In Pakistan, the magnitude of post-harvest losses of vegetables and fruits is about 35 per cent. Efforts are being made both at federal and provincial level to minimize these losses to safe guard the interest of growers, processors, traders, retailers and consumers.

However, the primary objective of research and development activities on post-harvest handling and quality preservation of vegetables and fruits is our national food security. The recent advances made in the area and research in Pakistan are discussed in this paper.

Agro-climatic conditions of Pakistan ranging from tropical to temperate allow growing 40 different kinds of vegetables and 21 types of fruits. Major vegetables grown include potato, onion, chilli, melons, cucumber, tomato, turnip, okra and pea, whereas, citrus, dates mango, guavas, apple, banana, apricot, grapes, almonds, peach, plum and pomegranate are the main fruit crops. At present area under fruits and vegetables is 0.995 million ha (4.3 per cent of the total cropped area) with the total production of 10.992 million tones. Area and production both increased in the past but at a very low pace. The major factor limiting increase in area and production remained high investment and low return to the grower. Post harvest losses in fruits and vegetables range from 25-40 per cent or even greater. Consumer’s prices rise in addition to hidden quality losses. These losses bring low return to growers, processors and traders and country suffers in terms of foreign exchange earning.

In fruits and vegetables, the quality of produce starts deteriorating right after their harvest. Primary factors responsible for post harvest produce losses are: poor pre-harvest measures-adoption of poor production techniques (varieties with low shelf life, imbalance use of nutrients, insect pest and disease infestation and a biotic stresses; low tech harvesting procedures-non-application of pre-harvest recommended treatments/practices, harvesting at improper stage and improper and improper care at harvest; and post-harvest problems-non-removal of field heat, dumping produce, moisture condensation causing pathogen infestation, packaging in bulk without sorting and grading of produce, improper transportation and storage, and distant and time consuming market distribution. In order to preserve the produce quality different post-harvest techniques are recommended for variety of produce. These techniques include; hyper cooling, refrigeration and freezing, modified atmosphere packaging, modified packaging storage, control atmosphere storage, skin coating, hypo-baric or low pressure storage, irradiation, dehydration, canning, high pressure processing and pulsed electric fields and pulsed light applications. In order to promote horticultural industry, standardization of pre-harvest and post-harvest management technologies minimizing post-harvest losses and to enhance foreign exchange earning to the maximum extent is therefore essentially required for necessary adoption. At present various R&D institutions are working on different aspects of post harvest management of vegetables and fruits.

Infrastructure: Information on institutions and their involvement in post-harvest handling, dehydration, processing and preservation of fruits and vegetables work is given on table -1.

For proper redressal of the key issues a well-coordinated research and development programme at national level is however lacking.

Advances: Information on recent advances made in post harvest technology and research at various institutions (also include as given under references) are summarised below:

Selection of varieties: (Vegetables). Riogrande, Roma AVRDC Cv. (tomato), NARC 91 (onion), Medium Long Green (chilies), local selections (cucumber) and VIP (pea) have shown better transportation quality and longer shelf life. (Fruits); Begum jangi (date palm), cardinal, flame seedless (grapes), local selections (fig), sultan (pomegranate) and ARS (N) Mingora No. 7, No. 8 & No. 9 (peach) were found high yielding with longer post-harvest life.

Influence of rootstocks: Studies carried out at Deciduous Fruit Development Centre, Sariab, Quetta revealed that on rootstock MM 106, apple cultivars (red delicious, golden delicious, Star King Delicious and Spartan) showed better performance than on M-9 rootstock for fruit texture and soluble solids. Based on organoleptic evaluation or consumers’ acceptability MM-106 showed partially better performance than M9. For skin colour of fruit, rootstock M9 showed better results over MM-106. However, rootstock MM-106 should better performance in terms of fruits texture, total soluble solid contents and consumers’ acceptability over M-9 rootstock.

Pre-harvest application of Benlate 50 WP minimized mould growth and increased shelf life of citrus (kinnow mandarin) at ambient storage temperature.

Growth hormone: GA3 when applied @ 20 ppm on grape Cv. “Kishmish” not only increased the berry size, yield, protein, reducing and non-reducing sugars, pectin and ascorbic acid but also, the mineral contents of berries (sodium, calcium magnesium and iron contents) were increased hence improved the quality of fruits and also its post harvest longevity.

Calcium chloride: Freshly harvested tomato fruits of variety “nagina” when dipped in 4 per cent CaCl2 solution and kept at 15oC maintained marketable quality up to 16 days.

De-greening: Studies on degreening of citrus and mango showed that citrus variety “salustiana” stored at 30oC and 85-90 per cent RH (controlled atmosphere) developed uniform colour after 24 hours, whereas in case of variety “honeymandrine” there was a slight colour development even after 36 hours. In case of mango variety, “chaunsa” stored at 17oC and 80-85 per cent RH after chilling resulted uniform colour development and produced natural flesh taste.

Wax-coating: Wax-coating studies are being carried out to make the produce more attractive with better shelf life. Carnauba based surface wax increased shelf life of kinnow 3-4 weeks by delaying senescence. Edible film coatings with gelatin (4 per cent), corn starch (3 per cent), HPMC (3 per cent) and stearic acid (1.5 to3 per cent) composition enhanced storage life of carrots variety, “T-29” upto 45 days with minimum (10-15 per cent) post-harvest water loss.

Potato storage: Autumn potato crop is the main crop grown in the plains of Punjab. The crop is harvested during the month of January. The produce is kept in the field until the end of February because of low temperature. Thereafter, potatoes are mostly stored in the field in ordinary storage structures, where weight loss, rotting and sprouting of tubers deteriorate the quality of produce. In cold storage, the produce is held at 4-5oC. At this temperature, starch is converted to sugar and therefore potatoes become sweet. In addition, because of high charges of electricity this costs much higher as compared to ordinary storage conditions or storage of potatoes at relatively higher temperature. Studies associated with these problems reveal that:

1. Improved low cost on-farm storage structure (where hot air is replaced by cool air during night using electric fan) the inside temperature was observed 3-4oC low and the stored potatoes retained marketable quality upto 90 days.

2. The sprout suppressant, “camptothecin” when applied (sprayed) @ 0.5 mm inhibited sprouting of tubers upto 45 days at 39oC, whereas in untreated control sprouting started after 30 days at 39oC.

3. The sprout suppressants CIPC @ 1500 ppm and 2000 ppm, IPC @ 1500 IPM and 2000 ppm and DECCO - 276E(combination of CIPC and IPC) @ 4.4 ml/100 ml water spray check weight-loss, sprouting and sweetening when potatoes were held at 5oC and 9oC storage temperatures and 90 per cent RH until 105 days.

4. Quality of potato tubers when held at 5oC or 9oC and 90% RH was retained until 60 days as the weight loss, rotting, sprouting and sweetening were checked.

Date palm: Results on date palm post-harvest storage indicated that ?3oC was the optimum storage temperature for variety “dakki”. After one month of storage T.S.S. increased from 38.5 per cent to 42.0 per cent with 38.6 percentage weight loss.

Tomato fruit: In case of tomato, variety “nagina” when dipped in 4 per cent CaCl2 solution and kept at 15oC maintained marketable quality upto 16 days.

Olive: Olive fruit when preserved using 15 per cent NaCl solution was found successful.

Apricots: Apricots when dipped @ 3 per cent solution of potassium meta-bisulphite for three hours and then dried proved to be successful.

Radiation: The Nuclear Institute for Food and Agriculture (NIFA), Peshawar demonstrated inhibitory effects on sprouting of onions and potatoes during storage; delay in ripening in banana, guavas, mangoes, pears, tomatoes and persimmon; rot control in oranges and improvement in quality of mature green peaches by using safe levels of Gama radiations.