Food Sci. Biotechnol. 22(4): 1063-1069 (2013) DOI 10.1007/s10068-013-0184-8
RESEARCH ARTICLE
Antioxidant Effect of Pomegranate Rind Powder Extract, Pomegranate Juice, and Pomegranate Seed Powder Extract as Antioxidants in Raw Ground Pork Meat Yu-Yue Qin, Zhi-Hong Zhang, Lin Li, Wei Xiong, Jin-Yu Shi, Tian-Rui Zhao, and Jian Fan
Received: 12 September 2012 / Revised: 3 February 2013 / Accepted: 5 February 2013 / Published Online: 31 August 2013 © KoSFoST and Springer 2013
Abstract The antioxidant potential of pomegranate rind powder extract (PRP), pomegranate juice (PJ), and pomegranate seed powder extract (PSP) was evaluated in raw ground pork meat stored at 4±1oC for 12 days. The pH values decreased from 5.88 to 5.61. The standard plate count in the PRP group was significantly (pPSP>control. Lightness (L* value) was lowered by the addition of PRP, PJ, and PSP. The overall acceptability scores of PRP, PJ, PSP, and BHT treated samples were higher than that of control samples. The results indicated the potential of natural functional ingredients to enhance quality of raw ground pork meat. Keywords: pomegranate rind powder, pomegranate juice, pomegranate seed powder, raw ground pork, natural antioxidant
Yu-Yue Qin (), Zhi-Hong Zhang, Wei Xiong, Jin-Yu Shi, Tian-Rui Zhao, Jian Fan Institute of Chemical Engineering, Kunming University of Science and Technology, Kunming 650550, China Tel: +86-13888195681; Fax: +86-68312939 E-mail:
[email protected] Lin Li College of Light Industry and Food Science, South China University of Technology, Guangzhou 510640, China
Introduction Lipid oxidation is a major cause of deterioration of the quality of precooked meat and meat products (1). Synthetic antioxidants like EDTA, butylated hydroxyl toluene (BHT), and butylated hydroxyl anisole (BHA) have successfully been used to reduce lipid oxidation in meat. However, these products suffer from a negative consumer image because they are artificial. Therefore, there is a growing interest in the use of natural antioxidants and antimicrobial agents in meat products. Examples of natural ingredients include cinnamon (2), ginger (3), and mint (4). However, natural products are often more expensive and less effective than synthetic antioxidants (5). As a result, special attention has been focused on antioxidants from inexpensive or residual sources from agriculture industries, such as apple peel (6), peach peel (7), and citrus peel (8). Pomegranate (Punica granatum) is native from Iran and now also cultivated in several provinces in China. Pomegranate rind and seeds are byproducts obtained during processing of pomegranate juice. Pomegranate rind, pomegranate juice, and pomegranate seeds are reported to possess significant antioxidant activity due to polyphenolic compounds (9). Recently, use of pomegranate juice, pomegranate seed powder, and pomegranate rind powder as natural antioxidant in chicken and goat meat products had been investigated (10,11). Because pigs have relatively high levels of polyunsaturated fatty acids (PUFA), including the long chain (C20-22) PUFA in adipose tissue and muscle, oxidization occur more rapidly in pork than either chicken or goat (12). Precooked pork is more susceptible to lipid oxidation than other meat products. So it is necessary to delay lipid oxidation for raw pork meat products through addition of antioxidants.
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The objective of this study was to determine the effectiveness of pomegranate rind powder extract, pomegranate juice, and pomegranate seed powder extract in raw ground pork meat as measured by pH, microbiological analysis, thiobarbituric acid reactive substances, peroxide value, color, and sensory evaluation during storage at 4±1oC.
Materials and Methods Materials and chemicals Fresh pomegranate was obtained from retail fruit market (Mengzi, Yunnan, China). Testing chemicals, including Folin-Ciocaltea’s reagent, DPPH, 1,1,3,3-tetraethoxypropane, and BHT, were purchased from Sigma-Aldrich (St. Louis, MO, USA). All other reagents and chemicals used in the study were of analytical grade. Preparation of pomegranate rind powder extract (PRP), pomegranate juice (PJ), and pomegranate seed powder extract (PSP) Mature and healthy pomegranate (Punica granatum) fruits were washed, cut manually, and peeled off. The seeds/arils were separated manually and the pulp was separated from seed. Then, it was filtered through cloth. The freshly prepared PJ was sterilized by the high pressure treatment and was stored at 4oC until use, no more than 24 h later. Pomegranate rind (peel) was dried in an air circulatory tray drier (DHG-9070A; Yiheng Instrument Co., Ltd., Shanghai, China) at 60oC for 48 h. Dried pomegranate rind was powdered using a mixer grinder. The pomegranate rind powder (5 g) was extracted with 100 mL of 80% ethanol overnight at 40oC in a shaking water bath. The solutions were filtered through 0.45-µm filter membrane and evaporated under vacuum with a rotary evaporator (RV10 basic V; IKA, Staufen, Germany) below 50oC. After evaporation of ethanol, 5 g of dried pomegranate rind powder was diluted with 100 mL distilled water and stored at 4oC until use, no more than 24 h later. Pomegranate seed powder was also extracted with 80% ethanol in a similar manner. Preparation of raw ground pork Fresh pork meat (M. longissimus thoracis muscle) was purchased 24 h after slaughter from a local processor. All muscles were trimmed to remove visible connective tissue as well as subcutaneous and intramuscular fat. Then, they were ground twice (1st ground through a 6 mm grinding plate followed by 4 mm plate). After mincing, meat samples were divided into batches of 100 g each and assigned to one of the following 5 treatments by mixing with antioxidant: Control group (no antioxidant added); PRP group (raw ground pork containing 20 mg equivalent pomegranate rind powder extract phenolics/
Qin et al.
100 g meat); PJ group (raw ground pork containing 20 mg equivalent pomegranate juice phenolics/100 g meat); PSP group (raw ground pork containing 20 mg equivalent pomegranate seed powder extract phenolics/100 g meat), and BHT group (raw ground pork containing 20 mg equivalent BHT/100 g meat) (10). Sodium chloride (2%, w/w) was added in each sample. BHT was dissolved in 5 mL sunflower oil before addition and the same volume of oil was used for other groups. Fresh ground meat and ingredients were mixed by blending for 5 min with a KitchenAid mixer (KitchenAid Inc., Detroit, MI, USA). Samples were formed into patties by hand and then aerobically packaged in low density polyethylene bags. The samples were stored at 4±1oC for 12 days and were analyzed at every 3 days (0, 3rd, 6th, 9th, and 12th day) (13). pH value measurement The pH value of meat sample was measured with a digital pH meter (PHS-3C; INESA Sciencetific Instrument Co., Ltd., Shanghai, China) using 10 g of sample, homogenized with 50 mL distilled water. Means of 3 replicates were reported for each treatment. Microbiological analysis To determine the bacterial count for each sample, pork sample (10 g) was aseptically transferred into a sterile stomacher bag and diluted with 90 mL, 0.1% sterile peptone water. The sample was then homogenized for 2 min using a Stomacher (Stomacher 400 Circulator; Seward Medical Ltd., London, UK) and 10-fold serial dilutions (using 0.1% sterile peptone water) were made. 0.1 mL aliquot from each dilution was plated onto standard plate count agar (PCA). The plates were incubated at 30±1oC for 48 h to determine the standard plate count after 0, 3, 6, 9, and 12 days of storage. Results were expressed as log colony forming units (CFU)/g pork meat. Thiobarbituric acid reactive substances (TBARS) value Lipid oxidation was monitored by measuring TBARS during storage. TBARS were determined using extraction method described by Witte et al. (14). Briefly, TBARS were extracted in chilled 20% trichloroacetic acid. Two mL extract was mixed with 2 mL of 0.1% thiobarbituric acid and heated for 30 min. After cooling, the absorbance was determined at 532 nm in a spectrophotometer (T90; Beijing Purkinje General Instrument Co., Ltd., Beijing, China). 1,1,3,3-Tetraethoxypropane (Sigma-Aldrich) was used as standard. TBARS value was expressed as mg of malonaldehyde/kg of the meat sample. Determination of peroxide value (PV) Lipid from meat samples was extracted following the method of Folch using 2:1 chloroform/methanol solvent system (15). The lipid extracts were evaporated and concentrated with a rotary evaporator. Then, the PV was analyzed for a 5 g
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Antioxidant Effect of Pomegranate Byproduct in Pork
sample of recovered lipids according to the Chinese National Standard (GB/T 5538-2005). The PV was evaluated by measuring the iodine released from potassium iodide titrated with standardised 0.01 N sodium thiosulfate solution. The PV was expressed as meq of peroxides/kg meat. Color measurement Surface color analysis was carried out using a colorimeter (Minolta Chroma Meter CR-300; Minolta Camera Co., Ltd., Osaka, Japan). Raw ground pork meat samples were placed in a measuring container, and the values for L* (lightness), a* (redness), and b* (yellowness) were recorded to evaluate surface color changes of samples during storage. Sensory evaluation A semi-trained panel of 50 students and laboratory coworkers from Department of Food Science and Technology, Kunming University of Science and Technology (Kunming, China), evaluated raw ground pork meat after 3, 6, 9, and 12 days of storage. Panelists were also asked to evaluate sample color and odor for overall acceptability. A 10-point category scale was provided to the panelists and it was anchored 1 as dislike extremely to 10 as like extremely. Statistical analysis A completely randomized designed was used. SPSS statistical computer software package (version 13.0; SPSS Inc., Chicago, IL, USA) was employed in this study. Storage data of pH, TBARS, and color values were analysed using two-way analysis of variance (ANOVA) with Duncan’s multiple range test. Three replicate experiments were carried out and the statistical significance was defined at p1 log10 reduction of L. monocytogenes in food during storage at 4oC. Hayrapetyan et al. (18) found that pomegranate peel extract could effectively inhibit L. monocytogenes in meat pâté at different temperatures. Plant extracts, such as rosemary and oregano possess potential as natural agents for meat preservation (19). On the basis of the above results, it can be concluded that antimicrobial activity of PRP, PJ, and PSP was related to the presence of phenolic compounds which were likely to be responsible for antibacterial activity. Because BHT did not possess antimicrobial functional group, it could not increase effect of antimicrobial property. Lipid stability (TBARS) of raw ground pork meat Effect of PRP, PJ, PSP, and BHT on the TBARS values during refrigerated storage of raw ground pork meat was shown in Table 2. The TBARS value was used to monitor lipid oxidation in these samples during storage (20). The TBARS value of raw ground pork meat increased during 12 days of storage in all samples. However, the TBARS production was significantly (pPJ> PSP>control. Previous researches have shown that the addition of sodium chloride to meat could result in increase of TBARS
Table 1. Effect of different antioxidant on total bacterial count (logCFU) in raw ground pork meat during storage at 4±1oC Time Day 0 Day 3 Day 6 Day 9 Day 12 1)
Control1) aA2)
3.48±0.13 4.63±0.23bC 5.39±0.32cB 6.11±0.28dB 7.01±0.40eB
PRP
PJ aA
3.43±0.11 3.98±0.29abA 4.55±0.36bA 5.43±0.22cA 5.96±0.19cA
PSP aA
3.45±0.07 4.14±0.16bAB 5.06±0.28cB 5.72±0.38dAB 6.62±0.33eB
BHT aA
3.40±0.15 4.27±0.21bABC 4.93±0.12cAB 5.78±0.13dAB 6.63±0.35eB
3.47±0.16aA 4.56±0.25bBC 5.38±0.17cB 6.03±0.17dAB 6.91±0.25eB
Control, no antioxidant; PRP, raw ground pork containing 20 mg equivalent pomegranate rind powder extract phenolics/100 g meat; PJ, raw ground pork containing 20 mg equivalent pomegranate juice phenolic/100 g meat; PSP, raw ground pork containing 20 mg equivalent pomegranate seed powder extract phenolics/ 100 g meat; BHT, raw ground pork containing 20 mg equivalent BHT/100 g meat 2) All values are mean±SD of 3 replicates; Values followed by different small letter (a-e) in the same column and different capital letter (A-C) in the same row are significantly different (p
