Valorization of pork by-products: Development of a plant-enriched pork skin pickle

Introduction

Meat has long been a fundamental part of the human diet, providing high-quality protein, essential amino acids and key micronutrients (Lawrie and Ledward, 2006) [9] . Among different types of meat, pork is one of the most widely consumed, valued for its taste, versatility, and nutritional benefits. While traditionally consumed in fresh or cured forms, innovative processing methods have expanded its culinary applications, one of which is pickling. Pork rind, derived from pig skin, is commonly used to produce crispy snacks but also has potential as a pickled delicacy. Pickling enhances its flavour, extends shelf life and creates a ready-to-eat product with significant market potential. This study focuses on the development and quality evaluation of pork rind pickles incorporating mango and elephant foot yam, assessing their physico-chemical, sensory and microbiological characteristics. By optimizing ingredient levels and storage stability, this research aims to introduce a valueadded, nutritious meat-based pickle to the market.

Materials and Methods Preparation of Pork Rind Pickle with Mango and Elephant Foot Yam

The preparation process began with roasting mustard seeds until they crackled, followed by roasting fenugreek seeds until they turned darker and released an aroma. Both were cooled and ground separately into fine powders. Fresh vegetables, including green chilies, garlic and ginger, were uniformly chopped and weighed. Pig skin was boiled with garlic, ginger, pepper powder, salt and turmeric in a closed chamber, then cut into pieces similar in size to the vegetables. The prepared pig skin and vegetables were combined in a bowl, followed by the addition of ground mustard and fenugreek powders, chili powders, salt, vinegar and oil in specified proportions. A tempering mix of hot oil, mustard seeds, split red chilies and asafoetida was added for enhanced flavour. For mango-incorporated pickle, blanched mango pieces were added to the mixture. For elephant foot yamincorporated pickle, boiled and shallow-fried yam pieces were used. The final products were weighed, stored in glass jars at room temperature and evaluated for chemical, microbiological and sensory qualities at seven-day intervals up to 28 days.

Product yield

The cooking yield percentage is determined by measuring the weight of the prepared pickle, multiplying it by 100 and then dividing the result by the pickle's initial weight before preparation.

pH

The estimation of pH of pickle was measured using a digital pH meter in accordance with AOAC (2016) [1] . About 10g of pickle was homogenized in a homogenizer with 50 ml of distilled water for about one minute. The pH was recorded by immersing the combined glass electrode of digital pH meter in the homogenate.

Proximate composition

The proximate composition, including moisture, crude protein, ether extract, crude fibre and total ash, of pork skin pickle was determined using the methods recommended by AOAC (2016) [1] .

Yeast and mould

The yeast and mould count per gram of the sample was estimated using the method outlined by Beuchat and Cousin (2001) [2] . Sabouraud's Dextrose Agar (HiMedia, Mumbai) served as the culture medium and the plates were incubated at 25-27 °C for three days. The results were recorded as log10 CFU/g.

Sensory evaluation

A semi-trained panel of seven members from the Department of Livestock Products Technology at the College of Veterinary and Animal Sciences, Mannuthy, Thrissur, conducted the sensory evaluation using an eightpoint Hedonic scale. Samples were evaluated for appearance, flavour, texture, juiciness, and over all acceptability using 8-point hedonic scale.

Statistical analysis

The physicochemical, proximate, and sensory characteristics of pork rind pickle were analysed using SPSS software (version 24.0), following the guidelines of Snedecor and Cochran (1994) [15] .

Results and Discussion

The study aimed to develop and evaluate the quality of pork skin pickle incorporated with mango and elephant foot yam. The products were stored at room temperature and analysed for physicochemical, sensory and microbiological characteristics at regular intervals over 28 days.

Product yield Fig 1: Product yield

The highest product yield (p<0.05) was observed in the M2 formulation, while the lowest was recorded in E1, suggesting that a greater proportion of pork skin positively influenced the overall yield. These findings align with Choe et al. (2009) [3] , who noted that incorporating pork skin significantly enhanced the cooking yield of sausages. According to Rokka (2013) [12] , pickling is an effective preservation method capable of extending shelf life for several months. This preservation is primarily achieved through reduced moisture content and lowered pH, both of which are essential for the stability of pickled products. Acidification to a pH of 4.6 or lower prevents the germination and toxin production of Clostridium botulinum spores, making the food microbiologically safe (VanGarde and Woodburn, 1999) [16] . The observed decrease in pH is attributed to the addition of vinegar, which act as key preservative agents. Beyond preservation, pickling also enhances sensory attributes such as flavour and taste, contributing to overall product appeal (Das et al., 2007) [5] . Proximate composition analysis showed significant differences (p<0.05) in moisture, protein, fat, ash and crude fibre contents across the various treatments. Moisture content was found to be highest in the E2 formulation and lowest in M2, while protein levels peaked in M2 and were lowest in M1. Fat content was greatest in E1 and lowest in M2. These findings align with Choe et al. (2016) [4] , who reported that incorporating swollen pig skin along with natural vinegars increased moisture levels while reducing fat and protein content in blood sausages. Pork rinds are naturally rich in protein and fat and contain no carbohydrates, making them an attractive option for lowcarb diets. Ash content, energy value, and crude fibre were most elevated in the E1 formulation. This may be attributed to the nutritional profile of elephant foot yam (EFY), which is rich in dietary fibre, carbohydrates, glucose, protein, sugars, and key minerals such as calcium, sodium, potassium, and vitamin C (Sheela Immanuel et al., 2020) [14] . Tubers like EFY are valued for their caloric content and are widely consumed as energy-dense foods (Santosa et al., 2014) [13] . However, EFY is relatively low in protein, with Peetabas et al. (2015) [10] noting its limited protein concentration. Despite their modest protein content, EFY tubers are highly nutritious and can contribute significantly to daily mineral intake. Essential minerals like phosphorus and calcium play vital roles in bone development, enzyme function, acid-base balance, and muscle activity (Jogi and Lahre, 2020) [7] .

Proximate composition

Sensory evaluation Table 3: Sensory evaluation

Sensory Attributes M1 M2 E1 E2 General appearance 7.00±0.15 6.93±0.20 6.93±0.20 7.07±0.13 Flavour 6.79±0.24 6.43±0.31 6.57±0.19 6.79±0.21 Texture 6.93±0.16 6.79±0.18 6.86±0.17 6.86±0.17 Juiciness 6.93±0.27 6.86±0.28 6.64±0.37 6.86±0.28 Overall acceptability 6.71±0.26 6.82±0.21 6.89±0.20 6.86±0.23 * Significant at 0.05 level; ** Significant at 0.01 level; ns-nonsignificant at 0.05 level. Means with different superscripts in rows differ significantly.

No significant differences (p>0.05) were observed among the treatments in terms of appearance, flavour, texture, juiciness and overall acceptability. Sensory analysis indicated that the E1 formulation (30% pork skin and 15% elephant foot yam) received the highest overall acceptability score, followed closely by M1. These findings align with those of Choe et al. (2009) [3] , who reported that incorporating pork skin enhanced the quality attributes of liver sausages. Similar results were also observed by de Oliveira Fagundes et al. (2017) [6] in pork skin-enriched burgers. A significant (p<0.05) increase in pH was observed across all treatments over the storage period, with the E2 formulation exhibiting the highest pH and M1 showing the lowest. According to Rokka (2013) [12] , the pH of pork pickle remains relatively stable, with only minimal increases noted even after 150 days of storage. In a study on pickled chicken meat, Reddy et al. (1997) [11] attributed the sustained low pH during storage to the preservative effects of mustard oil, citric acid and vinegar, which also played a significant role in inhibiting microbial growth. Similarly, Kumar and Bachhil (1993) [8] reported that in pork pickle, factors such as reduced moisture content, lower microbial load and the antimicrobial properties of vinegar and spices contributed effectively to the product's extended shelf life.

Storage study pH

Yeast and mould count

Microbiological analysis showed that although yeast and mold counts increased over time, they stayed within acceptable limits during the storage period. Rokka (2013) [12] suggested that the reduction in microbial load could be due to the preservative effects of the low pH from vinegar, along with the low moisture content and the antimicrobial properties of the spices. Furthermore, mustard oil was found to inhibit the growth of yeast and moulds.

Sensory evaluation

The sensory evaluation indicated that there were no significant (p>0.05) changes in appearance, flavour, texture, juiciness and overall acceptability of the treatment samples throughout the storage period. This suggests that the inclusion of pork skin did not negatively impact the sensory quality of the pickle. Similarly, Rokka (2013) [12] found no significant differences in appearance and overall acceptability between chicken and pork pickle samples during storage. The production costs for M1, M2, E1 and E2 pickles were ₹112, ₹106, ₹112 and ₹106 per kg, respectively. In comparison, the direct material costs for chicken meat and pork pickles were reported to be ₹277.86 and ₹417.86 per kg of the finished product, respectively, as per Rokka (2013) [12] .

Cost of production

Acknowledgement

AcknowledgementsThe authors are thankful to the Dean, College of Veterinary and Animal Sciences, Mannuthy for providing the facilities necessary to carry out the study.

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