REDUCTION OF ACRYLAMIDE FORMATION

Abstract

The invention relates to methods of reducing acrylamide during high temperature cooking of carbohydrate-containing foods, in particular vegetables or tubers which are deep fried. In particular, the invention relates to a method of reducing acrylamide during cooking of a carbohydrate-containing food, said method comprising at least the following steps: contacting said food with a first hydroxy acid selected from lactic, malic and tartaric acids at a pH less than or equal to its pK.sub.a, or its lowest pK.sub.a; part-cooking said food at a temperature at which the Maillard reaction occurs whereby to form a part-cooked food;optionally packaging and/or storing said part-cooked food; contacting said part-cooked food with a second α-hydroxy acid selected from lactic, malic and tartaric acids at a pH less than or equal to its pK.sub.a, or its lowest pK.sub.a; and subsequently further cooking said food at a temperature at which the Maillard reaction occurs.

Claims

1. A method of reducing acrylamide during cooking of a carbohydrate-containing food, said method comprising at least the following steps: contacting said food with a first α-hydroxy acid selected from lactic, malic and tartaric acids at a pH less than or equal to its pK.sub.a, or its lowest pK.sub.a; part-cooking said food at a first temperature at which the Maillard reaction occurs whereby to form a part-cooked food; optionally packaging and/or storing said part-cooked food; contacting said part-cooked food with a second α-hydroxy acid selected from lactic, malic and tartaric acids at a pH less than or equal to its pK.sub.a, or its lowest pK.sub.a; and subsequently further cooking said part-cooked food at a second temperature at which the Maillard reaction occurs.

2. A method as claimed in claim 1, wherein the first temperature and/or the second temperature are above about 120° C.

3. A method as claimed in claim 1 or claim 2, wherein the step of part-cooking said food comprises par-frying.

4. A method as claimed in claim 3, wherein par-frying is carried out at a temperature in the range of from 170 to 190° C., e.g. for a period of from 1 to 5 minutes.

5. A method as claimed in any one of claims 1 to 4, wherein the step of further cooking said part-cooked food comprises finish frying.

6. A method as claimed in claim 5, wherein finish frying is carried out at a temperature in the range of from 170 to 240° C., e.g. for a period of from 1 to 10 minutes.

7. A method as claimed in any one of the preceding claims, wherein the first and second α-hydroxy acids are identical.

8. A method as claimed in any one of the preceding claims, wherein the first and/or second α-hydroxy acid is lactic acid, preferably wherein the first and second α-hydroxy acids are both lactic acid.

9. A method as claimed in any one of the preceding claims wherein the first and/or the second α-hydroxy acid is provided by a microorganism, e.g. a lactic acid producing microorganism.

10. A method as claimed in any one of the preceding claims, wherein the first and/or the second α-hydroxy acid is used at a pH which is less than its pK.sub.a or, where appropriate, less than its lowest pK.sub.a.

11. A method as claimed in any one of the preceding claims, wherein the first and/or the second α-hydroxy acid is used at a pH which is from 0.1 to 3.0 units, for example from 0.5 to 2.0 units, or from 1.0 to 2.0 units lower than its pK.sub.a or, where appropriate, its lowest pK.sub.a.

12. A method as claimed in any one of claims 1 to 10, wherein the first and/or the second α-hydroxy acid is used at a pH which is in the range from x-0.5 to x-3.0, or in the range from x-0.5 to x-2.0, e.g. in the range from x-1.0 to x-1.5, wherein x is the pK.sub.a (or lowest pK.sub.a) of the α-hydroxy acid.

13. A method as claimed in any one of the preceding claims, wherein the first and/or the second α-hydroxy acid is used at a concentration in the range of from 1 to 500 mM, e.g. from 10 to 400 mM, from 20 to 350 mM, or from 30 to 300 mM.

14. A method as claimed in any one of claims 1 to 12, wherein the first and/or the second α-hydroxy acid is used at a concentration of at least 60 mM, more preferably at least 65 mM, e.g. at least 70 mM.

15. A method as claimed in any one of claims 1 to 12, wherein said food is a potato or a potato product, or a sweet potato and the first and/or the second α-hydroxy acid is used at a concentration in the range from about 70 to about 300 mM, preferably from 80 to 200 mM, more preferably from 90 to 150 mM, e.g. about 100 mM.

16. A method as claimed in any one of claims 1 to 12, wherein the first and/or the second α-hydroxy acid is used at a concentration which is selected based on the free amino acid content of the food, e.g. in a molar ratio (α-hydroxy acid : free amino acid) of from 1:1 to 10:1, preferably from 1:1 to 5:1, more preferably from 1:1 to 3:1, e.g. about 2:1.

17. A method as claimed in any one of the preceding claims, wherein contact of said food with the first α-hydroxy acid and/or contact of said part-cooked food with the second α-hydroxy acid is carried out a temperature in the range from 0 to 100° C., preferably from 20 to 95° C., e.g. from 30 to 80° C.

18. A method as claimed in any one of the preceding claims, wherein contact of said food with the first α-hydroxy acid and/or contact of said part-cooked food with the second α-hydroxy acid is carried out for a period of up to 10 minutes, e.g. up to 5 minutes, preferably from 1 second to 1 minute, more preferably from 20 to 45 seconds, e.g. about 30 seconds.

19. A method as claimed in any one of the preceding claims, wherein contact of said part-cooked food with the second α-hydroxy acid is carried out for a period of up to 2 minutes, preferably up to 1 minute, more preferably up to 30 seconds, yet more preferably up to 2 seconds, e.g. for 1 second.

20. A method as claimed in any one of the preceding claims, wherein contact of said food with the first α-hydroxy acid and/or contact of said part-cooked food with the second α-hydroxy acid is followed by a drying step.

21. A method as claimed in any one of the preceding claims, wherein the step of contacting said food with the first α-hydroxy acid comprises contacting said food with two or more α-hydroxy acids selected from the group consisting of lactic, malic and tartaric acids at a pH which is less than or equal to the pK.sub.a, or lowest pK.sub.a, of the α-hydroxy acid having the lowest pK.sub.a.

22. A method as claimed in any one of the preceding claims, wherein the step of contacting said part-cooked food with the second α-hydroxy acid comprises contacting said part-cooked food with two or more α-hydroxy acids selected from the group consisting of lactic, malic and tartaric acids at a pH which is less than or equal to the pK.sub.a, or lowest pK.sub.a, of the α-hydroxy acid having the lowest pK.sub.a.

23. A method as claimed in any preceding claim wherein the part-cooked food is packaged and frozen.

24. A method as claimed in any one of the preceding claims, wherein said food is a vegetable or a tuber, preferably a root vegetable or a tuber.

25. A method as claimed in claim 24, wherein said food is a potato or sweet potato.

26. A food obtained (e.g. obtainable) by a method as claimed in any one of claims 1 to 25, optionally in packaged form.

27. A container, preferably a sealed container, containing a food obtained (e.g. obtainable) by a method as claimed in any one of claims 1 to 25.

28. A package containing a part-cooked carbohydrate-containing food, wherein said package includes instructions to contact said food with an α-hydroxy acid selected from lactic, malic and tartaric acids at a pH less than or equal to its pK.sub.a, or its lowest pK.sub.a, prior to final cooking.

29. A package as claimed in claim 28, wherein the part-cooked food is prepared by a method comprising at least the following steps: contacting the food with an α-hydroxy acid selected from lactic, malic and tartaric acids at a pH less than or equal to its pK.sub.a, or its lowest pK.sub.a; and part-cooking said food at a temperature at which the Maillard reaction occurs.

30. A package as claimed in claim 29, wherein the part-cooked food is ready-to-cook French fries, e.g. frozen, ready-to-cook French fries.

31. A method of reducing acrylamide during final cooking of a part-cooked carbohydrate-containing food, said method comprising at least the following steps: contacting said part-cooked food with an α-hydroxy acid in at least partly non-dissociated form; and subsequently cooking said food (e.g. by finish-frying) at a temperature at which the Maillard reaction occurs, e.g. at a temperature above about 120° C.; wherein said part-cooked food is obtainable (e.g. obtained or prepared) by contacting the food with an α-hydroxy acid in at least partly non-dissociated form; and part-cooking (e.g. par-frying) said food at a temperature at which the Maillard reaction occurs, e.g. at a temperature above about 120° C.

Description

EXAMPLES

Example 1—French Fries

[0230] Ingredients:

[0231] Potatoes: Asterix variety (glucose content: 20-27 mM)

[0232] Frying oil: High oleic acid rapeseed oil

[0233] Pre-Treatment of Potatoes:

[0234] The raw potatoes were washed in water and the skin removed by cutting off the sides to produce skin-free cubes (approx. 5×7 cm). The cubes were divided using a cutter into 1×1 cm rods. The rods were transferred to a container filled with sufficient tap water to cover the rods.

[0235] Batches of rods (approx. 200 g) were blanched for 5 minutes in water at 100° C. before being submerged in a dipping solution at 60° C. for 30 seconds. Each dipping solution contained one inhibitor to be tested. All dipping solutions contained the same molar concentration (100 mM) of the inhibitor. All dipping solutions were adjusted to a pH of 2.29 using either HCl or NaOH prior to use. In each case the pH was more than one unit lower than the (lowest) pKa of the α-hydroxy acid.

[0236] As a control, dipping was also carried out in hydrochloric acid (pH 2.29) and in water (pH not adjusted).

[0237] Par-Frying:

[0238] Par-frying was performed in oil at 175-185° C. for 2 minutes 45 seconds. The par-fried samples were allowed to cool, packed in plastic bags and frozen.

[0239] Oven Cooking:

[0240] Four days later, the frozen samples were heated in a hot air oven at 225° C. for 7 minutes. Each sample was placed in the middle of a pan in the middle of the oven. Samples were packed and frozen prior to colour and acrylamide analyses.

[0241] Analyses:

[0242] Acrylamide content was determined by an accredited laboratory using GC-MS and acrylamide as an internal standard.

[0243] Colour was analysed as Lab-values using a Digieye instrument. Colour standards for frozen French fried potatoes (USDA, 5.sup.th Ed. 2007) were used as a comparison.

[0244] Results:

TABLE-US-00001 TABLE 1 Inhibitor Reduction in Inhibitor Compound acrylamide Functionality (100 mM) pH (%) L* value.sup.1,2 α-hydroxy acid Lactic acid 2.29 82 71.2 α-hydroxy acid Glycolic acid 2.29 89 70.0 α-hydroxy acid Malic acid 2.29 84 71.6 Inorganic acid Hydrochloric acid 2.29 64 74.7 Control Water 7.61 0 65.1 .sup.1L* = 100 is white, L* = 0 is black, i.e. the higher the L* value, the lighter the sample. .sup.2Colour standards for frozen French fried potatoes (USDA, 5.sup.th Ed. 2007): Colour std. 2: 84.5; Colour std. 3: 71.63; Colour std. 4: 63.55

[0245] Conclusions:

[0246] From the results it can be seen that dipping in the α-hydroxy acids compared to water had a profound effect in lowering acrylamide in the deep fried potatoes. The effect from the α-hydroxy acids was considerably higher than that with hydrochloric acid.

Example 2—French Fries—lactic Acid and Effect of pH

[0247] The conditions in this experiment were identical to those in Example 1 except for the changes noted below: [0248] All dipping solutions contained the same molar concentration (40 mM) of inhibitor (lactic acid). [0249] The pH of each dipping solution was adjusted to the target pH with 0.1 N HCl or 0.1 N NaOH. [0250] Par-frying was carried out for a period of 3 minutes 30 seconds at 185° C. [0251] The potato variety used was Peik. Glucose levels of the potatoes averaged 0.28% (15.5 mM).

[0252] Effect of pH:

[0253] The pK.sub.a value of lactic acid is 3.86. The pH values of the dipping solutions were chosen as pK.sub.a-2 (1.86), pK.sub.a-1 (2.86), and pK.sub.a (3.86).

[0254] Results:

[0255] The effect of pH of the lactic acid dipping solution on acrylamide levels in French fries following par-frying and cooking of frozen samples is shown in Table 2.

TABLE-US-00002 TABLE 2 Reduction in Concentration Target pH Actual Acrylamide acrylamide Dipping solution mM pK.sub.a − x pH μg/kg (%) Water (control) 0 7.32 570 0 Lactic acid (pKa-2) 40 1.86 1.62 280 50.9 Lactic acid (pKa-1) 40 2.86 2.69 250 56.1 Lactic acid (pKa) 40 3.86 3.57 370 35.1

[0256] Conclusions:

[0257] The samples treated with a lactic acid dipping solution having a pH lower than the pK.sub.a gave the lowest acrylamide levels following par frying and cooking. At these pH levels the concentration of undissociated lactic acid is far greater than 50% of the total lactic acid concentration. With less undissociated lactic acid present (pH equal to the pK.sub.a), the effect of lactic acid in preventing the formation of acrylamide is considerably lower.

[0258] The results are surprising since the formation of acrylamide has previously been linked to the protonation of asparagine which is considerable (50%) even at a pH as high as 8.8 (asparagine pK.sub.a1=8.80, pK.sub.a2=2.02).

Example 3—French Fries

[0259] The conditions in this experiment were identical to those in Example 1 except for the changes noted below: [0260] All dipping solutions contained the same molar concentration (40 mM) of inhibitor. [0261] The pH of each dipping solution was adjusted to a target pH with 0.1 N HCl or 0.1 N NaOH. [0262] Par frying was carried out for a period of 3 minutes 30 seconds at 185° C. [0263] The potato variety was Peik. Glucose levels of the potatoes averaged 0.28% (15.5 mM).

[0264] Effects of Chemical Structure:

[0265] Compounds with chemical structures similar to lactic acid, i.e. the presence of one or more hydroxyl groups, were tested as inhibitors for the formation of acrylamide. All acids were tested at a pH approximately one unit lower than their pK.sub.a or their lowest pK.sub.a (i.e. pK.sub.a-1, or pK.sub.a1-1).

[0266] Results:

TABLE-US-00003 TABLE 3 Reduction in Concentration Target pH Actual Acrylamide acrylamide Dipping solution mM pK.sub.a − 1 pH μg/kg (%) Water (control) 0 7.32 570 — Hydrochloric 40 2.98 610 −7 acid (control) (increase) Lactic acid 40 2.86 2.69 250 56 Malic acid 40 2.40 2.42 300 47 Tartaric acid 40 1.98 1.91 340 40 Citric acid 40 2.13 1.99 310 46 Ascorbic acid 40 3.17 2.73 300 47 Glycolic acid 40 2.83 2.64 370 35

[0267] Conclusions:

[0268] The results clearly and surprisingly demonstrate that the α-hydroxy acids: lactic acid, malic acid, tartaric acid, citric acid, ascorbic acid, and glycolic acid are particularly effective in the reduction of acrylamide when used at the selected pH. Hydrochloric acid failed to act as an inhibitor for acrylamide formation, surprisingly demonstrating that the inhibition reaction is not solely affected by the low pH.

Example 4—Carrot Chips

[0269] Materials and Methods:

[0270] Carrots were obtained from a commercial grower in Norway. Palm oil was used for frying. Lactic acid and hydrochloric acid were obtained from Sigma. The following brines were used: [0271] Lactic acid: 20 mM lactic acid in 1% NaCl, pH=3.9 [0272] Hydrochloric acid: 20 mM HCl in 1% NaCl, pH=3.5 [0273] Control: Water, pH=7.1

[0274] Pre-Treatment of Carrots:

[0275] Carrots were peeled and sliced to 1.5 mm thickness using a Robot Vertical Cutter 2 (Robot Coupe SA, Le Perreux, France). The carrot slices (500 g) were immediately added to one of the brines (1 L) and left at room temperature for 2 hours prior to deep frying. The control samples were rinsed in water and deep fried without delay.

[0276] Deep Frying:

[0277] The carrot slices were deep fried as 150 g portions in palm oil at 170° C. for 2 minutes 15 seconds.

[0278] Analyses:

[0279] Dry matter was determined in a vacuum oven at 70° C. overnight.

[0280] Soluble solids in the raw carrots were determined as ° Brix using a Mettler Toledo RE40 refractometer. Samples were homogenized and a few drops of the homogenates were applied on the refractometer. ° Brix is given as g sucrose/100 g sample.

[0281] Accredited analyses (GC/MS) of acrylamide were performed using acrylamide as an internal standard.

[0282] Results:

[0283] The ° Brix value of the carrots used for the experiments was 7.8.

[0284] Results from analyses of deep fried products soaked in acid prior to deep frying are shown in Table 4.

TABLE-US-00004 TABLE 4 Dry matter Acrylamide Acid of fried content of Acrylamide Carrot concentration product fried product reduction chips mmol/l g/100 g μg/kg % Untreated 0 97.2 690 0 (control) Lactic acid 20 96.2 260 62 Hydrochloric 20 96.9 490 29 acid

[0285] Conclusions:

[0286] All carrot samples were deep fried for the same period of time, rather than being deep fried until a certain product colour. Any difference in acrylamide levels thus reflects the ability of each treatment to prevent the formation of acrylamide on deep frying.

[0287] As the results show, soaking in lactic acid compared to rinsing in water had a profound effect in lowering acrylamide in the deep fried carrot chips. The effect from lactic acid was considerably higher than the effect from treatment with hydrochloric acid.

Example 5—Sweet Potato Fries

[0288] Materials:

[0289] Sweet potatoes were obtained from a local grocery. The material originated from the USA. Palm oil was used for frying. Lactic acid was obtained from Sigma.

[0290] Treatment:

[0291] 1×1 cm sticks of sweet potato were blanched in water at 100° C. for 5 minutes, dipped in water or 40 mM lactic acid at 60° C. for 40 seconds, dried at 60° C. for 10 minutes, and deep fried in palm oil at 180° C. for 2 minutes 40 seconds. The sticks were then frozen. The frozen sticks were subsequently heated in an oven at 225° C. for 12 minutes.

[0292] Acrylamide levels of the final products were determined by an accredited laboratory using GC-MS and acrylamide as an internal standard.

[0293] Results:

TABLE-US-00005 TABLE 5 pH of Acrylamide content of Acrylamide Sweet Dipping dipping fried product reduction potatoes solution solution μmol/kg % Untreated water 7.10 570 — (control) Lactic acid 40 mM 2.68 280 51 lactic acid

[0294] Conclusion:

[0295] The results demonstrate that treatment of blanched sweet potato rods with 40 mM lactic acid (pH 2.68) prior to par-frying resulted in a 51% reduction in the acrylamide level in the finished fries.

Example 6—French Fries—Combination of AHAs

[0296] Materials:

[0297] Peik potatoes were obtained for testing. Palm oil was used for frying. Dipping solutions were prepared using lactic acid, malic acid, and calcium lactate from Sigma.

[0298] The dipping solutions were combinations of 40 mM (0.36%) lactic acid, 40 mM (0.54%) malic acid, 0.5% (calcium lactate, “CaLA”) (2.3 mM) and water. 40 mM lactic acid was prepared by adding 4.5 g 80% lactic acid/I. 40 mM malic acid was prepared by adding 5.36 g malic acid/I.

[0299] Method:

[0300] Potatoes were peeled and cut into 250 g batons (1×1 cm), blanched at 100° C. for 5 minutes, dipped in water/various dips (60° C. for 40 seconds), dried (60° C. for 10 minutes) and then fried (180° C. for 2 minutes 40 seconds) in palm oil. Two control samples with water as the dip were also prepared. The acrylamide level of the control was calculated as the middle of the two, i.e. 1085 μg/kg.

[0301] Results and Conclusions:

TABLE-US-00006 TABLE 6 Sample Lactic Malic Acrylamide No. acid CaLA acid Water pH μg/kg Reduction % 1 0 0 0 Control 7.10 1200 (x = 1085) 2 40 mM 0 0 2.59 700 35 3 40 mM 0.5% 0 3.60 650 40 4 0 0.5% 0 7.63 1000 8 5 0 0 40 mM 2.63 720 34 6 0 0.5% 40 mM 3.37 430 60 7 40 mM 0 40 mM 2.51 430 60 8 0 0 0 Control 7.74  970 (x = 1085)

[0302] Experiment 1—Effect of Lactic Acid and Malic Acid Alone and in Combination (Sample Nos. 2, 5, 7 and Controls):

TABLE-US-00007 TABLE 7 Lactic acid Malic acid Acrylamide Reduction Sample No. (mM) (mM) pH μg/kg % 1 0 0 7.10 1085 2 40 0 2.59 700 35 5 0 40 2.63 720 34 7 40 40 2.51 430 60

[0303] The results demonstrate that dipping in 40 mM lactic acid or 40 mM malic acid has substantial and comparable effects for reducing acrylamide levels in deep-fried French fries. The reduction in acrylamide levels corresponds to nearly 35% of the levels obtained when dipping with water only. Combining the two acids increases the reduction in acrylamide to 60% of the control with water only.

[0304] The increased effect of the two acids in combination suggests that higher concentrations of AHA may be useful in achieving an effective reduction in acrylamide levels.

[0305] Experiment 2—Calcium Lactate (CaLA) as a Potential Inhibitor of Acrylamide Formation (Sample Nos. 2, 3, 4, 5, 6 and Controls):

TABLE-US-00008 TABLE 8 Sample Lactic Malic Acrylamide Reduction No. acid CaLA acid pH μg/kg % 1 0 0 0 7.10 1085 2 40 mM 0 0 2.59 700 35 3 40 mM 0.5% 0 3.60 650 40 (4.6 mM) 4 0 0.5% 0 7.63 1000 8 (4.6 mM) 5 0 0 40 mM 2.63 720 34 6 0 0.5% 40 mM 3.37 430 60 (4.6 mM) 7 40 mM 0 40 mM 2.51 430 60

[0306] Calcium lactate is used as a processing aid in the French fry industry as a cheap source of calcium ions. Typical concentrations used are 0.2-0.7%. The Ca.sup.2+ ions react with pectin and aid in producing a ‘crisp’ product. As calcium lactate contains lactic acid (two molecules per molecule of Ca lactate), it could also be a potential source of lactic acid as an acrylamide inhibitor.

[0307] To achieve an acrylamide-lowering effect, the pH of the solution is critical as the lactic acid must be in its non-dissociated form. CaLA dissolved in water gives a pH well above 7. Thus, the dissolved lactic acid molecules will be in the dissociated form. The pH must be lowered if any effect on inhibition of acrylamide is to be achieved. This can be obtained by combining the CaLA with one or more of the AHAs used for reducing acrylamide formation. With only CaLA present the pH is 7.63. When mixed with 40 mM lactic acid, the pH is 3.6 and when mixed with 40 mM malic acid, the pH is 3.37.

[0308] With CaLA only, very low (8%) acrylamide reduction was obtained. In samples with 40 mM lactic acid or malic acid, a 40 and 60% reduction in acrylamide was obtained, respectively. These samples contained 4.6 mM additional lactic acid.

Example 7—French Fries—Combination of AHAs

[0309] Materials:

[0310] Potatoes were obtained from Hoff SA. The potato variety was Peik which has a sugar content of 0.57% and a starch content of 14.85%.

[0311] Method:

[0312] Deep fried potato wedges (also known as “potato boats”) were processed with various inhibitors (AHAs) to study their inhibiting effects.

[0313] The potatoes were sampled after the raw, unpeeled potato wedges had been blanched for 5 minutes at 90° C. followed by blanching for 26 minutes at 84° C. The blanched material was then cooled in water. Further processing was done the next day.

[0314] Dipping solutions were prepared and kept in a heating cabinet at 60° C. overnight. 250 g samples of the potato wedges were dipped for 40 seconds in the various warm (60° C.) dipping solutions. The samples were then transferred to a fanned drying cabinet held at 60° C. The samples were dried for 10 minutes. After drying, the samples were deep fried in oil at 188° C. for 2 minutes 40 seconds. The temperature fell to 180° C. during each frying session.

[0315] The par-fried samples were cooled on paper at room temperature, packed in plastic bags, sealed and frozen. For final frying, samples were withdrawn from the freezer, removed from the plastic bags and thawed for 2 minutes on a rotating plate in a microwave oven (800 W).

[0316] Samples were then spread on a baking sheet and heated for 12 minutes in a convection oven at 225° C.

[0317] Fried potato wedges were evaluated for colour according to “Color Standards for Frozen French Fries Potatoes” (USDA, 5.sup.th Ed., 2007). Parts covered with potato skins were not evaluated. Samples were also evaluated for the presence of sour taste. Samples were packed in plastic bags, frozen and sent for acrylamide analysis.

[0318] The concentrations of inhibitors in the dipping solutions were 10 mmol/l and 40 mmol/l for each inhibitor. The relationship between dip concentration (mmol/l) and % inhibitor in the dips are seen in Table 9 below:

TABLE-US-00009 TABLE 9 Inhibitor Concentration in dip (AHA) mmol/l g/100 g (%) Lactic acid 40 0.36 Malic acid 40 0.54 Tartaric acid 40 0.60 Citric acid 40 0.84 Lactic acid 10 0.09 Malic acid 10 0.13 Tartaric acid 10 0.15 Citric acid 10 0.21

[0319] Results:

[0320] Concentrations (mmol/l, mM) of inhibitors, pH of dips, colour (USDA scale) and acrylamide levels (μmol/kg, ppb) in the deep fried potato wedges are provided in Table 10 below:

TABLE-US-00010 TABLE 10 Lactic Malic Tartaric Citric acid (LA) acid (MA) acid (TA) acid (CA) Colour Acrylamide Sample mmol/l mmol/l mmol/l mmol/l USDA μg/kg Reduction in No. (mM) (mM) (mM) (mM) pH scale (ppb) acrylamide (%) 1 0 0 0 0 8.02 2-3 1200 — 2 40 0 0 0 2.68  1.5 470 59 3 40 40 40 0 2.18 1  420 63 4 40 40 40 40 2.06 1  420 63 5 10 10 10 10 2.38 Weak 1 880 23 6 0 0 0 0 8.01  2.5 1100 — 7 0 40 0 0 2.49 1+ 470 59 8 0 40 40 0 2.18 1  540 53 9 0 40 40 40 2.06 1  490 57 10 0 0 40 0 2.30 1+ 810 30 11 0 0 40 40 2.12  1.5 670 42 12 0 0 0 40 2.28 1− 510 56 13 10 0 0 0 3.03 1-0 700 39 14 0 0 10 0 2.70 1+ 1200 −4 (increase)

[0321] Conclusions:

[0322] The best combinations of AHAs (2 combinations) revealed more than 60% inhibition of acrylamide formation. Five AHA mixtures revealed inhibition in the range of 60 to 50%. Five mixtures caused 40% or less reduction. These samples contained TA and/or low levels of AHA.

[0323] The pH in the dips ranged from 2.06 to 2.68. This is well below the pKa values for the AHAs. In most dips more than 90% of the AHA was non-dissociated. The exception was the dip with 40 mM TA (sample No. 12) where only 80% was non-dissociated. This dip caused only 30% inhibition in acrylamide formation.

[0324] The effects of 40 mM MA, MA and CA were comparable. The effect of tartaric acid was lower.

[0325] Little, if any, additional inhibitory effect is obtained when two AHAs are combined and the total AHA concentration is doubled (from 40 to 80 mM). The two pairs with MA+TA and TA+CA are less effective in reducing acrylamide than LA alone. The triple combination solutions with a total of 120 mM AHA are slightly more effective than LA alone at 40 mM. No additional effect was obtained by the addition of a 4.sup.th AHA, citric acid, even though the total concentration of AHA then reaches 160 mM.

[0326] The results illustrate the effect of concentration of AHA on reduction in acrylamide levels. 10 mM is insufficient to reach the effect of using 40 mM for both LA and TA. Even the mixture of the 4 AHAs (each at 10 mM), reaching a total of 40 mM, gave considerably lower inhibition that the effect of 10 mM LA, and even more so of LA at 40 mM. The mixture of the 4 AHAs, each at 40 mM, has the strongest inhibitory effect on acrylamide formation.

Example 8—Double Dipping

[0327] Materials and Methods:

[0328] The potato variety Innovator was used. The potatoes were considered to be of excellent quality (large potatoes, no germination, no shrinkage).

[0329] Dip 1—In Processing Line in the Factory

[0330] Par-frying: Raw potatoes—peel—cut—blanch—dip/spray (Dip 1)—dry—par-fry—freeze—store

[0331] Dip 2—At Home/Restaurant/Catering

[0332] Finishing step (final frying): Frozen par-fried potatoes—dip/spray (Dip 2)—(dry)—fry

[0333] Conditions:

[0334] Par-Frying [0335] Cutting: 1×1 cm potato sticks [0336] Blanching: 100° C. for 5 min [0337] Dipping (Dip 1): 40 seconds in water or lactic acid (0.4%) at 60° C. [0338] Drying: 10 minutes at 60° C. in oven equipped with fan [0339] Par-frying: 185° C. for 2 minutes [0340] Freezing: in sealed plastic bags at −20° C.

[0341] Finishing Step [0342] Material: Frozen par-fried sticks from freezer [0343] Dipping (Dip 2): 40 seconds in lactic acid (0.4%) at 60° C. No dipping of control [0344] Shaking for 10 seconds for samples dipped in acid [0345] Frying: 180° C. for 4 minutes 30 seconds [0346] Evaluation: Acrylamide analyses

[0347] Results:

TABLE-US-00011 TABLE 11 Dip 1 Par- Dip 2 Final frying Treatment Lactic frying Lactic 180° C. of sample acid 0.4% 185° C. acid 0.4% 4 mins Colour Acrylamide Reduction in 250 g or water 2 mins Freezing or water 30 secs USDA ppb acrylamide (%) Double dip Acid + + Acid + 1.30 440 56 Single dip Acid + + None + 1.42 650 35 (Dip 1) Single dip Water + + Acid + 1.71 620 38 (Dip 2) No Dip Water + + None + 1.63 1000 —

[0348] Conclusions:

[0349] The double dip process is highly effective in lowering acrylamide. Substantial reductions were also obtained with the two dips separately, although the double dip was most effective.

Example 9—Contact Times (Dipping in AHA)

[0350] Materials and Methods:

[0351] The potato variety Innovator was used. The potatoes were considered to be of excellent quality (large potatoes, no germination, no shrinkage).

[0352] Dip 1: [0353] Blanched potato batons [0354] Contact time: 1, 15, 29 and 40 seconds

[0355] Dip 2: [0356] Frozen, par-fried batons [0357] Contact time: 1, 29 and 40 seconds

[0358] The experiment was performed as two separate series. In the first series, samples 1-8 were only subjected to Dip 1 and the final frying was performed without additional dipping. In the second series, samples 9-12 were only subjected to Dip 2 and the experiment was performed on par-fried potatoes with no previous dipping. Par-frying and final frying was carried out under the same conditions as in Example 8.

[0359] Results:

TABLE-US-00012 TABLE 12 Dip 1 Dip 1 Dip 2 Dip 2 Sample Lactic Contact Lactic Contact No. acid 0.4% time acid 0.4% time Colour Acrylamide Reduction in 250 g or water (secs) or water (secs) USDA ppb acrylamide (%) 1 Acid 1 None 0 1.46 830  7 2 Water 1 None 0 2.04 890 — 3 Acid 15 None 0 1.92 930  7 4 Water 15 None 0 2.33 1000 — 5 Acid 29 None 0 1.58 740 15 6 Water 29 None 0 1.71 870 — 7 Acid 40 None 0 1.42 650 35 8 Water 40 None 0 1.63 1000 — 9 None 0 None 0 2.08 1300 10 None 0 Acid 1 1.50 970 25 11 None 0 Acid 29 2.00 820 37 12 None 0 Acid 40 2.12 990 24

[0360] Conclusions:

[0361] The effect of contact time in Dip 1 greatly influenced acrylamide reduction. The effect increased from about 7% when dipped for 1 and 15 seconds, to 15% and 35% with contact times of 29 and 40 secs, respectively.

[0362] With varying contact time for Dip 2, the effects deviated from those with Dip 1. One second was found to be sufficient for obtaining the effect of lowering acrylamide levels. The effect was similar to the effect of a contact period of 40 seconds.

Example 10—Effect of Frying Temperature

[0363] Materials and Methods:

[0364] The potato variety Innovator was used. The potatoes were considered to be of excellent quality (large potatoes, no germination, no shrinkage).

[0365] New EU regulations require that the frying temperature should not exceed 175° C. to avoid the formation of high acrylamide levels. However, this will impact the quality of the fried product. We propose that higher temperatures can still be used when the potatoes are dipped in lactic acid prior to par-frying and final frying. Samples were tested for acrylamide content. Colour (USDA), crispness and overall taste and texture were also determined.

[0366] Results:

TABLE-US-00013 TABLE 13 Dip 1 Dip 2 Sample Lactic Lactic No. acid 0.4% Par- acid Colour Acrylamide Reduction in 250 g or water Frying 0.4% Frying Crispness USDA ppb acrylamide (%) 1 Acid 185° C. Acid 180° C. + 1.30 440 56 2 mins 4 mins 30 secs 2 Water 185° C. None 180° C. + 1.63 1000 — 2 mins 4 mins 30 secs 3 Acid 145° C. Acid 170° C. + 0.71 200 72 4 mins 4 mins 30 secs 4 Water 145° C. None 170° C. + 1.71 720 — 4 mins 4 mins 30 secs

[0367] Conclusions:

[0368] When subjecting the French fries to lactic acid treatment prior to par-frying and final frying (double dipping), the acrylamide levels were lowered in both cases, to 440 and 200 ppb, respectively. The effect of double dipping was higher with the EU recommended frying conditions than with standard deep-frying conditions (72 vs. 56%).

[0369] The control samples for the two treatments (high temperature frying vs. low temperature frying) were comparable in colour. When subjecting to double dipping according to the invention, the low-temperature cooked fries were considerably lighter in colour than the high-temperature fries (the higher the number, the darker the colour). This is considered to reflect the acrylamide levels obtained. The fries produced following cooking at lower temperature were less crisp than those fried at the higher temperatures. Tasting of the fries revealed that fries from both treatments were fully cooked.