- 1 Green Pepper Products
- 2 White Pepper
- 3 Ground Pepper
- 4 Pepper Oil
- 5 Products of Black Pepper: Oleoresin
Green Pepper Products
Dehydrated green pepper
This product is prepared from immature green pepper fruits of suitable varieties by processing under controlled conditions. The fruits should be reasonably uniform in size having characteristic pungency, flavour and colour of green pepper. Pepper fruits are blanched in boiling water for a few minutes, drained, cooled and then soaked in sulphur dioxide solution to fix the green colour followed by drying in a cabinet drier at 50°C. Upon rehydration, this product will reconstitute to a good quality product possessing the characteristic pungent, spicy taste, colour and flavour of green pepper, when one part by mass of dehydrated green pepper is cooked for 20 minutes in presence of ten parts by mass of 1 per cent sodium chloride solution. To conform to international standards (ISO/DIS 10621, 1996), the product should have a moisture content of less than 8 per cent. Efforts are underway at various research institutions () to find an alternative for sulphur dioxide which is being phased out due to health hazards.
Canned green pepper
There has been lot of demand for canned green pepper. The pepper fruits after the removal from the spikes are washed in running water and are then kept soaked in water containing 20 ppm residual chlorine for about an hour. They are then covered with 2 per cent hot brine containing 0.2 per cent citric acid, exhausted at 80°C, sealed properly and processed in boiling water for 20 minutes. It is cooled immediately in a stream of running cold water. The addition of 2 per cent acetic acid instead of citric acid gave a product with better colour. However as per international standard, the only substance that may be added to the covering brine is a small quantity of citric acid not exceeding 0.6 per cent by mass of the packing medium and the covering brine must be 1–2 per cent by mass of edible common salt. It has been observed that pepper harvested one month prior to maturity is the best for the manufacture of green canned pepper.
Bottled green pepper
The manufacturing process consists of despiking the fresh green pepper fruits of uniform size and maturity immediately after harvest followed by cleaning, washing and steeping in 20 per cent brine solution containing citric acid. This is allowed to cure for three to four weeks. The liquid is drained off and fresh brine of 16 per cent concentration together with 100 ppm sulphur dioxide and 0.2 per cent citric acid is added. The resulting product is stored in container well protected from sun and rain. As per international standards (ISO/DIS 11162, 1996), the product shall have the characteristic odour and flavour of fresh green pepper, the colour varying from pale green to green.
Dry packed green pepper
This product is prepared just like the bottled green pepper except that the liquid at the final stage is drained off and packed in flexible pouches. Dry packed green pepper which has the same qualities of canned and bottled green pepper can partly replace these products.
Freeze dried pepper
Now-a-days good quality freeze dried pepper are available in the market at premium prices. This pepper retains the original green colour and shape. The details of the process of freeze drying is kept as a guarded secret by the manufacturers.
White pepper is prepared from ripe fruits by removing the outer pericarp either before or after drying. This product is mainly used in food products in which dark particles are undesirable such as in light coloured sauces, salad dressings, mayonnaise and soups. In certain countries white pepper is traditionally used and preferred to black pepper.
White pepper is manufactured by one of the following techniques: (1) water steeping and retting technique — either from ripened fresh berries or from dry berries (2) steaming or boiling technique (3) chemical technique and (4) decortication technique.
Water steeping technique or retting process
When one or two fruits in a spike start yellowing the crop is harvested, thrushed and heaped in tanks through which water is allowed to run for 7 to 10 days. The light fractions of the pepper like pin heads and light berries which come to the surface are removed and the remaining mass is rolled over at least thrice a day during the retting stage. On the eleventh day the outer skin is removed by gentle rubbing and the deskinned fruits(seeds) are put in another tank containing bleaching solution. It is then allowed to stay in the bleaching solution for two days after which they are drained, washed and sun dried.
This technique, developed at the Central Food Technology Research Institute (CSIR), Mysore, India involve steaming or boiling the mature green fruits for 10–15 minutes. The outer skin of the fruits gets softened during the steaming process and is removed by passing through a pulping machine. The deskinned fruits (seeds) are washed and treated with sulphur dioxide or bleaching powder solution after which they are washed and dried in the sun. The skin recovered from this process may be used for the recovery of pepper oil by steam distillation though it may not be economical.
There are several chemical methods reported for the preparation of white pepper by treatment with acid or alkali, but no commercially viable operation exists. Recently studies have been undertaken for the removal of the outer skin of dried black as well as fresh pepper by microbial decortication and the process is being optimised ().
Whole dried black pepper fruits can be processed to white pepper by employing decorticating machines. The loss of pepper due to breakage will result in reduced yield and hence the white pepper obtained by this method is expensive. Also the characteristic flavour associated with the traditional product is lacking in the white pepper obtained by decortication technique and hence not preferred.
Of the several processes described, the traditional retting process is the most popular and the product obtained by this process is preferred by the consumers. As per international standards (ISO/DIS 959–2, 1996) the product should have only 1 per cent maximum of extraneous matter, 4 per cent maximum of broken berries and 15 per cent maximum of black berries. Also the minimum bulk density should be 600 g/l.
Economics of white pepper production
On drying 100 kg of mature green pepper the yield of black pepper will be approximately 33 kg where as the white pepper obtained by the retting process will yield only 25 kg. Thus it is evident that the cost of white pepper should be atleast 35 per cent above that of the black pepper. The world demand for white pepper is about 38,000 MT which is almost 25 per cent of the black pepper produced world wide.
Black and white pepper powder
Ground pepper is obtained by grinding pepper without adding any foreign matter to the pepper. Grinding can be accomplished by employing equipments like hammer mill or plate mill. It has been observed that the silica content in the ground material obtained from a plate mill is above the permissible level and hence hammer mills with copper tipped hammers are employed for the grinding. The ground product is further sieved and material possessing the required size are packed. The overflow is sent back to the grinding zone for further size reduction.
In modern spice grinding units, pepper is first fluidised for the removal of extraneous matter and then passed through a magnetic separator for the removal of metal particles. It is then passed through a vibrating screen for further removal of extraneous matter and then sent to the hammer mill. The ground product coming out of the hammer mill is fed into a cyclone separator for the recovery of pepper powder. It is further sieved using appropriate sieves and the overflow is recycled. Bag filters are employed after the cyclone separator to prevent the escape of fines into the atmosphere. The ground spice matching the customer’s specification in terms of particle size, ash content, pungency, moisture, crude fibre, volatile oil etc. are packed in air tight containers prior to shipping.
Processing for white pepper powder is similar to the above operation except that the starting raw material is white pepper. The flavour of ground white pepper is characteristic, slightly sharp, very aromatic, must be free from extraneous odours and flavours including mouldy and rancid odours (ISO/DIS 959–2, 1996).
White pepper powder can also be produced from black pepper by selective grinding followed by sieving. Before the pepper is subjected to grinding it is conditioned by adjusting the moisture content. The skin fraction which is a by-product of the process can be a feed stock for essential oil or oleoresin extraction.
This new technique of grinding the spice at temperatures much below 100°F will cut down the oxidation of the oils present in the pepper during the grinding operation besides it will assist in the fine grinding of the spice by making the raw spice brittle at low temperatures employed. The cryoground spices disperse more uniformly in spice formulations and the loss of the volatile oil and flavour are very much reduced during the grinding operation.
The usual practice during the cryogrinding is to inject liquid nitrogen into the grinding zone. A temperature controller maintains the desired product temperature by suitably adjusting the liquid nitrogen flow rate. The exhausted gas is recirculated for the precooling of the spice.
The aroma of black pepper is attributed to the essential oil present in the spice, which can be recovered by steam distillation or water distillation. The essential oil contains mainly a mixture of terpenic hydrocarbons and their oxygenated compounds with boiling points in the range of 80 to 200°C. The composition of the oil has shown wide variation depending on the cultivar, agroclimatic conditions, region of origin, grades etc with pin heads having the least amount of oil and graded pepper having the highest. With respect to the variation in composition of the oil with different grades, the pin heads (PH) was found to contain the highest amount of sesquiterpenes. It is thus possible to make essential oils to meet different flavour requirements by suitable blending of oil from different grades of pepper.
Industrial process for the recovery of essential oil involves flaking of the black pepper using roller mills and conducting steam distillation in a stainless steel extractor. The material to be distilled is dumped into the distillation unit and compacted near the walls to avoid any channelling of the steam. Dry steam is passed through the bottom of the still. The still will also be heated through the jacket provided for the purpose. The steam comes in contact with the ground pepper particles rising its temperature. The oil present in the oil cells gets vaporised and will rise along with the steam through the still. It is then condensed and the oil being lighter than water, will float on the surface of the condensing water. The oil is recovered using an oil/ water separator.
Several studies have been conducted regarding the flow rate of steam, the direction of passage of steam — whether it should percolate up or down, and the particle size of the ground pepper. It has been observed that by keeping the steam flow rate at half the weight of the charge per hour, economical recoveries of the oil could be achieved in a short span of time. The steam, while rising up through the bed of the spice will condense on its surface and additional energy is required for the evaporation of this condensed water. Other wise there is a likelihood of some oil remaining in the bed itself along with this condensed water. To avoid this problem, a new method called hydrodiffusion is employed in which steam is passed from the top of the bed and the oil rich vapours are condensed and recovered from the stream coming out of the condenser. It is quite uncertain whether hydrodiffusion is being practised for the recovery of pepper oil even though hydrodiffusion is the preferred practice for the recovery of essential oil from flowers.
The oil recovered by steam distillation is allowed to stand over anhydrous sodium sulphate for the removal of traces of moisture. The hydrocarbons as well as the sesquiterpenes present in the pepper oil can undergo oxidation during long storage under the influence of air and light. Hence they are stored in airtight containers before being shipped.
Selections from the book: “Black Pepper. Piper nigrum”. Edited by P.N.Ravindran. Series: “Medicinal and Aromatic Plants — Industrial Profiles”. 2000.