GB1081365A - Yogurt manufacture - Google Patents

Abstract

In the production of packaged yoghurt, an inoculated yoghurt mix is placed in containers, the containers are stacked and the stacked containers are passed in substantially continuous operation through a processing tunnel having an <PICT:1081365/C6-C7/1> incubating zone in which heated gas or vapour is circulated to raise the yoghurt to the desired incubation temperature, an intermediate zone in which the yoghurt cools while incubation continues, and a cooling zone in which gas or vapour is circulated to cool the yoghurt. The temperature of the gas or vapour circulating in the heating and cooling zones is pre-selected and automatically controlled. A refrigerator is associated with the cooling zone. In the intermediate zone ambient air is drawn in and exhausted therefrom. Stacked containers, filled with inoculated yoghurt mix and sealed by automatic processing, are passed through the processing tunnel 20 while mounted on pallets 25, Fig. 1, which are moved stepwise over a rectangular circuit, formed by the tunnel 20 and conveyer tables 28, 29 and 30, by hydraulically and/or pneumatically operated pushers 34, 35, 37 and 38. Each pallet is made of a plastics material reinforced with glass fibres and has three runners (44) Fig. 2 (not shown) bonded to its base and made of nylon or polytetrafluoroethylene to be easily slidable over the floor of the tunnel and against side guides without jarring or vibration of the yoghurt cultures. Channels 46, Fig. 3 are formed in the pallets to receive one of the horizontally-slidable doors (24) defining the zones, rubber seals (47) being provided at the sides of the channels. The stacked containers are moved on to a pallet at position a by a pusher 33 and are removed at position k on to a gravity conveyer 31 by a pusher 36. The circulation of the pallets, the loading or unloading of the pallets with the stacked containers, the operation of fans for the circulation of gas or vapour, and the opening and closing of doors between the zones are controlled by limit switches actuated by the pushers. In the embodiment depicted in the drawing, the incubating zone is the length of four pallets, the intermediate and cooling zones are half this length and the pallets are moved forward every 1/2 hour. The sliding doors may be replaced by air curtains. Air curtains 27 are provided at each end of the tunnel. In the procedure described, a mixture of raw milk and skimmed milk fortified with 2 to 4% of milk solids-not-fat to bring the total solids to between 11 1/2 to 12 1/2 %, is heated first to 120 DEG F. and then to 160 DEG F., is clarified and homogenized, is heated to and held at 190 DEG F. for from three to five minutes and then is cooled to 100 DEG F. The cooled milk is inoculated with 1 1/2 to 2 1/2 % of mixed yoghurt cultures and is held at between 100 DEG and 60 DEG F. for 10-15 minutes. The inoculated yoghurt mix is then heated to 110 DEG F. and filled into paper, plastics or glass containers, and the filled containers are sealed. In the processing tunnel stacks four to ten containers high are maintained at 110 DEG F. for two hours, and are then cooled from 110 DEG to 90 DEG F. during one hour and cooled down to 40 DEG F. during a further hour.