getpdf NLM PubMed Logo https://doi.org/10.17113/ftb.62.04.24.8417                 

Quice Powder Increases Antioxidant Activity and Probiotic Survival in Yoghurt

Şenay Burak Çınar1orcid tiny, Gülfem Ünal2*orcid tiny, Gülşah Çalışkan Koç3orcid tiny, Safiye Nur Dirim4orcid tiny and Ayşe Sibel Akalın2orcid tiny

1Republic of Turkey Karabağlar District Directorate of Agriculture and Forestry, Izmir, Turkey

2Department of Dairy Technology, Faculty of Agriculture, Ege University, Bornova, Izmir, Turkey

3Eşme Vocational School, Food Processing Department, Food Technology Program, Uşak University, Eşme, Uşak, Turkey

4Department of Food Engineering, Faculty of Engineering, Ege University, Bornova, Izmir, Turkey

cc by Copyright © 2024 This is a Diamond Open Access article published under CC-BY licence. Copyright remains with the authors, who grant third parties the unrestricted right to use, copy, distribute and reproduce the article as long as the original author(s) and source are acknowledged.

Article history:

Received: 28 October 2023

Accepted: 27 October 2024

Keywords:

quince antioxidants; Bifidobacterium lactis BB-12®; quince powder; yoghurt

Summary:

Research background. In recent years, there has been a growing interest in incorporating fruit-based additives into yogurt formulations as a means to improve the functionality of the product. This study aims to produce a functional product by incorporating quince, which is rich in fibre, vitamins, minerals and antioxidant activity, into a yoghurt formulation.

Experimental approach. The influence of the addition of quince powder (0 (control), 0.5, 1.0 and 1.5 %) on the antioxidant and proteolytic activities and culture viability of probiotic yoghurt was investigated for 28 days.

Results and conclusions. The viable counts of yoghurt bacteria and Bifidobacterium lactis BB-12® were above 8 log CFU/g. Higher viability of all bacteria was obtained in yoghurt fortified with 1.5 % quince powder than those of other samples after 14 days. Probiotic yoghurt with added 1.5 % quince powder had the highest proteolytic activity during the last two weeks of storage, while the highest total phenolic content and (2,2-diphenyl-1-picrylhydrazyl) radical (DPPH˙) scavenging activity were obtained for the same sample throughout the storage period.

Novelty and scientific contribution. Quince powder supports the health of the digestive system thanks to its high fibre content, while it is also rich in vitamins, minerals and antioxidant activity. These properties emphasise the importance of using quince powder in yoghurt production. This innovation has the potential to provide consumers with a tasty alternative, while at the same time increasing the intake of health-promoting ingredients. Furthermore, such products offer higher nutritional value than conventional yoghurt, offering consumers with a healthier option. Therefore, the production of yoghurt with quince powder can be considered as an important innovation in the field of nutrition and a practice that contributes to increasing health awareness.

*Corresponding author: +902323112732
  +902323881864
  This email address is being protected from spambots. You need JavaScript enabled to view it.

INTRODUCTION

According to Food and Agriculture Organization of the United Nations (1) food production in the world should increase due to the increasing population. As more than 30 % of the produced food is wasted, this waste adversely affects food security and also comes at a high environmental cost. Therefore, in recent years, valorisation of fruit and vegetable by-products has received a great attention to support waste management. The use of quince-based products has been a subject of various studies, especially due to its high antioxidant activity. Bayav and Şahin (2) state that the market for processed quince-based products should grow to increase quince consumption and exports.

Quince (Cydonia oblonga) is a member of Maloideae subfamily that belongs to Rosaceae family. It shows a high variability according to geographical origin, maturity, climate, cultivar and genetics. Due to its hardness and astringent taste, it is mostly used to produce marmalade, jam, puddings and jelly (3). Quince is a good source of pectin, dietary fibre and minerals and also has a high antioxidant activity that depends on its phenolic content (4). The phenolic content and antioxidant activity of quince have been found to be higher than those of some other fruits such as apple and pear (5, 6). In addition, quince-based products have been reported to have beneficial effects on many diseases such as diarrhoea, ulcer, dysentery, constipation, diabetes, atherosclerosis and respiratory disorders (7).

Functional foods are considered as foods that, in addition to basic nutrition, offer health benefits and reduce the risk of chronic diseases (8). Functional dairy products, such as probiotic yoghurt, are already known as healthy due to the beneficial effect of viable bacteria. The use of fruit-based additives in yoghurt formulation has gained considerable interest in recent years to improve the product functionality. Probiotic yoghurt supplemented with a natural source of antioxidants provides consumers with nutrients, healthy effects of starter bacteria and antioxidant compounds, mainly phenolic compounds. An improvement in the viability of culture bacteria and/or antioxidant activity of grape extract (9), apple and banana fibre (10), passion fruit peel powder (11), jambolan fruit pulp (12) and pineapple peel (13) in yoghurts have been reported by many authors.

In recent studies, quince fruit has been used in different forms in the production of some dairy products and the properties of the final product have been investigated. For example, the positive effects of adding quince seed mucilage powder, quince boiling water or quince seed gel to different types of yoghurt and drinking yoghurt, such as doogh, have been shown in some studies (14-16). The enhancing effect of quince seed gum on the viability of Bifidobacterium lactis BB-12® in drinking yoghurt, doogh, was observed on the first day of storage compared to the control sample (17). On the other hand, the effects of quince seed, quince powder and quince seed gum on some other dairy products such as ice cream and whipped cream have also been studied (18, 19). In another study, quince seed mucilage was used as a coating material in a dairy dessert containing microencapsulated Lacticaseibacillus rhamnosus and the obtained results indicated good maintenance of probiotic viability in microencapsulation with quince seed mucilage (20). However, there is a lack of information about the use of whole quince powder in the production of probiotic yoghurt and the effect of this addition on the viability of both yoghurt starter bacteria and B. lactis and also proteolytic and antioxidant activities of yoghurt.

The aim of this study is to investigate the use of whole quince powder in the production of probiotic yoghurt and its effect on product quality throughout 28 days of storage. In this context, the influence of the addition of different amounts of quince powder on viable counts of bacteria, the total phenolic content, radical scavenging activity and proteolytic activity of probiotic yoghurt containing B. lactis BB-12 were determined.

MATERIALS AND METHODS

Materials

Fresh quinces of Gordes variety were purchased from a market in Izmir, Turkey. The freeze-dried direct vat set (DVS) yoghurt culture (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus and Bifidobacterium animalis ssp. lactis BB-12® were obtained from Chr. Hansen A/S, Hørsholm, Denmark, and contained 1011 and 1010 CFU/g, respectively. Nonfat milk powder was obtained from Pınar Dairy Products, Pınarbası, Izmir, Turkey.

Preparation of quince powder

After washing, the quinces were peeled, cored and sliced into 1-mm thick slices before drying and grinding. Quince peels and slices were dried and powdered separately under the same conditions. The mixture of 20 % quince peel powder and 80 % quince slice powder were used in the production of yoghurt.

The drying was carried out in a tray dryer (Armfield Ltd., Ringwood, Hampshire, UK). One mm thick quince slices were spread in a thin layer on the tray (dimensions 17.5 cm×22.5 cm). The inlet and outlet temperatures were (80±2) and (78±2) °C, respectively. The air velocity of the dryer was set at 1 m/s. The quince slices that came out of the dryer were ground with a blender (KB 6234 T B-Fit®; Arçelik, Istanbul, Turkey), hermetically packaged and stored under dry and dark conditions until the quince powder was used. Bags made of aluminium polyethylene (ALPE) were used for packaging the powders. The details of processing and powder properties were given in the study by Çınar et al. (21).

Yoghurt production

Whole milk with 4 % milk fat was used for the production of the experimental probiotic yoghurts. The solid content of nonfat milk was adjusted to 120 g/L with nonfat milk powder and then the standardised milk was divided into four samples. Three samples were enriched with 0.5, 1.0 or 1.5 % quince powder, while the fourth sample, without any addition, served as a control. After pasteurisation at 85 °C for 30 min, the preparations were cooled to 43 °C. Each milk base was inoculated with both yoghurt starter culture (L. bulgaricus and S. thermophilus) and B. lactis BB-12. Yoghurt starter culture was prepared by adding the freeze-dried commercial starter to 1 L of sterilised milk at 40 °C under aseptic conditions. After that, the prepared yoghurt starter culture (L. bulgaricus and S. thermophilus) was added to milk according to the manufacturer’s instructions. Then, the freeze-dried B. lactis BB-12 (0.02 %) culture was added to obtain a probiotic viability of 8 log CFU/g in the product. The mixtures were then fermented at 42 °C until pH=4.65. After fermentation, probiotic yoghurts were cooled at room temperature for about 30 min and refrigerated at 4 °C until use.

pH value

A pH meter (model 211; Hanna Instruments, Woonsocket, RI, USA) was used for the determination of pH values. The pH values of the yoghurt samples were measured weekly for 28 days.

Microbiological analyses

After preparing appropriate decimal dilutions, viable counts were determined according to Akalın et al. (22). The viable counts of S. thermophilus were determined using M17 agar (Merck, Darmstadt, Germany) after an aerobic incubation at 37 °C for 72 h, while the viability of L. bulgaricus was detected in de Man, Rogosa and Sharpe (MRS) agar after an anaerobic incubation at 42 °C for 72 h. Viable cells of B. lactis BB-12 were enumerated on MRS-NNLP (nalidixic acid, neomycin sulfate, lithium chloride and paramomycin sulfate) agar. The plates were incubated anaerobically at 37 °C for 72 h using anaerobic jars (Merck).

Proteolytic activity

The proteolytic activity was measured using the o-phtaldialdehyde (OPA) method, which is based on measuring the absorbance of a solution of amino acids and peptides (23). In the method, OPA reagent (50 mL of 1000 mmol/L sodium tetraborate, 5 mL of 20 % sodium dodecyl sulphate, 80 mg of OPA dissolved in 2 mL of methanol and 200 μL of β-mercaptoethanol topped up with dH2O to a final volume of 100 mL) was used and the absorbance of the solutions was measured at 340 nm using a spectrophotometer (Spekol 1300; Analytik Jena AG, Jena, Germany). The water extract of yoghurt was prepared by mixing 5 g of yoghurt sample with 5 mL of 24 % trichloroacetic acid (Sigma-Aldrich, Merck) and the mixture was left at room temperature for 1 h. After centrifugation (centrifuge model Sigma 3-16K; Sigma Laborzentrifugen GmbH, Osterode am Harz, Germany) of the mixture at 3743×g and 4 °C for 20 min, it was filtered through Whatman no. 42 filter paper. The permeate was added to 3 mL of OPA reagent and the absorbance of the solution was measured spectrophotometrically at 340 nm after 2 min at room temperature (20 °C). The proteolytic activity was expressed as the absorbance value.

Total phenolic content and antioxidant activity

The Folin-Ciocalteu method was used to determine the total phenolic content of experimental yoghurts (24, 25). Yoghurt extracts were prepared according to Singleton et al. (25). For this purpose, 10 g of yoghurt sample were centrifuged (model Sigma 3-16K; Sigma Laborzentrifugen GmbH) at 9383×g for 25 min, filtered through Whatman no. 1 filter paper and the supernatant was used in the method. A volume of 0.1 mL of sample extract was mixed with 6 mL of dH2O and 0.5 mL Folin-Ciocalteu reactive reagent (Carlo Erba Reagents, Val de Reuil, France) and left for 2 min. Then, 1.5 mL of 20 % sodium carbonate (Merck, Darmstadt, Germany) were added. After keeping the mixture at room temperature in the dark for 2 h, the absorbance was read at 760 nm using a spectrophotometer (Spekol 1300; Analytik Jena AG). A gallic acid standard curve was calculated using the following equation with the correlation coefficient R2=0.9987:


/1/

and the results were expressed in milligrams of gallic acid equivalents (GAE) per litre of sample.

The 2,2,-diphenyl-1-picrylhydrazyl (DPPH˙) scavenging activity of the samples was determined according to Unal and Akalın (26). A 0.1 mmol/L DPPH˙ solution in 95 % ethanol was prepared. A volume of 8 mL of ethanolic DPPH˙ solution was placed in a 50-mL centrifuge tube and mixed with 2 mL of sample or 95 % ethanol (as control), vortexed for 5 s and then incubated for 30 min at room temperature. The samples were then centrifuged (centrifuge model Sigma 3-16K; Sigma Laborzentrifugen GmbH) for 5 min at 9383×g and room temperature. Supernatants were filtered through Whatman no. 40 filter paper. The absorbance of each sample was measured at 517 nm. 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) was used as a reference antioxidant at a concentration of 0.25 mg/mL. DPPH˙ scavenging activity was calculated according to the following equation:


/2/

Statistical analysis

The experiment was repeated three times and the analyses were carried out at least in duplicate, i.e. six samples from each yoghurt type were evaluated in each analysis. The statistical analysis was carried out by one-way ANOVA using the general linear model (SPSS Statistica v. 25) (27). The significant differences were determined by Duncan’s multiple comparison test at the p<0.05 level.

RESULTS AND DISCUSSION

The physical properties of the quince powder were determined in our previous study (21). The moisture content, dispersibility and water-holding capacity values of quince powders were determined to be 3.07 %, 65.36 % and 3.05 g/g, respectively. The composition (total solids, fat and protein) of the experimental yoghurts was also analysed in our previous study (21). There was no significant difference in the fat (between (3.73±0.06) and (3.9±0.6) %) and protein (between (4.3±0.2) and (4.4±0.0) %) mass fraction among yoghurt samples, while total solids content of yoghurts increased significantly with the increase in quince powder amount (p<0.05).

Changes in pH values

Fig. 1 shows the pH changes of probiotic yoghurts during 28 days of refrigerated storage. A reduction was observed in the control sample and the yoghurt enriched with 0.5 % quince powder throughout the storage period. The pH values of the yoghurts supplemented with 1 and 1.5 % quince powder increased on day 7, but then decreased during the rest of the storage (p<0.05). The pH values were significantly influenced by the addition of quince powder. The probiotic yoghurts with added quince powder had generally lower pH values than the control sample. The lowering effect of quince powder on pH can be due to the quince composition and its beneficial effect on viable counts of starter culture bacteria in our yoghurt samples (Table 1). The lowest pH values were obtained for yoghurt supplemented with 1 % quince powder on the 1st, 21st and 28th day of storage.

Changes in pH values during refrigerated storage of yoghurts (error bars represent SD). PYC=probiotic yoghurt control without supplement, PY0.5, 1.0 and 1.5=probiotic yoghurt fortified with 0.5, 1.0 and 1.5 % quince powder, respectively. Different uppercase letters indicate significant differences among samples for the same storage period (p<0.05). Different lowercase letters indicate significant differences among different storage periods of the same sample (p<0.05)


Viable counts of Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus and B. lactis during refrigerated storage of yoghurts

t(storage)/day
Product 1 7 14 21 28
N(viable cell)/(log CFU/g)
S. thermophilus
PYC (9.06±0.01)Ba (8.81±0.00)ABa (8.2±0.2)Bb (8.8±0.3)Ba (8.9±0.2)Ba
PY0.5 (8.8±0.2)Bab (8.4±0.4)Bb (7.92±0.06)Bc (9.1±0.3)ABa (9.09±0.03)Aa
PY1.0 (8.8±0.2)Ba (9.07±0.03)Aa (8.2±0.4)Bb (8.8±0.1)Ba (9.08±0.08)Aa
PY1.5 (9.4±0.2)Aa (8.9±0.2)Abc (8.97±0.06)Abc (9.2±0.2)Aab (8.9±0.1)Bc
L. delbrueckii ssp. bulgaricus
PYC (9.20±0.04)Ba (9.39±0.04)Aa (8.4±0.4)Bc (8.70±0.03)Cb (8.49±0.04)Dbc
PY0.5 (9.21±0.08)Ba (8.3±0.4)Bb (8.2±0.1)Bb (9.38±0.03)Aa (9.39±0.06)Aa
PY1.0 (8.59±0.08)Cb (9.2±0.3)Aa (8.10±0.05)Bc (8.79±0.04)Bb (9.07±0.02)Ba
PY1.5 (9.6±0.1)Aa (9.1±0.1)Ac (9.25±0.02)Abc (9.34±0.06)Ab (8.6±0.1)Cd
B. lactis
PYC (9.07±0.04)Ba (8.87±0.05)Ab (8.60±0.06)Bc (8.54±0.03)Bc (8.5±0.2)Bc
PY0.5 (9.06±0.03)Bb (8.22±0.03)Bd (8.04±0.07)Ce (9.20±0.05)Aa (8.83±0.06)Ac
PY1.0 (9.3±0.1)Aa (8.85±0.01)Ab (8.0±0.1)Cd (8.67±0.08)Bc (8.78±0.04)Abc
PY1.5 (9.3±0.1)Aa (8.84±0.01)Abc (9.0±0.1)Ab (8.68±0.07)Bc (8.4±0.2)Bd

PYC=probiotic yoghurt control without supplement, PY0.5, 1.0 and 1.5=probiotic yoghurt fortified with 0.5, 1.0 and 1.5 % quince powder, respectively. Mean values±standard deviation in the same row with different lowercase letters in superscript are significantly different (p<0.05). Mean values±standard deviation in the same column with different uppercase letters in superscript are significantly different (p<0.05)

The pH values were also higher in the control yoghurt than in the sample with added 0.2 % quince seed mucilage powder, which was obtained by preparing aqueous quince seed solution, then applying agitation, filtration, evaporation and lyophilisation processes. The authors associated this with a correlation between the pH value and L. bulgaricus viability (16). Similarly, Trigueros et al. (14) measured lower pH values of low-fat yoghurt enriched with quince boiling water than of control yoghurt during fermentation. Lower pH values were determined for fibre-supplemented yoghurts than for the control group in other studies (10, 28). On the other hand, no significant effect of adding fruit fibre on the pH values of yoghurts was observed in a previous research (9, 29, 30). This difference from our study can be related to the different sources and forms of fruit fibre used in the production of yoghurt.

Microbiological properties

The viability of Streptococcus thermophilus, Lactobacillus bulgaricus and B. lactis during storage is shown in Table 1. The viable cell counts of yoghurt starter bacteria and B. lactis were above 8 log CFU/g during 28 days.

Quince powder addition had a promoting effect on the viability of B. lactis in general. Higher viable counts were enumerated in the sample containing 1.5 and 0.5 % quince powder during the first two weeks and the last two weeks of storage, respectively. Although the viability of B. lactis significantly decreased on the 28th day compared to the 1st day, it remained two log units above the recommended minimum value (106 CFU/g) (31) in all samples. The highest viability of B. lactis was found in the samples with added 1 and 1.5 % quince powder (PY1.0 and PY1.5, respectively) in the first two weeks of storage and in the sample with added 0.5 % quince powder (PY0.5) in the last two weeks. It has been reported that different fruit fibre increased the viability of Bifidobacterium species in fermented milk and yoghurt matrix (10, 11, 32, 33).

Pectin, which is a soluble dietary fibre found in various plant foods including quince, has a prebiotic effect and inhibits intestinal pathogens (34). Moreover, Thomas et al. (35) found that pectins are mostly found in the quince flesh, while the skin is quite rich in non-fibre compounds such as proteins and lipids. Therefore, the stimulating effect of quince powder on the viability of B. lactis can be due to the fact that most of the quince powder content used in our study (80 % quince slice powder and 20 % quince peel powder) consists of the fleshy part of the quince. In addition, Miletić et al. (34) reported that quince pectin-derived oligosaccharides act as a prebiotic and increase the amount of bifidobacteria probably due to various substances such as flavan-3-ol (epicatechin), procyanidin B2, 8-hydroxycinnamates, caffeoylquinic (CQA) and coumaroylquinic acid derivatives, kaempherol and quercetin derivatives, as well as monosaccharides.

The probiotic yoghurt fortified with 0.5 % quince powder had the highest viable counts of B. lactis on days 21 and 28 probably due to higher pH values on those days than other samples. The pH value of 4.5 and lower negatively affects the viability of Bifidobacterium species in yoghurt at 5 °C (36). Viable counts of L. bulgaricus were also found highest in PY0.5 on days 21 and 28 in our study. This is in agreement with the results obtained by Espírito Santo et al. (10), who found an increase in the viable cell counts of both L. bulgaricus and B. lactis HN019 in yoghurt towards the end of the 28 days. The authors reported that a symbiotic relationship between the fruit fibte and B. lactis HN019 may result in increased viability of L. bulgaricus in yoghurt. On the other hand, the simultaneous increase in the viability of both yoghurt culture bacteria and B. lactis in our study, which was also seen in the PY1.5 sample in the first two weeks, could also be a result of the symbiotic relationship between them. It has been reported that free amino acids formed by L. bulgaricus increase the growth of S. thermophilus and Bifidobacteria (37).

The addition of quince powder significantly affected the survival of S. thermophilus and the highest viability during storage was determined in the probiotic yoghurt with 1.5 % quince powder. On the other hand, there was no statistically significant difference between the yoghurts with 0.5 or 1.0 % quince powder. Although a decrease (p<0.05) in the viable counts of S. thermophilus was observed in yoghurts PYC, PY0.5 and PY1.0 on day 14, the values on day 28 did not change statistically compared to the beginning of storage. However, a fluctuation in the viability of S. thermophilus was observed during the storage of yoghurt supplemented with 1.5 % quince powder and a significant decrease in the number of viable bacteria was observed on day 28 compared to the beginning of storage.

The addition of quince powder to probiotic yoghurt generally improved the survival of L. bulgaricus. Gürbüz et al. (16) reported that the fortification with quince seed mucilage powder had a beneficial effect on the viability of L. bulgaricus, but the effect was not significant on S. thermophilus in set-style yoghurt. Trigueros et al. (14) found significantly higher counts of S. thermophilus and L. bulgaricus (p<0.05) in control yoghurt than in the samples with added quince boiling water during 28 days. The authors reported that this was correlated with the lower pH value of control yoghurts.

In some other studies (10, 11, 13, 38), an improving effect of the addition of fruit fibre on the viability of S. thermophilus and L. bulgaricus in probiotic yoghurts was observed. An increased growth of yoghurt bacteria was also obtained by adding the extract of blackcurrant polyphenols to yoghurt formulation before fermentation (39). Furthermore, the survival of yoghurt bacteria was also improved in fermented milk containing B. bifidum CECT 870 with orange or apple fibre (32). Chouchouli et al. (29) did not report any significant effect of grape seed extract on the viable counts of Lactobacillus populations throughout the shelf life of four weeks. The differences between the studies may be due to the different pectin polymerisation degrees of the dietary fibre in the used fruit. Bazzocco et al. (40) reported the relationship between the degree of polymerisation of a polysaccharide and its viability due to its fermentability.

Proteolytic activity of probiotic yoghurt

Table 2 shows that proteolytic activity of the probiotic yoghurt samples varied between A340 nm=0.63 and 0.95 and fluctuated during storage. The proteolytic activity of all yoghurt samples significantly increased (p<0.05) on days 7 and 14 and then there was no significant change until the end of storage. The increase in proteolytic activity was significant and dose-dependent in the yoghurts with quince powder compared to the control yoghurt without any additions. The proteolytic activity is estimated by the degree of protein hydrolysis carried out by the proteolytic enzymes of the culture bacteria. The peptide bonds of milk proteins are cleaved, which results in the formation of peptides and amino acids (41). Therefore, it is obvious that the positive effect of quince powder on the viability of culture bacteria is a consequence of the proteolytic activity of the supplemented yoghurts.

Proteolysis values of probiotic yoghurts

t(storage)/day
Product 1 7 14 21 28
A340 nm
PYC (0.63±0.00)Dc (0.67±0.02)Db (0.74±0.01)Da (0.73±0.01)Da (0.73±0.00)Ca
PY0.5 (0.67±0.00)Cd (0.73±0.00)Cc (0.81±0.00)Cb (0.83±0.00)Cab (0.85±0.06)Ba
PY1.0 (0.72±0.01)Bc (0.77±0.00)Bb (0.84±0.00)Ba (0.84±0.01)Ba (0.84±0.01)Ba
PY1.5 (0.73±0.01)Ac (0.89±0.01)Ab (0.89±0.00)Ab (0.95±0.00)Aa (0.95±0.01)Aa

PYC=probiotic yoghurt control without supplement, PY0.5, 1.0 and 1.5=probiotic yoghurt fortified with 0.5, 1.0 and 1.5 % quince powder, respectively. Mean values±standard deviation in the same row with different lowercase letters in superscript are significantly different (p<0.05). Mean values±standard deviation in the same column with different uppercase letters in superscript are significantly different (p<0.05)

Sah et al. (13) investigated the effect of the addition of pineapple peel powder on some properties of probiotic yoghurt. Yoghurt supplemented with pineallpe peel powder had higher proteolytic and stronger antioxidant activity than plain yoghurt. The study attributed the high proteolysis to the proteolytic activity of the starter culture. The authors also determined a positive but weaker correlation between the degree of proteolysis and DPPH˙ scavenging capacity (r=0.76) compared to other antioxidant capacity methods [reducing power (r=0.91), ABTS (r=0.89) and hydroxyl radicals (r=0.98)]. In our study, we also found a positive but weak correlation (r=0.576) between DPPH˙ scavenging activity and proteolytic activity.

Total phenolic content and antioxidant activity

The total phenolic content (TPC) and radical scavenging activity of probiotic yoghurts are shown in Fig. 2a and Fig. 2b, respectively. The TPC, espressed as gallic acid equivalents (GAE), of yoghurt samples was between 63.11 and 199.00 mg/L. The DPPH˙ scavenging activity of the yoghurts was between 80.02 and 95.22 %. The reference antioxidant, Trolox, at a concentration of 0.25 mg/mL, showed a radical scavenging activity of 97.09 %.

The results of: a) total phenolic content expressed as gallic acid equivalents (GAE) and b) antioxidant activity during storage (error bars represent SD). PYC=probiotic yoghurt control without supplement, PY0.5, 1.0 and 1.5=probiotic yoghurt fortified with 0.5, 1.0 and 1.5 % quince powder, respectively. Different uppercase letters indicate significant differences among samples during the same storage period (p<0.05). Different lowercase letters indicate significant differences within the same sample among different storage periods (p<0.05)


Fortification of yoghurt with quince powder significantly increased the TPC (p<0.05). Probiotic yoghurt enriched with 1.5 % quince powder had the highest TPC, while the control sample had the lowest values throughout storage. On the other hand, there were no significant differences in TPC (p>0.05) between the samples with added 0.5 and 1.0 % quince powder. The higher TPC in the PY1.5 sample may be mainly due to the quince powder content and higher viability of L. bulgaricus among probiotic yoghurts. Tabasco et al. (42) reported that L. bulgaricus can metabolise phenolic compounds, which results in increased phenolic content. Although there was a fluctuation in the TPC values of our experimental yoghurts during storage, a decrease (p<0.05) was detected at the end of 28 days compared to the 1st day, probably due to the degradation of phenolic compounds.

The addition of quince powder significantly affected the antioxidant activity of probiotic yoghurt and this effect varied with amount increase. Sample PY1.5 had the highest antioxidant activity for 28 days (p<0.05). As it has previously been reported, phenolic compounds have an important role in scavenging free radicals and providing hydrogen to prevent oxidation reactions (43). Therefore, as the antioxidant activity is strongly correlated with the quantity of phenolic compounds, the result obtained in our study is expected. A significant and robust positive correlation between total phenolic content and DPPH˙ scavenging activity of quince was also found by Silva et al. (44).

The high radical scavenging activity of sample PY1.5 could also be due to a high viability of the culture, which leads to the release of bioactive peptides with antioxidant properties during fermentation. In fact, sample PY1.5 also had higher viable counts (Table 1) and proteolytic activity (Table 2). Farvin et al. (45) investigated the antioxidant capacity of yoghurt fractions and concluded that the bioactive peptides with antioxidant properties could act as electron donors and thus create stable molecules from free radicals. The scavenging activities against DPPH˙ observed in all experimental yoghurt samples generally did not change significantly during storage.

Quince is known to be rich in potential antioxidants such as phenolic acids and flavonoids, and it has been suggested that caffeic acid and its derivatives are mainly responsible for the antioxidant capacity of quince (46). Najman et al. (47) determined caffeic acid mass fraction of 3.50 mg/100 g in quince powder obtained by convective drying at 70 °C, similar to our drying method, while the value for fresh quince was 0.61 mg/100 g. Studies have shown that higher phenolic content and antioxidant activity were found in quince peel than in the flesh part and whole fruit (3, 6, 4851). Sonmez and Sahin (51) also found a higher TPC and DPPH˙ scavenging activity in quince peel extract than in seed extract. Therefore, the presence of peel in the quince powder in this study provides an advantage in terms of antioxidant properties.

Grygorieva et al. (48) investigated the properties of phenolic compounds, free radical scavenging activity (DPPH˙ method) and molybdenum-reducing antioxidant power of different genotypes of quince fruit. The authors showed that all parameters differed significantly among the studied genotypes. They found significant positive correlations between the DPPH˙ scavenging activity and both total polyphenols and phenolic acids in the samples of Ukrainian origin. It was also reported that the pectin content, composition and physicochemical properties of quince vary according to the genotype. Qin et al. (52) investigated different pectic fractions of cell wall polysaccharides from quince. They determined that the DPPH˙ scavenging activity of all the studied fractions was affected by the pectin concentration. Furthermore, chelator-soluble pectin had the highest DPPH˙ scavenging activity (85 %) among the pectic fractions. Wojdyło et al. (53) suggested that there are different pathways for polyphenols to scavenge free radicals. They reported that the low-molecular-mass antioxidants (chlorogenic acid, (−)-epicatechin) present in quince are involved in the first step of the reaction with the radical. The polymerised procyanidins then react with free radicals after 10 min or later and thus develop antioxidant activity.

It has been shown that the total phenolic content and antioxidant activity of quince and foods with added quince can vary depending on the presence of certain polyphenolic compounds that are crucial for free radical scavenging activity (50). Moreover, various factors can influence these parameters, such as the genotype and geographical origin of the quince, its maturity, powder composition, especially the peel content and the antioxidant method used (54, 55).

CONCLUSIONS

In this study, a high viability of the yoghurt starter bacteria and Bifidobacterium lactis BB-12® was achieved in all probiotic yoghurts throughout storage. The addition of quince powder to the yoghurt improved the viability of B. lactis and also the yoghurt starter bacteria and increased the antioxidant and proteolytic activities. The highest viability of Streptococcus thermophilus, Lactobacillus bulgaricus and B. lactis was observed in the yoghurt with 1.5 % quince powder for 14 days, while the yoghurt with 0.5 % quince powder had the highest probiotic viable counts during the remaining storage days. Probiotic yoghurt fortified with 1.5 % quince powder had the highest antioxidant properties and proteolytic activity during refrigerated storage. The use of quince powder in the production of yoghurt, especially at amount of 1.5 %, offers the advantage of obtaining a dairy product with improved functional properties. This study showed the beneficial use of fruit waste, so the results are a guideline for further research in both functional food science and waste management.

FUNDING

This research received no specific funding from any public, commercial or non-profit organisation.

AUTHORS' CONTRIBUTION

Ş.B. Çınar contributed to obtaining the data, conducting the analysis and analysing the data. G. Ünal contributed to the conceptualisation and designing the study, conducting the analysis, analysing the data and writing the article. G.Ç. Koç contributed to obtaining thedata, conducting the analysis, analysing the data and drafting the article. S.N. Dirim contributed to the conceptualising and design of the study and the revision of the manuscript. A.S. Akalın contributed to conceptualising and designing of the study and revision of the manuscript.

REFERENCES
  1. Sustainability Pathways FAO. Food Loss and Waste; 2023. Available from: https://www.fao.org/nr/sustainability/food-loss-and-waste/en/
  2. Bayav A, Şahin M. Global economic importance of quince: Current situation, forecasting, and competitiveness analysis. Erwerbs-Obstbau. 2023;65(3):509-20, https://doi.org/10.1007/s10341-023-00850-7
  3. Silva B, Andrade P, Ferreres F, Domingues A, Seabra R, Ferreira M. Phenolic profile of quince fruit (Cydonia oblonga Miller) (pulp and peel). J Agric Food Chem. 2002;50(16):4615-8, https://doi.org/10.1021/jf0203139, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/12137485
  4. Nowak D, Gośliński M, Kłębukowska L. Antioxidant and antimicrobial properties of selected fruit juices. Plant Foods Hum Nutr. 2022;77:427-35, https://doi.org/10.1007/s11130-022-00983-2, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/35829820
  5. Karadeniz F, Burdurlu H, Koca N, Soyer Y. Antioxidant activity of selected fruits and vegetables grown in Turkey. Turk J Agric For. 2005;29:297-303
  6. Fattouch S, Caboni P, Coroneo V, Tuberoso C, Angioni A, Dessi S. Comparative analysis of polyphenols profiles and antioxidant and antimicrobial activities of Tunisian pome fruit pulp and peel aqueous acetone extracts. J Agric Food Chem. 2008;56(3):1084-90, https://doi.org/10.1021/jf072409e, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/18181568
  7. Abulizi A, Simayi J, Nuermaimaiti M, Han M, Hailati S, Talihati Z. Quince extract resists atherosclerosis in rats by down-regulating the EGFR/PI3K/Akt/GSK-3β pathway. Biomed Pharmacother. 2023;160, https://doi.org/10.1016/j.biopha.2023.114330, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/36746094
  8. Al-Sheraji S, Ismail A, Manap M, Mustafa S, Yusof R, Hassan F. Prebiotics as functional foods: A review. J Funct Foods. 2013;5(4):1542-53, https://doi.org/10.1016/j.jff.2013.08.009
  9. Karaaslan M, Ozden M, Vardin H, Turkoglu H. Phenolic fortification of yogurt using grape and callus extracts. LWT – Food Sci Technol. 2011;44(4):1065-72, https://doi.org/10.1016/j.lwt.2010.12.009
  10. do Espírito Santo A, Cartolano N, Silva T, Soares F, Gioielli L, Perego P. Fibers from fruit by-products enhance probiotic viability and fatty acid profile and increase CLA content in yoghurts. Int J Food Microbiol. 2012;154(3):135-44, https://doi.org/10.1016/j.ijfoodmicro.2011.12.025, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/22264421
  11. Espírito Santo A, Perego P, Converti A, Oliveira M. Influence of milk type and addition of passion fruit peel powder on fermentation kinetics, texture profile and bacterial viability in probiotic yoghurts. LWT – Food Sci Technol. 2012;47(2):393-9, https://doi.org/10.1016/j.lwt.2012.01.038
  12. Bezerra M, Araujo A, Santos K, Correira R. Caprine frozen yoghurt produced with fresh and spray dried jambolan fruit pulp (Eugenia jambolana Lam) and Bifidobacterium animalis subsp. lactis BI-07. LWT – Food Sci Technol.. 2015;62(2):1099-104, https://doi.org/10.1016/j.lwt.2015.01.049
  13. Sah B, Vasiljevic T, McKechnie S, Donkor O. Effect of refrigerated storage on probiotic viability and the production and stability of antimutagenic and antioxidant peptides in yogurt supplemented with pineapple peel. J Dairy Sci. 2015;98(9):5905-16, https://doi.org/10.3168/jds.2015-9450, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/26142843
  14. Trigueros L, Pérez-Alvarez J, Viuda-Martos M, Sendra E. Production of low-fat yogurt with quince (Cydonia oblonga Mill.) scalding water. Food Sci Technol.. 2011;44(6):1388-95, https://doi.org/10.1016/j.lwt.2011.01.012
  15. Pirsa S, Dalili R, Yazdani I. Effects of quince seed mucilage and guar gum on the physicochemical and sensory properties of doogh. J Agric Sci Technol. 2018;20(3):485-94
  16. Gürbüz Z, Erkaya-Kotan T, Şengül M. Evaluation of physicochemical, microbiological, texture and microstructure characteristics of set-style yoghurt supplemented with quince seed mucilage powder as a novel natural stabiliser. Int Dairy J. 2021;114, https://doi.org/10.1016/j.idairyj.2020.104938
  17. Khodashenas M, Jouki M. Optimization of stabilized probiotic doogh formulation by edible gums and response surface methodology: Assessment of stability, viability and organoleptic attributes. J Food Sci Technol. 2020;57(9):3201-10, https://doi.org/10.1007/s13197-020-04351-3, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/32728269
  18. Farahmandfar R, Asnaashari M, Salahi M, Rad T. Effects of basil seed gum, cress seed gum and quince seed gum on thephysical, textural and rheological properties of whipped cream. Int J Biol Macromol. 2017;98:820-8, https://doi.org/10.1016/j.ijbiomac.2017.02.046, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/28212934
  19. Kurt A, Atalar I. Effects of quince seed on the rheological, structural and sensory characteristics of ice cream. Food Hydrocoll. 2018;82:186-95, https://doi.org/10.1016/j.foodhyd.2018.04.011
  20. Dokoohaki Z, Sekhavatizadeh S, Hosseinzadeh S. Dairy dessert containing microencapsulated Lactobacillus rhamnosus (ATCC 53103) with quince seed mucilage as a coating material. LWT – Food Sci Technol. 2019;115, https://doi.org/10.1016/j.lwt.2019.108429
  21. Çınar Ş, Koç G, Dirim S, Ünal G, Akalın A. Textural and sensorial characteristics of set-type yogurt containing Bifidobacterium animalis subsp. lactis Bb-12 and quince powder. J Food Meas Charact. 2020;14:3067-77, https://doi.org/10.1007/s11694-020-00552-8
  22. Akalın A, Gonc S, Unal G, Fenderya S. Effects of fructooligosaccharide and whey protein concentrate on the viability of starter culture in reduced-fat probiotic yogurt during storage. J Food Sci. 2007;72(7):M222-7, https://doi.org/10.1111/j.1750-3841.2007.00436.x, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/17995644
  23. Donkor O, Henriksson A, Vasiljevic T, Shah N. Effect of acidification on the activity of probiotics in yoghurt during cold storage. Int Dairy J. 2006;16(10):1181-9, https://doi.org/10.1016/j.idairyj.2005.10.008
  24. Singleton V, Rossi J. Colorimetry of total phenolics with phosphomolybdic phosphotungistic acid reagents. Am J Enol Vitic. 1965;16:144-58, https://doi.org/10.5344/ajev.1965.16.3.144
  25. Singleton V, Orthofer R, Raventos L. Analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. Methods Enzymol. 1999;299:152-78, https://doi.org/10.1016/S0076-6879(99)99017-1
  26. Unal G, Akalin A. Antioxidant and angiotensin-converting enzyme inhibitory activity of yoghurt fortified with sodium calcium caseinate or whey protein concentrate. Dairy Sci Technol. 2012;92:627-39, https://doi.org/10.1007/s13594-012-0082-5
  27. Statistica SPSS. v.25.0, IBM, NY, USA; 2019. Available from: https://www.ibm.com/cn-zh/spss?lnk=flatitem
  28. Sah B, Vasiljevic T, McKechnie S, Donkor O. Physicochemical, textural and rheological properties of probiotic yogurt fortified with fibre-rich pineapple peel powder during refrigerated storage. LWT – Food Sci Technol. 2016;65:978-86, https://doi.org/10.1016/j.lwt.2015.09.027
  29. Chouchouli V, Kalogeropoulas N, Konteles S, Karvela E, Makris D, Karathanos V. Fortification of yogurts with grape (vitis vinifera) seed extracts. Food Sci Technol.. 2013;53(2):522-9, https://doi.org/10.1016/j.lwt.2013.03.008
  30. Issar K, Sharma P, Gupta A. Utilization of apple pomace in the preparation of fiber-enriched acidophilus yoghurt. J Food Process Preserv. 2017;41(4), https://doi.org/10.1111/jfpp.13098
  31. Tripathi M, Giri S. Probiotic functional foods: Survival of probiotics during processing and storage. J Funct Foods. 2014;9:225-41, https://doi.org/10.1016/j.jff.2014.04.030
  32. Sendra E, Fayos P, Lario Y, Fernández-López J, Sayas-Barberá E, Pérez-Alvarez J. Incorporation of citrus fibers in fermented milk containing probiotic bacteria. Food Microbiol. 2008;25(1):13-21, https://doi.org/10.1016/j.fm.2007.09.003, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/17993372
  33. Perina N, Granato D, Hirota C, Cruz A, Bogsan C, Oliveira M. Effect of vegetal-oil emulsion and passion fruit peel-powder on sensory acceptance of functional yogurt. Food Res Int. 2015;70:134-41, https://doi.org/10.1016/j.foodres.2015.01.014
  34. Miletić S, Nikolić-Kokić A, Jovanović D, Žerađanin A, Joksimović K, Avdalović J. Investigation of the antioxidant role of acidic and alkaline hydrolysates of pectin isolated from quince (Cydonia oblonga). Russ J Bioorg Chem. 2023;49:147-55, https://doi.org/10.1134/S1068162023010193
  35. Thomas M, Crépeau M, Rumpunen K, Thibault J. Dietary fibre and cell-wall polysaccharides in the fruits of Japanese quince (Chaenomeles japonica). LWT - Food Sci Technol. 2000;33(2):124-31, https://doi.org/10.1006/fstl.1999.0628
  36. Vinderola C, Mocchiutti P, Reinheimer J. Interactions among lactic acid starter and probiotic bacteria used for fermented dairy products. J Dairy Sci. 2002;85(4):721-9, https://doi.org/10.3168/jds.S0022-0302(02)74129-5, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/12018416
  37. Singh J, Khanna A, Chander H. Effect of incubation temperature and heat treatments of milk from cow and buffalo on acid and flavor production by Streptococcus thermophilus and Lactobacillus bulgaricus. J Food Prot. 1980;43(5):399-400, https://doi.org/10.4315/0362-028X-43.5.399, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/30822877
  38. Bosnea L, Kopsahelis N, Kokkali V, Terpou A, Kanellaki M. Production of a novel yogurt by incorporation of L. casei enriched fresh apple pieces, dried raisins and wheat grains. Food Bioprod Process. 2017;102:62-71, https://doi.org/10.1016/j.fbp.2016.11.010
  39. Sun-Waterhouse D, Zhou J, Wadhwas S. Drinking yoghurts with berry polyphenols added before and after fermentation. Food Control. 2013;32(2):450-60, https://doi.org/10.1016/j.foodcont.2013.01.011
  40. Bazzocco S, Mattila I, Guyot S, Renard C, Aura A. Factors affecting the conversion of apple polyphenols to phenolic acids and fruit matrix to short-chain fatty acids by human faecal microbiota in vitro. Eur J Nutr. 2008;47:442-52, https://doi.org/10.1007/s00394-008-0747-2, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/18931964
  41. Donkor O, Henriksson A, Vasiljevic T, Shah N. Proteolytic activity of dairy lactic acid bacteria and probiotics as determinants of growth and in vitro angiotensin-converting enzyme inhibitory activity in fermented milk. Lait. 2007;87(1):21-38, https://doi.org/10.1051/lait:2006023
  42. Tabasco R, Sánchez-Patán F, Monagas M, Bartolomé B, Moreno-Arribas M, Peláez C. Effect of grape polyphenols on lactic acid bacteria and bifidobacteria growth: Resistance and metabolism. Food Microbiol. 2011;28(7):1345-52, https://doi.org/10.1016/j.fm.2011.06.005, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/21839384
  43. Oliveira A, Costa R, Magalhães A, Pereira J, Carvalho M, Valentão P. Targeted metabolites and biological activities of Cydonia oblonga Miller leaves. Food Res Int. 2012;46(2):496-504, https://doi.org/10.1016/j.foodres.2010.10.021
  44. Silva V, Silva A, Ribeiro J, Aires A, Carvalho R, Amaral J. Screening of chemical composition, antimicrobial and antioxidant activities in pomegranate, quince, and persimmon leaf, peel, and seed: Valorization of autumn fruits by-products for a one health perspective. Antibiotics (Basel). 2023;12(7):1086, https://doi.org/10.3390/antibiotics12071086, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/37508182
  45. Farvin K, Baron C, Nielsen N, Jacobsen C. Antioxidant activity of yoghurt peptides: Part 1—In vitro assays and evaluation in ω-3 enriched milk. Food Chem. 2010;123:1081-9, https://doi.org/10.1016/j.foodchem.2010.05.067
  46. Gheisari H, Abhari K. Drying method effects on the antioxidant activity of quince (Cydonia oblonga Miller) tea. Acta Sci Pol Technol Aliment. 2014;13(2):129-34, https://doi.org/10.17306/J.AFS.2014.2.2, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/24876308
  47. Najman K, Adrian S, Hallmann E, Sadowska A, Buczak K, Waszkiewicz-Robak B. Effect of various drying methods on physicochemical and bioactive properties of quince fruit (Cydonia oblonga Mill.). Agriculture. 2023;13(2):446, https://doi.org/10.3390/agriculture13020446
  48. Grygorieva O, Klymenko S, Vergun O, Mňahončáková E, Brindza J, Terentjeva M. Evaluation of the antioxidant activity and phenolic content of Chinese quince (Pseudocydonia sinensis Schneid.) fruit. Acta Sci Pol Technol Aliment. 2020;19(1):25-36, https://doi.org/10.17306/J.AFS.2020.0738, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/32227695
  49. Sut S, Dall’Acqua S, Poloniato G, Maggic F, Malagoli M. Preliminary evaluation of quince (Cydonia oblonga Mill.) fruit as extraction source of antioxidant phytoconstituents for nutraceutical and functional food applications. J Sci Food Agric. 2019;99(3):1046-54, https://doi.org/10.1002/jsfa.9271, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/30014572
  50. Altuntas S, Korukoglu M. Biological activity of optimized phenolic extracts of quince (Cydonia oblonga Miller) parts before and after simulated in vitro gastrointestinal digestion. Food Chem. 2024;437(Pt 1), https://doi.org/10.1016/j.foodchem.2023.137846, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/37924760
  51. Sonmez F, Sahin Z. Comparative study of total phenolic content, antioxidant activities, and polyphenol oxidase enzyme inhibition of quince leaf, peel, and seed extracts. Erwerbs-Obstbau. 2023;65(4):745-50, https://doi.org/10.1007/s10341-022-00696-5
  52. Qin Z, Liu H, Lv T, Wang X. Structure, rheological, thermal and antioxidant properties of cell wall polysaccharides from Chinese quince fruits. Int J Biol Macromol. 2020;147:1146-55, https://doi.org/10.1016/j.ijbiomac.2019.10.083, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/31726165
  53. Wojdyło A, Oszmiański J, Bielicki P. Polyphenolic composition, antioxidant activity, and polyphenol oxidase (PPO) activity of quince (Cydonia oblonga Miller) varieties. J Agric Food Chem. 2013;61(11):2762-72, https://doi.org/10.1021/jf304969b, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/23461298
  54. Blanda G, Rodriguez-Roque M, Comandini P, Flores-Cordova M, Salas-Salazar N, Cruz-Alvarez O. Phenolic profile and physicochemical characterization of quince (Cydonia oblonga Mill) fruits at different maturity index. Not Bot Horti Agrobot Cluj-Napoca. 2020;48(4):2306-15, https://doi.org/10.15835/nbha48412108
  55. Baroni M, Fabani M, Adan F, Podio N, Wunderlin D. Effect of geographical location, processing and simulated digestion on antioxidant characteristics of quince (Cydonia oblonga). Heliyon. 2022;8(11), https://doi.org/10.1016/j.heliyon.2022.e11435, PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24377856/36444248