of 122–144 and 118–138, respectively. No correlation between average weight of the potato tuber and HI was found. Furthermore, there was no difference in HI between potatoes stored for 1–3 or 8–10 months, nor between varieties of new potato and winter potato. However, the HI was significantly lowered by temperature cycling at conditions known to promote retrogradation of amylopectin (6 °C, 48 h) compared with 6 °C for 24 h followed by 70 °C for 24 h. RS content was already substantial in boiled potatoes, 4.5 g 100 g^?1 (starch basis), and could be increased further by temperature cycling, the highest yield obtained, 9.8 g 100 g^?1 (starch basis), following heat treatment at 6 °C for 24 h followed by 70 °C for 24 h; that is at conditions known to favour amylose retrogradation. Copyright © 2004 Society of Chemical Industry     

FLAVOR QUALITY IN EXPLOSION PUFFED DEHYDRATED POTATO. 2. Flavor Contribution of 2-Methylpropanal, 2-Methylbutanal and 3-Methylbutanal

SUMMARY– Headspace vapor components previously associated with the intensity of an off-flavor in explosion puffed dehydrated potatoes were added to potatoes lacking the off-flavor to determine the flavor contribution of these compounds. 2-Methylpropanal produced a characteristic wet fur flavor note while 2- and 3-methylbutanal modified this flavor and contributed burnt flavor notes. While these flavor notes resembled some elements of the puffing off-flavor, the total off-flavor at its normal intensity could not be simulated by combinations of these compounds in potato at realistic concentrations. Acetone, which is also present in the headspace vapor of explosion puffed dehydrated potatoes, was found as a major headspace component of fresh boiled potatoes. This compound and smaller amounts of 2- and 3-methylbutanal were produced in overcooked fresh potatoes which lacked the puffing off-flavor.     

Heated Ascorbic/Citric Acid Solution as Browning Inhibitor for Pre-Peeled Potatoes

Treatment of pre-peeled potatoes with heated ascorbic acid (AA)/citric acid (CA) solution to extend shelf-life was investigated. Potatoes were abrasion or high pressure steam peeled, heated for 5–20 min in 1% AA + 2% CA at 45–55°C cooled, and then dipped for 5 min in browning inhibitor (BI) solution containing 4% AA +1% CA +1% sodium acid pyrophosphate. Combined treatment inhibited potato discoloration for 14 days at 4°C compared to 3–6 days with BI treatment alone. Raw material and treatment conditions were selected to minimize graying and textural abnormalities encountered with some treatments. Treatment with heated AA/CA may be an alternative to use of sulfites to control browning in pre-peeled potatoes.     

EFFECTS OF COOKING METHODS ON SENSORY QUALITIES AND CAROTENOID RETENTION IN SELECTED VEGETABLES1

The effects of induction boiling, conventional boiling and microwave steaming on the sensory qualities and carotenoid retention of broccoli, carrots, green beans and sweet potatoes were investigated. Significantly higher cooking yields were obtained for vegetables that were induction and conventionally boiled. No differences in the retentions of alpha‐carotene (α‐carotene), beta‐carotene (β‐carotene) and lutein/zeaxanthin were observed for vegetables by the cooking method, with the exception of β‐carotene retention in broccoli and sweet potatoes where retentions were higher for those that were induction boiled (90.3 and 86.1%, respectively) than those that were microwave steamed (62.2 and 66.4%, respectively). A trained panel judged the color scores of three vegetables by the cooking method as similar. The mean flavor scores (1 = extremely bland; 9 = extremely intense) for three vegetables that were conventional (4.7–5.4) and induction (5.3–5.5) boiled were lower than those that were microwave steamed (5.9–7.0). The mean texture scores (1 = extremely mushy/tender; 9 = extremely firm/tough) for all induction‐boiled (5.0–6.0) vegetables were higher than those that were conventionally boiled (3.4–5.2) and lower than those that were microwave steamed (5.1–6.6).     

c4-Heptenal: An Influential Volatile Compound in Boiled Potato Flavor

Analysis of headspace volatile concentrates from freshly boiled Russet Burbank potatoes revealed a variety of lipid oxidation products including t2,c6-nonadienal which is further degraded to c4-heptenal through a water-mediated retro-aldol condensation reaction. Dilute aqueous solutions of c4-heptenal exhibited boiled potato-like aromas, and at relatively high concentrations (greater than 0.7 ppb) added c4-heptenal contributed distinct staling-type flavor defects to both fresh, mashed potatoes and reconstituted dehydrated potatoes. When added at levels between 0.1–0.4 ppb, c4-heptenal enhanced overall earthy, potato-like flavors in freshly boiled mashed potatoes, but these levels caused stale flavors in reconstituted dehydrated potatoes.     

Losses of pectic substances during cooking and the effect of water hardness

Differences in the extent of loss of pectic substances from potato (Solanum tuberosum L.) after boiling, steaming and pressure cooking were investigated. Losses were found to be significantly greater (P< 0.001) after boiling than after pressure cooking or steaming. The pectic substance content (g 100 g^?1 dry matter) of potatoes (cv. Pentland Crown) was 2.98 for raw peeled tubers, 0.97 after boiling for 35 min, 1.22 after steaming for 35 min and 1.24 after pressure cooking at 103.4 kPa (15 psi) for 15 min. The roles of cooking time, cooking temperature and heat transfer medium are discussed. The effects of calcium sulphate (at levels typical of ‘hard’ and ‘soft’ water supplies) in the cooking water on losses of pectic substances from potato (Solanum tuberosum L.), carrot (Daucus carota L.), and swede (Brassica napus L. var. napobrassica Peterm.) after boiling and pressure cooking were also investigated. Water hardness did not influence losses during pressure cooking but samples boiled in hard water had decreased losses of pectic substances compared to those boiled in soft water. The increase in retention of pectic substances due to hard water was about 8 % for potatoes (cv. Pentland Dell), about 33 % for sliced carrots (cv. Berlicum, approved maintenance Perfecta) and about 23% for diced swedes (cv. Acme). The interaction of water hardness with cooking method was significant for potato (P< 0.05) and swede (P<0.001) and approaching significance (P=0.055) for carrot.     

Digital imaging for evaluation of potato after-cooking darkening and its comparison with other methods

After‐cooking darkening (ACD) phenomenon occurs when potato tubers develop greyish dark colour after boiling, frying, or steaming. The pigment responsible for ACD is a complex of chlorogenic acid and iron, which is formed during cooking and oxidised during cooling. The evaluation of ACD is thus based either on the amount of chlorogenic acid in raw tubers or the greyish colour intensity on cooked tuber surfaces. This study introduced a new method, the digital imaging method, for evaluation of potato ACD. The comparison of this new method with visual evaluation and the measurement of chlorogenic acid using HPLC were also presented. The digital imaging method is based on the direct measurement of the degree of dark colour on cut tuber surfaces, expressed by pixel levels. The new method is faster, more reliable and simpler when compared with any methods presently used. It is particularly applicable to handling large sample numbers.     

EFFECTS OF BLANCHING METHOD ON THE QUALITY CHARACTERISTICS OF FROZEN PEAS

This study evaluated the effects of microwave blanching prior to freezing as an alternative pretreatment for frozen peas. Peas were blanched (steam‐, boiling water immersion‐, microwave‐ or microwave‐blanched in a bag), frozen and evaluated after 0, 6 and 12 weeks for moisture and ascorbic acid content, peroxidase activity, visual appearance and instrumental color, and after 6 and 12 weeks for aroma, flavor and texture. All blanch treatments reduced peroxidase activity by 97% compared with controls (unblanched); blanching methods did not differ. Steam blanching resulted in significantly better ascorbic acid retention than all other treatments; microwave blanch treatments were either equivalent to or better than boiling water immersion. Both microwave treatments darkened (L* value) peas. Microwave‐blanched peas were visually greener than other treatments, but their appearance was less intact. Aroma and flavor were similar among blanch treatments. Texture of boiling water immersed peas was similar to the two microwave treatments.     

MODELING THE SENSORY QUALITIES OF PROCESSED APPLES AFTER CONTROLLED ATMOSPHERE STORAGE AND FROZEN STORAGE1

Durational effects of controlled atmosphere storage (CA) and frozen storage on apple quality were studied for commercially processed pies made from Northern Spy, Idared and Nova Spy apples. Sensory tests on apple pie quality indicated that the duration of apples in CA significantly affected the quality of the processed apple. Extending the CA duration of the apples to 45 weeks resulted in a pie filling with reduced apple flavor, tartness and astringency, and with increased sweetness and off‐flavor. To minimize flavor/taste changes throughout the processing season, close attention must be given to the product's sugar/acid formulation: by week 27 for Idared apples and by week 33 for Northern Spy and Novaspy apples. The texture and appearance of processed Novaspy and Idared fruits were affected earlier in CA than Northern Spy apples. The frozen product was relatively stable for all three varieties, especially for apples processed early in the storage season (15–27 weeks). A strategy that utilizes short‐ to medium‐term CA with longer‐term frozen storage would optimize quality across the season.     

A DAIRY-BASED ESPRESSO BEVERAGE MANUFACTURED USING THREE DIFFERENT COFFEE BEAN ROASTS

The objective of this study was to evaluate the effects of coffee bean roast on the acceptability of a dairy‐based espresso drink. Espresso coffee was made from freshly ground coffee beans with light‐medium roast, between roast (between medium and dark) and dark French roast in order to show the influence of roasting on flavor. Samples were prepared by blending skim milk, soft‐serve ice cream mix, ice and fresh espresso extracts. No significant differences (P < 0.05) were detected in total solids and fat content among treatments. Viscosity for the light‐medium roasted beverage was significantly (P < 0.05) higher than the others. The beverage pH increased with increased darkening of roast. The beverage made with the light‐medium roasted coffee had significantly (P < 0.05) higher preference scores for coffee flavor and overall flavor than beverages made with the between and French roasts. The between and French roasted treatments were shown to have a more intense coffee flavor by trained sensory panelists. Consumers in this study preferred a less intense coffee flavor.     

FLAVOR ENHANCEMENT OF POTATO PRODUCTS

SUMMARY— The effect of selected compounds on flavor of various potato products was studied by sensory panels. The minimum detectable amount of each of six compounds in four brands of dehydrated mashed potatoes was determined. The difference thresholds of the six compounds in the reconstituted potato products varied from 0.05–3.1 ppm. Only 2-methoxy-3-ethylpyrcxine (0.1–0.2 ppm) was effective in increasing the flavor level of all four brands of dehydrated potatoes; it also proved to be effective in increasing the potato flavor level of potato salad, dehydrated scalloped potatoes and potato soup. Potato salad stored at 3°C for 1 wk required at least 0.2 ppm of this compound to maintain its initial flavor difference from the control sample.     

The effect of either raw or boiled liquid extract from potato (Solanum tuberosum) on the digestibility of a diet based on barley in pigs

The nitrogen (N) of raw potato is poorly digested by the pig and the hypothesis tested in the experiment was that this is due to an anti-nutritive substance present in the tuber and not simply due to the physical inaccessibility of much of the potato protein to enzyme attack or to the protein of the potato being refractory to gut enzymes. Four growing pigs, each fitted with an ileal cannula were fed on a basal diet of barley plus minerals and vitamins to which was added minced raw potato (RP) or a liquid extract of potatoes which was either freeze-dried (LE) or boiled and concentrated (BE). These materials each contributed 12 g N day^?1 for each pig. Each pig was given 2.1 kg organic matter (OM) day^?1. In diet RP 25.5% of this was from potato compared with 7.2 and 7.8% in diets LE and BE, respectively. The digestibility of N determined at the terminal ileum was reduced with RP by 9.5% (NS) and with LE by 23% (P<0.01) while BE increased it by 24.7% (P<0.01) compared with the coefficient of digestibility for the N of the barley diet. The digestibility of OM was significantly (P<0.001) reduced by 9.5% with RP but with LE and BE it was similar to the control value. Over the whole gut, coefficients for N changed by ?19.8% (P<0.001), ?4.7% (NS) and +9.0% (P<0.05) when RP, LE or BE, respectively were included in the basal diet. Corresponding changes in OM were +2.4% (NS), +1.9% (NS) and +3.6% (P<0.05). It is suggested that the anti-nutritive factor in potatoes should be denatured by appropriate treatment to improve the digestibility of dietary protein.     

The Quality Changes of Postharvest Mulberry Fruit Treated by Chitosan‐g‐Caffeic Acid during Cold Storage

This study aimed to characterize the effects of chitosan‐g‐caffeic acid (CTS‐g‐CA) on improving the quality and extending the shelf life of postharvest mulberry fruit during storage at 4 °C for 18 d. CTS‐g‐CA was enzymatically synthesized using laccase from Pleurotus ostreatus as a catalyst. The synergistic effects of CTS‐g‐CA treatment on mulberry fruit were evaluated using a co‐toxicity factor (cf). The results showed that the rotting rate of CTS‐g‐CA‐treated fruit was 37.67% (compared with that of the control at 97.67%) on day 18. The weight loss and malondialdehyde (MDA) contents of the CTS‐g‐CA‐treated mulberry fruit were significantly lower (P < 0.05) than those of the control, CA, CTS, and CA+CTS treatments. Moreover, the DPPH and ABTS radical scavenging activities of the CTS‐g‐CA treatment were both higher than those of the control. Furthermore, the CTS‐g‐CA treatment also maintained higher levels of main active substances, such as anthocyanins, ascorbic acid, polyphenols and flavones, in mulberry fruit than the other treatments. Therefore, CTS‐g‐CA could be used to improve the quality and extend the shelf life of postharvest mulberry fruit during cold storage.     

How much reducing sugar may potatoes contain to avoid excessive acrylamide formation during roasting and baking?

For many consumers, potatoes fried or roasted in professional or private kitchens are the most important source of exposure to acrylamide. Acrylamide formation can be reduced by appropriate preparation techniques, but suitable potatoes are a prerequisite. The tendency of potato to form acrylamide can be approximated by the content of reducing sugar. Roast potatoes (hash browns, Rösti) and oven-fried potatoes (Bratkartoffeln) were prepared to optimum culinary quality regarding crispiness and then evaluated in terms of browning, roasting flavor and acrylamide content. Preparation procedures were optimized to produce a minimum of acrylamide. It is concluded that potatoes with less than 0.2 g/kg fresh weight fructose and glucose are not suitable for roasting (insufficient browning and flavor), while roasted products of minimum crispiness prepared from potatoes with more than 1 g/kg reducing sugar contain more than 500 µg/kg acrylamide. It is proposed that potatoes which may be used for roasting and frying should contain less than 1 g/kg fresh weight of reducing sugar. This can easily be fulfilled with the most important potato cultivars grown in Switzerland, but presupposes that potatoes are no longer stored at 4 °C.