INFLUENCE OF PACKAGING MATERIALS AND STORAGE CONDITIONS ON THE QUALITY ATTRIBUTES OF POTATO (Solanum tuberosum L.) TUBERS

Abstract

Agro ecological diversity and favorable environment have enabled Pakistan to harvest bulk of potato crop however facing problems of poor post harvest management practices and unavailability of superior raw material for the potato processing industry. A comprehensive study was planned to identify best packaging material and appropriate storage conditions for the premium potato variety. The present study has been divided in to three different phase to address specific objectives. The first phase of study encompasses physico-chemical, functional and processing attributes in prominent potato varieties. The selected variety was subjected to different post harvest storage conditions along with their processing parameters analysis in second phase of the study. The last phase of study evaluated the storage stability of premium variety under best results identified in the second phase. In the first phase of study, physical attributes (tuber size, geometric mean diameter, sphericity, surface area, firmness, specific gravity, total soluble solids, pH, sprouting %, tuber color) Chemical attributes (dry matter, starch, protein, fat, sugar, fibre, ash and predominant minerals) functional attributes (ascorbic acids, glycoalkaloids, total phenolic contents, radical scavenging activity) and processing performance (chip moisture contents, fat absorption, color and sensorial attributes) were evaluated in ten commercial varieties i.e. Agria, Atlantic, Cardinal, Chipsona, Courage, Desi, Desiree, Hermes, Lady Rosetta, and Satellite. In general Lady Rosetta followed by Hermes was the most appreciable variety regarding their physical attributes. Lady Rosetta followed by Atlantic attained maximum dry matter and starch contents. Least sugar contents were recorded in Agria and maximum fat and protein contents were quantified in Desiree. In general; functional attributes were found maximum in Desi followed by Desiree. A promising correlation was estimated between most of these parameters with distinctive correlation (R=0.903) identified between total phenolic contents and radical scavenging activity. Post processing parameters like moisture contents, fat absorption, and sensory evaluation in Lady Rosetta showed its preference over all other varieties followed by Hermes. In the second phase variety” Lady Rosetta” was evaluated under different storage conditions 1 2 (packaging, light, temperature, and anti sprouting agents) on the basis of transition in their quality attributes (reported in 1st phase) and enzymatic (polyphenol oxidase, peroxidase) activities. Potatoes were stored under different packaging materials (jute, nylon, polypropylene, cotton, low density polyethylene, medium density polyethylene, high density polyethylene) at ambient temperature (25±2oC). Results revealed that polypropylene packaging and low density polyethylene packaging were found best and maintained tubers quality attributes up to 63 days, while other packaging materials were also found effective as compare to control. Thirty days storage of tubers under different illuminations (blue, fluorescent, green, mercury, red, dark) at ambient temperature (25 ±2oC) was carried out. Potato tubers kept under dark presented minimum loss of quality parameters however green and mercury lights posed best storage performance over all other illuminations during one month. Tubers were found highly susceptible to fluorescent light with poor processing attributes were recorded in red and blue light exposures. Results under comparative temperature regimes (5, 15 and 25oC) showed maximum storage stability up to 126 days under 5oC, however associated with low enzyme activity, elevated sugars contents in tubers and poor processing performances in fried chips. Exposing tubers to different anti sprouting agents (hot water treatment, spearmint oil, clove oil, CIPC) showed that CIPC and Clove oils applications were found significant in preventing tuber sprouting at the end of 80 days storage. In general, both retained superior tuber characters with remarkable processing characters during the storage period. Tuber dormancy was ensured under both treatments till the end at ambient temperature (25 ± 2oC) storage. In the last phase integrated post harvest management of potato variety “Lady Rosetta” on the basis of best results identified in second phase ensured tuber dormancy and prolonged storage life up to 180 days with appreciable retention of tuber quality attributes and superior processing performance as compare to 100% sprouting observed in control on the 80th day of storage. Coating of potato chips with 20% aloe vera gel presented best results with reduced fat uptake along with appreciable sensorial scores.