Thumbnail Image

Theses

Browse

2018 - 201912020 - 20221
Reset filters
Subject: Post Harvest Technology × Author: Geethu, M × Start date: 2015 × Type: Thesis ×
Reset filters

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    ThesisItemOpen Access
    Post harvest characterisation and management of avocado(Persea americana Mill.)
    (Department of Post Harvest Technology, College of Agriculture, Vellanikkara, 2022) Geethu, M; KAU; Saji Gomez
    Avocado is a subtropical fruit crop, belonging to the family Lauraceae, and is rich in proteins, vitamins, minerals and monounsaturated fatty acids such as oleic acid, contributing to its high nutritive and therapeutic value. Even though there are a large number of genotypes with widely varying characteristics, inadequate characterisation and identification result in the lack of awareness, improper utilisation and insufficient post harvest management of avocado. Hence, the present study titled, „Post harvest characterisation and management of avocado (Persea americana Mill.)‟ was carried out in the Department of Post Harvest Technology, College of Agriculture, Vellanikkara during 2018-2021. The main objectives of the study were to characterise avocado accessions collected from different parts of Kerala and to evaluate the effect of post harvest management practices to extend the shelf life of avocado fruits and to study the effect of food additives on the quality of frozen slices, fruit pulp, freeze dried fruit powder and subsequently to standardise an instant avocado fruit shake. For the characterisation of avocado genotypes, 27 accessions were collected, among which 14 accessions were from RARS, Ambalavayal in Wayanad and 12 from Kanthaloor in Idukki and one accession was collected from Thanniyam in Thrissur. Characterisation of avocado genotypes based on the horticultural and biochemical traits, accession 25 from Idukki had comparatively higher TSS, vitamin C, total carbohydrates, total flavonoids, oleic acid, calcium, potassium, iron, total ash and crude fibre content. Hence, accession 25 was selected for subsequent post harvest management studies. Antioxidant activity of the methanolic extract of fresh fruit of accession 25 was evaluated by DPPH, FRAP and ABTS assays. Greatest free radical scavenging activity was observed in ABTS assay with lowest IC50 value of 0.10 μg/mL. Fresh and mature avocado fruits, surface sanitised with 2 ppm ozone and pretreated with 2 % calcium chloride, followed by shrink packaging with 25 μ polyolefin film and subsequently stored in refrigeration (T8) as well as cool chamber (T9) were found to be the ideal storage conditions with longest shelf life of 27 days. Calcium chloride pre-treated fruits with shrink packaging, stored under refrigeration had lowest physiological lossin weight, respiration rate, ethylene evolution rate and decay per cent, with better retention of firmness. Fruits of this treatment retained significantly higher total carbohydrates, total protein and total phenols during storage. Avocado slices pre-treated with 40 % sucrose, ascorbic acid (0.5 %) and potassium metabisulphite (0.1 %), quick frozen to -20 ºCin 30 minutes followed by packing in 200 gauge LDPE pouches and held under frozen temperature (-18 0C) was the most ideal pre-treatment for storage. This treatment recorded significantly higher TSS, vitamin C, total carbohydrates, total protein and organoleptic acceptability throughout storage and lowest water activity, peroxide value and microbial population. For preparation and storage of avocado pulp, pre-treatments with ascorbic acid (0.5%) and KMS (0.1%) followed by vacuum packaging LDPE bags (T10) as well as in glass jars (T12), stored under refrigeration resulted in longest shelf life and better quality. Total protein, total phenols, total carbohydrate, total fat, viscosity and organoleptic scores were highest in these treatments with lowest water activity, polyphenol oxidase activity and microbial population during storage. For preparation of avocado fruit powder, addition of 5% maltodextrin, ascorbic acid (1%), tricalcium phosphate (0.15%), EDTA (0.05%) and potassium sorbate (0.05%) followed by freeze drying at -70 ºCand 100 mtorr vacuum for 36 hours followed by packing in LDPE laminated aluminium pouches (T14) and glass jars (T16) stored under refrigeration were the ideal methods with longest shelf life and quality. Significantly higher bulk density, solubility, colour value L*, TSS, vitamin C, total carbohydrates, total fat and organoleptic scores were recorded in these treatments during storage along with lowest hygroscopicity, colour value a* and b*, peroxide value, water activity and microbial population. An instant avocado shake was standardised by combining avocado fruit powder with skimmed milk powder, sucrose and water in the proportion of 1:2:1:2 with appealing appearance, light yellowish colour, unique blend of taste and flavour of avocado fruit and skimmed milk powder.
  • Thumbnail Image
    ThesisItemOpen Access
    Standardisation of packaging and storage techniques for green chillies (capsicum spp.)
    (Department of Post Harvest Technology, College of Horticulture, Vellanikkara, 2018) Geethu, M; KAU; Sheela, K B
    The study entitled ‘Standardisation of packaging and storage techniques for green chillies (Capsicum spp.)’ was carried out in the Department of Post Harvest Technology, College of Horticulture, Vellanikkara during 2016-2018. The objectives of the study were standardisation of pre-storage treatments, packaging and storage methods for green chillies. Six accessions of green chillies belonging to three species of Capsicum viz C. annuum, C. frutescens and C. chinense were selected for the study. Variety Ujwala, belonging to the species Capsicum annuum was selected for the surface sanitisation studies. The fruits were surface sanitised with tap water, brine solution (2%), Veggie Wash (1%), sodium hypochlorite (100ppm) and ozone (2 ppm). Fruits sanitised with sodium hypochlorite (100 ppm) recorded the longest shelf life (15days) and lowest microbial load. Lowest Physiological Loss in Weight (PLW %) was observed in fruits sanitised with 2 ppm ozone, followed by sodium hypochlorite. Hence sodium hypochlorite was selected as the best surface sanitisation treatment for further studies. The effect of clipping of pedicel on shelf life of fruits was studied in six accessions of chillies. The accessions selected were Ujwala and Vellayani Athulya (Capsicum annuum) Vellayani Samrudhi and local accession Green Chuna (C. frutescens) and Vellayani Thejus and local accession CC65 (C. chinense). Significant differences were not observed for PLW between the clipped and non clipped fruits. Non clipped fruits in C. annuum accessions registered higher microbial count, comparatively lower shelf life and poor appearance. Packaging and storage studies were conducted in six chilli accessions by subjecting fruits to five methods of packaging viz. control (T0), packaging in micro ventilated polythene cover (T1), polystyrene tray overwrapped with cling film (T2), polypropylene punnets (T3) and shrink wrapping in polystyrene tray (T4). The storage conditions were, ambient (28-36 0C), refrigeration (4-7 0C) and cold storage (10-12 0C). In the varieties belonging to C. annuum and C. frutescens, shelf life could be extended to more than 30 days in shrink wrapped fruits under cold storage. Shelf life was longer in accessions of C. chinense (Vellayani Thejus and CC65) under refrigerated storage. Changes in respiration rate were not pronounced under ambient storage. The physiological loss in weight (PLW %) in all the accessions increased during storage irrespective of treatments and storage conditions and it was higher in unwrapped fruits. Unwrapped fruits had higher TSS under the three storage conditions in all the varieties, one week after storage. Significant variation was not observed in titrable acidity among the treatments except in Vellayani Samrudhi. Fruits of Vellayani Athulya and Vellayani Samrudhi packaged in polythene cover under refrigerated storage and shrink wrapped fruits of Ujwala and Vellayani Thejus under cold storage had high ascorbic acid content. Fruits of Vellayani Athulya and CC65 packaged in polypropylene punnets recorded high β carotene content under ambient conditions and Green Chuna under cold storage. Fruits under cold storage recorded higher capsaicin content in Ujwala, Vellayani Samrudhi, Green Chuna and Vellayani Thejus. Unwrapped fruits had highest total phenols in the three storage conditions in the varieties Vellayani Samrudhi and Green Chuna. Microbial load was analysed by recording the population of bacteria, yeast and fungi. Microbial load was found to increase towards the end of storage. Bacterial population was comparatively low under refrigeration and cold storage. Yeast population was not significant during the storage of green chillies. Population of fungi was found to be lesser under refrigerated conditions. Organoleptic scores were found to decrease in all the varieties, during storage, however the fruits were acceptable for consumption. Shrink wrapped fruits and fruits packaged in polythene cover had higher overall acceptability in all the varieties.