Table A1.

Overview of studies investigating the food-processing effects on polyphenols content and antioxidant activity.

Food Processing	Procedure	Food Matrix	Investigated Polyphenols	Effects on Polyphenols Content and/or Antioxidant Activity	Reference
Thermal Processing
Heat treatment	Boiling for 60 min	Onions and asparagus	Flavonols	Flavonols decreased by 20.6% in onions and by 43.9% in asparagus Antioxidant activity decreased by 10.65%.	[64]
	Cooking in smaller and larger amounts of water	Zucchini, beans, carrots, potatoes	Rutin (zucchini), rutin and quercitrin (beans), chlorogenic acid (carrots), caffeic acid (potatoes)	Cooking in small water volumes caused a decrease by 11.1% in rutin (zucchini), by 1.8% in rutin (beans), by 0.9% in quercetin (beans), by 25.4% in chlorogenic acid (carrots), and by 38.6% in caffeic acid (potatoes). Cooking in larger water volumes caused a decrease by 30.6% in rutin (zucchini), by 29.7% in rutin (beans), by 26.7% in quercetin (beans), by 62.8% in chlorogenic acid (carrots) and by 42.3% in caffeic acid (potatoes).	[66]
	Cooking 15 min at 100 °C	Cherry tomato	Naringenin and chlorogenic acid	NS difference in meals containing raw and cooked tomatoes, however, the content of analyzed polyphenols was higher in those with raw tomatoes.	[72]
	Microwave (900 W) cooking for 12 or 20 min	Purple carrots	Acylated and non-acylated anthocyanin content	Decrease in both acylated (by 22.93%) and non-acylated (by 22.52%) anthocyanin content.	[75]
	Pasteurization (HTST—90 °C for 30 s and PEF 4 µs bipolar pulse with an electric field strength of 35 kV/cm and a frequency of 1200 pulses per second)	Apple juice	TPC	TPC after HTST pasteurization decreased by 32.3%. TPC after PEF pasteurization decreased by 14.49%.	[71]
	Oven-roasting (180 °C/15 min and 200 °C/30 min); frying (180 °C/4 min and 180 °C/8 min); microwaving (450 W/4 min and 750 W/4 min); boiling (for 30 and 60 min)	Onions	Flavonols and anthocyanins	Quercetin diglucoside decreased after all treatments. Quercetin monoglucoside decreased after microwaving and boiling and increased after frying and oven-roasting. All anthocyanins (cyanidin 3-glucoside, cyanidin 3-laminaribioside, cyanidin 3-(6″-malonylglucoside), cyanidin 3-(6″-malonyl-laminaribioside) decreased after all treatments.	[65]
	Blanching 2.5 min at 96–98 °C and cooking 10 min at 100 °C	Kale leaves	Quercetin, kaempferol, caffeic acid, p-cumaric acid, sinapic acid, ferulic acid, total polyphenols	All analyzed compounds decreased, with more severe decrease observed in the case of cooking. Antioxidant activity decreased by 32.6% in steamed, and by 45.45% in cooked kale leaves.	[68]
	Boiling, steaming, and microwaving (700 W) for 5, 10, and 15 min	Eggplants (4 varieties)	TPC	TPC Increased in all samples. Antioxidant activity increased in all samples.	[69]
	Baking (the baked product used 34 g of frozen blueberries as a polyphenol source; the comparison was carried out with a drink made by dissolving the same amount of frozen blueberries in water)	Blueberries	Total polyphenols, total anthocyanins, total procyanidins, quercetin, chlorogenic acid, caffeic acid, ferulic acid	Total polyphenols decreased but n.s. Total anthocyanins decreased significantly by 42.2% Total procyanidins increased but n.s. Quercetin increased but n.s. Chlorogenic acid increased significantly by 23.46% Caffeic acid increased but n.s. Ferulic acid increased but n.s.	[76]
	Tomato-sauce production (cooking for 60 min at 99 °C and crushing)	Tomato	Phenolic acids, flavanones and flavonols	Phenolic acids decreased by 43.18% Flavanones increased by 245.03% Flavonols increased by 17.21%	[73]
	Boiling, steaming, and microwaving	Cassava	Total extractable polyphenols	Total extractable polyphenols: increased by 152%, 236% and 164% after boiling, steaming and microwaving, respectively. Antioxidant activity: increased by 151.56%, 208.60% and 173.44% after boiling, steaming and microwaving, respectively.	[74]
	Sterilization until the temperature reached 123 °C	Runner bean	TPC	TPC decreased by 29.63% and 45.68% after 4 months and 12 months of storage, respectively. Antioxidant activity decreased by 87.89% and 89.47% after 4 months and 12 months of storage, respectively.	[70]
	Cooking in water (10 min), steaming (15 min, 97 ± 2 °C), microwaving (5 min, 800 W), and baking (15 min, 200 °C)	Sweet potatoes (2 varieties grown in Slovakia and Croatia)	TPC, TAC and phenolic acids (chlorogenic, neochlorogenic, and trans-ferulic)	TPC increased after almost all treatments and all varieties except in Beauregard from Croatia. TAC increased in all samples. chlorogenic acid decreased except after steaming in Beauregard from Slovakia. Neochlorogenic acid decreased in all samples. Trans-ferulic acid decreased in almost all samples except in boiled 414-purple from Croatia. Antioxidant activities increased in all samples.	[67]
Canning	Canning in syrup with thermal treatment	Cherries	TAC	TAC decreased by 44.89% Antioxidant capacity decreased by 33.03% measured by FRAP assay.	[78]
	Canning in 5% brine	Peanuts	Trans-resveratrol and three conjugates, caffeic acid, luteolin, genistein, quercetin and catechin	All measured compounds (except genistein) decreased in all samples.	[80]
	Canning—industrial vs. domestic thermal processing	Apricots	TPC, procyanidins, phenolic acids	TPC decreased by 13–47% in industrial setting and decrease by 2–33% in domestic setting Procyanidins decreased by 44% in industrial setting, and decreased by 2.4% in domestic setting Phenolic acids: higher decrease was observed in industrial vs. domestic cooking	[79]
	Canning of apricot pulps, followed by exhaustion under steam, and finally processed in an autoclave at 121 °C for 30 min	Apricots	Chlorogenic, neochlorogenic acid, catechin, kaempferol, quercetin, procyanidin B2	Chlorogenic acid increased by 31.31%, Neochlorogenic acid increased by 19.06%, Catechin increased by 37.19%, Kaempferol increased by 35.58%, Quercetin increased by 26.08%, Procyanidin B2 increased by 26.16% *The presented changes refer to only one variety, while two more varieties were used in the study.	[121]
	Canning vs. freezing (−18 °C) vs. drying (65 °C)	Apricots	Ellagic acid, gallic acid, ferulic acid, epicatechin, epigallocatechin, rutin	Ellagic acid, gallic acid, ferulic acid, epicatechin and epigallocatechin were all affected by the treatments in the following order: canning yielded the highest content, followed by freezing and drying (in all three varieties). Canning yielded the highest content in rutin, followed by freezing and drying in one variety, while in other two varieties the rutin content was the highest in the case of canning, followed by drying then freezing.	[122]
Drying	Drying at 55 and 75 °C	Apricots (two cultivars)	Neochlorogenic, chlorogenic acid, catechin, epicatechin, rutin, quercetin-3-O-glucoside	Neochlorogenic and chlorogenic acid and catechin—decreased (higher decrease after 55 °C). Epicatechin, rutin and quercetin-3-0-glcoside—decreased (higher decrease after 75 °C). Antioxidant activity increased in one variety with higher increase after 75 °C drying.	[84]
	Drying (31–34 °C) for 8 days	Figs (2 varieties)	Total proanthocyanidin content	Total proanthocyanidin content increased in yellow figs And decreased in purple figs. Antioxidant activity (ABTS, DPPH, and FRAP assays) decreased in both varieties.	[88]
	Convection-oven-drying, freeze-drying (FD), microwave-drying, and air-drying with the sun exposure and without the sun exposure	Spearmint	TPC, hydroxycinammic acid derivatives	TPC—FD gave the highest TPC, followed by air with sun exposure, without sun exposure, microwave-drying and finally convection-drying. Caffeic acid—FD gave the highest content, followed by air-drying with and then without sun, convection-oven-drying and microwave-drying. Antioxidant activity: FRAP—the highest value in FD sample, followed by air-drying with sun, without sun, convection-drying, and microwave-drying; DPPH—the highest value in FD sample, followed by air-drying with sun, without sun, while microwave-and oven-drying gave similar values.	[123]
	Convective hot-air-drying at 65 and 80 °C vs. freeze-drying (FD)	Murtilla fruit	TPC, TAC, gallic acid, catechin, quercetin-3-glucoside, myricetin, kaempferol, quercetin	TPC—decreased by 37.33% after 65 °C, increased by 27.24% and 90.77% after 80 °C and FD, respectively. TAC—decreased by 38.46% and 66.67%, respectively, after 65 °C and 80 °C, and increased by 71.79% after FD. Gallic acid increased in all samples Catechin increased in 80 °C and FD, decreased in 65 °C Quercetin 3-β-d-glucoside, myricetin, kaempferol—decreased in all samples Quercetin—increased in 65 °C and 80 °C, decreased in FD Antioxidant activity—increase in all samples	[124]
	Drying (70 °C, 36 h)	Tomatoes	TPC, TFC	Rutin apioside, rutin, naringenin chalcone, chlorogenic acid—decrease Naringenin—was not identified in raw, but it was in dried tomato Antioxidant activity—increase in antioxidant capacity (ABTS, DPPH, CUPRAC assays)	[87]
	Hot-air-oven-drying or freeze-drying (FD)	Pumpkin flower	Free, bound, total phenols	Free phenols—similar values in case of oven-drying and FD, bound and total phenols—higher values after oven-drying. Antioxidant activity—hot-air-oven-dried pumpkin flours had slightly higher antioxidant activities than FD pumpkin flour samples.	[89]
	Drying at 60, 70, and 80 °C, respectively, at relative humidity level of 50% for heating time ranging from 0 to 40 h	Cocoa beans	TPC	Maximum TPC at 70 °C, and it decreased with the increased drying time.	[85]
	Drying at 40, 50, and 60 °C	Cocoa beans	TPC	TPC decreased by 45% after drying at 40 °C. Higher decrease with higher temperature.	[83]
	Freeze-drying (FD), drying at 50 °C for 48 h, 65 °C for 20 h, or 130 °C for 2 h until a moisture 89 content below 15% was obtained	Berries	Anthocyanins (individual), TPC	Anthocyanins—FD preserved them the best, 130 °C drying degraded them. TPC—highest values obtained after 65 °C drying, followed by FD, 50 °C and 130 °C drying. Antioxidant activity: ABTS•+ radical scavenging activity and ferric-reducing power varied depending on the berry type—raspberry and boysenberry showed the highest ABTS in the case of 65°C drying and redcurrant and blackcurrant in the case of FD, the same was observed for ferric-reducing power	[86]
	Vacuum/microwave-drying (480, 120 W), hot-air-drying (70, 60, 50 °C), and combined methods, such as pre-drying and finish-drying (60 °C + 480/120 W)	Jujube fruits (3 varieties)	TPC	TPC decreased in all samples; the lowest decrease was observed in the lowest temperature regime and in the combined process. Antioxidant activity decreased in ORAC values after drying, higher decrease in the case of higher temperature; lower decrease in the case of microwave-drying. Combined treatment gave lower decrease than hot-air-drying.	[82]
	Drying at 65 °C	Apricots	Chlorogenic, neochlorogenic acid, catechin, kaempferol, quercetin, procyanidin B2	Chlorogenic acid decreased by 16.02% Neochlorogenic acid decreased by 2.52% Catechin decreased by 3.66% Kaempferol decreased by 9.20% Quercetin decreased by 11.80% Procyanidin B2 decreased by 14.57% *The presented changes refer to only one variety, while two more varieties were used in the study.	[121]
Cold Processing
Freezing/ Chilling	Freezing at −30 °C	Red Raspberries	Total phenolics, anthocyanins, lambertianin C, sanguiin H-6, ellagic acid	There was n.s. change in all analyzed compounds.	[91]
	Individual quick-freezing process	Berries	TPC, total monomeric anthocyanins	There was n.s. change in all analyzed compounds.	[94]
	Freezing	Blanched/cooked kale leaves	TPC	TPC decreased by 3%. Antioxidant activity decreased by 7%	[68]
	Cooling at 5 °C in the refrigerator, or freezing at −20 °C	Maqui fruits	Polyphenol and anthocyanin concentration	Polyphenol and anthocyanin increased in both cases, with higher increase in the case of frozen samples.	[92]
	Freezing by immersion at liquid nitrogen and freeze-drying at −50 °C	Apples	TPC	TPC decreased before digestion in both freezing methods. Antioxidant activity decreased before and after digestion (ABTS, CUPRAC, and FRAP assays).	[95]
	Slow vs. quick freezing	Strawberries	TPC and total monomeric anthocyanin content	TPC and total monomeric anthocyanin content increased in the case of quick-frozen samples compared with slow frozen samples.	[93]
	Deep-freezing to −18 °C	Apricots	Chlorogenic, neochlorogenic acid, catechin, kaempferol, quercetin, procyanidin B2	Chlorogenic acid increased by 6.55% Neochlorogenic acid increased by 1.08% Catechin increased by 17.69% Kaempferol increased by 15.95% Quercetin increased by 4.35% Procyanidin B2 increased by 7.95% *The presented changes refer to only one variety, while two more varieties were used in the study.	[121]
	Freeze-drying vs. hot-air-drying vs. infrared-drying vs. pasteurization of apple puree)	Red-fleshed apples	Phenolic acids, flavan-3-ols, flavonols, anthocyanins, flavanones, dihydrochalcones	Compared with the freeze-dried snack: Infrared-drying caused important losses in most of the apple (poly)phenolics Purée pasteurization maintained 65% the (poly)phenols Hot-air-drying maintained 83% the (poly)phenols Anthocyanins were degraded to a higher extend after all thermal processing technologies.	[125]
Biochemical Processing
Fermentation	Fermentation of red grape	Red wine, dealcoholized red wine, and red grape juice	Malvidin-3-glucoside (M-3-G)	M-3-G—red wine (68 mg), dealcoholized red wine (58 mg) and red grape juice 117 mg	[103]
	Black-tea fermentation	Black vs. green tea	Quercetin, kaempferol	Eight cups of black tea (4 g tea solids) provided 108 µmol of quercetin glycosides (equivalent to 32.5 mg as free quercetin) and 72 µmol of kaempferol glycosides. The green tea (4 g tea solids) provided 104 µmol of quercetin glycosides and 58 µmol of kaempferol glycosides per day.	[105]
	Fermentation (red-wine production)—comparison between red wine and red grape juice	Red grape	Anthocyanins	Total anthocyanin content was almost equal in both red grape juice and red wine.	[102]
	Fermentation to apple cider	Apple (5 varieties)	TPC, catechin, caffeic acid	TPC decreased only in two varieties. Catechin increased in all varieties Caffeic acid increased in two varieties	[101]
	Natural fermentation	Legumes—pigeon pea, bambara groundnut, African yam bean, and kidney bean	Free and bound soluble phenol content	Free soluble phenol content increased, Bound phenol content decreased Antioxidant activity: free soluble phenolic compounds of fermented legumes had increased reducing power, free radical scavenging ability, and inhibition of lipid peroxidation compared with unfermented legumes.	[100]
	Fermentation with naturally present bacteria and with lactic acid bacteria	Eight legumes: black cow gram, mottled cowpea, speckled kidney bean, lentil, small rice bean, small runner bean and two soya beans	TPC	TPC increased in almost all samples Antioxidant activity increased in mottled cowpea, speckled kidney bean and small rice bean, and n.s. changes in all other samples.	[99]
	Fermentation with Aspergillus awamori	Millet	TPC	TPC—increase (more than 2-fold) Antioxidant activity (measured both by DPPH and ABTS assays)—slight increase by 3.75% and by 2.12%	[98]
	Ting fermentation (at different time and temperature regimes)	Sorghum	TPC, total flavonoid and total tannin content	All analyzed compounds—optimal values at 27 °C for 72 h Antioxidant activity—the best one was obtained in a sample fermented at 27 °C for 24 h	[97]
	Lactic acid fermentation (milk enriched with dates)	Two types of yoghurt enriched with dates	TPC and antioxidant activity	TPC: 34 and 37 mg of GAE 100 g−1 for, respectively, yogurt made with dates blended with milk and yogurt produced using small pieces of dates that were added to milk. Antioxidant activity (measured by DDPH) was 51% and 57% for yogurt made with dates blended with milk and yogurt produced using small pieces of dates that were added to milk, respectively.	[126]
Pickling	Pickling (with variable salinity and the addition of Lactobacillus plantarum)	Potherb mustard	The total free phenolic acids, the total phenolic acids, total phenolics	Total free phenolic acids increased. Total phenolics and total phenolic acids decreased. Antioxidant activity decreased by 35%.	[127]
	Pickling	Papaya	TPC, TFC	TPC decreased by 68.40% TFC decreased by 65.90% Antioxidant activity (DDPH assay) decreased.	[128]
	Pickling	Green beans, green pepper, chili pepper, white cabbage, cauliflower, cucumber, sneak melon, tomato, carrot, garlic	TPC	TPC—after 15 days—decreased in all vegetable; after 30 and 60 days increased in all vegetables. Antioxidant activity: the Trolox equivalent antioxidant capacity decreased after 15 days, then increased after 30 and 60 days for green beans, green pepper, chili pepper, cauliflower, white cabbage, cucumber and sneak melon. For tomato, carrot and garlic it increased during all time points. DPPH assay: RSA decreased followed by increase in all except green pepper, cauliflower, cucumber and sneak melon which decreased during all time points.	[129]
	Pickling	Soybeans	TPC, TPA content, TFC, naringenin, and vanillin	TPC and TFC increased by 47% and 42%, respectively. TPA decreased by 35% Naringenin and vanillin increased (24 and 2.5-fold, respectively).	[130]
Mechanical Processing
Peeling	Peeling, trimming and chopping	Onions	Flavonoids (quercetin and kaempferol)	Flavonoids decreased by 39%.	[108]
	Removal of periderm material in purée processing	Peaches	TPC, chlorogenic, neochlorogenic acid, catechin, caffeic acid	TPC—minor differences between the samples with and without the peel. Chlorogenic and neochlorogenic acid decreased in puree with peel (vs. puree without peels) Catechin increased in samples with peels (vs. puree without peels). Caffeic acid—slight decreased slightly in puree with peels (vs. puree without peels). Antioxidant activity: Peach puree with periderm tissue that underwent blanching and pasteurization had 7–11% higher antioxidant activity (measured by beta-carotene/linoleic acid assay).	[110]
	Peeling	Clingstone peaches	TPC	TPC decreased by 13–48%	[111]
	Fermentation with Saccharomyces bayanus BC (with and without skins)	White grape	Total polyphenol index, total flavonoids	Total polyphenol index increased especially in grapes with skins. Total flavonoids decreased in samples without skins, while they increased in samples with skins.	[112]
Grinding	Superfine grinding (included sieving through a 180 µm sieve once, or for 20–120 min)	Green tea	Catechins	Catechins decreased in all analyzed catechins Antioxidant activity increased in OH scavenging rate between the sample that was once sieved through a 180 µm sieve and those that underwent sieving for 20–120 min.	[116]
	Grinding and sieving	Hieracium pilosella L.	Flavonoids and phenolic acids	Increase in luteolin-7-glucoside, umbelliferone, luteolin, 3,5-dicaffeoylquinic acid, and chlorogenic acid (the maximum values in the case of 180–315 and 315–500 µm). Antioxidant activity increased in sieved samples (the maximum activity obtained at 180–315 and 315–500 µm).	[114]
	Grinding to produce American, Turkish, and Espresso coffees	Coffee beans	TPC	TPC—the highest observed in the case of fine–coarse powder. Further grinding decreased TPC. Antioxidant activity—the highest observed in the case of fine–coarse powder. Further grinding decreased the antioxidant activity (DPPH assay).	[115]
	Superfine grinding method	Brazilian green propolis	TPC	TPC increased (regardless of the particle size) Antioxidant activity increased (measured by ABTS and DPPH, regardless of the particle size)	[117]

Abbreviations: TPC—total phenolic content, TAC—total anthocyanin content, TPA—total phenolic acid content; TFC—total flavonoid content, HSTS—high-temperature short-time; PEF—pulsed electric field; sig—significant, n.s.—non significant; DPPH—2,2-diphenyl-1-picrylhydrazyl; ABTS—2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid; FRAP—ferric reducing antioxidant power; CUPRAC—cupric-reducing antioxidant capacity; GAE—gallic acid equivalent; RSA—radical scavenging activity.