Actividad: Ajustar la escuadra de tope a la derecha con volante

A certain on-site stock of raw materials is re quired to ensure smooth pro duc tion and avoid un planned stops. Stocks are generally kept as small as pos- si ble to min i mise storage space and inventory cap i tal. How ev er, stocks are also used to take ad van tage of the market sit u a tion when changes in supply prices are forecast.

Raw materials arrive in several different forms. Concentrate for high-volume production arrives by road tank er. Other raw materials may ar rive in frozen drums and aseptic bag-in-box containers. Specialty and add-back products come in various smaller con tain ers, such as drums, boxes and cans. Sugar, for pro duc tion of nectars and juice drinks, is de liv ered in granular form or as a liquid solution. Sampling and lab analysis to check that in- com ing raw materials meet agreed spec i fi ca tions is carried out reg u lar ly. Such routine checks for or ange con cen trate are de scribed in Table 7.1. Authenticity checks to en sure product origin are

carried out as deemed necessary.

Analyses to con trol product au then tic i ty are quite elaborate and re quire so phis ti cat ed an a - lyt i cal equipment (see also Section 11).

7.2.1 TANKS FOR CONCENTRATE STORAGE Concentrate arriving in refrigerated road tank ers is pumped directly to storage tanks (20–50 m3₎

lo cat ed in a refrigerated area. The refrigerated area is pref er a bly maintained at –5 °C to 0 °C, al- though this is not always the case. The maximum stor age period de pends on the actual refrigeration temperature. There should be no signifi cant in- crease in microbial load of the con cen trate while in on-site storage.

Instead of using standard tanks stored under re frig er a tion, individual storage tanks may be equipped with double walls with a coolant fl ow- ing in the jack et.

Microbial growth is slow in orange con cen - trate due to its high sugar content, i.e. high os- mot ic pres sure. Ba si cal ly, there is no microbial growth in con cen trates of 66 °Brix at tem per a- tures be low 0 °C. However, a liquid layer of low sugar con cen tra tion may form on top of the

If this leads to mi cro bi al problems, a UV lamp can be fi t ted in the top of the tank to inactivate mi cro or gan isms.

The concentrate tanks, which are vented, are equipped with slow and gentle agitators to avoid lay er ing of prod uct. For relatively short on-site storage periods, the con cen trate tanks are not al- ways equipped with ni tro gen blan ket ing. How ev er, meas ures should be taken to prevent air from be- ing mixed into the concentrate during ag i ta tion or tank emptying.

Concentrate is pumped from stor age tanks to the blend ing system area, typ i cal ly by us ing pos i tive dis place ment pumps. Con cen trate at low tem per a tures is very vis cous and therefore the fi t ting of valves be tween the tank and pump is avoid ed as they cause high pres sure drops. Pipe routing for prod uct trans fers made in the con cen - trate room is usu al ly carried out man u al ly using swing bend pan els or fl exible hos es. Au to mat ed rout ing sys tems are not com mon be cause of the

TABLE 7.1 QUALITY CONTROL OF INCOMING CONCENTRATE Sampling of road tankers

– one representative sample per compartment taken at 10 cm minimum below the surface – one microbiological sample

– temperature Sampling of drums

– one representative sample per batch At >55 °Brix direct sampling

At <55 °Brix sampling after thawing and mixing Testing of concentrate

– Brix by refractometer – Acid content – Brix corrected for acid – Brix/acid ratio – Total microbial count

Testing of fi nal product

(prepared in lab. according to own formula)

– Brix dilution – Taste

– Acid content – Appearance

– Colour - Flavour

– Defects

– Sinking and fl oating pulp

Source: Döhler-Eurocitrus

Water fl ushing and cleaning-in-place of the con- cen trate lines are carried out less fre quent ly than in the down stream part of the plant. This is be- cause good op er at ing rou tines, and the high Brix val ues and low tem per a ture of the con cen trate, hinder mi cro bi al growth. More o ver, dur ing fl ush- ing, the wa ter/con cen trate in ter phase and pos si ble re sid u al pock ets of liq uid at low Brix val ues cre- ate con di tions for spoil age or gan isms to mul ti ply rap id ly. The wa ter from fl ush ing is col lect ed in sep a rate tanks to be used for the re con sti tu tion of juice prod ucts.

7.2.2 DRUMS WITH FRO ZEN CON CEN TRATE Product frozen in 200 l drums (typ i cal ly frozen con cen trate, NFC and pulp) is placed in frozen stor age at –18 °C or low er. As FCOJ at –18 °C is prac ti cal ly not pumpable, its tem per a ture is raised to about –5 °C or high er at the time of use. This is achieved through sev er al meth ods, such as a hot jacket around the drum, hot air cir cu la tion or sim ply leav ing the drum in a nonre frig er at ed area. The pre ferred method de pends on the dai ly pro duc tion vol ume and how much ad vanced no tice is re ceived from sched ul ing.

Concentrate is either pumped out of a drum using a submersible hose pump, or emptied into an open ves sel con nect ed to a discharge pump (a quicker meth od). Con cen trate fl ows either di rect ly to the di lu tion tanks for blend ing with wa ter or to a con cen trate buffer tank for mixing with oth er concentrate(s). As some prod uct re mains in side the bag, it is re cov ered by man gling the plas tic bag or rins ing it with water which is then added to the blend ing tanks.

7.2.3 DRUMS CONTAINING SOL ID FROZEN PRODUCTS

Raw products such as NFC, pulp and con cen - trates of low er Brix freeze solid at –18 °C. These are pre pared for process ing by plac ing them to thaw out in a nonrefrigerated area or by us ing a system for quick thaw ing and crush ing of prod uct in drums. Fig ure 7.4 shows the prin ci pal steps for rap id thaw ing of fro zen prod uct.

The drum pass es through a hot air tun nel to

The drum con tents are then emptied into a ves sel hav ing ro tat ing knives which chop up the fro zen prod uct into a slur ry of ice. The slur ry then pass es through a tu bu lar heat er to melt. The liq uid prod- uct is col lect ed in a buff er tank.

A quick-thaw ing line can proc ess a large number of drums per hour (up to 60 drums per hour equiv a lent to 10,000 l/h of prod uct). As hot air and steam are used to heat and melt the ice, it is an en er gy-in ten sive sys tem that en tails a sig nifi cant investment. Juice pack ing plants that re ceive only a lim it ed amount of fro zen prod uct in drums have often de vel oped their own less cost ly so lu tions for thaw ing.

Partial thaw ing of the drum con tents at am- bi ent tem per a ture is fol lowed by crush ing with a small er “chop per” be fore the slur ry is add ed to the blend ing tank. As there is a risk of mi cro bi al growth while the juice or pulp slow ly thaws at am bi ent tem per a ture, this meth od must be care- ful ly mon i tored.

Ice fl akes

Pre-thawing

Liquid juice to buffer tank Drums from frozen storage

Drum tipper

Ice-chopper

Ice-slurry melter

7.2.4 ASEPTIC BAG-IN-BOX CONTAINERS Orange concentrate in aseptic bag-in-box con- tain ers (200 l drums) is placed in cold or frozen storage on site. Long-term storage should be at max. 5 °C to lim it quality deg ra da tion. When re quired for process ing, con cen trate is pumped from bags in a sim i lar way to FCOJ in drums. (See sub sec tion 7.2.2.)

While aseptic bags are not often used for or ange con cen trate, large vol umes of NFC are stored and trans port ed in aseptic bags – typ i cal ly about 1,000 l (300 gal) juice per bag.

There are three methods of emp ty ing juice from asep tic bags:

• Manually with a hose pump inserted through the fi lling spout or through a cut at the top of the bag.

• Controlled emptying by connecting a pump to an emptying spout at the bottom of the bag. In this way the product may be less ex posed to air.

• Aseptic withdrawal of juice through an asep- tic con nec tion to the emptying spout. If this is fol lowed by aseptic transfer, the juice does not re quire repasteurisation prior to pack ag ing. After emptying, NFC is sent to a buffer tank pri or

to pas teur i sa tion. Blending of NFC of dif fer ent or i gins may also take place here.

7.2.5 TANKS FOR NFC

NFC may also be delivered to the juice packer by refrigerated tank car, either prepared by crushing at a blending house or transferred from aseptic storage tanks at a juice processing plant or a re- ception terminal. Transport in tank cars is done under hygienic but not aseptic conditions. Upon arrival at the juice packer, NFC should be kept in refrigerated tank storage at 0–4 °C for a limited time before blending, pasteurisation and fi lling consumer packages.

7.2.6 RECLAIM PRODUCT

Although reclaim, or rework, product is not a raw material supplied to the gate of the juice pack ing plant, it is still used as a basic in gre di ent in juice pro duc tion.

At many points in the juice packing plant, prod uct is collected which, for some reason, is not al lowed to be routed further in the process or pack ag ing sections. This “reject product“ can be: • liquid rinsed out from concentrate containers

and delivery trucks

• product/water interphase from water fl ushing at the start of cleaning cycles

• juice left in a batch blending tank at the end of a production run

• juice of too low (or too high) Brix level at the start of in-line blending operation • juice rejected from the pasteuriser due to

underpasteurisation

• juice rejected from the pasteuriser due to overprocessing caused by (excessive) recircu- lation through the pasteuriser

• juice fi lled into unacceptable containers The reclaim “juice” is too valuable to be sent to drain. It has incurred costs in the form of raw ma te ri al, im port duty, freight charges and process- ing up to the point of col lec tion. More o ver, its dis charge as ef fl u ent would not be ac cept a ble for en vi ron men tal reasons.

As far as possible the reject product is used to pro duce the same type of juice as it was col lect ed from. This, however, is not always pos si ble for prod ucts demanding strict qual- ity spec i fi ca tions. In this case the reclaimed juice is used in orange products not intended as pre mi um brands, or in the man u fac ture of multi-fruit juic es and fruit drinks.

Operating procedures and equipment design in the juice packing plant should aim at min i mis ing re claim volumes. Rework product not only entails re proc ess ing costs but often ends up in a fi nal prod uct of lower value than that it was originally intended for.