تاثیر عصاره هیدروالکلی برگ به پیش تیمار شده با پلاسمای سرد روی ویژگی‌های فیزیکی-شیمیایی گوشت قرمز در مدت نگهداری سرد

Introduction: Ensuring the safety and quality of fresh meat during storage remains a significant challenge for the global food industry. Beef is particularly susceptible to quality deterioration due to its relatively high moisture content and the presence of oxidation-prone lipids, which can accelerate physicochemical changes during storage. These changes adversely affect sensory attributes such as color, flavor, texture, and overall consumer acceptability. Although refrigeration and synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are widely used to retard quality deterioration, increasing consumer demand for natural and clean-label products has encouraged the development of alternative preservation strategies. Plant-derived extracts rich in polyphenols and flavonoids have gained attention as effective antioxidants and antimicrobial agents. Among these, quince (Cydonia oblonga) leaves represent an underutilized agricultural by-product containing substantial amounts of bioactive compounds with free radical scavenging capacity. However, factors such as limited extraction efficiency, variability in phytochemical composition, and degradation of active constituents may restrict their practical application. Cold plasma technology has recently emerged as a promising non-thermal processing approach capable of modifying plant matrices and enhancing the accessibility of bioactive compounds. The reactive oxygen and nitrogen species (RONS) generated during plasma treatment may induce structural modifications in plant tissues, facilitating the release of phenolic constituents and potentially improving their functional properties.



Additionally, cold plasma treatment is solvent-free and low-temperature, aligning with green technology principles and clean-label food production. This offers an environmentally friendly alternative to conventional methods. Despite growing interest in cold plasma applications, information regarding the use of extracts obtained from plasma-treated quince leaves for meat preservation remains limited. Therefore, the objective of the present study was to evaluate the effectiveness of hydroalcoholic extracts prepared from cold plasma-treated quince leaves in maintaining the physicochemical quality of refrigerated beef during 15 days of storage at 4°C. Key physicochemical parameters including pH, moisture content, ash, thiobarbituric acid reactive substances, and total volatile basic nitrogen, were monitored to assess the preservative potential and stability provided by the treatment.
Materials and Methods: Fresh quince leaves were harvested in September 2024 from orchards in Khalkhal, Iran. After being thoroughly washed, the samples were air-dried in the shade for several days and then oven-dried at 38 °C for 48 hours. The dried leaves were ground using a laboratory mill, and the resulting powder was passed through a No. 18 sieve to ensure a uniform particle size. For the cold plasma treatment, 100 g of the powdered leaf samples were weighed with a precision of 0.001 g and evenly spread as a single layer (5 mm thickness) in glass Petri dishes with a diameter of 10 cm. The samples were exposed directly to cold plasma treatment at a distance of 3 cm from the electrode, under a pressure of 500 mTorr, voltage of 1.2 kV, and current of 90 mA for two exposure times (5 and 10 minutes). Untreated leaves were used as the control. Extraction of both treated and control samples was carried out using a hydroalcoholic solvent system (ethanol-water, 60:40 v/v), following a previously optimized method. The extraction took place at 25°C for 24 hours in a laboratory shaker set at 100 rpm. The resulting solution was filtered through Whatman No. 42 filter paper, and any remaining solids were separated by centrifugation. The extract obtained was then concentrated to one-third of its original volume under reduced pressure at 50°C and 200 rpm using a rotary evaporator. The concentrated extract was poured onto glass plates and dried in an oven at 38°C. The dried samples were stored in a desiccator until a constant weight was achieved, and then placed in a refrigerator, wrapped in aluminum foil, for further analyses. Fresh beef was obtained from a local supplier, trimmed of visible fat, and cut into cubes measuring 2 × 2 × 1 cm. The samples were divided into seven treatment groups, immersed in quince leaves extract (QLE) solutions (10% or 20% w/v) for 24 h at 4 °C, and subsequently packed in polyethylene bags. The treatments were as follows: T1: Control (sterile distilled water); T2: 10% QLE; T3: 10% QLE, pretreated with cold plasma (5 min); T4: 10% QLE, pretreated with cold plasma (10 min); T5: 20% QLE; T6: 20% QLE, pretreated with cold plasma (5 min), and T7: 20% QLE, pretreated with cold plasma (10 min). Samples were stored at 4°C for 15 days and analyzed on days 1, 5, 10, and 15. The physicochemical and microbial properties of the meat samples were evaluated by measuring pH, moisture content, thiobarbituric acid reactive substances (TBARS) as an indicator lipid oxidation, total volatile basic nitrogen (TVB-N), and total bacterial counts. The experiment was conducted using a completely randomized design (CRD) with seven treatments and three replicates. Measurements were performed on days 1, 5, 10, and 15 of meat storage at 4°C. Data were analyzed using SAS software (Version 9.2). Repeated measures analysis was applied to evaluate the effects of treatment, storage time, and their interaction. Whenever significant main effects or interactions were detected, mean comparisons were performed using the Least Squares Means test at a significance level of P < 0.05.
Results and Discussion: Plasma pre-treatment significantly impacted the moisture, ash, and pH levels of quince leaf extracts. The moisture content decreased as the plasma exposure time increased. On the other hand, the ash content increased, possibly due to the higher concentration of mineral components resulting from plasma-induced dehydration. Additionally, the plasma treatment raised the pH of the extracts, consistent with the results of Pogorzelska-Nowicka et al. (2021), indicating the generation of reactive nitrogen species and the partial neutralization of acidic components. These changes collectively suggest that plasma exposure can alter the chemical composition of extract matrices.
Moisture content plays a crucial role in determining the juiciness, tenderness, and overall consumer acceptance of meat. Over a period of 15 days, all samples experienced a gradual decrease in moisture content, primarily due to evaporation. However, beef that was treated with quince leaf extract showed significantly higher levels of moisture retention compared to the control group (p < 0.05), especially at higher concentrations of the extract. The treatment that resulted in the highest moisture retention was T7 (20% extract, pretreated with cold plasma for 10 min), indicating that the improved water-holding capacity may be attributed to the hydrophilic interactions between meat proteins and polyphenolic compounds present in the extract. This finding is consistent with previous studies that have shown enhanced moisture retention in meat products treated with plant-derived extracts such as green tea and rosemary. The pH of meat is a sensitive indicator of microbial and enzymatic activity. In all treatments, an initial decline in pH was observed until day 5, due to lactic acid production by fermentative bacteria. After that, pH values increased as proteolytic bacteria produced alkaline metabolites such as ammonia and amines. By day 15, control samples had a pH of 6.54, indicating advanced spoilage, while treatment T7 maintained the lowest and most stable pH at 6.21. The delayed increase in pH observed in treated samples may indicate a slower progression of quality deterioration processes during storage compared with the control group. These results align with previous studies by Daszkiewicz et al. (2003) and Stanišić et al. (2012), which showed that natural plant antimicrobials can reduce post-storage pH increases in meat products. Lipid oxidation is a significant factor contributing to the deterioration of meat quality, resulting in rancid odors and reduced nutritional value. TBARS values increased in all samples during storage, although at varying rates. The control group showed the highest accumulation of malondialdehyde (MDA), indicating extensive oxidative damage, while all extract-treated samples had significantly lower TBARS levels (p < 0.05). The inhibitory effect was more pronounced with higher extract concentration and longer plasma exposure time. Treatment T7, in particular, achieved a reduction of over 50% in TBARS compared to the control, showcasing a strong antioxidant effect. This improvement is likely due to plasma-induced modifications of phenolic compounds, potentially increasing their radical-scavenging capacity. Similar enhancements in antioxidant activity following plasma exposure have been observed in olive leaf, ginger, and pomegranate peel extracts. TVB-N is a key indicator of microbial spoilage and protein degradation. Control samples showed a sharp increase in TVB-N, exceeding acceptable freshness limits by day 15. In contrast, all groups treated with QLE exhibited lower TVB-N values, with the most significant reduction seen in T7. By the end of storage, TVB-N levels in T7 were around 40% lower than in the control group, indicating significant inhibition of spoilage. These results are consistent with the findings of Saleh et al. (2020), who showed that olive leaf extract decreased both TBARS and TVB-N levels in refrigerated poultry. It was also found that meat samples treated with quince leaf extract had lower total bacterial counts than the control sample. The results suggest that extracts obtained from plasma-treated leaves were more effective in preserving physicochemical and microbial parameters than extracts obtained from untreated leave.
Conclusion: The results of this study clearly demonstrate that hydroalcoholic quince leaf extract, especially when pretreated with cold plasma, can effectively enhance the physicochemical stability and shelf life of refrigerated beef. The treatment that combines 20% extract with a 10-minute plasma exposure provided the best results. Furthermore, establishing regulatory frameworks and quality standards will be crucial for industrial adoption to ensure product safety and consumer trust. Overall, integrating cold plasma technology with natural plant extracts shows promise as an eco-friendly approach to improving food preservation, which supports both environmental sustainability and public health.